Description:FIELD
The present disclosure relates to a process for recycling of a waste rubber.
DEFINITIONS
As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.
Devulcanization: The term “Devulcanization” refers to a process that breaks the sulphur cross linkages in the vulcanized rubber products and recycling it so that it can be revulcanized.
Cross-linking density: The term “Cross-linking density” refers to a measure of cross-linked point (sulphur cross-linking) per unit volume of vulcanized rubber.
Flory-Rehner cross-linking density: The term “Flory-Rehner cross-linking density” refers to a measurement of cross-linking density of a vulcalnized rubber, calculated by Flory-Rehner equation.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Recycling of used or discarded tyres and other rubber products, which are in vulcanized state or cross linked by any means, has proven to be an extremely challenging task. The resultant cross-linked rubber or elastomer is a thermoset material that cannot be melted or reformed into other products unlike thermoplastic polymers or metals.
An increasing environmental concern exists to recover the used or discarded tyres and other rubber products in uncured or devulcanized form. Moreover, the rubber manufacturing feedstocks are basically dependent on natural resources such as petroleum, natural gas, coal and the like which requires more attention in view of natural resources. Globally, focus is given on recycling of vulcanized rubber waste products which can provide major solutions in terms of environment threats that would arise in near future.
Conventionally, a variety of devulcanization processes have been carried out to recover or reclaim rubber from the used or discarded tyres and other rubber products comprising cured, or vulcanized, rubber or elastomer. These processes involve treating waste rubber with devulcanizing agents such as peroxides, free radical initiators (such as azoisobutyronitrile, persulphates) and metathesis catalysts. However, with these devulcanizing agents, the process of devulcanization requires to be carried out at a high temperature and for longer time duration. Further, peroxides have strong oxidizing and explosive properties at higher temperature and detonating pressure. Thus, there is risk associated with the use of peroxides or free radical initiators at higher temperature as it is unsafe and prone to accidents. Therefore, there is a room to develop a process for recycling/devulcanization of waste rubber.
Therefore, there is, felt a need to provide a process for recycling of a waste rubber that mitigates the drawbacks mentioned herein above or at least provides a useful alternative.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
It is an object of the present disclosure to ameliorate one or more problems given in the background or to at least provide a useful alternative.
An object of the present disclosure is to provide a process for recycling of a waste rubber.
Another object of present disclosure is to provide a process for recycling of a waste rubber which is carried at a low temperature and at a lesser reaction time.
Yet another object of the present disclosure is to provide a process for obtaining a recycled rubber having a cross linking density reduced by at least 90%.
Still another object of the present disclosure is to provide a recycled rubber (devulcanized rubber) that can be used with a virgin rubber to obtain a revulcanized rubber composite.
Yet another object of the present disclosure is to provide a process for recycling of a waste rubber that is simple and efficient.
Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.
SUMMARY
The present disclosure relates to a process for recycling of a waste rubber. The process comprises obtaining the waste rubber having a particle size in the range of 0.1 mm to 5 mm. Separately, an oxidizer is dissolved in a mixture of at least one swelling agent and at least one fluid medium to obtain a homogeneous solution. The waste rubber is mixed into the solution at a predetermined temperature for a predetermined time period to obtain a slurry. The slurry is filtered to obtain a residue, followed by washing the residue with the fluid medium to obtain the recycled rubber.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
The present disclosure will now be described with the help of the accompanying drawing, in which:
Figure 1 illustrates a graphical representation of cross linking density profile of waste rubber (vulcanized rubber) and recycled rubber (devulcanized rubber) of the present disclosure;
Figure 2 illustrates a revulcanizing process for preparing revulcanized rubber composite by using a recycled rubber (devulcanized rubber) of the present disclosure and a virgin rubber; and
Figure 3 illustrates an animated depiction of the relationship between cross link density and Molecular weight between cross link (Mc) in (a) a virgin rubber and (b) a revulcanized rubber composite.
DETAILED DESCRIPTION
The present disclosure provides a process for recycling of waste rubber.
Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.
Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well-known apparatus structures, and well-known techniques are not described in detail.
The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a,” "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," “including,” and “having,” are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.
The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.
