FORM 2
THE PATENTS ACT, 1970 (39 of 1970) & THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13)
1. Title of the invention: A PROCESS FOR RECOVERY OF CARBON BLACK
2. Applicant(s)
NAME NATIONALITY ADDRESS
CEAT LIMITED Indian RPG HOUSE, 463, Dr. Annie Besant Road, Worli, Mumbai Maharashtra 400030, India
3. Preamble to the description
COMPLETE SPECIFICATION
The following specification particularly describes the invention and the manner in which it
is to be performed.

FIELD OF INVENTION
[0001] The subject matter described herein relates to the field of rubber and in particular relates to carbon black in rubber, and more particularly relates to a process of recovering carbon black from rubber articles.
BACKGROUND OF THE INVENTION
[0002] Waste management and recycling of rubber articles has become an evident field of interest in recent days. Further to recycling, there has been huge exertions taken to reuse the recovered materials from the waste rubber articles or rubber products Various components of the rubbers are separated out and the fillers which are used in large quantities are potential component to be recovered from these rubbers. The fillers especially carbon black have been widely used in the rubber compounds especially in tires. In the process of preparing the tires, the fillers are added in such a way that they completely blend with rubber and provide required mechanical properties to the tires. Thus, the strength and durability of the tires are dependent on the amount and the type of carbon black used. The very same property of the carbon black poses challenges while attempting to recover these carbon black from used rubber compounds/ tires. There have been various research efforts carried out to separate the fillers especially carbon black from the rubber compounds. However the efforts were all in vain since the recovery resulted in the alteration of the structural properties of the recovered carbon black.
[0003] US8350105B2 discloses a hybrid system and process for converting whole tires and other solid carbon based materials into syngas, oil, carbon black and steel. [0004] US7329329B2 discloses tire pyrolysis systems and processes to produce a hydrocarbon-containing gas stream and carbon-containing solid, followed by further processes to separate the carbon black.
[0005] Although a lot of attempts have been made to obtain carbon black from rubbers, there is still a need in the state of art for a simple and efficient process to

recover carbon black without altering their structural properties especially from used rubber articles.
SUMMARY OF THE INVENTION
[0006] In an aspect of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, said process comprising: a) pyrolyzing a rubber article to obtain a mixture; b) digesting the mixture in the presence of at least two acids to recover a slurry mixture; and c) processing the slurry mixture to recover the carbon black, wherein pyrolyzing is carried out at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes.
[0007] In another aspect of the present disclosure, there is provided a carbon black obtained by the process comprising: a) pyrolyzing a rubber article to obtain a mixture; b) digesting the mixture in the presence of at least two acids to recover a slurry mixture; and c) processing the slurry mixture to recover the carbon black, wherein pyrolyzing is carried out at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes.
[0008] These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
DETAILED DESCRIPTION OF THE INVENTION
[0009] Those skilled in the art will be aware that the present disclosure is subject to variations and modifications other than those specifically described. It is to be understood that the present disclosure includes all such variations and modifications. The disclosure also includes all such steps, features, compositions, and compounds

referred to or indicated in this specification, individually or collectively, and any and
all combinations of any or more of such steps or features.
Definitions
[0010] For convenience, before further description of the present disclosure, certain
terms employed in the specification, and examples are delineated here. These
definitions should be read in the light of the remainder of the disclosure and understood
as by a person of skill in the art. The terms used herein have the meanings recognized
and known to those of skill in the art, however, for convenience and completeness,
particular terms and their meanings are set forth below.
[0011] The articles "a", "an" and "the" are used to refer to one or to more than one
(i.e., to at least one) of the grammatical object of the article.
[0012] The terms "comprise" and "comprising" are used in the inclusive, open sense,
meaning that additional elements may be included. It is not intended to be construed as
"consists of only".
[0013] Throughout this specification, unless the context requires otherwise the word
"comprise", and variations such as "comprises" and "comprising", will be understood
to imply the inclusion of a stated element or step or group of element or steps but not
the exclusion of any other element or step or group of element or steps.
[0014] The term "including" is used to mean "including but not limited to".
"Including" and "including but not limited to" are used interchangeably.
[0015] Ratios, concentrations, amounts, and other numerical data may be presented
herein in a range format. It is to be understood that such range format is used merely
for convenience and brevity and should be interpreted flexibly to include not only the
numerical values explicitly recited as the limits of the range, but also to include all the
individual numerical values or sub-ranges encompassed within that range as if each
numerical value and sub-range is explicitly recited. For example, a range of 85 to 98
% should be interpreted to include not only the explicitly recited limits of 85 % to 98
% but also to include sub-ranges, such as 86 to 97 %, 85 to 95 % and so forth, as well

