Field of the I nvention Present invention relates to surface modification of the carbon blacks by oxidation reaction. More specifically, the advancement relates to treatment of carbon blacks be it fluffy, granules, or powder having different bulk densities or with different surface area and structures involving ozone gas. Background of the I nvention

The surface chemistry of carbon blacks depends on the manufacturing processes. I n case of furnace process, carbon blacks are produced in a highly reducing atmosphere, so very negligible amount of surface oxides are present to the surface of furnace black and produced carbon blacks are hydrophobic in nature. The amount of oxides present on the surface is called volatile content which is measured according to DIN 53552. pH of carbon black (measured according to ASTM D1512) also indicates the extent of carbon black surface oxidation.

It has long been recognized that oxidized carbon blacks have properties that are important for specific applications. For example, they have improved wettability and rheology in paints and coatings, and ink applications. Oxidised carbon blacks are also used in polymer compounds which improve filler-polymer interaction, thus increases hardness, modulus, tensile and tear strength of the unfilled polymer. A good dispersion and adhesion between the filler and the polymer matrix is required for optimum mechanical properties. The filler surface energy is also of great importance: it should be greater than, or equal to the surface energy of the polymer.

The untreated carbon black exhibits a small surface energy and is apparently unable to form strong adhesive bonds with the polymer. However, this issue can be resolved by surface modification of carbon black particles employing oxidative post-treatments. Several oxidation treatments on carbon black have been described using oxidizing agents such as acid medium (HNO3) , ozone, nitric oxide, ammonium peroxydisulfate, hydrogen peroxide, plasma and so on. Although all these treatments increase successfully the level of oxygen on the surface, they produce changes on the surface structure and morphology of carbon black. Oxidative post-treatments of carbon black reduce the time needed for the dispersion into the polymer matrix. Additionally, such treatments improve dispersion stability and wettability of carbon surfaces by promoting the formation of hydrophilic groups [Marius Ciobanu et al. / Materials Today: Proceedings 3S (2016) S252 - S257] .

For wet oxidation technique to oxidize carbon blacks, liquid oxidants like nitric acid (US 3383232) or hydrogen peroxides (US6120594) are used as oxidant. These liquids are mixed with carbon powder for oxidation to prepare slurry/lumps. Then the liquid is evaporated from carbon black by heating, providing slurry cake type or solid hard oxidized carbon black of different shape/ sizes. To get powder material, the oxidized carbon black is grinded. Another demerit in wet oxidation is handling difficulty as these are highly hazardous chemicals to health and environment. NOx is generated during oxidation of carbon black by nitric acid.

Compared to dry oxidation (oxidation by gas) , wet oxidation requires more steps like heating and grinding - making the former as the preferred one. In several patents, post treatment of carbon black using ozone gas has been mentioned. Patents like US6471763, US8574527, US3247003, and US3353980 have described oxidation of fluffy gas black using fluidized bed reactor, wherein only fluffy black is used for fluidization using fluidizing agent. This process of oxidation may not be suitable for coarse or beaded carbon black. As foreign particles are used as fluidizing agent, there is the chance of contam ination of oxidized carbon black by fluidizing agent.

US6471933B1 discloses a process for the ozone — oxidation of a carbon black wherein the ozone — oxidized carbon black is generated by scrubbing (or, intimately contacting) the gas stream with water prior to m ixing it with the carbon black. Disclosures like US3216843, US3301694, US3353980 and US3245820 have demonstrated the oxidation of fluffy carbon black using cyclone separator attached to carbon black production reactor. It is a continuous process, carbon black exposure time to ozone gas is very less. Hence oxidized carbon black of high volatile content is not possible. This process is suitable only for fluffy black. As this process is attached to the carbon black production reactor, very lim ited grades of carbon blacks those are produced from carbon black production reactor can be post treated. Carbon black produced from other reactors cannot be post treated. I n addition, there is no detailed process description about the carbon black oxidation (from carbon black feeding to the reactor to the packing of oxidized carbon blacks) .

From the traversal of the related prior arts, it is apparent that most of the advancem ent dealt with only fluffy carbon black oxidization employing a vertical fluidized bed reactor or cyclone separator system . These systems are neither suitable for coarser or granulated carbon black particles nor efficient enough for adequate fluidization of carbon blacks of high bulk density leading to improper oxidation. Application of additional fluidizing agent for said fluidization m akes the system more prone towards contam ination. Thus, there is an urgent need for development of a process which will be devoid of all the shortcom ings. But in this regard, dearth of details about carbon black oxidation process in order to produce oxidized carbon black for com m ercial scale m akes the endeavor of developm ent of a process m uch more challenging.

Object of the invention

The prime object of this invention is to provide a system to carry out post treatm ent process for carbon blacks using ozone gas which would be amenable for a post treatment of all forms of carbon black, be it fluffy, granules, or powder, using ozone gas.

Another obj ect of the present invention is to provide said system for post treatm ent of carbon blacks which would be applicable for carbon blacks of different surface area, different oil absorption number and having different bulk density. Another object of the present invention is to provide said system for post treatment of for carbon blacks wherein horizontal fluidized bed reactor fitted with helical ribbon will be employed for the fluidization of the reactant carbon blacks.

