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WO2002010271A2 - Proprietes a temperatures de melange elevee de composes caoutchouc charges de silice comportant des agents de couplage de silice et de disulfane - Google Patents

Proprietes a temperatures de melange elevee de composes caoutchouc charges de silice comportant des agents de couplage de silice et de disulfane Download PDF

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Publication number
WO2002010271A2
WO2002010271A2 PCT/US2001/024152 US0124152W WO0210271A2 WO 2002010271 A2 WO2002010271 A2 WO 2002010271A2 US 0124152 W US0124152 W US 0124152W WO 0210271 A2 WO0210271 A2 WO 0210271A2
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Prior art keywords
silica
disulfide
bis
coupling agent
temperature
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WO2002010271A3 (fr
Inventor
Chen-Chy Lin
William Hergenrother
Ashley Hilton
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Bridgestone Corp
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Bridgestone Corp
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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
    • C08K5/00—Use of organic ingredients
    • C08K5/54—Silicon-containing compounds
    • C08K5/548—Silicon-containing compounds containing sulfur
    • 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
    • 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
    • B60C1/0016—Compositions of the tread
    • 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
    • B60C1/0025—Compositions of the sidewalls
    • 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
    • C08K3/01—Use of inorganic substances as compounding ingredients characterized by their specific function
    • C08K3/013—Fillers, pigments or reinforcing additives
    • 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
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/80—Technologies aiming to reduce greenhouse gasses emissions common to all road transportation technologies
    • Y02T10/86—Optimisation of rolling resistance, e.g. weight reduction 

Definitions

  • the invention generally relates to vulcanizable elastomeric compounds containing silica as a reinforcing filler.
  • elastomeric compositions for use in rubber articles, such as tires, power belts, and the like
  • these elastomeric compositions are easily processabie during compounding and have a high molecular weight with a controlled molecular weight distribution, glass transition temperature (T g ) and vinyl content.
  • T g glass transition temperature
  • reinforcing fillers such as silica and/or carbon black, be well dispersed throughout the rubber in order to improve various physical properties, such as the compound ooney viscosity, elastic modulus, tan delta ( ⁇ ), and the like.
  • Rubber articles, especially tires, produced from vulcanized elastomers exhibiting these improved properties will have reduced hysteresis, better rolling resistance, snow and ice traction, wet traction, and improved fuel economy for vehicles equipped with such tires.
  • improved dispersion of reinforcing fillers has been accomplished by lengthened mixing times. However, in commercial applications, prolonged mixing times result in decreased production and increased expense. With the increasing use of silica as a reinforcing filler for rubber, filler dispersion in rubber stocks has become a major concern.
  • silica particles Because polar silanol groups on the surface of silica particles tend to self-associate, reagglomeration of silica particles (the Payne effect) occurs after compounding, leading to poor silica dispersion and a high compound viscosity.
  • the strong silica filler network results in a rigid uncured compound that is difficult to process in extrusion and forming operations.
  • silica-filled rubber stocks containing natural rubber or diene polymer and copolymer elastomers have focused on the use, during compounding, of bifunctional silica coupling agents having a moiety (e.g., an alkoxysilane group) reactive with the silica surface, and a moiety (e.g., a mercapto, amino, vinyl, epoxy or sulfur group) that binds to the elastomer.
  • silica coupling agents are mercaptosilanes and bis-
  • (trialkoxysilylorgano) polysulfides such as bis-(3-triethoxysilylpropyl) tetrasulfide which is sold commercially as Si69 by Degussa.
  • Bifunctional polysulfide organosilanes, particularly Si69 are very efficient silica-rubber coupling agents and have been used for many years in tire tread compounds where the combination of silica and bifunctional silane gives lower viscosity compounds with a reduced tendency to form a silica-silica network, resulting in reduced rolling resistance, enhanced wet traction and improved abrasion resistance (i.e., tread wear).
