Description:FIELD
The present disclosure relates to a process for recycling of waste vulcanized elastomer.
BACKGROUND
The background information herein below relates to the present disclosure but is not necessarily prior art.
Vulcanized elastomer (rubber) is the most common part of automobiles which is inevitable for wear or irreparable damage rendering them waste. The rubber materials are vulcanized to make them highly durable and are not easily broken. The waste rubber includes polymer materials, carbon, textile reinforcement materials, beads, steel frame, and the like. Chemically these rubbers are thermoset polymers, thus components cannot be used further to produce any building block of value added materials. These waste rubbers are generally disposed of in landfills, which generally take several years for decomposition and could pose ecological threats due to their non-biodegradability nature.
The conventional process for recycling waste vulcanized elastomer includes incineration, pyrolysis, chemical treatment, and the like. The process of incineration results in the emission of harmful gases such as COx, NOx, SOx, and the like. The process of pyrolysis involves injecting waste rubber into a furnace with a carrier gas and decomposing them by a direct heating method. The burning process does not provide sustainable components, in addition, it uses expensive carrier gases that include methane, ethane, propane, butane, pentane, hexane, and ammonia group components in a mixed form. Further, the chemical treatments require a huge amount of solvents, and high temperatures which are not cost-effective and environment friendly to produce low molecular weight hydrocarbon liquids. Other processes include degrading the rubber at a very high temperature of 1200-1300°C to prepare soot materials, useful in carbon black manufacturing. However, such processes are not energy efficient.
Even though, recycled rubbers are used in various other areas, such as civil engineering, decorative architecture, wood and furniture industry, decorative objects, doornail industry, and the like. However, the usage has been limited due to various drawbacks.
Therefore, there is felt a need to provide a process of recycling waste vulcanized elastomer that mitigates the aforestated drawbacks or at least provide an alternative solution.
OBJECTS
Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.
Another object of the present disclosure is to provide a process for the recycling of waste vulcanized elastomer.
Yet another object of the present disclosure is to provide a sustainable and eco-friendly process for the recycling of waste vulcanized elastomer.
Still another object of the present disclosure is to provide a process for the recycling of waste vulcanized elastomer to produce oligomers as value added reusable components.
Another object of the present disclosure is to provide a sustainable, eco-friendly, and economically viable process for the recycling of waste vulcanized elastomer.
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 the recycling of waste vulcanized elastomer. The process comprises obtaining a predetermined amount of waste vulcanized elastomer followed by adding a catalyst to obtain a first mixture. The first mixture is milled for a first predetermined time period to obtain a uniform mixture. The uniform mixture is passed through a mixer at a first predetermined speed at a predetermined temperature to obtain a devulcanized elastomer sheet. The devulcanized elastomer sheet is dispersed in a fluid medium for a second predetermined time period to obtain a second mixture. The second mixture is subjected to centrifugation at a second predetermined speed for a third predetermined time period to separate a carbon black to obtain a resultant mixture. The resultant mixture is filtered to obtain a filtrate comprising oligomers. The filtrate comprising oligomers is dried at a second predetermined temperature for a fourth predetermined time period to obtain oligomers.
BRIEF DESCRIPTION OF THE DRAWING
Figure 1 illustrates the molecular weight chromatogram obtained from GPC analysis of the recovered oligomer.
DETAILED DESCRIPTION
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.
As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.
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.
The conventional process for recycling waste vulcanized elastomer includes incineration, pyrolysis, chemical treatment, and the like. The process of incineration results in the emission of harmful gases such as COx, NOx, SOx, and the like. The process of pyrolysis involves injecting waste rubber into a furnace with a carrier gas and decomposing them by a direct heating method. The burning process does not provide sustainable components, in addition, it uses expensive carrier gases that include methane, ethane, propane, butane, pentane, hexane, and ammonia group components in a mixed form. Conventionally known chemical treatments require a huge amount of solvents and high temperatures that provide low molecular weight hydrocarbon liquids. Other processes include degrading the rubber at a very high temperature of 1200°C to 1300°C to prepare soot materials useful in carbon black manufacturing however such processes are not energy efficient and not environment friendly.
The process of the present disclosure provides a simple process for recycling waste vulcanized elastomer. The process of the present disclosure is a solvent free and eco-friendly process that provides reusable components such as carbon black and low molecular weight elastomeric materials (oligomers).
In an aspect of the present disclosure, there is provided a process for the recycling of waste vulcanized elastomer.
The process is described in detail.
