WO2023286072A1 - Rubber composition with waste / recycled rubber material in rubber compound and method thereof - Google Patents

Rubber composition with waste / recycled rubber material in rubber compound and method thereof Download PDF

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Publication number
WO2023286072A1
WO2023286072A1 PCT/IN2022/050130 IN2022050130W WO2023286072A1 WO 2023286072 A1 WO2023286072 A1 WO 2023286072A1 IN 2022050130 W IN2022050130 W IN 2022050130W WO 2023286072 A1 WO2023286072 A1 WO 2023286072A1
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Prior art keywords
rubber
tyre
minutes
rubber composition
compound
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PCT/IN2022/050130
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French (fr)
Inventor
Balu ANANDA BABU
Kadambanathan THIAGARAJAN
Viswanathan Sivaramakrishnan
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Tvs Srichakra Limited
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Publication of WO2023286072A1 publication Critical patent/WO2023286072A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60C—VEHICLE TYRES; TYRE INFLATION; TYRE CHANGING; CONNECTING VALVES TO INFLATABLE ELASTIC BODIES IN GENERAL; DEVICES OR ARRANGEMENTS RELATED TO TYRES
    • B60C1/00—Tyres characterised by the chemical composition or the physical arrangement or mixture of the composition
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/06—Sulfur
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/04—Oxygen-containing compounds
    • C08K5/09—Carboxylic acids; Metal salts thereof; Anhydrides thereof
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K5/00—Use of organic ingredients
    • C08K5/36—Sulfur-, selenium-, or tellurium-containing compounds
    • C08K5/45—Heterocyclic compounds having sulfur in the ring
    • C08K5/46—Heterocyclic compounds having sulfur in the ring with oxygen or nitrogen in the ring
    • C08K5/47—Thiazoles
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L17/00—Compositions of reclaimed rubber
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
    • C08K3/20—Oxides; Hydroxides
    • C08K3/22—Oxides; Hydroxides of metals
    • C08K2003/2296—Oxides; Hydroxides of metals of zinc
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/04—Carbon
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L2207/00—Properties characterising the ingredient of the composition
    • C08L2207/20—Recycled plastic
    • C08L2207/24—Recycled plastic recycling of old tyres and caoutchouc and addition of caoutchouc particles
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

  • the present invention relates to the field of rubber compositions with higher proportion of waste/recycled rubber material in rubber compound. More particularly, the present invention relates to a rubber composition with higher dosage of whole tyre reclaimed rubber provide Mooney scorch time values ranging from 4.5 minutes to 11.0 minutes which provides, better polymer-filler interaction, lower rolling resistance and consistent physical properties of rubber vulcanizate.
  • US20170114155 relates to rubber formulations and a method for manufacturing a chemically functionalized, renewed rubber composition
  • a method for manufacturing a chemically functionalized, renewed rubber composition comprising the steps of blending a micronized rubber powder with a processing aid and a chemical functionalizing agent to produce a blended mixture; processing the blended mixture under conditions of high shear and low temperature to produce a reacted mixture; adding a stabilizer to the reacted mixture to produce the chemically functionalized renewed rubber composition.
  • US2010009152A1 relates to the methods comprising forming mixtures by (i) treating an aqueous thermoplastic acrylic or vinyl polymer to increase the particle size thereof to a weight average particle size of 1 mum or more, and, optionally, dewatering to form a crumb mixture; and (ii) combining a thermoplastic acrylic or vinyl polymer with one or more waste rubber vulcanizate having a sieve particle size ranging from 10 to 600 mum in the amount of from 15 to 95 wt. %, based on the total weight of polymer and rubber to form a crumb slurry.
  • IN 201817009564 relates to a rubber composition for tire tread which even when adding a large amount of recycled rubber can suppress reduction in abrasion resistance and to provide a tire that uses said rubber composition.
  • This rubber composition for tire tread is characterized by containing 30-60 parts by mass of recycled rubber and 3.5 parts by mass or more of zinc oxide per 100 parts by mass of a rubber component comprising at least one rubber selected from the group consisting of a natural rubber and a synthetic rubber.
  • the present invention aims to provide a method of for selection of whole tyre reclaim for higher dose usage in rubber composition and to obtain optimum properties of rubber vulcanizate.
  • the principal object of the present invention is to provide a rubber composition containing higher proportion of whole tyre reclaim or waste/ recycled rubber material that provide Mooney scorch time values ranging from 4.5 minutes to 11 minutes.
  • Another object of the invention is identification of a Mooney scorch time as the appropriate pre vulcanization characteristic to select or choose a whole tyre reclaim, which when used in composition for tyre provides optimum properties to the rubber vulcanizate.
  • Another object of the invention is Mooney scorch time (pre-vulcanization characteristics) as a test method to select the whole tyre reclaims to obtain optimum physical properties of the rubber vulcanizate.
  • Yet another object of the invention is to provide a rubber composition containing higher whole tyre reclaim (WTR) wherein the Mooney scorch time values of the WTR used range from 4.5 to 11/8 minutes is to provide better rubber filler interaction.
  • WTR whole tyre reclaim
  • Yet another object of the invention is rubber composition containing whole tyre reclaim provides Mooney scorch time value ranging from 4.5 to 11/8 minutes is to provide lower rolling resistance of tyre. It is another object of the present invention to provide a rubber composition having higher dosage of whole tyre reclaim or waste/recycled rubber material mixed in rubber compound.