  • the coupling reaction of silica and Si69 can be divided into two separate reactions, i.e., the triethoxysilyl group of the Si69 reacts with the silanol groups on the silica during mixing, with the evolution of a considerable amount of ethanol, and the tetrasulfide chain reacts with the polymer under curing conditions to form rubber-to- filler bonds.
  • the upper processing temperature limitation results in a marked reduction in the mechanical activity of mixing which is essential for an optimum dispersion of the silica throughout the polymer matrix. Therefore, compared with carbon black-filled compositions, silica-silane tread compounds require a longer mixing time at a lower temperature to achieve improved performance, resulting in decreased production and increased expense.
  • tetrasulfide organosilane silica coupling agents Another disadvantage of the use of tetrasulfide organosilane silica coupling agents is that the upper processing temperature limitation results in the retention, in the compounded product, of unreacted triethoxysilyl groups that are available to further react with the silica and moisture during storage, extrusion, tire build, and/or curing, resulting in an undesirable increase in the compound viscosity, and a shorter shelf life. Moreover, the continuing reaction in the compound evolves more (unevaporated) ethanol, resulting in porous zones or blisters which can form surface defects in the resulting formed rubber articles and/or can impair the dimensional stability of treads during extrusion and tire building.
  • organosilane polysulfide silica coupling agents have been introduced which are structurally similar to the tetrasulfide Si69 but contain a preponderance of disulfide chains.
  • Examplary of this category of coupling agents are bis-(3- triethoxysilylpropyl) disulfide ("TESPD”), containing greater than 80% disulfanes, and "VP Si 75", containing about 75% disulfanes, both available from Degussa, and
  • Silquest® A1589 containing about 75% disulfanes, available from Crompton (formerly Witco).
  • the disulfide organosilanes have been described as having better thermal stability than the tetrasulfide, Si69, because the reaction between the disulfane chain and the polymer only occurs in the presence of added sulfur. (KGK Kautschuk Kunststoffe 53(1), 10-23, February 2000; Tire Technology International, pp. 52-59, March 2000).
  • vulcanizable elastomeric compounds containing silica and VP Si 75 showed constant in-rubber properties when mixed to a temperature of 140°C to 160°C, compounds mixed to higher temperatures (e.g., 187°C to >200°C) showed poor physical properties, such as higher compound viscosity, shorter scorch times, increased modulus, and the like. (Tire Technology International, ibid).
  • improved sulfur-vulcanized elastomeric compounds comprising silica and disulfide organosilane silica coupling agents are obtained by mixing the polymer, the silica, and the disulfide silica coupling agent in the initial (master batch) stage or a subsequent remill stage at a temperature of 165°C to about 195°C, preferably about 170°C to about 195°C and, more preferably, about 175°C to about 195°C.
  • the vulcanized elastomeric compounds obtained by the method of the present invention demonstrate improved dispersion of silica and reduced filler flocculation after compounding, resulting in lower hysteresis in the vulcanized product.
  • the compounds of the invention exhibit about a 10% to about a 40% decrease in filler flocculation after compounding, and/or about a 5% to about a 20% decrease in tangent delta (tan ⁇ ) at 65°C, compared to a similar compound comprising a bis(trialkoxysilylorgano) tetrasulfane silica coupling agent compounded at a temperature of 160°C or less.
  • the compounds of the invention exhibit about a 10% to about a 75% decrease in filler flocculation after compounding, and/or about a 5% to about a 30% decrease in tan ⁇ at 65°C, compared to a similar compound comprising a bisftrialkoxysilyl-organo) disulfane silica coupling agent compounded at a temperature of 160°C or less.
  • the compounds of the invention demonstrate longer scorch times, faster curing rates, and a decrease in evolution of ethanol during storage, extrusion, curing and tire build, resulting in less porosity with fewer blisters, and a more stable compound viscosity during storage.