Conventionally, a variety of devulcanization processes have been carried out to recover or reclaim rubber from the used or discarded tyres and other rubber products comprising cured, or vulcanized, rubber or elastomer. These processes involve treating waste rubber with devulcanizing agents such as peroxides, free radical initiators (such as azoisobutyronitrile, persulphates) and metathesis catalysts. However, with these devulcanizing agents, the process of devulcanization requires to be carried out at high temperature and for longer time duration. Further, peroxides have strong oxidizing and explosive properties at higher temperature and detonating pressure. Thus, there is risk associated with the use of peroxides at higher temperature as it is unsafe and prone to accidents.
The present disclosure provides a process for recycling of a waste rubber. The process comprises the following steps:
a. obtaining the waste rubber having a particle size in the range of 0.1 mm to 5 mm;
b. separately dissolving an oxidizer in a mixture of at least one swelling agent and at least one fluid medium to obtain a homogeneous solution;
c. mixing the waste rubber into the solution at a predetermined temperature for a predetermined time period to obtain a slurry;
d. filtering the slurry to obtain a residue; and
e. washing the residue with the fluid medium to obtain a recycled rubber.
The process is described in detail herein below.
Firstly, a waste rubber is obtained.
In an embodiment of the present disclosure, the waste rubber is a vulcanized rubber selected from the group consisting of styrene-butadiene rubber (SBR), polybutadiene rubber (PBR), butyl rubber and ethylene propelene diene rubber (EPDR). In an exemplary embodiment of the present disclosure, the waster rubber is PBR.
In an embodiment of the present disclosure, the waste rubber is in the shredded form having a particle size in the range of 0.1 mm to 5 mm. In an exemplary embodiment, the particle size of the shredded waste rubber is 0.2 mm to 2 mm.
In accordance with the present disclosure, the waste rubber is vulcanized rubber which contain sulphur cross linkages.
Separately, an oxidizer is dissolved in a mixture of at least one swelling agent and at least one fluid medium to obtain a homogeneous solution.
In an embodiment of the present disclosure, the oxidizer is organic peroxides. The organic peroxide can be selected from the group consisting of acetyl acetone peroxide, diacetyl peroxide, cumyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, t-butyl hydroperoxide, methyl ethyl ketone peroxide, peracetic acid, peracids and methane hydroperoxide. In an exemplary embodiment of the present disclosure, the oxidizer is benzoyl peroxide.
The oxidizer is used in an amount in the range of 0.1 mass% to 10 mass% with respect to mass of the waste rubber. In an exemplary embodiment of the present disclosure, the amount of the oxidizer is 5 mass% with respect to the mass of waste rubber.
In an embodiment of the present disclosure, the swelling agent can be at least one selected from the group consisting of turpentine, paraffinic oil, naphthenic oil, petroleum spirit and paint thinner (mixture of various petroleum fractions). In an exemplary embodiment, the swelling agent is turpentine.
In an embodiment of the present disclosure, the fluid medium can be at least one selected from toluene, xylene, 1,2,3-trimethylbenzene, ethyl benzene, diethyl benzene and any other solvent having C7 or more number of carbon atoms with an aromatic ring. In an exemplary embodiment of the present disclosure, the fluid medium is toluene.
In an embodiment of the present disclosure, a mass ratio of the swelling agent to the fluid medium is in the range of 1:1 to 4:3. In an exemplary embodiment of the present disclosure, the mass ratio of turpentine to toluene is 3:2.
The swelling agent in the fluid medium is used to swell the rubber, thereby assists the oxidizer to penetrate the sulphur cross linked sites efficiently. Hence, swelling agent enhances delinking ability of the sulphur network at a room temperature and in a lesser time period. Therefore, the presence of the swelling agent eliminates the need of higher temperature and detonating pressure which is generally required for devulcanization by using the oxidizers. The oxidizer alters the cross linking by specifically targeting sulphur linkages which are prone to undergo oxidation. Further, the recycled product is resulted into soft breakable material and is soluble in the fluid medium.
Further, the waste rubber in shredded form is mixed into the solution at a predetermined temperature for a predetermined time period to obtain a slurry.
In an embodiment of the present disclosure, the predetermined temperature is in the range of 10 °C to 50 °C. In an exemplary embodiment of the present disclosure, the temperature of the slurry is 25 °C.
In an embodiment of the present disclosure, the predetermined time period is in the range of 1 hour to 5 hours. In an exemplary embodiment of the present disclosure, the time period is 3 hours.
Still further, the slurry is filtered to obtain a residue.
In an embodiment, the filtration is carried out by using Buchner funnel with Whatman filter paper (Grade 42).
The residue is washed with the fluid medium to obtain a recycled rubber.