as individual amounts, within the specified ranges, such as 88 %, 92 % and 94 % for
example.
[0016] The term "at least one" is used to mean one or more and thus includes individual
components as well as mixtures/combinations.
[0017] The term “rubber article” refers to any article made of rubber or rubber
compound or used rubber, scrapped rubber or used tires. The rubber article in the
present disclosure comprises at least one carbon black as disclosed herein.
[0018] The term “mixture” refers to a compound obtained by pyrolyzing the rubber
article and comprises carbon black with other chemicals. The other chemicals include
but not limited to zinc oxide, sulfur, clay and so on.
[0019] The term “recovery yield of carbon black” or “yield of recovered carbon black”
refers to amount of carbon black separated from the rubber article. The percetange
recovery yield refers to the amount of carbon black recovered as against the original
amount of carbon black used in making the rubber article. The recovery yield of the
carbon black in the present disclosure is in the range of 85 to 98%. The original amount
of the carbon black may vary from 30 to 70% by weight of the rubber article used in
the recovery of carbon black.
[0020] The term “BET surface area” refers to total surface area of a material and is
determined by physical adsorption of gas by the surface of the material. In the present
disclosure, the BET surface area of the carbon black is determined and is used to
identify the grade of the carbon black. For instance, the carbon black of the present
disclosure BET surface area in the range of 8 to 250 m2/g. In the present disclosure,
ASTM D 6556 method is used to measure the total and external surface area of carbon
blacks based on multipoint nitrogen adsorption based on the BET theory and it includes
the total surface area, inclusive of micropores, and pore diameters.
[0021] 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 disclosure belongs. Although any methods and materials similar or equivalent to

those described herein can be used in the practice or testing of the disclosure, the preferred methods, and materials are now described. All publications mentioned herein are incorporated herein by reference.
[0022] The present disclosure is not to be limited in scope by the specific embodiments described herein, which are intended for the purposes of exemplification only. Functionally-equivalent products, compositions, and methods are clearly within the scope of the disclosure, as described herein.
[0023] As discussed in the background, it is essential to develop a process which is simple and efficient to recover the carbon black from the rubbers. The existing processes results in separation of carbon black but alters their structural properties. Also it is important that such processes result in higher yield with higher purity so that their reuse can become advantageous. Apart from said challenges, such processes also incurs high cost thereby ending up in decreased commercial feasibility of such recycling/ reuse. Therefore obtaining a process for recovering unaltered carbon black with higher yield and purity has always been challenging. The present disclosure provides a process for recovery of carbon black with sustained surface area from rubber articles, which is a simple, efficient and an economically viable process. The process of the present disclosure provides a process comprising, pyrolyzing the rubber article followed by digesting and further processing to recover the carbon black. The present disclosure also provides a process for recovering carbon black with high yield and identifying the various grades of the carbon black.
[0024] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, said process comprising: a) pyrolyzing a rubber article to obtain a mixture; b) digesting the mixture in the presence of at least two acids to obtain a slurry mixture; and c) processing the slurry mixture to recover the carbon black, wherein the pyrolyzing is carried out at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes.

[0025] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, said process comprising: a) pyrolyzing a rubber article to obtain a carbon black and other chemicals; b) digesting the carbon black and other chemicalsin the presence of at least two acids to obtain a slurry mixture; and c) processing the slurry mixture to recover the carbon black, wherein the pyrolyzing is carried out at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes.
[0026] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein pyrolyzing is carried out at a temperature in the range of 580°C to 820°C in the presence of inert atmosphere for a time period in the range of 7 to 18 minutes. In yet another embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein pyrolyzing is carried out at a temperature in the range of 590°C to 800°C in the presence of inert atmosphere for a time period in the range of 9 to 12 minutes. In one another embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein pyrolyzing is carried out at a temperature of 600°C in the presence of inert atmosphere for a time period of 10 minutes. In further embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein pyrolyzing is carried out at a temperature of 800°C in the presence of inert atmosphere for a time period of 10 minutes.
[0027] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein the carbon black has recovery yield in the range of 85 to 98% and has BET surface area in the range of 8 to 250 m 2 /g. In another embodiment of the present

disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein the carbon black has recovery yield in the range of 85 to 95% and has BET surface area in the range of 10 to 230 m 2 /g. In yet another embodiment of the present disclosure there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein the carbon black has recovery yield in the range of 87 to 95% and has BET surface area in the range of 20 to 200 m2 /g. In one another embodiment of the present disclosure there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein the carbon black has recovery yield in the range of 90 to 95% and has BET surface area in the range of 30 to 150 m2 /g.
[0028] In an embodiment of the present disclosure there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein the carbon black has recovery yield is of 98%.
[0029] In an embodiment of the present disclosure there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein the carbon black has purity of more than 99%. In another embodiment of the present disclosure there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein the carbon black has purity in the range of 99% to 99.9%.
[0030] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein the rubber article has at least one carbon black selected from N134, N220, N330, N550, or N660.
[0031] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article said process comprising: a) pyrolyzing a rubber article having at least one carbon black selected from N134, N220, N330, N550, or N660 to obtain a mixture; b) digesting the mixture

in the presence of at least two acids to obtain a slurry mixture; and c) processing the slurry mixture to recover the carbon black, wherein pyrolyzing is carried out at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes.
[0032] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process comprising: a) pyrolyzing a rubber article at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes to obtain a mixture; b) digesting the mixture in the presence of at least two acids to obtain a slurry mixture; and c) processing the slurry mixture to recover the carbon black, wherein the carbon black has recovery yield in the range of 85 to 98% and has BET surface area in the range of 8 to 250 m2 /g.
[0033] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein pyrolyzing is carried out at a temperature of 560°C to 800°C in the presence of nitrogen gas or inert gas with a flow rate of 50ml/min for a time period of 10 minutes in a muffle furnace.
[0034] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein wherein pyrolyzing is carried out at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes followed by cooling the mixture to a temperature in the range of 25 to 40°C. [0035] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein digesting the mixture is carried out in the presence of at least two acids selected from nitric acid, hydrochloric acid, sulphuric acid, or hydrofluoric acid. In another embodiment of the present disclosure, there is provided a process for recovery

of carbon black from a rubber article as disclosed herein, wherein digesting the mixture is carried out in the presence of nitric acid and hydrochloric acid.
[0036] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein digesting the mixture is carried out in the presence of nitric acid and hydrochloric acid in the weight ratio range of 2:1 to 1:1.
[0037] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein digesting the mixture is carried out in the presence of nitric acid and hydrochloric acid in the weight ratio range of 1.75:1 to 1:1. In another embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein digesting the mixture is carried out in the presence of nitric acid and hydrochloric acid in the weight ratio range of 1.5:1 to 1:1. In yet another embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein digesting the mixture is carried out in the presence of nitric acid and hydrochloric acid in the weight ratio of 1:1.
[0038] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein digesting is carried out for a time period in the range of 6 to 19 minutes. In another embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein digesting is carried out for a time period in the range of 8 to 17 minutes. In yet another embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein digesting is carried out for a time period of 15 minutes.
[0039] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process

comprising: a) pyrolyzing a rubber article to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio range of 2:1 to 1:1 for a time period in the range of 6 to 19 minutes to obtain a slurry mixture; and c) processing the slurry mixture to recover the carbon black, wherein pyrolyzing is carried out at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes.
[0040] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein processing the slurry mixture comprises a process selected from filtering, washing, drying or combinations thereof.
[0041] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein processing the slurry mixture is carried out by filtering and washing the residue of the slurry mixture with water. In another embodiment of the present disclosure, there is provided a process for recovery of carbon black from a rubber article as disclosed herein, wherein processing the slurry mixture is carried out by filtering, and washing followed by drying at a temperature of 125°C for time period of 2 hours.
[0042] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process comprising: a) pyrolyzing a rubber article at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio range of 2:1 to 1:1 for a time period in the range of 6 to 19 minutes to obtain a slurry mixture; and c) processing the slurry mixture by a process selected from filtering, washing, drying or combinations thereof, to recover the carbon black.