  • It is another object of the present invention is to provide the consistent rubber composition containing higher proportion of Whole Tyre Reclaim with Mooney Scorch time values ranging from 4.5 minutes to 11.0. It is another object of the present invention, wherein the whole tyre reclaim rubber is manufactured by known polymer composition having glass transition temperature (T g ) in the range of -65°C to -45°C.
  • composition for tyre, wherein the composition comprises components selected from
  • Cure accelerators - 0.6 PHR; and Cross-linking agent - 3 PHR Cure accelerators - 0.6 PHR; and Cross-linking agent - 3 PHR.
  • the present invention relates to the method of selection of Whole Tyre Reclaim (WTR) to allow for higher proportion whole tyre reclaim usage in rubber composition to provide an optimum property of the rubber vulcanizate.
  • WTR Whole Tyre Reclaim
  • Mooney scorch time is an important cure characteristic for the selection of whole tyre reclaims types.
  • One object of the present invention is to increase the quantity of WTR in rubber composition for the reasons: It is economic. Reclaim-added compounds are much cheaper. Even in a high-quality compound, reclaimed rubber if used in judicious proportions can give considerable savings. Ease of processability in the mixing mill, extruder, calendar, frictioning, and skim coating operations. Reclaimed rubber is uniform and is compatible with most accelerators, and has a retarding effect on Vulcanization.
  • Faster curing compounds can be made with reclaimed rubber. It also addresses the problem of enormous scrap tyres that create major environmental and recycling solutions.
  • the present invention aimed and achieved a solution to a long-standing problem in the Tyre Rubber Industry of recycling and reusing Whole Tyre Reclaim. It has both environmental advantages, economical and also provided good quality Tyre Rubber Composition.
  • Embodiments of the present invention provide rubber compositions containing higher proportion of whole tyre reclaim or waste / recycled rubber material mixed in rubber compound need to provide consistently higher Mooney scorch time values ranging from 4.5 minutes to 11.0 minutes.
  • This invention also relates to the rubber composition that provides better polymer-filler interaction, lower rolling resistance and consistent physical properties of rubber vulcanizate.
  • the present invention is aimed at providing a rubber composition with high concentration of WTR.
  • Embodiments of the present invention relates to a method of selection of Whole Tyre Reclaim or WTR to allow for higher proportion whole tyre reclaim usage in rubber composition to provide an optimum property of the rubber vulcanizate. SELECTION OF WTR’s.
  • Mooney scorch time is an important cure characteristic for the selection of whole tyre reclaims types.
  • the rubber compositions were prepared by four different WTR’s and tested for various properties (Table 1) which comprised the preliminary characterization or analysis.
  • WTR Wood's trademark for Rubber
  • Table 2 The four types of WTR’s chosen were then formulated as compositions comprising activator, softener and filler, Mercaptobenzothiazole accelerator, and cross-linking agent, as provided in Table 2 below. Further, Tyre rubber compositions containing higher proportion of whole tyre reclaim or waste / recycled rubber material mixed in rubber compound were studied and the results indicated that rubber compositions with consistently higher Mooney scorch time values ranging from 4.5 minutes to 11.0, with preferred range is 4.5-8.0 minutes provide optimum tyre rubber properties. This invention also relates to the rubber composition that provides better polymer-filler interaction, low rolling resistance and consistent physical properties of rubber vulcanizate.
  • the invention discloses a method of choosing or selection of WTR by study of WTR properties.
  • the exemplary embodiment of the present invention discloses 4 types of WTR labelled as Type 1 , 2, 3, 4 procured from the market available WTR’s.
  • These sample WTR’s are studies for their WTR properties selected from Volatile Content, Mooney Viscosity, and TGA decomposition data of the selected WTR’s, for example T g °C (by DSC), State of Cure/Curing Temp (°C), Thermal Heat Capacity, J/g, Total Sulphur Content, %.
  • T g °C by DSC
  • State of Cure/Curing Temp °C
  • Thermal Heat Capacity J/g
  • Total Sulphur Content %.
  • Volatile content It determines the percentage of volatile (at 105°C) constituents of Reclaim rubber in accordance with IS 6306.
  • Mooney viscosity The determination of Mooney viscosity of reclaimed rubber by shearing disk viscometer in accordance with ASTM D1646.
  • Thermogravimetric Analyzer (TGA): Thermogravimetric analysis carried out in accordance with ASTM E 1131 & ISO 11358. Differential Scanning Calorimetry: The measurement carried out in accordance with ASTM D 3418 - 15.
  • Total Sulphur content It is measured in accordance with ASTM D 3418. Results of the tests performed on Type 1, 2, 3, 4 are provided in Table 1 below.
  • Example 1 Four Samples of different and random WTR’s are taken and subjected to characterization to study the properties.
  • Table- 1 Whole Tyre Reclaim Properties After the WTR’s (Type 1, 2, 3 and 4) are studied WTR based compositions were prepared and details of the composition is provided in Table 2. The compounds are further analyzed for various physical parameters (Table 3) ANALYSIS OF WHOLE TYRE RECLAIM IN STANDARD FORMULATION (TABLE 2, 3):
  • the property of Whole tyre reclaim rubber can be best assessed through compound properties.
  • the method comprises formulation of a standard rubber composition with the four types of WTR. This method allows further assessment of the effect of WTR type on the tyre properties.
  • the quality of the Reclaimed Rubber can be determined by compounding of Whole tyre Reclaimed Rubber, and testing of Physical properties which were carried out by standard procedures set out as per RR:8 of IS 6306 - Reclaimed Rubber Specification IS 7490).