Another object of the present invention is to provide said system for post treatment of carbon black which would enable oxidation of carbon blacks as per desired oxidation level with no limit for Retention time of carbon black in oxidation reactor.

Another object of the present invention is to provide said system for post treatment of carbon black which could be advantageously adapted as a batch process preferably having separate unit from the carbon black production facility or could be amenable to a continuous process or as an integrated unit with carbon black production.

Another object of the present invention is to provide said system for post treatment of carbon substrate which would be an environment friendly controlled oxidation process devoid of any system leakage and release of ozone to the environment.

Another object of the present invention is to provide said system for post treatment of carbon substrate which would enable furnishing carbon black suitable for application in paint, ink, toner, and coatings providing improved wettability and rheology, characteristics which are important in these applications.

Sum m ary of the I nvention

The primary aspect of the present invention is directed to provide a system for treatment of carbon substrate to generate oxidized carbon substrate including carbon black selectively anyone or more of fluffy, granules and powder carbon black comprising: a horizontal reactor (5) including atleast a rotary ribbon means (19) operatively connected to a rotating mechanical shaft inside said horizontal reactor for controlled carbon black fluidization and motion inside the reactor involving said rotary ribbon means for desired full exposure of the carbon black particles inside said horizontal reactor alongwith selectively and controlled feed of an ozone oxidizing gas; said horizontal reactor (5) having an inlet end (6) for feeding said carbon black to be treated an ozone generator (3) operatively connected to said horizontal reactor (5) for said selectively and controlled feeding of the ozone oxidizing gas for desired oxidation of the carbon black in fluidized form throughout the entire volume of said reactor; a filter bag unit (9) for collecting outgoing unused ozone and separating therefrom the carbon black carried through said outgoing ozone gas; and a discharge outlet (14) of said reactor for discharging the thus generated surface treated carbon black including anyone or more of the said fluffy, granules and powder carbon black.

Another aspect of the present invention is directed to provide said system for treatment of carbon substrate comprising said rotating mechanical rotary shaft (8) operatively connecting said rotary ribbon means ( 19) preferably a double helix; and including an oxygen generator (1 ) operatively connected to said ozone generator (3) for feeding ozone gas into said reactor (5) ; said filter bag unit (9) operatively connected to means for air pulsing (18) to reduce the blockage of bag filter from the fine carbon powder coming out with the outgoing unused ozone with oxygen carrier gas effect filtration of the carbon black particles mixed with outgoing gas and said outgoing unused ozone with oxygen carrier gas is passed to an ozone destructor unit (1 1 ) wherein the u nused ozone is converted to oxygen and released to environment or recirculated in the system as the oxygen carrier gas. Another aspect of the present invention is directed to provide said system for treatment of carbon substrate comprising said horizontal reactor (5) with said double helix ribbon ( 19) operatively fitted to the rotating mechanical rotary shaft (8) for controlled rotation of double helix ribbon effecting proper fluidization and motion of the substrate inside the reactor; wherein said horizontal reactor (5) is operatively connected with feeding bin (4) to feed the horizontal reactor (5) through loading inlet (6) cooling jacket (12) for controlling treatment temperature in the reactor; sample collection point (13) for the testing of pH and volatile content; discharge point (14) to the discharge bin ( 15) for removal of oxidized substrate from the reactor (5) ; ozone generator (3) through the inlet (7), motor ( 17) for rotation of rotating mechanical rotary shaft (8), bag filter (9) where substrate/product mixed with the outgoing gas is filtered and pass to ozone destructor (1 1 ) through pass point( 10) , the ozone outlet point from bag filter.

Further aspect of the present invention is directed to provide said system for treatment of carbon substrate wherein said fed carbon substrate for oxidation post treatment includes furnace black, gas black, acetylene black, plasma black, arc black, in any forms as fluffy, granules, or powder form said horizontal reactor and including means for controlled feed in of the carbon black substrate and ozone gas in combination with rotary ribbon means for controlled carbon black fluidization and motion free of any fluidizing agents and having capability for variety of carbon black substrate of varied surface area and structure to be suitably oxidized as per any target oxidation level for various end utilities.

Still further aspect of the present invention is directed to provide said system for treatment of carbon substrate for producing surface modified carbon substrates including any of fluffy, granular and powdered carbon black substrates by oxidation reaction involving ozone gas comprising a leak proof horizontal reactor (5) including rotating m echanical rotary shaft with ribbon means, whereby the carbon black substrate particles fed into said reactor are fluidized throughout the entire volume of the reactor, motor m eans adapted for selective controlled rotation of the said mechanical rotary ribbon m eans of said reactor and means for controlled flow of the ozone gas involving ozone concentration measuring means based on the nature of carbon substrate particulate being oxidized. Another aspect of the present invention is directed to provide said system for treatm ent of carbon substrate comprising said horizontal reactor (5) , fitted with double helix ribbon ( 19) , motor means for controlling the rotation of said double helix ribbon ( 19) for perpetual turbulent movem ent of substrate particles in a leakage free condition without requiring any external fluidizing agent in combination with i. ozone generation and m easuring means for selective concentration of ozone from oxygen for passing through the horizontal reactor (5) ; ii. feeding bin for charging of substrate to the reactor (5) iii. rotating mechanical rotor shaft (8) speed control m eans based fluidization of carbon black in the said reactor (5) for uniform exposure to the ozone/ oxygen gas m ixture by controlling rotational speed of said double helix ribbon ; iv. discharge point ( 14) to the bin ( 15) for discharge of oxidized substrate from the reactor (5) .