[0043] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process comprising: a) pyrolyzing a rubber article at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio range of 2:1 to 1:1 for a time period in the range of 6 to 19 minutes to obtain a slurry mixture; and c) processing the slurry mixture by a process selected from filtering, washing, drying or combinations thereof, to recover the carbon black, wherein the recovery yield of the carbon black is in the range of 85 to 98% and the carbon black has BET surface area in the range of 8 to 250 m 2 /g. [0044] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process comprising: a) pyrolyzing a rubber article at a temperature of 600°C in the presence of inert atmosphere for a time period of 10 minutes to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio of 1.75:1 for a time period of 15 minutes to obtain a slurry mixture; and c) processing the slurry mixture by a process selected from filtering, washing, drying or combinations thereof, to recover the carbon black, wherein the carbon black has recovery yield in the range of 85 to 98% and has BET surface area in the range of 8 to 250 m 2 /g .
[0045] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process comprising: a) pyrolyzing a rubber article at a temperature of 600°C in the presence of inert atmosphere for a time period of 10 minutes to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio of 1:1 for a time period of 15 minutes to obtain a slurry mixture; and c) processing the slurry mixture by a process selected from filtering, washing, drying or combinations thereof, to recover the carbon black, wherein the carbon black has recovery yield in the range of 85 to 98% and has BET surface area in the range of 8 to 250 m 2 /g.

[0046] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process comprising: a) pyrolyzing a rubber article at a temperature of 800°C in the presence of inert atmosphere for a time period of 10 minutes to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio of 1.75:1 for a time period of 15 minutes to obtain a slurry mixture; and c) processing the slurry mixture by a process selected from filtering, washing, drying or combinations thereof, to recover the carbon black, wherein the carbon black has recovery yield in the range of 85 to 98% and has BET surface area in the range of 8 to 250 m 2 /g .
[0047] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process comprising: a) pyrolyzing a rubber article at a temperature of 800°C in the presence of inert atmosphere for a time period of 10 minutes to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio of 1:1 for a time period of 15 minutes to obtain a slurry mixture; and c) processing the slurry mixture by a process selected from filtering, washing, drying or combinations thereof, to recover the carbon black, wherein the carbon black has recovery yieldin the range of 85 to 98% and has BET surface area in the range of 8 to 250 m 2 /g .
[0048] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein the process further comprises the step of identifying the grade of the recovered carbon black.
[0049] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article as disclosed herein, wherein the process further comprises the step of identifying the grade of the recovered carbon black by determining surface area of the carbon black.
[0050] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process

comprising: a) pyrolyzing a rubber article at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio range of 2:1 to 1:1 for a time period in the range of 6 to 19 minutes to obtain a slurry mixture; c) processing the slurry mixture by a process selected from filtering, washing, drying or combinations thereof, to recover the carbon black and d) identifying the grade of the recovered carbon black.
[0051] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process comprising: a) pyrolyzing a rubber article at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio range of 2:1 to 1:1 for a time period in the range of 6 to 19 minutes to obtain a slurry mixture; c) processing the slurry mixture by a process selected from filtering, washing, drying or combinations thereof, to recover the carbon black and d) identifying the grade by determining surface area of the recovered carbon black.
[0052] In an embodiment of the present disclosure, there is provided a process for recovery of carbon black with sustained surface area from a rubber article, the process comprising: a) pyrolyzing a rubber article at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio range of 2:1 to 1:1 for a time period in the range of 6 to 19 minutes to obtain a slurry mixture; c) processing the slurry mixture by a process selected from filtering, washing, drying or combinations thereof, to recover the carbon black and d) identifying the grade by determining the surface area, of the recovered carbon black.