  • 5- Sulphur is from Standard Chemicals - India. Rubber grade Sulfur is a widely used as a cross linking agent between the rubber chains in the vulcanization process.
  • Table-3 Whole Tyre Reclaim Rubber Compound to determine physical properties as per IS: 6306
  • Table 2 & 3 discloses the 4 different rubber compositions, each with 200 PHR of Type 1 WTR, Type 2, Type 3 and Type 4 WTR.
  • the compositions are subjected to physical testing to evaluate TGA Decomposition (%), Tg (by DSC), State of Cure/Curing Temp, °C, Thermal Heat Capacity, J/g, Mooney Scorch @ 125°C MV, MU
  • Mooney Scorch time @ 125°C It is measured in accordance with ASTM D 1646 Table 3 represents the comparison results of Type 1 compound Mooney scorch value: t5 value: 3.37 - very low & Type 2, 3 & 4 compound Mooney scorch t5 values are 4.29, 5.75 & 7.32 respectively.
  • t5 value indicates the pre-vulcanization tendency of the compound. Higher scorch time indicates lower pre-vulcanization tendency. The higher Scorch time t5 trial 2, 3 & 4 showed lower the pre-vulcanization tendency, and, therefore, the rubber compound can be more reliably processed on mill, calendar or extruder. Therefore, the compounds Types 2, 3, 4 are better according to the results above.
  • a compound with a lower Mooney Scorch time values (Type 1) cures more rapidly than a compound with a higher scorch time. It is observed that higher scorch time -based compound samples gave improved tensile strength and elongation at break as compared to lower scorch time- based compound Type 1.
  • DMA Properties Dynamic mechanical properties are carried out in accordance with ASTM D 5279. In general, Tan delta at 60°C refers to the rolling resistance of the compound (lower is better). From the data, it is clearly observed that the higher scorch time base compound compounds provide lower rolling resistance as compared with the lower scorch time -based compound Type 1.
  • the above inference was verified with typical factory-based formulation as below in Table 4.
  • the scope of the present invention is characterized by the Factory Rubber composition comprising of higher dosage of reclaim rubber - 120 parts per 100 parts of rubber component selected from one of natural rubber and synthetic rubber, Activators - 2 parts; Softeners / filler dispersing agent - 1.5 parts; Cure accelerators - 0.6 parts; and Cross-linking agent - 3 parts.
  • Rubber compositions are prepared based on standard Factory formula as illustrated in Table 4.
  • the activators are selected from zinc oxide; softeners/ filler dispersing agent are selected from stearic acid; cure accelerators are selected from Mercaptobenzothiazole; crosslinking agent is selected from sulphur.
  • the preparation method is carried out using Two Roll Mixing Mill (Make: Shaw). masticating of Natural rubber and whole tyre reclaim rubber for 1 minute to obtain 10mm to 12mm thickness; closing mill nip to obtain uniform thickness of around 5.0 mm - 7.0 mm; pre -blending of chemicals such as zinc oxide and stearic acid, MBTS and sulphur;
  • Table-5 Thermal Properties of Factory Based Formulations Table 5 shows the comparison results of factory-based formulations on TGA composition, Glass Transition temperature (Tg), State of cure, Thermal Heat capacity.
  • Table-6 shows the comparison results of Type A compound Mooney scorch value: below 4.5 Minutes (T5 value: 4.05) & Type B, C & D compound Mooney scorch value above 4.5 minutes t5 value: 4.56, 6.02 & 7.58).
  • t5 value indicates the pre-vulcanization tendency of the compound. The larger t5 (Type B, C & D) is, the lower the pre-vulcanization tendency, and, therefore, the rubber compound can be more reliably processed on mill, calendar or extruder.
  • Vulcanization time (t35) the time interval (measured from rotor start) corresponding to a viscosity increase of 35 units over the MV value.
  • Vulcanization index - DT30 t35 — 15; provides indications about the vulcanizing ability of a rubber compound.
  • a compound with a low vulcanization index (Type B, C & D), has high cure rate than a compound with a higher vulcanization index (Type A).
  • ODR Oscillating Disc Rheometer
  • tS2 Compound scorch time
  • t9o Optimum time of vulcanization
  • Table-7 Polymer -filler Interaction (Payne effect) Better polymer-filler interaction (Payne effect) will lead to better physical properties.
  • the polymer- filler interaction results are compared with each other.
  • G ’difference (kPa) lower the value better the polymer-filler interactions.
  • Table 7 shows the comparison results of Payne effect difference for Type A, B, C & D.
  • the Payne effect, G' difference (kPa) for Type B, C & D results are substantially lower than Type A indicating improved polymer-filler interaction in trials having reclaim scorch time of minimum 4.5 minutes. It also reflected in improved 300% modulus (Table-8).
  • the physical properties results are compared with each other comparison results of physical properties for Type A, B, C and D.
  • Type B, C, and D has improved tensile strength, modulus values, elongation at break as compared to lower scorch time -based compound Type A.
  • the rubber composition provides consistent physical properties of the rubber vulcanizate, when the Mooney scorch time value ranging from 4.5 minutes to 11 minutes, preferably range is from 4.5 to 8 minutes and above (Type B, C and D). Higher the scorch time better the physical properties of the rubber vulcanizate ⁇ Table-9: DMA Properties
  • Tan delta at 60°C refers to the rolling resistance of the compound (lower is better). From the data, it is clearly observed that the Type B, C & D compounds have lower rolling resistance as compared with the Type A compound.