Another preferred aspect of the present invention is directed to provide a process for surface modification of carbon substrate to generate oxidized carbon substrate including carbon black selectively from anyone or more of fluffy, granules and powder carbon black comprising : carrying out said surface modification of carbon substrate involving a horizontal reactor (5) including atleast a rotary ribbon m eans ( 19) operatively connected to a rotating mechanical shaft (8) inside said horizontal reactor for controlled carbon black fluidization and motion inside the reactor involving said rotary ribbon m eans for desired full exposure of the carbon black particles inside said horizontal reactor alongwith selectively and controlled feed of an ozone oxidizing gas; feeding said carbon black to be treated into said horizontal reactor (5) through an inlet end (6) of said horizontal reactor; selectively and controlled feeding of the ozone oxidizing gas from said ozone generator (3) operatively connected to said horizontal reactor (5) for said desired oxidation of the carbon black in fluidized form throughout the entire volume of said reactor; collecting outgoing unused ozone and separating therefrom the carbon black carried through said outgoing ozone gas involving an online filter bag unit (9) at the other end opposite to said feed end of the horizontal reactor; and discharging the thus generated surface treated carbon black including anyone or more of the said fluffy, granules and powder carbon black through said discharge outlet ( 14) of said horizontal reactor.

Another aspect of the present invention is directed to provide said process wherein said selectively and controlled feeding of the ozone oxidizing gas from said ozone generator (3) is done at selective concentration of ozone in carrier gas preferably oxygen is ranged from 0.5 to 10 wt.% preferably 6 wt% .

Yet another aspect of the present invention is directed to provide said process wherein said carbon black substrate for oxidation includes carbon materials carbon black, graphite, graphene, carbon nanotubes, carbon nanofibers, fullerenes with powdery final form preferably carbon blacks.

Yet fu rther Another aspect of the present invention is directed to provide said process wherein said carbon black substrate used includes furnace black, gas black, thermal black, lamp black, channel black, plasma black, blacks produced as by-product of chem ical production processes, and hybridized carbon black materials and Carbon blacks having oil absorption number (OAN) value (ASTMD 2414) ranging from 65 to 550 ml/100 g, BET surface area (ASTM D 4820) from 30 to 1270 m ² /g, including fluffy, powder, and pellets form of carbon blacks. Another aspect of the present invention is directed to provide said process wherein retention time of carbon black in oxidation reactor (5) is selectively controlled based on the desired level of oxidation, volatile content and pH of the treated carbon black substrate and its related end utilities.

Another aspect of the present invention is directed to provide said process which is tailored to generate selective level of carbon black substrate oxidation by selectively involving rpm of the rotating mechanical shaft carrying the ribbon connected to the reactor, ribbon cross section and pitch, clearances between the outer ribbon and the trough wall, and number of spirals on the ribbon can change the state of carbon powder fluidization for the desired oxidized black productivity Still Another aspect of the present invention is directed to provide surface treated oxidized carbon substrate including carbon black selectively anyone or more of fluffy, granules and powder carbon black comprising: carbon powders having BET surface area from 30 to 325m ² /g and oil absorption number (OAN) value ranging from 60 to 120 m l/ 100 g. obtained of ozone treatment in horizontal reactor following said process for a duration of 15 to 60 minutes for advanced coating performance selected from colour strength 95 to 105 reduction strength 107 to 160 viscosity 195 to 4176 m Pa.S and Gloss (60°) 50 to 80.

Description of the invention The present invention discloses a system for post treatment of carbon substrates wherein carbon blacks of different surface area, structure and bulk density can be efficiently fluidized and oxidized at any targeted oxidation level using this system . Fluffy carbon black refers to carbon black straight from the carbon black producing furnace reactor, granules refer to carbon black in pellets form, and powder carbon black refers to carbon black pellets pulverized (finely divided) in air under compression-impact.

For the present invention fluidization process is performed in a closed horizontal reactor by the rotation of double helix ribbon attached to the shaft of reactor. Fluidization takes place without use of any fluidizing agents. Carbon black of different surface area and structure can be oxidized using this process at any targeted oxidation level. The treated carbon black can be used in a wide range of applications, including but not restricted to inks, paints, and coatings.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention of a system for post treatment of carbon black in a closed horizontal reactor and oxidized carbon black obtained thereof. The advancement according to the present invention is discussed in further detail in relation to the following non-limiting exemplary illustrations wherein.

Figure 1 : Schematic drawing of the setup to carry out the oxidation of carbon substrates as disclosed for the present invention comprising : Oxygen generator ( 1 ), Oxygen storage tank (2) . Ozone generator (3) , Feeding bin (4), Reactor (5), carbon black loading inlet (6) , Ozone flow i n let ( 7) , Rotor shaft of Double helical ribbon (8) , Bag filter (9) , Ozone outlet point from bag filter (10) , Ozone destructor (1 1 ), Cooling jacket ( 12), Sample collection point (13), Discharge point (14) , Discharge bin (15) , Powder packer ( 16), Motor (17), Air Pulsing to bag filter ( 18) , Double helix ribbon (19).