In accordance with the present disclosure, the step of washing is repeated at least three times to obtain the recycled rubber (devulcanized rubber).
In accordance with the present disclosure, the recycling of the waste rubber is carried out by devulcanization process. The delinking of the sulphur cross linkages in the vulcanized waste rubber is achieved by using oxidizer (devulcanizing agent) in the presence of the mixture of the swelling agent and the fluid medium. Extent of sulphur cross linking is determined by using Flory-Rehner cross linking density analysis. The cross linking density of the recycled rubber (devulcanized rubber) is reduced by at least 90% compared to the waste rubber (vulcanized rubber). Reduction in the cross linking density thus confirms the breakage of sulphur cross linkages and hence the devulcanization.
In accordance with the present disclosure, the recycled rubber (devulcanized rubber) is further used in tyre making process by mixing with virgin rubber. In an embodiment of the present disclosure, the recycled rubber (devulcanized rubber) is mixed with the virgin rubber such as PBR/SBR in an amount in the range of 5% to 50% to synthesize revulcanized rubber composites. In an exemplary embodiment, the amount of recycled rubber (devulcanized rubber) added to the virgin rubber is 25%.
The process for recycling of the waste rubber in accordance with the present disclosure helps in reducing the net carbon foot print which is contributed due to burning or heat decomposition treatment of the waste rubber products such as tyres.
Throughout this specification the term “devulcanized rubber” is synonymously used with the term “recycled rubber”.
The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.
The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.
Experimental details:
Experiment 1: Process for recycling of the waste rubber to obtain a recycled rubber (devulcanized rubber)
Example 1: Process for recycling of the waste rubber in accordance with the present disclosure: Devulcanization in turpentine/toluene mixture (with BPO)
Waste tyre rubber (vulcanized PBR) crumbs in shredded form having a particle size of 0.2 mm to 2 mm (rubber particles) were taken. Separately, 5 g of benzoyl peroxide (amount: 5 mass% with respect to waste rubber) was dissolved in a mixture of 240 ml turpentine and 160 ml toluene (in the mass ratio of 3:2) to obtain a homogeneous solution. 100 g of the rubber particles were treated (devulcanized) with 5% benzoyl peroxide (oxidizer) solution at 25 ºC for 3 hours to yield a black colored slurry comprising softened rubber. At the end of reaction, the slurry comprising the softened rubber was filtered by using Buchner funnel with Whatman filter paper (Grade 42) to obtain a black residue which was washed with toluene to obtain a softened rubber. This step of washing was repeated 3 times to obtain a recycled rubber (devulcanized rubber).
The extent of cross linking was studied by using Flory-Rehner cross linking density analysis. Reduction in the cross linking density confirmed the breakage of sulphur cross linkages and thus assured that the devulcanization process has been completed.
Comparative example 1: Process for recycling of waste rubber: Devulcanization in toluene and turpentine (without BPO)
A waste tyre rubber (vulcanized PBR/SBR) crumbs in shredded form having a particle size of 0.2 mm to 2 mm (rubber particles) were taken. 100 g of the rubber particles were treated (devulcanized) with a mixture of 240 ml turpentine and 160 ml toluene (in the mass ratio of 3:2) at 25 ºC for 3 hours to yield a black colored slurry comprising softened rubber. At the end of reaction, the slurry comprising the softened rubber was filtered to obtain a black residue which was washed with toluene to obtain a softened rubber. This step of washing was repeated 3 times to obtain a recycled rubber (devulcanized rubber).
Comparative example 2: Process for recycling of waste rubber: Devulcanization in toluene with BPO
A waste tyre rubber (vulcanized PBR/SBR) crumbs in shredded form having a particle size of 0.2 mm to 2 mm (rubber particles) were taken. Separately 5 g of benzoyl peroxide (amount: 5 mass%) was dissolved in 400 ml toluene to obtain a homogeneous solution. 100 g of the rubber particles were treated (devulcanized) with 5% benzoyl peroxide (oxidizer) solution at 25 ºC for 48 hours to yield a black colored slurry comprising softened rubber. At the end of reaction, the slurry comprising the softened rubber was filtered to obtain a black residue which was washed with toluene to obtain a softened rubber. This step of washing was repeated 3 times to obtain a recycled rubber (devulcanized rubber).
The following Flory-Rehner equation was used to calculate the cross linking density values of the recycled rubber (devulcanized rubber) samples. In polymer science, Flory-Rehmer equation describes the mixing of polymer and liquid molecules as predicted by the equilibrium swelling theory of Flory and Rehner.