[0053] In an embodiment of the present disclosure, there is provided a carbon black with sustained surface area obtained by the process comprising: a) pyrolyzing a rubber article to obtain a mixture; b) digesting the mixture in the presence of at least two acids to obtain a slurry mixture; and c) processing the slurry mixture to recover the carbon black, wherein pyrolyzing is carried out at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes. [0054] In an embodiment of the present disclosure, there is provided a carbon black with sustained surface area obtained by the process comprising: a) pyrolyzing a rubber article at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes to obtain a mixture; b) digesting the mixture in the presence of nitric acid and hydrochloric acid in the weight ratio range of 2:1 to 1:1 to obtain a slurry mixture; and c) processing the slurry mixture to recover the carbon black, wherein processing the slurry mixture comprises a process selected from filtering, washing, drying or combinations thereof; the carbon black has recovery yield in the range of 85 to 98% and has BET surface area in the range of 8 to 250 m 2 /g .
[0055] Although the subject matter has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present subject matter as defined.
EXAMPLES
[0056] The disclosure will now be illustrated with the working examples, which is intended to illustrate the working of disclosure and not intended to take restrictively to imply any limitations on the scope of the present disclosure. Unless defined otherwise,

all technical and scientific terms used herein have the same meaning as commonly understood to one ordinary person skilled in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice of the disclosed methods and compositions, the exemplary methods, devices and materials are described herein. It is to be understood that this disclosure is not limited to particular methods, and experimental conditions described, as such methods and conditions may apply.
[0057] The forthcoming examples explains that how the present disclosure provides a process for recovering carbon black from a rubber article and identifying the grade of recovered carbon black. The present disclosure provides a process of recovering the carbon black without altering its structural properties. The carbon black used while preparing the rubber article is recovered by the process of the present disclosure. The process involves pyrolyzing the rubber article followed by digesting in the presence of two acids and further processing the mixture to recover the carbon black. The grade of recovered carbon black is identified by measuring its BET surface area. Thus, the following examples illustrates the simple and efficient process of recovering carbon black from any rubber article and identifying their grades.
Materials and Methods
[0058] Table 1 illustrates the materials and methods used in the process of the present
disclosure.
Table 1

Material Composition/Operating range
Muffle furnace nitrogen/inert gas Purging and Range up to 800°C 600-800°C
Nitric Acid : Hydrochloric acid(36.5%) 2:1 to 1:1
Water Conductivity 1-80 μS/cm
Sonicator 80-140 kHz
Nitrogen 99.99%
Instrument to measure BET Surface area Nitrogen surface area analyzer

Degasser Part of nitrogen surface area analyzer
EXAMPLE 1
General process for recovery of carbon black
[0059] A muffle furnace of size 12"X6"X6" was set to a temperature in the range of 600°C and purged with nitrogen gas at a flow rate of 50ml/min. After 30 minutes of attaining the set temperature, 20 gm of a dry rubber sample (from rubber article) was pyrolyzed in the muffle furnace for 10 minutes to obtain a mixture of carbon black and other chemicals. The mixture of carbon black with other chemicals was then removed from furnace and cooled to room temperature (25 to 40°C) in a dessicator. The cooled mixture was then digested in the presence of an acid solution comprising conc. HNO3 (65%) and conc. HCl (36.5%) in the volume ratio of 1:1 to obtain a slurry mixture. Digesting the mixture was carried by stirring for a time period of 15 minutes. The obtained slurry mixture was then subjected to further processing such as flitering, washing and drying. The slurry mixture was filtered and the residue of the slurry mixture was washed using water until a pH of 7 was achieved. The washed slurry mixture was dried at a temperature of 125°C for a time period of 2 hours to obtain the carbon black. Thus the carbon black used in the rubber sample was recovered and the yield of the recovered carbon black was found to be 98%.
EXAMPLE 2
Identifying grade of recovered carbon black
[0060] The recovered carbon black from the example 1 was then subjected to BET
surface area analysis (ASTM D6556 method). The BET surface area of the recovered
carbon black was determined using nitrogen surface area analyzer (Quanta chrome,
NOVA USA) along with degasser. A precalibrated sample cell was taken and the
recovered carbon black was loaded and was allowed to degas for 2 hours at a
temperature of 300°C. Then the process parameters were set as mentioned in Table 2
below. Then the dewar flask was filled with liquid nitrogen and was allowed to reach

temperature equilibrium for 0.5 hour. The surface area was measured in the analyzer to obtain a minimum of five data points evenly spaced in the 0.05 to 0.5 relative pressure (P/Po) range as mentioned below (Table 2). The obtained surface area data was correlated with standard carbon black surface area and the grades were identified.
Table 2