In a first step, a predetermined amount of waste vulcanized elastomer is obtained, followed by adding a catalyst to obtain a first mixture.
In accordance with an embodiment of the present disclosure, the waste vulcanized elastomer is at least one selected from the group consisting of waste tyre rubber crumb, cut tyre, shredded tyre, tyre production waste, rubber aggregates, retreading waste, and diene based rubber vulcanizates. In an exemplary embodiment of the present disclosure, the waste vulcanized elastomer is a waste tyre rubber crumb.
In an embodiment of the present disclosure, the waste vulcanized elastomer materials include nitrile rubber, ethylene propylene diene monomer (EPDM) rubber, diene rubbers, polymer materials, rubbers that bears double bond or olefinic moieties.
In accordance with an embodiment of the present disclosure, the particle size of waste vulcanized elastomer is in the range of 20 mesh to 200 mesh. In an exemplary embodiment of the present disclosure, the particle size of waste vulcanized elastomer is 40 mesh.
In accordance with an embodiment of the present disclosure, the catalyst is at least one selected from the group consisting of Grubbs 2nd generation catalyst, Grubbs 3rd generation catalyst, and ruthenium based Grubbs metathesis catalyst. In an exemplary embodiment of the present disclosure, the catalyst is Grubbs 2nd generation catalyst.
The chemical name for Grubbs 2nd generation catalyst (246047-72-3) is 1,3-Bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene)dichloro(phenylmethylene) (tricyclohexylphosphine)ruthenium.
In accordance with an embodiment of the present disclosure, the weight ratio of the waste vulcanized elastomer to the catalyst is in the range of 1:0.0002 to 1:0.006. In an exemplary embodiment of the present disclosure, the weight ratio of waste vulcanized elastomer to the catalyst is 1:0.0006. In another exemplary embodiment, the weight ratio of waste vulcanized elastomer to the catalyst is 1:0.0004.
In a second step, the first mixture is milled for a first predetermined time period to obtain a uniform mixture.
In accordance with an embodiment of the present disclosure, the first predetermined time period is in the range of 10 minutes to 20 minutes. In an exemplary embodiment of the present disclosure, the first predetermined time period is 15 minutes.
In a third step, the uniform mixture is passed through a mixer at a first predetermined speed at a first predetermined temperature to obtain a devulcanized elastomer sheet.
In accordance with an embodiment of the present disclosure, the first predetermined temperature is in the range of 20°C to 70°C. In an exemplary embodiment of the present disclosure, the first predetermined temperature is 30°C.
In accordance with an embodiment of the present disclosure, the mixer is at least one selected from the group consisting of two roll mill, internal mixer, and extruder. In an exemplary embodiment of the present disclosure, the mixer is two roll mill.
The use of two roll mill is preferred because,
• no dissolution of material or solvent medium is required to perform the reaction;
• no solvent removal process or product drying on post-reaction;
• fast process due to direct interactions of reagents; and
• hence melt mixing by two roll mill is a green process, economical and sustainable.
In accordance with an embodiment of the present disclosure, the thickness of the devulcanized elastomer sheet is in the range of 1 mm to 10 mm. In an exemplary embodiment of the present disclosure, the thickness of the devulcanized elastomer sheet is 2 mm.
In accordance with an embodiment of the present disclosure, the first predetermined speed is in the range of 30 rpm to 100 rpm. In an exemplary embodiment of the present disclosure, the first predetermined speed is in the range of 50 rpm.
In a fourth step, the devulcanized elastomer sheet is dispersed in a fluid medium for a second predetermined time period to obtain a second mixture.
In accordance with an embodiment of the present disclosure, the fluid medium is a hydrocarbon solvent at least one selected from the group consisting of toluene, xylene, benzene, hexane, cyclohexane, heptane, octane, and decane. In an exemplary embodiment of the present disclosure, the fluid medium is toluene.
In accordance with an embodiment of the present disclosure, the second predetermined time period is in the range of 5 hours to 8 hours. In an exemplary embodiment of the present disclosure, the second predetermined time period is 6 hours.
In a fifth step, the second mixture is centrifuged at a second predetermined speed for a third predetermined time period to separate carbon black to obtain a resultant mixture, followed by filtering the resultant mixture to obtain a filtrate comprising oligomers.
In accordance with an embodiment of the present disclosure, the second predetermined speed is in the range of 1000 rpm to 6000 rpm. In an exemplary embodiment, the second predetermined speed is 4000 rpm.
