WO2015022706A2

WO2015022706A2 - New devulcanised rubber with superior properties

Info

Publication number: WO2015022706A2
Application number: PCT/IN2014/000526
Authority: WO
Inventors: Nedumaran Thiruganasambandam
Original assignee: Sundaram Industries Limited; Levgum Ltd
Priority date: 2013-08-16
Filing date: 2014-08-14
Publication date: 2015-02-19
Also published as: WO2015022706A3

Abstract

A novel devulcanised rubber product and process for manufacturing the same by mixing maltenes/bitumen to devulcanised reclaimed rubber in a predetermined ratio, passing the mixture through nip refiners at near ambient temperature and repeatedly re-rolling the calendared sheets under the same pressure and temperature for half an hour; the said devulcanised rubber with improved rheo properties being capable of used by itself or along with other master batch compounds in all conventional applications of reclaimed rubber.

Description

NEW DEVULCANISED RUBBER WITH SUPERIOR PROPERTIES

FIELD OF THE INVENTION

The present invention aims at modifying the properties of the de vulcanized recycled rubber i.e. the Levgum product with superior physical properties through its innovative manufacturing method and obtaining a devulcanised rubber product with enhanced properties, hereinafter referred to as Sil compound. The novelty lies in the enhanced physical properties of the sil compound, which is derived out of the5. use of recycled elastomers along with families of maltenes (a petroleum derived product)/bitumen and other end products, under specific proportions, temperature and pressure ranges. BACKGROUND OF THE INVENTION

Vulcanized rubber are among the largest source of waste. Attempts have been made to regenerate the vulcanized rubber to be reused in other products through the method of devulcanization. There are a variety of products available manufactured through conventional methods which are presently being used by the Rubber Formulation Industry. Under traditional methods, reclaim rubber is recycled Rubber produced from vulcanized Rubber granules b breaking down the Vulcanized structure using heat, pressure, chemicals and mechanical techniques. Reclaim rubber has the plasticity of a new unvulcanized rubber compound due to thermal degradation. However it has poor physical properties as polymer chains have been broken. Crumb rubber is ground rubber powder produced by mechanical grinding technique. In this process vulcanized rubber pieces are placed in a serrated grinder for preparation of ground rubber of various mesh sizes. Mechanical grinding has a limitation on the lowest size it can be ground or milled.

Levgum Devulcanization is latest cutting edge technology in the domain of reclaiming rubber. Levgum, an Israeli company, together with its licensees, is leading a global change in the rubber recycling industry through its breakthrough technology. It has formulated the first high performance chemical modifier for the de-vulcanization of rubber waste, called EDV for Ecological De-Vulcanizer. The highly efficient de-vulcanization process involves adding a small percentage of EDV modifier to vulcanized rubber crumb, which is stressed with multiple passes through a two-roller mill . Due to the heavy stress induced by the heavy rollers only the Sulfur -sulfur bonds are severed, leaving the rest of the compound intact. The near ambient temperature of the process conserves almost all the original properties of the products. The superior quality De-vulcanized Rubber Compound (DRC), substitute's part of the virgin compound, thus leading to significant savings in raw material costs while maintaining the compound's original properties in terms of plasticity. The mechanical -chemical process is carried out at room temperature, does not use harmful chemicals, does not produce or emit any hazardous waste or gases and is 100% environmentally safe. The whole process offers a better, more environmentally-friendly and more lucrative future for the rubber and recycling industries.

The De-vulcanized Rubber Compound (DRC) manufactured using the Levgum process (Indian Patent No. 199621) has a limitation of resulting in higher viscosity in the end product and hence affects flow-ability of the product. The reason for increased viscosity in the Levgum end product is due to the presence of randomly placed long elastomer strands.

Another reason for the high viscosity is due to the attachment of high ionic severed sulphur with the EDV residues with the broken, unstable and charged polymer chains. This attachment creates a mechanical and chemical strain, as well as electrical strain due to the large electron cloud. The electron cloud makes a gridlock and hinders the relative movement of the polymer molecules, thereby affecting the flow ability of the end product.

The drawbacks of the Levgum products are as follows:

1. The end product does not retain its original plasticity like Natural rubber in spite of the cleavage of sulphur bonds.

2. The end product has the presence of long (elastomer) carbon strands thereby causing an increase in viscosity of the end product.

3. The end product is obtained in agglomerated state due to the intermixing of the long strands.

4. The agglomerated state of the product affects the flow properties which make it difficult to mix with the master batches of rubber formulations. 5. Introduction of higher percentages of DRC into the compounds leads to drop in Physical and other properties.