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Abstract

The present invention relates to the field of rubber compositions with higher proportion of waste/recycled rubber material in rubber compound. More particularly, the present invention relates to a rubber composition comprising higher dosage of Whole Tyre Reclaimed rubber (WTR) with Mooney Scorch time values ranging from 4.5 minutes to 11.0 minutes which provides better polymer-filler interaction, lower rolling resistance and consistent physical properties of rubber vulcanizate. Additionally, the invention relates to method of selection of WTR based on Mooney Scorch time for providing rubber compositions with improved processability. Advantageously the invention relates to use of WTR for environmental and economical benefit.

Description

RUBBER COMPOSITION WITH WASTE / RECYCLED RUBBER MATERIAL IN RUBBER COMPOUND AND METHOD THEREOF
FIELD OF THE INVENTION
The present invention relates to the field of rubber compositions with higher proportion of waste/recycled rubber material in rubber compound. More particularly, the present invention relates to a rubber composition with higher dosage of whole tyre reclaimed rubber provide Mooney scorch time values ranging from 4.5 minutes to 11.0 minutes which provides, better polymer-filler interaction, lower rolling resistance and consistent physical properties of rubber vulcanizate.
BACKGROUND OF THE INVENTION
Recycling of waste rubber products has been practiced since the beginning of 20th century. Recovering of polymer chain from used rubber products/whole tyre reclaim is achieved by cleaving the chemical bond in the vulcanized rubber by the process of Reclamation. Once rubber is retrieved from the used rubber, it has to be vulcanized again (re -vulcanized) to fit it into any application. The proportion of reclaimed rubber in the compound has certain limitation with respect to cure kinetics to achieve the desired physical properties and dynamic mechanical properties. Low Scorch is an issue observed during re-vulcanization and this is associated with reclaim rubber. The considerable reduction in scorch time of the reclaim sample during re-vulcanization is a common observation.
US20170114155 relates to rubber formulations and a method for manufacturing a chemically functionalized, renewed rubber composition comprising the steps of blending a micronized rubber powder with a processing aid and a chemical functionalizing agent to produce a blended mixture; processing the blended mixture under conditions of high shear and low temperature to produce a reacted mixture; adding a stabilizer to the reacted mixture to produce the chemically functionalized renewed rubber composition.
US2010009152A1 relates to the methods comprising forming mixtures by (i) treating an aqueous thermoplastic acrylic or vinyl polymer to increase the particle size thereof to a weight average particle size of 1 mum or more, and, optionally, dewatering to form a crumb mixture; and (ii) combining a thermoplastic acrylic or vinyl polymer with one or more waste rubber vulcanizate having a sieve particle size ranging from 10 to 600 mum in the amount of from 15 to 95 wt. %, based on the total weight of polymer and rubber to form a crumb slurry. IN 201817009564 relates to a rubber composition for tire tread which even when adding a large amount of recycled rubber can suppress reduction in abrasion resistance and to provide a tire that uses said rubber composition. This rubber composition for tire tread is characterized by containing 30-60 parts by mass of recycled rubber and 3.5 parts by mass or more of zinc oxide per 100 parts by mass of a rubber component comprising at least one rubber selected from the group consisting of a natural rubber and a synthetic rubber.
The above all publications do not mention about the usage of higher proportions of whole tyre reclaim or waste/recycled rubber material in rubber compositions.
Hence, the present invention aims to provide a method of for selection of whole tyre reclaim for higher dose usage in rubber composition and to obtain optimum properties of rubber vulcanizate.
OBJECTS OF THE INVENTION:
The principal object of the present invention is to provide a rubber composition containing higher proportion of whole tyre reclaim or waste/ recycled rubber material that provide Mooney scorch time values ranging from 4.5 minutes to 11 minutes.
Another object of the invention is identification of a Mooney scorch time as the appropriate pre vulcanization characteristic to select or choose a whole tyre reclaim, which when used in composition for tyre provides optimum properties to the rubber vulcanizate.
Another object of the invention is Mooney scorch time (pre-vulcanization characteristics) as a test method to select the whole tyre reclaims to obtain optimum physical properties of the rubber vulcanizate.
Yet another object of the invention is to provide a rubber composition containing higher whole tyre reclaim (WTR) wherein the Mooney scorch time values of the WTR used range from 4.5 to 11/8 minutes is to provide better rubber filler interaction.
Yet another object of the invention is rubber composition containing whole tyre reclaim provides Mooney scorch time value ranging from 4.5 to 11/8 minutes is to provide lower rolling resistance of tyre. It is another object of the present invention to provide a rubber composition having higher dosage of whole tyre reclaim or waste/recycled rubber material mixed in rubber compound.
It is another object of the present invention to provide effective utilization (higher dosage) of whole tyre reclaim or waste/recycled rubber in rubber compound mixing and also it provides safer processability through higher scorch safety.
It is another object of the present invention is to provide the consistent rubber composition containing higher proportion of Whole Tyre Reclaim with Mooney Scorch time values ranging from 4.5 minutes to 11.0. It is another object of the present invention, wherein the whole tyre reclaim rubber is manufactured by known polymer composition having glass transition temperature (Tg) in the range of -65°C to -45°C.
SUMMARY OF THE INVENTION
It is a primary aspect of the present invention to provide a rubber composition for tyre, comprising: one or more polymers; carbon black & inorganic fillers; one or more wax, antioxidants and oil materials; and one or more wax, antioxidants and oil materials, wherein the rubber composition contains higher proportion of whole tyre reclaim in the range of 120-200 PHR with Mooney Scorch time values ranging from 4.5 minutes to 11.0 minutes.