A batch type process has been designed for the present disclosure, to oxidize the carbon materials using ozone gas as an oxidizing agent. A schematic drawing of detail oxidation setup of the present invention is presented in Fig. 1.

As per the drawing in Fig 1 , oxygen ( O2) gas from oxygen generator (1 ) is passed through O2 storage tank (2) to the ozone generator (3) for O3 gas formation. The feed gas used for ozone generation is oxygen. The oxygen concentration, humidity and feed gas flow rate are measured and controlled. An ozone analyzer is employed to measure the ozone concentration in the ozone /carrier gas composition to be used for carbon black oxidation. Initially, desired amount of carbon black stored in feeding bin (4) is fed to the horizontal reactor (5) through carbon black loading inlet (6). After carbon black feeding, reactor is sealed and ozone gas from O3 generator (3) is fed to the reactor by O3 inlet (7). O3 gas is continuously fed to the carbon black which are in fluidized form throughout the entire volume of reactor by the controlled rotation of double helix ribbon fitted to the rotor shaft (8). During continuous flow of O3 to the reactor, some unused O3 with O2 carrier gas from reactor is passed to bag filter (9) wherein carbon black powder mixed with the outgoing gas is filtered and the unused O3 gas with O2 gas is passed through point ( 10) to the ozone destructor (1 1 ). The unused O3 is converted to O2 and then released to environment or reused. Treatment temperature is controlled by the cooling jacket (12) attached to the reactor. Throughout the reaction, at specific time intervals, oxidized carbon black sample is collected from reactor though sample collection point ( 13) for testing of pH and volatile content to understand the extent of oxidation. After oxidation as per requirement, oxidized carbon black is purged by oxygen or air or nitrogen gas to remove trapped O3 gas inside treated carbon black and then treated carbon black is removed through discharge point ( 14) to the discharge bin ( 15). Oxidized carbon black from discharge bin is packed by a powder packer (16).

I n the primary embodiment the present invention surprisingly solved the problem of inefficient fluidization encountered by the other reported FBRs- mostly vertical, while using granular carbon black or carbon black having high bulk density by carrying out the fluidization process in a horizontal FBR fitted with ribbons employing mechanical fluidization. Usually, gas is used for carbon black fluidization, but in horizontal reactor, double helix ribbon is used to fluidize the carbon black by mechanical process. Apparently, the rotation of the ribbon ensures the promotion of high levels of contact between gases and solids and, thus, fluidization. The ozone remains in constant touch with the carbon black while the ribbon in reactor is under rotation for a pre-decided duration resulting in surface modified carbon black at desired level of oxidation. The use of two ribbons increases the strength and circulation flow and provides a high mixing rate. However single helix ribbon can also be used to solve the problem of inefficient fluidization encountered by the other reported FBRs- mostly vertical, while using granular carbon black or carbon black having high bulk density. Carbon black fluidization and the bulk motion inside the reactor can be controlled by the rotation of double helix ribbons attached in reactor.

In another embodiment of the present invention eliminates the limitations of vertically fluidized bed. Vertical fluidized bed is suitable mainly for the very fine powder (fluffy) carbon black. Heavier particles are generally not fluidized, and the gas used for fluidization is passed through formation of channels. Sometimes fluidizing agents are used for the fluidization of powder materials, where chance of contamination is more. No fluidizing agents are required for the present invention.

In another embodiment the invented system improves on the limitations of rotational movement of particles inside horizontal fluidized reactor, where said rotational movement inside the drum induces a centrifugal force. This centrifugal force drives the powder particles away from the center towards the cylindrical wall of drum and the powder particles are not fully exposed to the oxidizing gas. Installation of double helix ribbons induce a perpetual movement of carbon black inside the reactor and thus enables efficient fluidization. The level of fluidization of carbon black is adjusted by changing the rotational speed of the ribbon. Oxidation time and extent of oxidation can be varied to achieve required level of volatile content and pH of carbon blacks. The present invention allows for installation of a powder filtering system to filter powder from the gas coming out from the reaction chamber. The set up makes it possible to operate the entire oxidation setup under leakage free condition, which is difficult in a horizontal rotating drum, difficult to ensure in rotating horizontal reactors.

Horizontal reactor (static) without ribbon is not available, but horizontal rotating drum reactor is known where horizontal reactor is rotated. Material is fed at one side and removed in another side. Material movement is one sided and is a continuous process. Material residence time is less, so oxidized carbon black with high volatile content may be difficult. In case of horizontal ribbon reactor, reactor is static and double ribbon is used for fluidization. Material residence time/reaction time may be varied up to achievement of required volatile content. As mentioned hereinbefore rotating reactor may not be gas leakage free as reactor is always in rotation.

For the uniform surface treatm ent, carbon black particles should be exposed to the ozone gas. Uniform exposure of carbon black particles to the ozone gas is possible by the fluidization of carbon particles inside the reaction container. For the fluidization of material, agitation of any kind is required- otherwise the carbon black particle settles down and adheres to the surface of the reactor. For the present invention, double helix ribbon is used to create fluidization of carbon particles inside the reactor. Without ribbon, carbon particles can’t be fluidized for proper exposure to ozone gas.