Following Table 1 shows the cross linking density values of waste rubber and the devulcanized rubber samples prepared in Example 1 and comparative example.
Table 1: Cross linking density calculations
Properties Abbrevation (s) Control Rubber (Waste tyre rubber) (Comparative example 1)
Rubber + toluene + turpentine (Comparative example 2)
BPO in Toluene Example 1 (BPO in Turpentine and Toluene)
Total wt of the compound (g) T 1.03 1.06 1.04 1.03
Wt in dry state (g) D 0.94 0.89 0.86 0.89
Wt fraction of the insoluble part (g) F 0.35 0.35 0.35 0.35
Wt of the absorbed solvent (g) A 1.6 1.6 2.9 4.8
Density of the rubber ?r 0.92 0.92 0.92 0.92
Density of the solvent ?s 0.87 0.87 0.87 0.87
Initial Wt of rubber compound 1.03 1.06 1.04 1.03
wt after drying 0.94 0.89 0.86 0.89
Wt after 96 hours 2.7 2.7 3.9 5.8
Absorbed Solvent (Toluene) 1.63 1.64 2.85 4.75
Swelling % 158.3 154.7 274.1 461.6
(Volume of rubber = Wt of Dried rubber- Wt of insoluble part)/density of solvent (D-F*T)/?r 0.64 0.57 0.55 0.58
Volume of solvent A/?s 1.87 1.89 3.28 5.46
Volume fraction of rubber Vr 0.25 0.23 0.14 0.096
0.25 0.29 0.29 0.29
Rubber-toluene interaction parameter ? 0.39 0.39 0.39 0.39
Mole volume of used solvent at room temperature
in cm3/mol Vs 105.9 105.9 105.9 105.9
3v Vr 0.64 0.64 0.64 0.64
1-Vr 0.75 0.77 0.86 0.9
ln(1- Vr) -0.29 -0.26 -0.15 -0.1
Vr/2 0.13 0.12 0.07 0.05
Cross Link Density in X10-5 12.5 9.7 2.7 1.0
Average molecular weight of the rubber between the crosslinks Mc in X103 4 5.1 18.1 48.2
From the of Table 1, it is observed that the devulcanized rubber solution preparation as per Example 1 (with turpentine/toluene mixture) has maximum swelling% and the lowest cross linking density as compared to the recycled rubber (devulcanized rubber) preparation of the comparative examples 1 and 2. The low cross linking density values indicate the high level of devulcanization.
Figure 1 represents a graphical representation of cross linking density profile of waste rubber (vulcanized rubber) and recycled rubber (devulcanized rubber). Cross links per unit weight or area represents cross link density. Vulcanized rubber is cross linked through sulphur and hence found to have highest cross linking density. Any reduction of such suphur linkages i.e. cross linking indicates devulcanization of rubbers. From the Figure 1, it is observed that on treating vulcanized rubber with benzoyl peroxide (BPO) in toluene (comparative example 2), its sulphur cross linking density was reduced by 78% with respect to the cross linking in non-treated vulcanized rubber control. Further, on treating vulcanized rubber with the mixture of BPO in turpentine and toluene (Example 1) indicates maximum reduction of cross linking density i.e. by 91% with respect to the cross linking in non-treated vulcanized rubber control.
Furthermore, from the above examples it is observed that the time required for devulcanization of waste rubber in example 1 is 16 times lesser than the time required in comparative example 2.
In order to study the effect of the combination of oxidizer (benzoyl peroxide), toluene and turpentine on the reaction time and reaction temperature, the inventors of the present disclosure have compared the process of devulcanization of the rubber in accordance with the present disclosure with the process of devulcanization of the rubber of the prior art, wherein the use of combination of BPO and toluene is disclosed (Example A) and the use of only turpentine is disclosed (Example B). The results of the study have been summarized in the Table 1a below.
Table 1a: Study of effect of BPO+ Toluene + Turpentine on reaction conditions
Reaction Parameter Example A (BPO+ Toluene) Example B
(Turpentine) Example 1 of the present disclosure (BPO + Toluene + Turpentine)
Temperature 80 °C 70 °C 25 °C
Time 4 hours 14 days 3 hours
From the results of the Table 1a, it is observed that the reaction time and reaction temperature required for devulcanizing the waste rubber as per the Example 1 of the present disclosure is very less as compared to the temperature and time required for devulcanizing the rubber as per the Example A (wherein BPO and toluene are used) and Example B (wherein only turpentine is used).