The present invention aims to overcome these problems by innovating a method of manufacturing improved devulcanized rubber with higher tensile strength, better elongation, superior modulus strength and exceptional abrasion resistance, and overall improvement in rheo properties, with low hysteresis loss.

PRIOR ART

US 5602186 A titled "Rubber devulcanization process" provides for a A process for devulcanizing a rubber vulcanizate by desulfurization involves suspending a rubber vulcanizate crumb in a solvent which preferably swells the rubber vulcanizate before or during the devulcanization reaction and adding an alkali metal, such as sodium, to the suspension. The alkali metal cleaves mono-, di- and polysulfidic cross-linkages in the rubber vulcanizate to liberate rubber polymer having a molecular weight substantially equal to that of the rubber polymer prior to vulcanization. Carbon black may also be recovered for re-use in accordance with the process of the present invention. Devulcanized rubber may be subjected to a re- vulcanization reaction without separation of rubber polymer from the solvent by addition of an appropriate curing mixture.

US 6956065 B2 titled "Method for devulcanizing rubber with an amine" provides a method for devulcanizing a sulphur-cured rubber, which rubber contains a network of a polymer, which polymer has a main chain of carbon atoms, in which for the vulcanization per 40 carbon- carbon bonds in the main chain a maximum of 1 unsaturated carbon-carbon bond occurs, by heating the rubber in the presence of a devulcanizing agent. The devulcanizing agent is an amine compound.

US 4021393 A titled "Method and composition for surfacing and repairing broken pavements with an elastomeric material having improved flexing properties at freezing temperatures without any significant loss of viscosity at high application temperatures" provides for a method and material is provided for surfacing and repairing broken pavements with an elastomeric paving material comprised of the reaction product between a paving grade asphalt and a non-oil resistant rubber having petroleum maltenes admixed with said reaction product to improve the flexing properties at freezing temperatures of said paving material without any significant loss of viscosity at the high temperatures of application.

WO 2001029122 Al titled "Modifier for devulcanization of cured elastomers, mainly vulcanized rubber and method for devulcanization by means of this modifier" provides a modifier for devulcanization of cured elastomers, and especially vulcanized rubber, said modifier containing a first chemical substance, which is disposed towards dissociation and the formation of an organic cation and amine, and further containing a second chemical substance as promoter of dissociation of the first chemical substance, said promoter containing a functional group constituting an acceptor of said amine. The above stated prior art relates to the method of devulcanization process of cured elastomers.

SUMMARY OF THE INVENTION

The present invention aims at modifying the properties of the de vulcanized recycled rubber, i.e. the Levgum product with superior physical properties through its innovative manufacturing method. The novelty lies in the enhanced physical properties of the new compound known as "sil" rubber, which is derived out of the use of recycled elastomers along with families of maltenes (a petroleum derived product)/bitumen and other end products under specific proportions, temperature and pressure ranges.

The close interaction derived out of the inter mixing of the two products at appropriate proportions results in a gel like structure at the interface which helps in increasing the stickiness of the end product and the formation of sheets as it is rolled through closed nip refiners. Melting the maltenes at appropriate temperature and infusing them into the elastomeric matrix further enhances the reaction. The maltene gel gets embedded with the rubber- carbon black gel of the DRC, the hydrocarbon (elastomer) bonds are not broken during the devulcanization process. The two gels mix under the pressure of the rolling mill to create a more uniform gel mixture. The resultant product is viscous and sticky in nature and forms beautiful thin sheets. These sheets can be used to manufacture products as such or by blending them with other master batch compounds such as the ones used for tyre manufacture, moulded goods, extrusions, conveyor belts, procured treads etc. resulting in products with excellent properties suitable for various applications. The DRC strands are in a highly reactive stage (uncured). They are chemically and electrically unstable because of the severed sulphur bonds and presence of an electron cloud. The maltenes/bitumen, due to its small size, are able to penetrate into the rubber matrices and serve as mechanical and chemical lubricants. Chemically and electro-statically it makes it easier for the large polymer molecules to move mechanically. The migration of lower fraction oils enables swelling at the surface and a total dissolution of matrix in some areas, thereby shortening the length of the elastomeric strand. This shortening results in improving the miscibility of the end product in the rubber compounds.