It is worth mentioning that- as per knowledge of the inventors, no literature is available regarding the employment of ribbon for such type of work, and the change in features like ribbon cross section and pitch, clearances between the outer ribbon and the trough wall, and number of spirals on the ribbon can modulate the state of carbon powder fluidization and change the oxidized black productivity.

Another embodiment of the present invention discloses that the gas stream is supplied from one end of reactor during oxidation process, and the unreacted gas (unused ozone gas along with oxygen gas) is removed via the opposite end of the reactor by passing through a bag filter followed by an ozone destructor before venting it to the atmosphere. After selective residence time, the treated carbon black is collected at the bottom of the reactor. Although the carbon black is oxidized batch-wise with this set up, a continuous mode can also be accom modated with the appropriate arrangement.

I n this system, a bag filter is attached to the one end of the reactor opposite to the ozone gas insertion point. As ozone gas is continuously passed through the reactor, carbon particles are carried over with the gas m ixture coming out of reactor. To filter the carbon particles from the outgoing gas this bag filter is used. While passing ozone gas from one end to other end of the reactor followed by bag filter, carbon powder is continuously exposed to the gas. For the present invention Ozone gas is produced with an ozone generator by means of extremely high voltage prior to the treatment reactor. This method involves the decomposition of the oxygen molecule, which causes oxygen radical formation that can bind to oxygen molecules, form ing ozone ( O3) .

I n another embodiment of the present invention oxygen is used as the carrier gas (feeding gas), but dry air can also be used as a carrier gas. Oxygen concentration in air is about 21 % . When air is used as feeding gas to ozone generator, production of ozone is extremely less compared to oxygen as a feeding gas by the present system . For air, the concentration of oxygen inside the ozone cells becomes lower, so probability of bombardment between oxygen molecule and oxygen radical inside the corona cell of ozone generator becomes smaller, leading to a decrease in ozone output. Ozone output of the generator using oxygen is usually four times more than using dry air (4X) . Due to lesser ozone generation in case of air as a feeding gas, oxidized carbon black production is less. Accordingly, oxygen is used as feeding gas for ozone formation, for this invention.

Productivity of oxidized black depends on the quantity of ozone exposed to the surface of carbon black and on the fluidized condition. High O3 concentration in carrier gas means high O3 production/hr. Hence at high O3 concentration, more ozone will be exposed to carbon black and productivity is expected to be high. I n vertical reactor, air is used for ozone generation. As mentioned above compared to oxygen when air is used for ozone generation, concentration of ozone in carrier gas (air) becomes much less because of lesser amount of ozone generation and the same lesser concentration of ozone is exposed to carbon particles. Hence productivity of oxidized black becomes low. As ozone production is low, more time is required to produce high volatile content carbon black. Hence oxidation through fluidized bed reactor is a time-consuming process to produce carbon black of high volatile content.

Air medium for ozone generation is used for US6471763 and US8574527 for surface oxidation of carbon black employing vertical fluidized bed reactors wherein channel black only in fluffy form (soot like material) has been used for oxidation however, there was no demonstration for beaded/coarser carbon black oxidation. I n this system the air medium was used not only for ozone generation but also for the fluidization of fluffy carbon black of very low bulk density (90 - 148 g/l) . This system is neither suitable for coarser or granulated carbon black particles nor efficient enough for adequate fluidization of carbon blacks of high bulk density leading to improper oxidation.

For the present invention involving horizontal blender with double helix ribbon, carbon black is fluidized through mechanical process and fluidization is controlled by residence time and rpm of the mechanical shaft connected to the reactor. Hence carbon black can be treated at concentration level 0.1 to 12 wt% as per the requirement. I n this system , fluidization is not dependent on the flow rate/pressure of carrier gas. Controlling the flow and purity of oxygen, ozone gas productivity can be increased and exposed to the carbon black.

The concentration of ozone and output of ozone generator can be varied by changing the flow of oxygen and applied electric current, and the percentage of oxygen in carrier gas. I n this invention, oxygen gas with purity up to 95 % is used as a feeding gas for the ozone generation. The gas used for surface oxidation is a mixture of ozone and oxygen gas, where O3 concentration is around 6 wt.% . Effective ozone concentration level is ranged from 0.5 to 10 wt.% . Below 0.5 wt.% O3 concentration, desirable level of surface oxidation is not achieved. Above the 10 wt.% , the unused ozone gas after surface treatment remains higher. When ozone concentration is above 6 wt.% , some of the ozone molecules are not reacted with the carbon black and this unused ozone gas is removed from reactor with the carrier oxygen gas. Considering safety concern and to minimize the loss of ozone gas after surface treatment, 6 wt.% is selected for the process.

I n a further embodiment of the present invention the disclosed oxidation set up can be used for post treatment of any form of carbon blacks like fluffy, powder, and pellets. The carbon black used may be furnace black, gas black, thermal black, lamp black, channel black, plasma black, blacks produced as by-product of chemical production processes, and any other materials hybridized with carbon blacks. Furnace black is used in these tests. This oxidation setup may also be suitable for all type of carbon materials like graphite, graphene, carbon nanotubes, carbon nanofibers, fullerenes etc.