P/Po Measure
0.05 Adsorption Multi BET Not measured
0.1 Adsorption Multi BET Not measured
0.15 Adsorption Multi BET Not measured
0.2 Adsorption Multi BET Thickness
0.25 Adsorption Multi BET Thickness
0.3 Adsorption Multi BET Thickness
0.35 Adsorption Not measured Thickness
0.4 Adsorption Not measured Thickness
0.45 Adsorption Not measured Thickness
0.5 Adsorption Not measured Thickness
[0061] The above processes as exemplified in Example 1 and Example 2 were repeated by varying temperature of the muffle furnace between 450°C to 800°C. For this purpose, Compound A a rubber article with N134 carbon black was taken and was subjected to the process of the present disclosure, by varying the temperature. Table 3 shows the process carried out at different temperatures and the identifying the carbon black grade by analyzing theBET surface area of the carbon black present in Compound A.
Table 3

Temperature (°C) Carbon black grade in compound (A) BET surface area of raw carbon black Recovered Carbon black BET surface area from compound
450 N134 98.45
500

100.12
550

130.12
600

142.69

800 142 143.65
[0062] Table 3 depicts that at temperatures 600°C and 800 °C, the carbon black was recovered with BET surface area same as that of the original carbon black present in the compound, which implied the recovery occurs without any impact to its structural property. Hence it is important to maintain the pyrolysis temperature in the range of 600 °C to 800°C for recovering the structurally unaltered carbon black.
[0063] Examples 1 and 2 were further repeated by varying the ratios of the nitric acid and hydrochloric acid used while digesting the mixture. Compound B with carbon black grade N220 was used and by varying the ratio of the acids the process was carried out. Table 4 illustrates the different acid ratios used in the recovery process and identification of the carbon black grade.
Table 4

HNO3: HCl acid ratio Carbon black grade in compound (B) BET surface area of raw carbon black Recovered Carbon black BET surface area from compound (B)
10: 90 (0.1 :1) N220 116 160.45
70: 40 (1.75:1)

115.7
10: 10 (1:1)

117.26
100: 0

150.12
70: 50 (1.4:1)

129.12
0: 100

145.65
[0064] Table 4 shows that among varying ratios in the mixture of conc. nitric acid and conc. hydrochloric acid for acid digestion of the recovered carbon black, the range of 1:1 to 2:1 weight ratio was surprisingly found to be suitable for obtaining unchanged surface area for carbon black by this recovery process. Whereas if the acids were taken in alone or in ratios outside said ranges, result in a different carbon black with varying BET surface area. Thus the ratio of the nitric acid and hydrochloric acid plays a significant role in retaining the structure of the carbon black in the recovery process.

[0065] Similarly, the Examples 1 and 2 were repeated by varying the stirring time while digesting the mixture in the presence of nitric acid and hydrochloric acid (1:1). To identify the suitable stirring time, Compound C with N220 carbon black grade was used and was subjected to the process of the present disclosure. Table 5 depicts the stirring time variation during the digestion step between 5 to 20 minutes and identification of the BET surface area of the recovered carbon black.
Table 5

Stirring Time (min) Carbon black grade in compound (C) BET surface area of raw carbon black Recovered Carbon black BET surface area from compound (C)
5 N220 116 160.45
15

116.34
20

162.34
[0066] From Table 5, it can be confirmed that the stirring time variation in digesting the mixture causes difference in the BET surface area of the recovered carbon black. Stirring time of 15 minutes which is in the said range of 6 to 19 minutes was found to be the appropriate time period for stirring while digesting the mixture and thereby resulting in a structurally unaltered carbon black.
[0067] The above examples clearly illustrated that the present disclosure provides a a simple and an efficient process for recovering the carbon black from the rubber compounds without altering their structural properties. Any deviation in the process steps or parameters resulted in undesired/ altered carbon black.
EXAMPLE 3
Process of recovery of carbon black of known rubber article
[0068] The process explained above was performed using rubber articles for which the
grade of carbon black is already known. Table 6 illustrates the process of recovery of
carbon black and further identifying their grades using BET surface area was
performed on the rubber articles with known carbon black grades. It can be observed
that the obtained surface area for the recovered carbon black matched closely with the
standard surface area. This implied that the carbon black present in the rubber article

was recovered without any alteration to its structural properties. And the yield of the recovered carbon black was found to be 98%. Also, it can be noted that the process of the present disclosure recovers and identifies wide range of various grades of carbon black i.e carbon black with BET surface area in the range of 8 to 250 m2/g.
Table 6