Another effect of the maltenes/bitumen is to short-circuit the electron cloud. Squeezing it between rollers for a greater amount of time intensifies the interaction and infusion between the maltenes/bitumen and DRC. This creates a mechanical effect as well as a frictional effect, thereby increasing the temperature and aiding the maltenes/ bitumen to penetrate the thin strands. This results in better rheological properties of the end product.

The gel like structure at the surface due to the ingress of maltenes increases the lubricity of the strands. . This increased lubricity improves flow properties. The resinous nature of certain constituents in the maltenes helps the strands to stick together and form continuous sheets. The improved sil sheets also exhibit excellent abrasion resistance.

Thus the novelty of this invention is the cleavage of the long elastomer strands and short circuiting the electron cloud through the penetration of the maltene gel.

Another significant feature of this invention is that the present invention results in low hysteresis loss. Hysteresis is defined as the energy lost when the rubber product is stretched and then relaxed; the energy loss is due to the internal friction. High hysteresis indicates a high loss of energy. It is widely known that carbon black present in the rubber products results in high hysteresis. The addition of maltenes/bitumen can lower hysteresis loss due the linking of maltenes/bitumen to the reinforcing resins, thereby reducing the levels of carbon black or silica in the rubber product.

Further when the improved devulcanized reclaimed rubber is loaded in high levels, it results in two important phenomena: increase in stiffness and damping factor or lack of resilience at room temperature and reduction in heat build up at high temperature due to higher speeds of operation. The loss factor or damping factor is defined as the ratio of dynamic hysteresis to dynamic elastic modulus. The damping factor is thus a measure of the fraction of the mechanical energy in vibrating rubber that is regenerated into heat. A large damping factor directly results in low noise characteristics in products made from materials with such properties. Yet another object of the invention is the creation of a homogenous mixture constituing the sil compound comprising of the maltene, based gel and the rubber-carbon black based gel. This sil compound has a low hysteresis loss because of the difference in self resonance frequencies of the two gels, thus the two gel mixtures assist in relaxing the vibration frequencies, thereby resulting in low heat build up. Therefore this unique feature of the sil compound behaves advantageously at low speeds and high speeds, when used in manufacturing. The tire industry in particular has well documented data that the high hysteresis and high heat build up in tyres is the primary reason for destruction of the tyres. Thus, the properties of low hysteresis and low heat build up help in extending the life period of tyres. The above two phenomena result in low noise factor at low speeds and less heat build up at high speeds.

BRIEF DESCRIPTION OF THE DRAWINGS AND TABLES

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 illustrates a pictorial representation gel like structure formed at the interface due to the interaction between the maltene gel and rubber carbon gel.

Table 1 provides for the change in physical properties when the maltenes and DRC are infused by rolling in between rollers for different amount of time

Table 2 provides Change in Physical characteristics of 18 phr Sil Sheet when rolled in different amount of time Table 3 provides for the comparison of the physical characteristics of new Sil Compound versus other conventional reclaimed products including the proprietary de vulcanised Levgum product. Table 4 provides for the comparison of Rheo property of Sil Sheet with DRC.

Table 5 depicts the flexibility and abrasion resistance of Silsheet in comparison to Super fine Reclaim rubber and high tensile reclaim rubber

Table 6 provides for a comparison of physical properties of Sil Sheet versus the Levgum Product.

Table 7 shows the difference in the physical properties at higher percentages of addition of conventional reclaim, crumb rubber, Levgum and Silsheet.

Table 8 provides for the comparison of physical properties of Sil Sheet (28% addition of Sil Sheet) versus the Control Batch (7.5% DRC) Table 9 provides for the performance of compound containing 70% Silsheet and 30% Virgin Compound

Table 10 provides the result of rebound resilience Test for various types of Silsheet (differs in the amount of Silsheet added) and DRC

Table 11 provides for the performance of tyres manufactured from 70% Silsheet. Table 12 provides for comparison of temperature profile between Control Tyre and tyres manufactured from 70% Silsheet.

DETAILED DESCRIPTION OF THE DRAWINGS AND TABLES

Figure 1 illustrates a pictorial representation gel like structure 2 formed at the interface due to the interaction between the maltene gel 3 and rubber carbon gel 1. The migration of lower fraction oil enables swelling at the surface 4mas depicted in figure and a total dissolution of matrix in some areas 5, thereby shortening the length of the elastomeric strand.

Table 1 depicts the change in physical properties like modulus, tensile strength and elongation break when the maltenes and DRC rolled in between rollers for 10 min, 20 min, 30min etc. It was observed that 30 min of rolling the sheets leads to optimal infusion of maltenes with DRC. The tensile strength reaches optimum levels by the 30^th minute after which the tensile strength kind of plateaus off.