It is another aspect of the present invention to provide a rubber composition for tyre, wherein the whole tyre reclaim has a Mooney Scorch time of 4.5 minutes to 8 minutes.
It is another aspect of the present invention to provide a rubber composition for tyre, wherein the composition comprises components selected from
Natural Rubber and Synthetic Rubber - 0 - 40 parts;
Reclaimed rubber - 120 - 200 PHR;
Activators - 2 PHR;
Softeners / filler dispersing agent - 1.5 PHR;
Cure accelerators - 0.6 PHR; and Cross-linking agent - 3 PHR.
It is another aspect of the present invention to provide a rubber composition for tyre, wherein in the natural rubber activators is selected as zinc oxide.
It is another object of the present invention to provide a rubber composition for tyre, wherein the softeners / filler dispersing agent is selected as stearic acid.
It is another aspect of the present invention to provide a rubber composition for tyre, wherein the cure accelerators are selected as Mercaptobenzothiazole.
It is another object of the present invention to provide a rubber composition for tyre, wherein the cross-linking agent is selected as sulphur.
It is yet another object of the present invention to provide a method of preparing the rubber composition with high WTR, comprising steps selection of whole tyre reclaim of Mooney Scorch in the range of 4.5 minutes to 11 minutes; preparation of rubber tyre composition comprising masticating of Natural Rubber or Synthetic Rubber and Whole Tyre Reclaim rubber for 1 minute to obtain 10 mm to 12 mm thickness; closing mill nip to obtain uniform thickness of around 5.0 mm - 7.0 mm; pre-blending of chemicals such as zinc oxide and stearic acid, MBTS and Sulphur; forming band of Natural Rubber and reclaim rubber; mixing of the pre-blended zinc oxide and stearic acid on the band and rolling of compound; mixing of Sulphur, MBTS and rolling of compound; and mixing of compound for homogenous dispersion of chemicals for around 12 - 17 minutes, to yield the rubber composition, wherein the composition comprises of WTR in the range of 120-200 PHR.
DETAILED DESCRIPTION OF THE INVENTION.
The present invention relates to the method of selection of Whole Tyre Reclaim (WTR) to allow for higher proportion whole tyre reclaim usage in rubber composition to provide an optimum property of the rubber vulcanizate. Mooney scorch time is an important cure characteristic for the selection of whole tyre reclaims types. One object of the present invention is to increase the quantity of WTR in rubber composition for the reasons: It is economic. Reclaim-added compounds are much cheaper. Even in a high-quality compound, reclaimed rubber if used in judicious proportions can give considerable savings. Ease of processability in the mixing mill, extruder, calendar, frictioning, and skim coating operations. Reclaimed rubber is uniform and is compatible with most accelerators, and has a retarding effect on Vulcanization. Faster curing compounds can be made with reclaimed rubber. It also addresses the problem of enormous scrap tyres that create major environmental and recycling solutions. The present invention aimed and achieved a solution to a long-standing problem in the Tyre Rubber Industry of recycling and reusing Whole Tyre Reclaim. It has both environmental advantages, economical and also provided good quality Tyre Rubber Composition.
Embodiments of the present invention provide rubber compositions containing higher proportion of whole tyre reclaim or waste / recycled rubber material mixed in rubber compound need to provide consistently higher Mooney scorch time values ranging from 4.5 minutes to 11.0 minutes. This invention also relates to the rubber composition that provides better polymer-filler interaction, lower rolling resistance and consistent physical properties of rubber vulcanizate. The present invention is aimed at providing a rubber composition with high concentration of WTR.
Presently, it has been reported that only low dosage of reclaim has been used in rubber composition (up to 60 phr dosage). Higher dosage of reclaim leads to inconsistency in processability and Mooney characteristics. Hence, it is a challenge to develop rubber composition with higher dosage of reclaim rubber (above 100 phr dosage) that maintains or improves physical properties of the compound. However, if a higher dosage of WTR can be incorporated in the compound there is potential for high cost savings. Apart from the cost effectiveness, usage of higher dosage of WTR leads to better recycling of scrap/waste tyres and reduces carbon load in the environment.
Embodiments of the present invention relates to a method of selection of Whole Tyre Reclaim or WTR to allow for higher proportion whole tyre reclaim usage in rubber composition to provide an optimum property of the rubber vulcanizate. SELECTION OF WTR’s.
Mooney scorch time is an important cure characteristic for the selection of whole tyre reclaims types. The rubber compositions were prepared by four different WTR’s and tested for various properties (Table 1) which comprised the preliminary characterization or analysis.
The four types of WTR’s chosen were then formulated as compositions comprising activator, softener and filler, Mercaptobenzothiazole accelerator, and cross-linking agent, as provided in Table 2 below. Further, Tyre rubber compositions containing higher proportion of whole tyre reclaim or waste / recycled rubber material mixed in rubber compound were studied and the results indicated that rubber compositions with consistently higher Mooney scorch time values ranging from 4.5 minutes to 11.0, with preferred range is 4.5-8.0 minutes provide optimum tyre rubber properties. This invention also relates to the rubber composition that provides better polymer-filler interaction, low rolling resistance and consistent physical properties of rubber vulcanizate.
To select the whole tyre reclaim or WTR, the invention discloses a method of choosing or selection of WTR by study of WTR properties.