Carbon blacks having any oil absorption number (OAN) value (ASTMD 2414) , any BET surface area (ASTM D 4820) may be oxidized through this system. Treated carbon blacks prepared by this invention may be used as a filler, reinforcing filler, UV stabilizer, pigment for inks, paints, coatings, toners, plastics, and rubbers.

The said oxidation set up or fluidization system operated/controlled by mechanical fluidizer offers in addition to the above also the following advantages:

1. This process can be extended to feeding any type of oxidizing gases for desired oxidation of the carbon black in fluidized form throughout the entire volume of said reactor. Oxidizing agent includes pure oxygen, gas containing free oxygen radicals, ozone, ozonized air, carbon dioxides etc. The carrier gas used to carry out oxidation includes air, oxygen, nitrogen, and argon etc.

2. This process can be utilized for the oxidation of other heterogenous materials, where final product will be a free-flowing material. This process can also be used for disinfection of different types of powdery foodstuffs.

3. The designed rotary ribbon reactor can be utilized for mixing/reaction of other heterogeneous solid (powder) with any type of gases, provided final treated product should be free flowing dry product. For any other heterogenous materials other than carbon material, the state of final product may be free flowing otherwise formation of lumps will dictate the utility of the present system. To utilize the by-product gas, system attached to reactor may be modified as per requirement

Exam pies

For the present process, oxygen gas with purity up to 95 % is used as a feeding gas for ozone generation. The gas used for surface oxidation is a m ixture of ozone and oxygen gas, where O3 concentration is around 6 wt.% . Effective ozone concentration level is ranged from 0.5 to 10 wt.% . Below 0.5 wt.% O3 concentration, desirable level of surface oxidation is not achieved. Above the 10 wt.% , the unused ozone gas after surface treatment remains higher. When ozone concentration is above 6 wt.% , some of the ozone molecules are not reacted with the carbon black and this unused ozone gas is removed from reactor with the carrier oxygen gas.

The selective operating parameters used for oxidation of carbon blacks

Three types of carbon blacks were oxidized using the apparatus shown in Figure 1. All categories of carbon blacks are manufactured through furnace process.

Table 1 shows the properties of the three types of carbon black used. For each experiment, 3 kg of carbon black was oxidized.

Table 1 : Carbon blacks used for the oxidation reaction Exam ple 1

Carbon black A in power form having nitrogen surface area of 36 m ² /g, OAN of 91 ml/100g and bulk density of 234 g/l was oxidized by varying rotation speed (rpm-rotation per m inute) of ribbon. 3 kg of black powder was oxidized for a constant time of 60 min in order to observe the effect of rotation speed of ribbon on the surface oxidation of carbon black. Table 2 shows the results obtained after treating Carbon Black A powder at different rpm of ribbon.

Table 2 : Properties of Carbon Black A after oxidation at different rpm Note.: rpm study above 90 rpm was not performed due to the machine limitation.

With the increase in rpm of ribbon in the reactor, volatile content on the surface of carbon black was increased and pH value was decreased. This higher level of oxidation at higher rpm may be due to more carbon particles are exposed to oxidizing gas. At higher rpm produces better fluidization of carbon powders inside the reactor.

Exam ple 2

Carbon black A of different physical forms like granules, power, and fluffy with different bulk density were taken for oxidation. Carbon black A with nitrogen surface area of 36 m ² /g and OAN of 91 ml/100g having bulk density of 418 g/l, 234 g/l and 145 g/l in granules form , power form (coarser particles) and fluffy form (highly fine particles) respectively. Each form of carbon black A of a constant weight of 3 kg was oxidized for a constant time of 60 min in order to measure the efficiency of oxidation system of the present invention to oxidize any form of carbon blacks. Table 3 shows the results obtained after treating Carbon Black A in three forms. Table 3 : Properties of Carbon Black A before and after treatment

From Table 3, it is observed that non oxidized carbon black A granules is basic in nature having pH 8.34 and volatile content 0.43 wt.% . After oxidation, pH of each form of black has been drastically reduced and became significantly acidic in nature. Similarly, percentage of volatile constituents is increased after oxidation. This decrease in pH and increase in percentage of volatile constituents suggest the successful oxidation of carbon black surface. All the forms of carbon blacks are well oxidized indicating the designed oxidation set up is suitable for all type of carbon blacks from coarser to fine form. Exam ple 3

Carbon Black B of different physical forms like granules, power, and fluffy with different bulk density were taken for oxidation. Carbon black B is having nitrogen surface area of 102 m ² /g and DBP of 102 m l/ 100 g and bulk densities 368 g/l, 220 g/l and 165g/l for granules, powder and fluffy form respectively. pH of non - oxidized black is 7.42, but after oxidation, value is drastically reduced and at the same time volatile content is significantly increased suggesting coherent oxidation of carbon blacks (Table 4) Like carbon black A, carbon black B of different bulk density is efficiently oxidized through the invented system