Table 2 provides the change in physical characteristics of 18 phr Sil Sheet when rolled in different amount of time. Test was conducted on the sample sheet (18 phr Sil Sheet) and the hardness, specific gravity, Abrasion , modulus, tensile strength and Elongation Break were measured at the 10^th min, 20^th min and 28^th min. The test results have been provided in table.

Table 3 provides for the comparison of the physical characteristics like hardness, specific gravity, modulus of elasticity, tensile strength and elongation break of new Sil Sheet versus other conventional reclaimed products including the proprietary de vulcanised Levgum product. The physical characteristics like Tensile, Elongation, and Modulus in the new sil product were found to be far superior to those of other conventional reclaimed products as listed in the table including the proprietary de vulcanised Levgum product.

Table 4 provides for the comparison of Rheo property of Sil Sheet with DRC. It is observed from the table that there is almost a 32% drop in minimum torque when silsheet of the same percentage (7%) is used in comparison to DRC. Minimum torque is the indicator of flow ability of the product.

Table 5 depicts the flexibility and abrasion resistance of Silsheet in comparison to Super fine Reclaim rubber and high tensile reclaim rubber. The Table indicates that Silsheet is a more flexible product than the super fine reclaim rubber and high tensile reclaim rubber. Abrasion test indicates wear loss of the product. It is evident from the table that the Silsheet wear rate is lower than that of the other products.

Table 6 provides for a comparison of physical properties between DRC and DRC infused with maltenes/bitumen at appropriate temperature and pressure. It was observed from the results that the tensile values was higher in the product with the Silsheet (from new compound) as compared to the one which had only DRC. The elongation was more than twice and in-fact higher than the normal Silsheet obtained from tread compounds.

Table 7 shows the difference in properties at higher percentages of addition of conventional reclaim, crumb rubber, Levgum and Silsheet. As depicted from the results, best physical properties were achieved with Silsheet added batches. Table 8 provides for the comparison of physical properties of Sil Sheet (28% addition of Sil Sheet) versus the Control Batch (7.5% DRC). As evidenced from the table, the new product had acceptable tensile and other physical properties even up to 28% addition in the master batches. This is a major deviation from the traditional range which is around 5% to 7%. Table 9 provides for the performance of compound containing 70% Silsheet and 30% Virgin Compound. The 70% addition of the new product showed considerable drop in tensile and other properties.

Table 10 provides for the performance of tyres manufactured from 70% Silsheet. The samples with 70% addition of the new product performed equal to the control compound of 15% DRC additions due to the lower heat build up

Table 11 provides the result of rebound resilience Test for various types of Silsheet (differs in the amount of Silsheet added) and DRC. The hysteresis loss is inversely proportional to the percent rebound measured. The percentage rebound can be measured using the rebound pendulum. Rebound resilience is determined by a freely falling pendulum hammer that is dropped from a given height . The pendulum hammer impacts a test specimen and imparts to it a certain amount of energy. A portion of that energy is returned by the specimen to the pendulum and is measured by the extent to which the pendulum rebounds, whereby the restoring force is determined by gravity. As evidenced from Table 10, it was observed that the 70%) Silsheet had a high percent rebound, thereby indicating that the Silsheet had low hysteresis loss

Table 12 provides for comparison of temperature profile between Control Tyre and tyres manufactured from 70% Silsheet. The temperature profiles were similar between Control tyres and tyres with 70%) loading of Silsheet due to lower hysteresis loss.

Patent Mechanism The interaction between rubber and maltenes results in a gel like structure at the interface. The swelling of the rubber is due to the migration of lower fraction oils, which is attributed as the main form of interaction to form a gel like structure. The gel like structure at the interface helps in improving binding properties. The main change in the composite system bitumen -rubber is the swelling of rubber due to the migration of lighter fractions of bitumen through the cross- linked polymeric network. The maltene gel gets embedded with the rubber- carbon black gel of the DRC, the hydrocarbon (elastomer) bonds are not broken during the devulcanization. The two gels mix under the pressure of the rolling mill to create a more uniform gel mixture. The resultant product is viscous and sticky in nature, lending itself for a variety of sizes and shapes and forms.