The exemplary embodiment of the present invention discloses 4 types of WTR labelled as Type 1 , 2, 3, 4 procured from the market available WTR’s. These sample WTR’s are studies for their WTR properties selected from Volatile Content, Mooney Viscosity, and TGA decomposition data of the selected WTR’s, for example Tg °C (by DSC), State of Cure/Curing Temp (°C), Thermal Heat Capacity, J/g, Total Sulphur Content, %. The results are depicted in Table 1.
Method: Samples of WTR type 1, 2, 3, 4 are subject to analysis of the parameters provided below to choose the WTR. (Table 1).
The following parameters were chosen to represent the whole tyre reclaim samples:
Volatile content: It determines the percentage of volatile (at 105°C) constituents of Reclaim rubber in accordance with IS 6306.
Mooney viscosity (MV): The determination of Mooney viscosity of reclaimed rubber by shearing disk viscometer in accordance with ASTM D1646.
Thermogravimetric Analyzer (TGA): Thermogravimetric analysis carried out in accordance with ASTM E 1131 & ISO 11358. Differential Scanning Calorimetry: The measurement carried out in accordance with ASTM D 3418 - 15.
State of Cure/Curing Temp: Higher State of Cure / Curing temperature will exhibit better scorch safety. Thermal Heat capacity: Vulcanization reactions are Exothermic reactions exhibit negative enthalpy in DSC curves. Negative enthalpy indicates that higher degree of crosslinking, require more heat as well as having better scorch safety.
Total Sulphur content: It is measured in accordance with ASTM D 3418. Results of the tests performed on Type 1, 2, 3, 4 are provided in Table 1 below.
Whole tyre reclaims rubber samples Type 1, 2, 3 & 4 taken for complete characterization according to Table 1.
Example 1: Four Samples of different and random WTR’s are taken and subjected to characterization to study the properties.
Table- 1: Whole Tyre Reclaim Properties
Figure imgf000008_0001
After the WTR’s (Type 1, 2, 3 and 4) are studied WTR based compositions were prepared and details of the composition is provided in Table 2. The compounds are further analyzed for various physical parameters (Table 3) ANALYSIS OF WHOLE TYRE RECLAIM IN STANDARD FORMULATION (TABLE 2, 3):
The property of Whole tyre reclaim rubber can be best assessed through compound properties. The method comprises formulation of a standard rubber composition with the four types of WTR. This method allows further assessment of the effect of WTR type on the tyre properties. The quality of the Reclaimed Rubber can be determined by compounding of Whole tyre Reclaimed Rubber, and testing of Physical properties which were carried out by standard procedures set out as per RR:8 of IS 6306 - Reclaimed Rubber Specification IS 7490).
Compounding Ingredients: Whole tyre reclaim rubber - SF (100 parts by mass as Rubber Hydrocarbon), Zinc oxide (activator), Stearic acid (filler and dispersing agent), MBTS (accelerator) and Sulphur (cross linking agent). The standard formulation comprises of a 200 PHR of WTR Reclaim, activator- 2 PHR, softener and a filler dispersing agent within rubber compounds 1.5 PHR, Sulfur as a cross linking agent between the rubber chains in the vulcanization process (3 PHR), MBTS or Mercaptobenzothiazole (0.6 PHR)
Table: 2-Whole Tyre Reclaim Rubber Compound Standard Formulation
Figure imgf000009_0001
1 - WTR Reclaim SF types from Balaji Rubber Industries, Salem, India
2 - Zinc Oxide from Pondy Oxides & chemicals Ltd, Chennai, India. It acts as an activator.
3 - Stearic acid from Godrej Industries - India. It acts as a softener and a filler dispersing agent within rubber compounds 4 - MBTS (Mercaptobenzothiazole) from Nocil - India acts as a medium-fast cure accelerator.
5- Sulphur is from Standard Chemicals - India. Rubber grade Sulfur is a widely used as a cross linking agent between the rubber chains in the vulcanization process.
The WTR based rubber compositions were analyzed for standard physical properties as per IS:6306. The results are displayed in Table 3 below.
Table-3: Whole Tyre Reclaim Rubber Compound to determine physical properties as per IS: 6306
Figure imgf000010_0001
Figure imgf000011_0001
** Mooney scorch t5
The compound ingredients along with supplier details (Type 1, 2, 3 & 4) & Whole Tyre Reclaim Rubber compound to determine the physical properties as per IS STD 6306 results are shown in
Table 2 & 3 respectively. Table 2 discloses the 4 different rubber compositions, each with 200 PHR of Type 1 WTR, Type 2, Type 3 and Type 4 WTR. The compositions are subjected to physical testing to evaluate TGA Decomposition (%), Tg (by DSC), State of Cure/Curing Temp, °C, Thermal Heat Capacity, J/g, Mooney Scorch @ 125°C MV, MU
Mooney Scorch time @ 125°C: It is measured in accordance with ASTM D 1646 Table 3 represents the comparison results of Type 1 compound Mooney scorch value: t5 value: 3.37 - very low & Type 2, 3 & 4 compound Mooney scorch t5 values are 4.29, 5.75 & 7.32 respectively.
State of Cure/Curing Temp: It is observed that the higher State of Cure / Curing temperature of compound exhibit better scorch safety.
Thermal Heat capacity: It is observed that higher scorch time -based compound sample exhibit Negative enthalpy indicates higher degree of crosslinking. Physical properties were measured in accordance with ASTM D 412. The test results with Type 1, 2, 3 & 4 are compared with each other.