Experiment 2: Preparation of the revulcanized rubber composite using devulcanized rubber of the present disclosure and virgin rubber
The recycled rubber (devulcanized rubber) as prepared in the Example 1 was mixed with the virgin rubber (PBR) in a ratio of 1:3 (25 mass% of devulcanized rubber and 75 mass% of virgin rubber) at 50 °C for 30 minutes in two roll mixer to get initial composite mass. Product prepared from the two roll mixer was soft and well mixed within rubber matrix of the virgin rubber which was observed from its texture and physical appearance. Figure 2 represents a vulcanizing process which involves mixing of devulcanized rubber of the present disclosure with the virgin rubber for 10 minutes. 266 g of the composite mass consists of the following components (formulation of revulcanized rubber composite) which are enlisted in Table 2. Carbon black was used as filler for the composite material. The vulcanization of composite was carried out as per ASTM D-3189 formulation in banbury mixer. Mixing was performed for 9 minutes at 120 ºC and maximum torque was observed after first minute from time of mixing initiation.
Table 2: Formulations for vulcanized virgin rubber and revulcanized rubber composite
Vulcanizing Chemicals Vulcanized virgin rubber Revulcanized rubber composite (devulcanized rubber of the present disclosure: Virgin Rubber – 25:75)
PBR/ SBR 145 109
DV Rubber - 36
Sulphur 2.9 2.9
Stearic Acid 2.92 2.92
TBBS 1.31 1.31
Carbon black 87.5 87.5
Oil 21.8 21.8
Total 266 266
Experiment 3: Product performance studies
I. Curing Property Study
A rheological study of revulcanized rubber was conducted considering virgin PBR as standard. Table 3 shows the torque properties of virgin rubber and devulcanized PBR composite.
Table 3: Torque values of virgin rubber and revulcanized rubber composite
Oscillating Disc Rheometer (ODR) @ 160 oC, 100 cpm Reference Values Vulcanized virgin rubber Revulcanized rubber composite (25% devulcanized rubber of the present disclosure + 75% virgin rubber)
Min Torque (lb-in) 8.5 - 12.5 10.2 11.18
Max Torque -MH (Ib-in) 31 - 44 41.5 46.6
Scorch Time TS-1 (min) 2.5 - 5.5 3.9 3.3
Curing Time T50 (min) 6.5 - 10.5 9.5 7.8
Curing Time T90 (min) 9.5 - 14.5 13 10.7
*scorch time is defined as the amount of time required at a given temperature before the rubber compound begins to vulcanize.
It was observed from Table 3 that the torque properties of revulcanized rubber composite (devulcanized rubber of the present disclosure + virgin rubber) showed comparable results with virgin rubber properties. Lowest torque value measures stiffness and curing properties of revulcanized rubber composite that are found to be comparable with the virgin rubber properties.
II. Physical Property Study
Physical properties of revulcanized rubber composite were studied. Table 4 enlists the tensile strength, modulus at 300% at elongation and elongation % values of virgin rubber and revulcanized rubber composite (devulcanized rubber of the present disclosure + virgin rubber). Elongation at break is the percentage increase in length where specimen sample breaks. Elongation of rubber is the length at breaking point which is expressed as a percentage of its original length.
Table 4: Physical property values of virgin rubber and revulcanized rubber composite
Properties Reference Values Virgin rubber (Regular PBR) Revulcanized rubber composite (25% devulcanized rubber of the present disclosure + 75% virgin rubber)
Tensile Strength (Mpa) 13.0 min 14.0 13.5
Modulus at 300 % Elongation (Mpa) 8.0 - 10.8 10.5 11
Elongation (%) 350 min 421 355
From Table 4, it is observed that even after replacing 25% of virgin rubber with recycled rubber (devulcanized rubber); tensile properties are at par with virgin rubber. However, 300% modulus properties are slightly at higher side which may be due to the presence of trace amount of excess filler in the recycled material. It is also observed that elongation at break properties are slightly inferior to that of virgin rubber properties which may be due to the presence of excess filler which show higher interaction with polymer chain and hence reduces elongation.
III. Cross link density Study
Cross link density properties of the revulcanized rubber composite (containing 25% of devulcanized rubber as prepared in Example 1) and the regular virgin rubber were studied. Table 5 shows the cross link density values.