S. No. Rubber
article
(known
carbon black
grade) BET surface
area of raw
carbon black Recovered Carbon Black BET surface area

R1 R2
1 N134 142 145.27 143.65
2 N220 116 115.7 117.26
3 N330 76.6 76.55 76.35
4 N550 38.1 38.879 37.17
5 N660 33 33.87 33.21
EXAMPLE 4
Process of recovery of carbon black and identifying the grade of unknown rubber
article
[0069] The process of the present disclosure was further extended to recover and
identify the carbon black of unknown rubber samples. Table 7 depicts the recovery and
identification of the grades of carbon black in unknown rubber samples. Compounds
A to D are the rubber samples for which carbon black grades are unknown.
Table 7

Recovery and Identification of unknown grade
Sample CB Grade BET Surface area (N2 Absorption)
Compound A N134 142.69
Compound B N220 117.94
Compound C N330 76.41
Compound D N660 33.35

[0070] From Example 3, it can be understood that the carbon blacks were recovered without any alteration in their structural properties. This implied that the process is advantageous in recovering and identifying the carbon black used originally in the making of the rubber samples. Carbon black from these samples were recovered by the process exemplified in Example 1 and their grades were identified using BET surface area analysis as explained in Example 2. On comparing the obtained surface area with standard surface area, the grades of the carbon black were identified. Therefore, the process of the present disclosure provided a qualitative and quantitative recovery of carbon black.
Advantages of the present disclosure
[0071] The present disclosure provides a process for recovery of carbon black from a rubber article comprising pyrolyzing the rubber article to obtain a mixture followed by digesting the mixture in the presence of at least two acids and further processing the slurry mixture to obtain the carbon black. The present disclosure provides a simple and efficient process for recovering carbon black from any rubber article and especially used rubber articles. The process results in recovering high purity carbon black i.e., more than 99% purity with high recovery yield in the range of 85 to 98%. Thus the process of the present disclosure is environment friendly as it aids in reuse of the recovered carbon black. The process of the present disclosure helps in recovering and identifying various grades of carbon black with BET surface area in the range of 8 to 250 m2/g. The process of the present disclosure provides recovery of carbon black without altering its structural properties. Thus, the process possess dual advantage of recovery of carbon black with high yield as well as identifying their grades even from an unknown rubber article. Overall the process of the present disclosure also provides an economically viable, simple and an efficient process to recover the carbon black from any rubber articles.

I/We Claim:
1. A process for recovery of carbon black with sustained surface area from a
rubber article, said process comprising:
a) pyrolyzing a rubber article to obtain a mixture;
b) digesting the mixture in the presence of at least two acids to obtain a slurry mixture; and
c) processing the slurry mixture to recover the carbon black, wherein the pyrolyzing is carried out at a temperature in the range of 560°C to 850°C in the presence of inert atmosphere for a time period in the range of 5 to 20 minutes .

2. The process as claimed in claim 1, wherein the rubber article has at least one carbon black selected from N134, N220, N330, N550, or N660.
3. The process as claimed in claim 1, wherein the carbon black has recovery yield in the range of 85 to 98% and has BET surface area in the range of 8 to 250 m 2 /g.
4. The process as claimed in claim 1, wherein the at least two acids are selected from nitric acid, hydrochloric acid, sulphuric acid, or hydrofluoric acid.
5. The process as claimed in claim 4, wherein the at least two acids are nitric acid and hydrochloric acid.
6. The process as claimed in claim 5, wherein the nitric acid to the hydrochloric acid weight ratio is in range of 2:1 to 1:1.
7. The process as claimed in claim 1, wherein digesting is carried out for a time period in the range of 6 to 19 minutes.
8. The process as claimed in claim 1, wherein processing the slurry mixture comprises a process selected from filtering, washing, drying or combinations thereof.

9. The process as claimed in claim 1, wherein the process further comprises the step of identifying the grade of the recovered carbon black.
10. The process as claimed in claim 9, wherein the identifying the grade of the recovered carbon black is carried out by determining surface area of the carbon black.
11. A carbon black obtained by the process as claimed in any one of the claims 1 to 10.