Rheological properties @ 160°C in ODR (Oscillating Disk Rheometer): for Type 1, 2, 3 & 4 compound tS2 (Compound scorch time) & t90 (Optimum time of vulcanization) results are Type 1 tS2 & t90 values are lower than other compounds indicating more consistent cure kinetics and earlier vulcanization characteristics.
In general, t5 value indicates the pre-vulcanization tendency of the compound. Higher scorch time indicates lower pre-vulcanization tendency. The higher Scorch time t5 trial 2, 3 & 4 showed lower the pre-vulcanization tendency, and, therefore, the rubber compound can be more reliably processed on mill, calendar or extruder. Therefore, the compounds Types 2, 3, 4 are better according to the results above.
A compound with a lower Mooney Scorch time values (Type 1), cures more rapidly than a compound with a higher scorch time. It is observed that higher scorch time -based compound samples gave improved tensile strength and elongation at break as compared to lower scorch time- based compound Type 1.
DMA Properties: Dynamic mechanical properties are carried out in accordance with ASTM D 5279. In general, Tan delta at 60°C refers to the rolling resistance of the compound (lower is better). From the data, it is clearly observed that the higher scorch time base compound compounds provide lower rolling resistance as compared with the lower scorch time -based compound Type 1.
Based on the above comparison with IS: 6306 formulations it can be inferred that compounds with higher scorch time exhibit better properties with respect to Tensile strength, Elongation at Break, Dynamic properties etc.
The above inference was verified with typical factory-based formulation as below in Table 4. The scope of the present invention is characterized by the Factory Rubber composition comprising of higher dosage of reclaim rubber - 120 parts per 100 parts of rubber component selected from one of natural rubber and synthetic rubber, Activators - 2 parts; Softeners / filler dispersing agent - 1.5 parts; Cure accelerators - 0.6 parts; and Cross-linking agent - 3 parts.
Rubber compositions are prepared based on standard Factory formula as illustrated in Table 4.
Table 4 - Factory Based Formulation:
Figure imgf000012_0001
Figure imgf000013_0001
1 - RSS 5 Natural Rubber from RI international Pvt Ltd, Cochin, India.
2 - WTR Reclaim SF types from Balaji Rubber Industries, Salem, India.
3 - Zinc Oxide from Pondy Oxides & chemicals Ltd, Chennai, India.
4 -Stearic acid from Godrej Industries. India.
5 - MBTS (Mercaptobenzothiazole) from Nocil, India.
6- Sulphur is from Standard Chemicals. India.
According to an embodiment of the present invention the activators are selected from zinc oxide; softeners/ filler dispersing agent are selected from stearic acid; cure accelerators are selected from Mercaptobenzothiazole; crosslinking agent is selected from sulphur.
Thus, according to embodiments of the present invention, there is provided a method of preparing the higher scorch time-based rubber composition (Table-4), comprising (Mixing mill sequence):
For exemplary purpose the preparation method is carried out using Two Roll Mixing Mill (Make: Shaw). masticating of Natural rubber and whole tyre reclaim rubber for 1 minute to obtain 10mm to 12mm thickness; closing mill nip to obtain uniform thickness of around 5.0 mm - 7.0 mm; pre -blending of chemicals such as zinc oxide and stearic acid, MBTS and sulphur;
-forming band of Natural Rubber and reclaim rubber;
-mixing of the pre-blended zinc oxide and stearic acid on the band and rolling of compound;
-mixing of Sulphur, MBTS and rolling of compound; and
-mixing of compound for homogenous dispersion of chemicals for around 12
- 17 minutes. The factory formulation is analyzed for Thermal properties (Table 5), Rheological Properties (Table
6),
Table-5: Thermal Properties of Factory Based Formulations
Figure imgf000014_0001
Table 5 shows the comparison results of factory-based formulations on TGA composition, Glass Transition temperature (Tg), State of cure, Thermal Heat capacity.
Table: 6 - Rheological Properties
Figure imgf000014_0002
Figure imgf000015_0001
Mooney scorch properties @ 125°C & ODR @ 160°C & 190°C,
Table-6 shows the comparison results of Type A compound Mooney scorch value: below 4.5 Minutes (T5 value: 4.05) & Type B, C & D compound Mooney scorch value above 4.5 minutes t5 value: 4.56, 6.02 & 7.58). t5 value indicates the pre-vulcanization tendency of the compound. The larger t5 (Type B, C & D) is, the lower the pre-vulcanization tendency, and, therefore, the rubber compound can be more reliably processed on mill, calendar or extruder.
Vulcanization time (t35) - the time interval (measured from rotor start) corresponding to a viscosity increase of 35 units over the MV value.
Vulcanization index - DT30 = t35 — 15; provides indications about the vulcanizing ability of a rubber compound. A compound with a low vulcanization index (Type B, C & D), has high cure rate than a compound with a higher vulcanization index (Type A).
The ODR (Oscillating Disc Rheometer) @ 160°C & 190°C for Types A, B, C & D compound tS2 (Compound scorch time) & t9o (Optimum time of vulcanization) results are compared.
State of Cure/Curing Temp: It is observed that the higher State of Cure / Curing temperature of compound exhibit better scorch safety.
Thermal Heat capacity: It is observed that higher scorch time -based compound sample exhibit Negative enthalpy indicates higher degree of crosslinking.
Table-7: Polymer -filler Interaction (Payne effect)
Figure imgf000015_0002
Better polymer-filler interaction (Payne effect) will lead to better physical properties. The polymer- filler interaction results are compared with each other. For Payne effect, G ’difference (kPa), lower the value better the polymer-filler interactions. Table 7 shows the comparison results of Payne effect difference for Type A, B, C & D. The Payne effect, G' difference (kPa) for Type B, C & D results are substantially lower than Type A indicating improved polymer-filler interaction in trials having reclaim scorch time of minimum 4.5 minutes. It also reflected in improved 300% modulus (Table-8).