Table 4 : Properties of Carbon Black B - before and after oxidation Exam ple 4

Similar to Example 2 and Example 3 - Carbon Black C with nitrogen surface area of 300 m ² /g and OAN of 68 ml/g of different physical forms like granules, power, and fluffy of different bulk density were also taken for oxidation. The pH and volatile content of carbon black C before and after oxidation are shown in Table 5. This carbon black C is of high surface area with different form s. In granules form , bulk density is 525 g/l and in powder form, its bulk density is 230 g/l, and in fluffy form , bulk density is 101 g/l. Black C in all forms are exposed to oxidation for a constant residence time and observed that volatile percentage is increased, and pH is decreased in case of all forms of blacks after oxidation. Table 5 : Properties of Carbon Black C - before and after oxidation Examples 2, 3 and 4 demonstrate that different physical forms like granules, coarse and fluffy form of different types of carbon blacks such as carbon black A, carbon black B, and carbon black C having different bulk densities can be efficiently oxidized through the invented system.

Exam ple 5 ( Com parative exam ple- Horizontal rotating drum reactor)

Surface treatment study was performed using one horizontal rotating drum reactor having drum length 12 ft and diameter 4 ft. Carbon powder A of bulk density 234 g/l was injected continuously to the reactor at 3 kg/hr. speed. I n order to avoid carbon powder agglomeration and maintain higher residence time of carbon powder in reactor, rpm of reactor was maintained at 1 -2 rpm. Ozone with oxygen carrier gas was passed continuously at rate 12 LPM, where amount of ozone was 63 g/hr. It was observed that total residence time of carbon black inside the reactor was 34 minutes at 2 rpm . In order to observe the effect of rpm on the oxidation performance of black, oxidation of carbon black was carried out varying the rpm of rotating drum . The pH and volatile content of oxidized carbon black are mentioned in Table 6.

Table 6 : Properties of Carbon Black A before and after treatment using one rotary drum reactor

Decrease in pH value and increase in volatile content suggest surface of carbon particles are well oxidized, but due to limited exposure time, volatile content was not increased above 1.2% . With the increase in rpm, volatile content of carbon black was decreased, and pH value was increased. This low oxidation at higher rpm is due to the low residence time of carbon black inside the reactor. As it is a continuous reactor system , with the increase in rpm , residence tim e of black is reduced. So, this system has limitation to develop carbon black of high volatile content. Drawback of this system is the low residence time. Observed maximum residence time is 34 minutes at 2 rpm . In order to produce oxidized black of high volatile content, more residence time is required. I n this system , Due to very low rpm, carbon powder was not properly exposed to the ozone gas which reduces the extent of oxidation. Exam ple 6 ( Com parative exam ple- vertical reactor)

I n another study, carbon black A powder having bulk density 234 g/l was oxidized using one fluidized bed reactor of height 180 cm and diameter 20 cm. 3 kg of carbon black powder was introduced to the reactor. The height of bed was around 43 cm. The powder was subjected to a flow of 20 LPM (similar amount used for horizontal double ribbon reactor) ozone and oxygen gas m ixture. Amount of ozone flow was 63 g/hr. A stable fluidized bed was not formed. Only gas was passed through few channels and some carbon particles were thrown upwards from the mouth of channels. Ozone gas was passed through channels without reacting with carbon particles. There was not homogenous exposure of carbon particles to ozone gas. pH and volatile content of carbon powder after 60 m inutes exposure is mentioned in Table 7.

Table 7 : Properties of Carbon Black A before and after treatment using fluidized bed reactor. Due to inefficient fluidization, surface of carbon powder was not oxidized properly, and the value of pH and volatile content was very marginally changed.

Effect of Residence time on pH and volatile percentage of carbon black Exam ple 7

Carbon black A having bulk density 234 g/l has been oxidized at different residence times in the fluidizing chamber in order to assess the effect of treatment time on the pH and volatile percentage of carbon black. Carbon black A has been oxidized for 15 min, 30 min, and 60 m inutes. It is observed that with increase in oxidation time, pH value is decreased, whereas volatile content is increased (Table 8) . Volatile content of carbon black can be synchronized as per requirement by proper selection of the treatment time. Thus, both pH value and volatile percentage can be modulated as per requirement by varying the treatment time of carbon black. Table 8 : Effect of treatment time on the pH and volatile content of carbon black A

Exam ple 8

Carbon black B (bulk density 220 g/l) having nitrogen surface area 102 m ² /g, 3 times higher than carbon black A has been oxidized for different times in order to understand the extent of oxidation on the surface properties of such type of blacks. Oxidation behavior of carbon black B is similar to carbon black A, where pH value is reduced, and volatile content is increased with the increase in oxidation time (Table 9) .

Table 9 : Effect of treatm ent time on the pH and volatile percentage for carbon black B

Exam ple 9

Carbon black C (bulk density 230 g/l) used in example 9 is different in colloidal properties from carbon black A and B having nitrogen surface area of 300 m ² /g and OAN of 68 m l/ 100 g. Effect of oxidation treatment time on the pH and volatile percentage has been shown in Table 10. With the increase in oxidation treatm ent time, percentage of volatile constituents is increased, and pH val ue is decreased.