Table 5: Cross link density values of virgin rubber and revulcanized rubber composite
Properties Virgin rubber (Regular PBR) Revulcanized rubber composite (25% devulcanized rubber of the present disclosure + 75% virgin rubber)
Cross Link Density in 10-5 11.4 18.6
Mc (average molecular weight of the rubber between the crosslinks) 4400 2690
Results of Table 5 showed that the cured revulcanized rubber composite containing devulcanized rubber of the present disclosure contained higher cross linking properties as compared to the cured virgin rubber. The cured revulcanized rubber composite contained about 63% higher cross linking points as compared to the cured virgin rubber. Higher cross linking may be attributed to the presence of unreacted benzoyl peroxide in the devulcanized product. This has been supported based on the result that devulcanized rubber was found to contain unreacted peroxide as determined by iodine test method. Benzoyl peroxide is known to provide cross linking in the rubber and hence provides additional cross linking to the rubber chains in the final virgin rubber mixed product.
Further, higher cross linking density also confirmed by decrease in average molecular weight of the rubber between the crosslinks (Mc). This is attributed to the higher molecular chain length if there is less cross link point and vice a versa as depicted in the animation of Figure 3. It showed that due to lower cross link density in cured virgin PBR, there is higher Mc as compared to that with revulcanized rubber composite. Higher cross link density found to provide improved mechanical properties hence, revulcanized rubber composite can provide better performances when compared to raw rubber cured product.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of a process for recycling of the a waste rubber that;
? is simple, safe and economic;
? provides efficient breaking of sulphur cross links, thereby reducing the cross linking density in recycled rubber (devulcanized rubber) by at least 90 %; and
? can be carried out at a comparatively low temperature and at lesser time period.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.
The numerical values given for various physical parameters, dimensions, and quantities are only approximate values and it is envisaged that the values higher than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.
While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. , Claims:WE CLAIM:
1. A process for recycling of a waste rubber, said process comprising the following steps:
a. obtaining said waste rubber having a particle size in the range of 0.1 mm to 5 mm;
b. separately dissolving an oxidizer in a mixture of at least one swelling agent and at least one fluid medium to obtain a homogeneous solution;
c. mixing said waste rubber into said solution at a predetermined temperature for a predetermined time period to obtain a slurry;
d. filtering said slurry to obtain a residue; and
e. washing said residue with said fluid medium to obtain a recycled rubber.
2. The process as claimed in claim 1, wherein said waste rubber is vulcanized rubber selected from the group consisting of styrene-butadiene rubber (SBR), polybutadiene rubber (PBR), butyl rubber and ethylene propelene diene rubber (EPDR).
3. The process as claimed in claim 1, wherein said oxidizer is selected from organic peroxides, wherein said organic peroxide is selected from the group consisting of acetyl acetone peroxide, diacetyl peroxide, cumyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, t-butyl hydroperoxide, methyl ethyl ketone peroxide, peracetic acid, peracids and methane hydroperoxide.
4. The process as claimed in claim 1, wherein said oxidizer is used in an amount in the range of 0.1 mass% to 10 mass% with respect to mass of said waste rubber.
5. The process as claimed in claim 1, wherein said swelling agent is selected from the group consisting of turpentine, paraffinic oil, naphthenic oil, petroleum spirit and paint thinner.
6. The process as claimed in claim 1, wherein said at least one fluid medium is selected from the group consisting of toluene, xylene, 1,2,3-trimethylbenzene, ethyl benzene, diethyl benzene and triethyl benzene.
7. The process as claimed in claim 1, wherein a mass ratio of said swelling agent to said fluid medium is in the range of 1:1 to 4:3.
8. The process as claimed in claim 1, wherein said predetermined temperature is in the range of 10 °C to 50 °C.
9. The process as claimed in claim 1, wherein said predetermined time period is in the range of 1 hour to 5 hours.
10. The process as claimed in claim 1, wherein a cross linking density of said recycled rubber is reduced by at least 90%.
11. The process as claimed in claim 1, wherein said recycled rubber is used with a virgin rubber in an amount in the range of 5% to 50% to obtain a revulcanized rubber composite.
Dated this 20th day of December, 2022

_______________________________
MOHAN RAJKUMAR DEWAN, IN/PA – 25
of R.K.DEWAN & CO.
Authorized Agent of Applicant

TO,
THE CONTROLLER OF PATENTS
THE PATENT OFFICE, AT MUMBAI