The DRC strands are in a highly reactive stage due to the severed sulphur bonds and presence of electron cloud. The migration of lower fraction oil enables swelling at the surface as depicted in Figure 1 and a total dissolution of matrix in some areas, thereby shortening the length of the elastomeric strand. The maltenes/bitumen also has an effect to short circuit the electron cloud. This results in better physical properties and the effect is increased when the interaction and infusion between the maltenes and DRC is intensified by squeezing it between rollers for more amount of time. The mechanical and frictional effect increases the temperature which aids the lighter fractions to penetrate the thin strands. From the result as depicted in Table.l, it was observed that 30 min of rolling the sheets leads to optimal infusion of maltenes with DRC. The tensile strength reaches optimum levels by the 30^th minute after which the tensile strength kind of plateaus off. Another test was also conducted on the sample sheet (18 phr Sil Sheet) and the hardness, specific gravity, Abrasion , modulus, tensile strength and Elongation Break were measured at the 10^th min, 20^th min and 28^th min. The test results have been provided in Table 2. The lubricity created at the surface of the strands improves flow properties and "resinous" nature of certain constituents in the maltenes help the strands to adapt to any form, shape or size. Another interesting hypothesis is that the randomly placed DRC strands held in an electro-static grid-lock, is oriented in a specific direction during the sheeting process apart from the charged bodies which are grounded. This orientation can be advantageously used in lowering the viscosity and hence increasing the mobility of this product into the matrix of rubber compounds.

As observed from Table 3, the physical characteristics like Tensile, Elongation, and Modulus in the new sil compound were found to be far superior to those of other conventional reclaimed products as listed therein including the proprietary de vulcanised Levgum product. In addition, other tests to determine the change in Rheo and flex properties were also conducted. As evidenced from Table 4, it is observed that there is almost a 32% drop in minimum torque when silsheet of the same percentage (7%) is used in comparison to DRC. Minimum torque is the indicator of flow ability of the product. It also indicates increased resistance to mixing and increased viscosity. Table 5 indicates that silsheet is a more flexible product than the super fine reclaim rubber and high tensile reclaim rubber. Abrasion test indicates wear loss of the product. It is evident from Table 5 that the silsheet wear rate is lower than that of the other products.

A comparison study was also conducted between DRC and DRC infused with maltenes/bitumen i.e. "sil" compound at appropriate temperature and pressure. It was observed from the results as provided in Table 6 that the tensile values was higher in the product with the Silsheet (from new compound) as compared to the one which had only DRC. The elongation was more than twice and in-fact higher than the normal Silsheet obtained from tread compounds. In order to check the efficacy of the new product the percentage inclusion of this new product was continuously increased. Table 7 shows the difference in properties at higher percentages of addition of conventional reclaim, crumb rubber, Levgum and Silsheet. As depicted from the Table 7, best physical properties were achieved with silsheet added batches. As evidenced from Table 8, the new product had acceptable tensile and other physical properties even up to 28% addition in the master batches. This is a major deviation from the traditional range which is around 5%-7%.

The trials were conducted up to 70% addition of the product .It was observed, as evidenced from Table 9 , that the 70% addition of the new product showed considerable drop in tensile and other properties. However, when the improved de vulcanized reclaimed rubber is loaded in high levels, it resulted in two important phenomena: increase in stiffness and damping factor or lack of resilience at room temperature and reduction in heat build up at high temperature due to higher speeds of operation. This behaviour is in contrast to that of traditional rubber or tread master batches. The above said phenomena facilitate the tyres to run quieter at low speed and have less heat build up at high speeds. Thus, as evidenced from Table 10, the samples with 70% addition of the new product performed equal to the control compound of 15% DRC additions due to the lower heat build up. This important observation noticed in this product was confirmed when tested on tyre drum test for solid tyres with 'new product' it was found that under similar conditions of tests, the heat build up in the solid tyres were 130°C in the layers between the core and the tread of the tyres. In the normally used compounds it went as high as 150°C. This very important property could be a reason for the tyres performing so well in real road conditions even though the tensile properties and other physical properties were lower than the standard accepted requirement.