In accordance with an embodiment of the present disclosure, the third predetermined time period is in the range of 10 minutes to 30 minutes. In an exemplary embodiment, the third predetermined time period is 15 minutes.
In accordance with an embodiment of the present disclosure, the fluid medium from the filtrate is separated to obtain oligomers. The fluid medium is separated by filtering through any mesh size of more than 2.0µm
In the final step, the filtrate comprising oligomers is dried at a second predetermined temperature for a fourth predetermined time period to obtain oligomers.
In accordance with an embodiment of the present disclosure, the second predetermined temperature is in the range of 60°C to 90°C. In an exemplary embodiment of the present disclosure, the second predetermined temperature is 70°C.
In accordance with an embodiment of the present disclosure, the fourth predetermined time period is 150 minutes to 250 minutes. In an exemplary embodiment of the present disclosure, the fourth predetermined time period is 180 minutes.
In accordance with an embodiment of the present disclosure, the oligomers are at least one selected from the group consisting of alkenes. In an exemplary embodiment of the present disclosure, the oligomers are dienes.
In accordance with an embodiment of the present disclosure, the purity of the oligomers is in the range of 90% to 95%.
In accordance with an embodiment of the present disclosure, the oligomers are characterized by having
• a molecular weight in the range of 1400 g/mol to 1600 g/mol;
• a specific gravity in the range of 1.02 to 1.1;
• a polydispersity in the range of 1.5 to 2.5; and
• a weight average molecular weight in the range of 100 g/mol to 10000 g/mol.
The process of the present disclosure effectively disintegrates the C-C bond in addition to the carbon-sulphur bond cleavage of the polymeric backbone, thus producing lower Mw than virgin rubber. The cleavage of the C-C bond produces smaller hydrocarbon oligomeric fragments which are used for various industrial applications.
The recycling involves a metathesis reaction of vulcanized elastomer in two roll mill through the extrusion process. During this metathesis reaction, waste tyre rubber material yields low molecular weight chemicals which can further undergo devulcanization thus converting thermoset polymer to recyclable polymers.
The metathesis reaction works on double bond moieties through ring-opening metathesis polymerization (ROMP) or acyclic diene metathesis polycondensation mechanism. Vulcanized rubber materials tend to retain double bonds that were not involved in sulphur cross-linking which are targeted in the process of the present disclosure to alter the chain backbone. The process enables longer chain length rubber molecules to be broken down into smaller rubber components.
The foregoing description of the embodiments has been provided for purposes of illustration and is 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 purposes 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
Example -1
70 g of waste tyre rubber crumb powder (crosslinked rubber) of 40 mesh was mixed with 40 mg of Grubbs 2nd generation catalyst (C827) to obtain a first mixture. The first mixture was milled at room temperature for 15 minutes to obtain a uniform mixture. The uniform mixture was passed through a two-roll mill at speed of 50 rpm at room temperature to obtain a rubber sheet (devulcanized) (2 mm thickness). The so obtained rubber sheet was dispersed in 200 ml of toluene for 6 hours to obtain a second mixture (dissolve rubber oligomers). The second mixture was subjected to centrifugation at 4000 rpm for 15 min to separate a carbon black to obtain a resultant mixture. The resultant mixture was filtered to obtain a filtrate comprising oligomers. The filtrate was dried by using hot air at a temperature of 70°C for 180 minutes to obtain oligomers.
The so obtained oligomer is characterized by having a molecular weight in the range of 1400 g/mol to 1600 g/mol by GPC analysis, as illustrated in Figure 1. Figure 1 shows the molecular weight distribution of the recovered oligomer sample obtained in example 1.
It is evident from the graph that the polydispersity of this sample was very narrow in the range of 1.9 to 2.0. Weight average molecular weight was found to be in the range of 100 g/mol to 10000 g/mol; having a maximum molecular weight of 1516 g/mol. The number average molecular weight was highest at 790 g/mol.
Example -2
500 g of waste tyre rubber crumb powder (crosslinked rubber) of 40 mesh was mixed with 214 mg of Grubbs 2nd generation catalyst (C827) to obtain a first mixture. The first mixture was milled at room temperature for 15 minutes to obtain a uniform mixture. The uniform mixture was passed through a two-roll mill at a speed of 50 rpm at room temperature to obtain a rubber sheet (devulcanized) (2 mm thickness). The so obtained rubber sheet was dispersed in 1500 ml of toluene for 6 hours to obtain a second mixture (dissolve rubber oligomers). The second mixture was subjected to centrifugation at 4000 rpm for 15 min to separate a carbon black to obtain a resultant mixture. The resultant mixture was filtered to obtain a filtrate comprising oligomers. The filtrate was dried by using hot air at a temperature of 70°C for 180 minutes to obtain oligomers.