Table 1 0 : Effect of oxidation treatm ent time on the pH and volatile percentage Examples 7, 8 and 9 demonstrate that different types of carbon blacks like carbon black A, carbon black B, and carbon black C undergo oxidation wherein extent of oxidation in all three exam ples depends on exposure/ reaction time and accordingly pH value and volatile percentage can be achieved as per requirement by varying the treatm ent time of carbon black.

Coating perform ance study of oxidized carbon black

Exam pie 1 0

Carbon black products of exam ples 7 - 9 were evaluated in a standard spray coating form ulation prepared through a Vibro shaker. Each sample was grinded by Vibro shaker for 60 m in. This example illustrates the effect of different type of carbon blacks oxidized at different tim e on an acrylic based spray coating form ulation. The coating compositions are prepared as follows:

One plastic container was charged with 4 g carbon black, 3 g dispersion additive BYK 21 17, 63 g Synpol B resin (Acrylic based thermoset resin) , 30 g xylene, and 25 g glass bead. The whole composition was grinded for 60 m inutes for the comparative perform ance study. A Hunter Color Meter was used to measure color and reduction strength of the coatings. Viscosity and Gloss of coating was m easured in m Pas units using a rotational viscometer and a glossm eter respectively.

Table 1 1 shows the coating characteristics of carbon black A oxidized at different time intervals. Color strength of oxidized blacks is nearly sim ilar to non-oxidized black, but reduction strength of oxidized black is higher com pared to non - oxidized black because of better dispersion of oxidized black in coating medium . Viscosity of non - oxidized black is too high which is reduced drastically after oxidation. Viscosity of carbon black is decreased with increase in oxidation time. The very high viscosity of non- oxidized black makes it not suitable for coating purposes, but after oxidation, viscosity of carbon black is reduced which is suitable for coating. Controlling the oxidation tim e, the flow behavior of carbon black can be designed as per requirem ent. Gloss of non- oxidized black is also lower than the oxidized black and increases with the increase in oxidation time or with the extent of oxidation. Similar behavior has been observed in case of oxidized carbon black B and C.

Table 1 1 : Coating properties of carbon black A oxidized for different time intervals

Table 12 and Table 13 show the coating performance study of carbon black B and C oxidized for different time. Behaviors of oxidized carbon black B and C are similar to oxidized carbon black A. Reduction strength of oxidized black is higher than the non-oxidized blacks. Very low viscosity has been observed after oxidation and a reduction in viscosity is observed with the increase in oxidation time. Gloss of oxidized blacks are higher than the non - oxidized blacks.

Table 1 2: Coating performance study of carbon black B Table 1 3: Coating performance of carbon black C oxidized for different time intervals

Thus, it can be inferred from the above examples that carbon blacks of different surface area and viscosity can be subjected to efficient oxidation of the surface through the invented system wherein the extent of oxidation can be controlled based on the exposure time/residence time leading to transformation of carbon blacks having drastically reduced viscosity and concomitant improvement of gloss and reduction strength (% ) making them suitable for improved coating performance.

Present invention offers the following advantages: a. The designed process is suitable for the oxidation of all forms of carbon blacks (may be fluffy or powder, or granules) . As per present knowledge only fluffy black is used by other patents for oxidation. b. For specific volatile content, oxidation time of carbon black in the present system is less compared to the process available in different patents. Productivity of oxidized black depends on the quantity of ozone exposed to the surface of carbon black and on the fluidized condition. High 03 concentration in carrier gas means high 03 production/hr. Hence at high 03 concentration, more ozone will be exposed to carbon black and productivity will be high. I n vertical reactor, air is used for ozone generation. Compared to oxygen when air is used for ozone generation, concentration of ozone in carrier gas (air) is less and less amount of ozone is produced and exposed to carbon particles at the same time. Hence productivity of oxidized black will be low. As ozone production is low, more time is required to produce high volatile content carbon black. Hence oxidation through fluidized bed reactor is a time-consuming process to produce carbon black of high volatile content.

I n present system (mechanical fluidization), oxidation process is easier than the gas fluidization process. Inside the gas fluidizer the gas becomes the controlling factor. The suspension of particles using compressible fluids is inefficient both in the propulsion of the particles and the conditioning of propellant gas. Inside the mechanical fluidizer the carbon black fluidization is directly controlled by the rotational speed ( Rotation Per Minute) of ribbon, and it is a simple mechanical variable to command.

Thus, present invention successfully demonstrates an improved system for the post treatment for carbon black using ozone gas. It is amenable for a post treatment of all forms of carbon black, be it fluffy, granules, or powder having different bulk densities using ozone gas. Carbon black of different surface area and structures can be oxidized at any targeted oxidation level using this system . Fluidization process is performed in a closed horizontal reactor by the rotation of double helix ribbon attached to the shaft of reactor wherein said fluidization takes place without addition of any fluidizing agents. Incorporation of bag filter for restricting the out flow of carbon blacks, operation of the system under leakage free condition and destruction of excess ozone in the destructor before releasing to the atmosphere makes the system environment friendly. Although the process is demonstrated as a batch process but can be suitably modified to a continuous process. Advantageously the treated carbon black or the oxidized carbon black obtained as a product of the invented system can be used in a wide range of applications, including but not restricted to inks, paints, and coatings.