Another significant feature of this invention is that the present invention resulted in low hysteresis loss . This is due to the linking of maltenes/bitumen to the reinforcing resins, thereby reducing the levels of carbon black or silica in the rubber product. Low level of carbon black leads to reduction in hysteresis loss. The hysteresis loss is inversely proportional to the percent rebound measured. The percentage rebound can be measured using the rebound pendulum. Rebound resilience is determined by a freely falling pendulum hammer that is dropped from a given height . The pendulum hammer impacts a test specimen and imparts to it a certain amount of energy. A portion of that energy is returned by the specimen to the pendulum and is measured by the extent to which the pendulum rebounds, whereby the restoring force is determined by gravity. As evidenced from Table 11, it was observed that the 70% silsheet had a high percent rebound, thereby indicating that the Silsheet had low hysteresis loss. Due to lower hysteresis loss it was observed that, as depicted from Table 12, that the temperature profiles were similar between Control tyres and tyres with 70% loading of silsheet. The tire industry in particular has well documented data that the high hysteresis and high heat build up in tyres is the primary reason for destruction of the tyres. Thus, the properties of low hysteresis and low heat build up help in extending the life period of tyres

Although embodiments of this invention have been shown and described, it is to be understood that various modification and substitutions, can be made by those skilled in the art without departing from the novel spirit and scope of the invention.

Claims

We claim:

1 . A process for a compound of devulcanised rubber comprising of devulcanised rubber enhanced by maltenes/bitumen; the said compound characterised by improved rheological properties; obtained by adding maltenes/bitumen to devulcanised reclaimed rubber in a pre-determined proportion; melting the maltenes/bitumen between 30-80° C temperature; passing the mixture through nip refiners; at near ambient temperature, under a minimum of 25kg/cm pressure; repeatedly re-rolling the calendared sheets under the same pressure and temperature for half an hour; the repeated mechanical process resulting in short circuit of the electron cloud resulting in a mechanical effect as well as a frictional effect, thereby increasing the temperature; aiding the maltenes to penetrate the thin strands; embedding the maltenes in the rubber-carbon gel without breaking the hydrocarbon bonds; the migration of the lower fraction oils enabling the swelling at the surface and total dissolution of the matrix in some areas thereby shortening the length of the elastomeric strand; cleaving the long elastomer strands; the resinous nature of certain constituents in the maltenes/bitumen resulting in enabling the strands to stick together to form continuous sheets; thereby improving miscibility of the end product in the rubber compounds; the increased lubricity resulting in better flow properties; resulting in viscous, sticky in nature thin sheets of improved rheological properties such as better modulus, elongation, tensile strength, better flow properties, excellent abrasion resistance, low hysteresis loss occurring due to the difference in the self-resonance frequencies of the two gels mixtures, aiding in the relaxing the vibration frequencies thereby resulting in low heat build-up; the said low heat build-up being futher contributed by the plastic nature of the maltenes themselves; an increased stiffness and increased damping factor; lack of resilience at room temperature; reduction in heat build-up at high temperatures due to high speeds of operation; the low hysteresis loss and low heat build-up resulting in low noise factor at low speeds and less heat build-up at high speeds and an increased life for the improved devulcanised rubber compound; the said devulcanised rubber capable of being used by itself or along with other master batch compounds in all conventional applications of reclaimed rubber; the said process being a predominantly physical process which produces no hazardous waste as no dangerous chemicals are involved being environmentally friendly: the said process leading to direct enhanced life of the devulcanised rubber leading to lowering of costs; such costs being further lowered due to the low cost of raw materials, thereby leading to direct economic advantage.

2. A devulcanised rubber compound as claimed in Claim 1.

3. The predetermined ratio of devulcanised reclaimed rubber to maltenes/Bitumen as claimed in Claim 1 is 75 to 90 parts to 25 to 10 parts.

4. The tensile strength as claimed in claim 1 reaches optimum levels in the 30^th minute after which the tensile strength plateaus off.

5. The modulus as claimed in Claim 1 increases by 10% to 12% as compared to control compound.

6. The elongation as claimed in Claim 1 is around 240% - 260%.

7. The better flow properties as claimed in Claim 1 is indicated by lower initial and minimum torque (in Rheo meter) of the control compound as compared to test compound.

8. The tensile strength as claimed in Claim 1 is a minimum of 83 kgs /cm .

9. The excellent abrasion resistance as claimed in Claim 1 is 208/210/mm for the devulcanised rubber as compared to 250/256 mm for HT.

10. The low hysteresis loss as claimed in Claim 1 is due to the better stiffness and is evidenced by lower heat build-up oh the Drum test, where a 20°C difference in temperature inside of test (solid) tyres as compared to control compound.

11. The low heat build-up and low hysteresis results in an enhanced life of the improved devulcanised rubber in terms of higher performance over other conventionally used reclaimed rubber products, thus directly resulting in economic advantage as well as being environmentally friendly.

12. The devulcanised rubber compound as claimed in any one of the preceding claims.

13. The devulcanised rubber compound as substantially described herein with reference to accompanying drawings and tables.