The molecular weight of the oligomers obtained in Example 1 and Example 2 are provided below in Table 1.
Table 1: Molecular weight of oligomers
Example Mw Molecular weight (g/mol)
1 1516
2 1465

It is evident from the above table that the efficiency of the process was consistent. When the quantity of the waste tyre rubber crumb increased from 70 gms to 500 gms, the recycling process was more efficient even by using a lower amount of catalyst when compared to Example 1. From the data, it is concluded that the process developed is reproducible even at a higher scale and yields a similar type of product.
TECHNICAL ADVANCEMENTS
The present disclosure described hereinabove has several technical advantages including, but not limited to, the realization of a process for the recycling of waste vulcanized elastomer, which:
• uses a greener process for recycling waste vulcanized elastomer;
• is a solvent free process;
• is carried at room temperature;
• is time efficient;
• avoid evolution/emission of harmful gases;
• uses a low volume of catalyst; and
• a simple, environment-friendly, and cost-efficient process for the recycling of waste vulcanized elastomer.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
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 disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments 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 waste vulcanized elastomer, wherein said process comprising the following steps:
a) obtaining a predetermined amount of waste vulcanized elastomer followed by adding a catalyst to obtain a first mixture;
b) milling said first mixture for a first predetermined time period to obtain a uniform mixture;
c) passing said uniform mixture through a mixer at a first predetermined speed at a first predetermined temperature to obtain a devulcanized elastomer sheet;
d) dispersing said devulcanized elastomer sheet in a fluid medium for a second predetermined time period to obtain a second mixture;
e) centrifuging said second mixture at a second predetermined speed for a third predetermined time period to separate a carbon black to obtain a resultant mixture, followed by filtering said resultant mixture to obtain a filtrate comprising oligomers; and
f) drying said filtrate comprising oligomers at a second predetermined temperature for a fourth predetermined time period to obtain oligomers.
2. The process as claimed in claim 1, wherein said waste vulcanized elastomer is at least one selected from the group consisting of waste rubber crumb, cut tyre, shredded tyre, tyre production waste, rubber aggregates, retreading waste and diene based rubber vulcanizates.
3. The process as claimed in claim 1, wherein said catalyst is at least one selected from the group consisting of Grubbs 2nd generation catalyst, Grubbs 3rd generation catalyst, and ruthenium based Grubbs metathesis catalyst.
4. The process as claimed in claim 1, wherein said first predetermined time period is in the range of 10 minutes to 20 minutes.
5. The process as claimed in claim 1, wherein said first predetermined temperature is in the range of 20°C to 70°C.
6. The process as claimed in claim 1, wherein said mixer is at least one selected from the group consisting of two roll mill, internal mixer, and extruder.
7. The process as claimed in claim 1, wherein said first predetermined speed is in the range of 30 rpm to 100 rpm.
8. The process as claimed in claim 1, wherein the thickness of said devulcanized elastomer sheet is in the range of 1 mm to 10 mm.
9. The process as claimed in claim 1, wherein said fluid medium is hydrocarbon solvent at least one selected from the group consisting of toluene, xylene, benzene, hexane, cyclohexane, heptane, octane, and decane.
10. The process as claimed in claim 1, wherein said second predetermined time period is in the range of 5 hours to 8 hours.
11. The process as claimed in claim 1, wherein the weight ratio of said waste vulcanized elastomer to said catalyst is in the range of 1:0.0002 to 1:0.006.
12. The process as claimed in claim 1, wherein said oligomers are alkenes.
13. The process as claimed in claim 1, wherein said second predetermined speed is in the range of 1000 rpm to 6000 rpm and said third predetermined time period is in the range of 10 minutes to 30 minutes.
14. The process as claimed in claim 1, wherein said second predetermined temperature is in the range of 60°C to 90°C and said fourth predetermined period is 150 minutes to 250 minutes.
15. The process as claimed in claim 1, wherein said oligomers has a purity in the range of 90% to 95%.
16. The process as claimed in claim 1, wherein said oligomers are characterized by having
a) a molecular weight in the range of 1400 g/mol to 1600 g/mol;
b) a specific gravity in the range of 1.02 to 1.1;
c) a polydispersity in the range of 1.5 to 2.5; and
d) a weight average molecular weight in the range of 100 g/mol to 10000 g/mol.

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