Table-8: Physical properties
Figure imgf000016_0002
The physical properties results are compared with each other
Figure imgf000016_0001
comparison results of physical properties for Type A, B, C and D.
It is observed that Type B, C, and D has improved tensile strength, modulus values, elongation at break as compared to lower scorch time -based compound Type A. The rubber composition provides consistent physical properties of the rubber vulcanizate, when the Mooney scorch time value ranging from 4.5 minutes to 11 minutes, preferably range is from 4.5 to 8 minutes and above (Type B, C and D). Higher the scorch time better the physical properties of the rubber vulcanizate· Table-9: DMA Properties
Figure imgf000017_0001
In general, Tan delta at 60°C refers to the rolling resistance of the compound (lower is better). From the data, it is clearly observed that the Type B, C & D compounds have lower rolling resistance as compared with the Type A compound.
Higher Mooney Scorch time (ts value - Minimum 4.5 minutes) based whole Tyre reclaim rubber composition (as per Table-4) samples Type 2, 3, 4 provides, better polymer-filler interaction (Payne effect), better dynamic mechanical properties (Low Rolling Resistance), improved tensile strength, elongation at break than lower scorch time (ts) based whole tyre reclaim rubber composition Type 1.
Although, the invention has been described and illustrated with respect to the exemplary embodiments thereof, it should be understood by those skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto, without parting from the spirit and scope of the present invention.

Claims

WE CLAIM
1. A rubber composition for tyre, comprising: one or more polymers; carbon black & inorganic fillers; one or more wax, antioxidants and oil materials; and one or more wax, antioxidants and oil materials, characterized in that the rubber composition contains higher proportion of whole tyre reclaim in the range of 120-200 PHR with Mooney Scorch time values ranging from 4.5 minutes to 11.0 minutes.
2. The rubber composition for tyre as claimed in claim 1, wherein the whole tyre reclaim has a Mooney Scorch time of 4.5 minutes to 8 minutes.
3. The rubber composition for tyre as claimed in claim 1, wherein the composition comprises components selected from
Natural Rubber and Synthetic Rubber - 0 - 40 parts;
Reclaimed rubber - 120 - 200 PHR;
Activators - 2 PHR;
Softeners / filler dispersing agent - 1.5 PHR;
Cure accelerators - 0.6 PHR; and Cross-linking agent - 3 PHR.
4. The rubber composition for tyre as claimed in claim 1, wherein in the natural rubber activators is selected as zinc oxide.
5. The rubber composition for tyre as claimed in claim 1, wherein wherein the softeners / filler dispersing agent is selected as stearic acid.
6. The rubber composition for tyre as claimed in claim 1, wherein the cure accelerators are selected as Mercaptobenzothiazole.
7. The rubber composition for tyre as claimed in claim 1, wherein the cross-linking agent is selected as sulphur.
8. A method of preparing the rubber composition with high WTR, comprising steps: selection of whole tyre reclaims of Mooney Scorch in the range of 4.5 minutes to 11 minutes; preparation of rubber tyre composition comprising masticating of Natural Rubber or Synthetic Rubber and Whole Tyre Reclaim rubber for 1 minute to obtain 10 mm to 12 mm thickness; closing mill nip to obtain uniform thickness of around 5.0 mm - 7.0 mm; pre-blending of chemicals such as zinc oxide and stearic acid, MBTS and sulphur; forming band of Natural Rubber and reclaim rubber; mixing of the pre-blended zinc oxide and stearic acid on the band and rolling of compound; mixing of Sulphur, MBTS and rolling of compound; and mixing of compound for homogenous dispersion of chemicals for around 12 - 17 minutes, to yield the rubber composition, wherein the composition comprises of WTR in the range of 120-200 PHR.
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Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
ANONYMOUS: "Effect of scorch time on production process of tire reclaimed rubber products", 19 October 2020 (2020-10-19), XP093024717, Retrieved from the Internet <URL:https://en.hsxjw.com/luntaizsjbaike_1211.html> [retrieved on 20230216] *
ANONYMOUS: "Wholetyre Reclaimed Rubber", PRODUCT DATA SHEET, 1 January 2015 (2015-01-01), XP093024716, Retrieved from the Internet <URL:https://www.rubberreclaim.com/Pdf/Balaji_Rubber_Product_Specification_Grade_WTR_5504.pdf> [retrieved on 20230216] *
CHARLES JULIE: "Characterization of Reclaim rubber and Reclaim rubber/Natural rubber blend", INTERNATIONAL JOURNAL OF CHEMTECH RESEARCH (PRINT), SPHINX KNOWLEDGE HOUSE, INDIA, vol. 10, no. 7, 1 January 2017 (2017-01-01), India , pages 359 - 371, XP093024718, ISSN: 0974-4290 *
DARESTANI FARAHANI T.; BAKHSHANDEH G.R.; ABTAHI M.: "Mechanical and Viscoelastic Properties of Natural Rubber/ Reclaimed Rubber Blends", POLYMER BULLETIN, SPRINGER, HEIDELBERG., DE, vol. 56, no. 4-5, 24 January 2006 (2006-01-24), DE , pages 495 - 505, XP037824890, ISSN: 0170-0839, DOI: 10.1007/s00289-006-0508-4 *

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