  • Rubber compounds produced by the method according to the invention also possess favorable viscoelastic properties, such as a lower elastic modulus (G') at -20°C, a higher tan ⁇ at 0°C, and a lower tan ⁇ at 50°C.
  • G' elastic modulus
  • Such properties have been commonly used in the tire industry to predict tire performance in the categories of snow and ice traction (G' at -20°C), wet traction (tan ⁇ at 0°C), and rolling resistance (tan ⁇ at 50°C).
  • the invention provides sulfur-vulcanizable elastomeric compounds demonstrating the above improved properties, prepared by a method comprising the steps of (a) mixing together at a temperature of 165°C to 195°C, in the absence of added sulfur and cure agents, a diene elastomer, a reinforcing filler comprising silica or a mixture thereof with carbon black, and a bis(trialkoxysilylorgano) disulfide silica coupling agent containing an average of about 2 to about 2.5 sulfur atoms in a polysulfide bridge; (b) allowing the mixture to cool below 165°C; and (c) mixing the mixture obtained in step (b), at a temperature lower than a vulcanization temperature, with a cure agent and an effective amount of sulfur to achieve a satisfactory cure.
  • the mixture can then be cured at about 140°C to about 190°C for about 5 to about 120 minutes.
  • the mixing temperature in step (a) is about 170°C to about 195°C, and more preferably about 175°C to about 195DC.
  • the mixing temperature of step (c), in which the curing agents, including sulfur, are added, is about 40°C to about 120°C, typically about 60DC to about 110°C and, especially, about 75°C to about 100°C.
  • step (a) of the method can be divided into two or more substeps in which a portion of the silica and a portion of the silica coupling agent can be mixed in one substep and the remainder, if any, of the silica and the remainder, if any, of the silica coupling agent can be mixed in a subsequent substep.
  • the mixing temperature is 165°C to 195°C, preferably about 170°C to about 195°C and, more preferably, about 175°C to about 195°C.
  • the mixture is cooled to a temperature below 165°C.
  • the method can also comprise a step in which the mixture obtained in step (a) is remilled without the addition of further ingredients.
  • the remill temperature is about 130°C to about 165°C, especially about 145°C to about 155°C.
  • the sulfur-vulcanized elastomeric compounds produced by the method of the invention possess favorable viscoelastic properties that are indicators of improved snow, ice and wet traction, improved rolling resistance, improved abrasion and wear resistance, and reduced hysteresis, when the vulcanized compounds are incorporated into tire treads.
  • the invention further provides a pneumatic tire comprising at least one component produced from the vulcanized elastomeric compound of the invention.
  • Figure 1 illustrates the results of a strain sweep test of an invention rubber stock (DS in MA) and comparative examples after annealing at 171°C for 15 minutes.
  • Figure 2 illustrates the results of a temperature sweep test of an invention rubber stock (DS in MA) after annealing at 171°C for 15 minutes.
  • a method for preparing sulfur-vulcanizable elastomeric compounds containing silica, preferably for tire treads comprising at least an initial step to obtain a first mixture by loading into a mixer (e.g., a Banbury-type mixer) and mixing together at least a cross-linkable diene chain polymer base, a reinforcing filler comprising silica or a mixture of silica and carbon black, and a bis(trialkoxysilylorgano) disulfide silica coupling agent containing an average of about 2 to about 2.5 sulfur atoms in a polysulfide bridge, in the absence of added sulfur and cure agents.
  • a mixer e.g., a Banbury-type mixer
  • a reinforcing filler comprising silica or a mixture of silica and carbon black
  • a bis(trialkoxysilylorgano) disulfide silica coupling agent containing an average of about 2 to about 2.5 sulfur atoms in a poly
  • the initial step of the method is arrested upon the first mixture reaching a temperature from 165°C to about 195°C, preferably about 170°C to about 195°C and, more preferably, about 175°C to about 195°C.
  • the mixture is then cooled to a temperature lower than 165°C, followed by mixing, at a temperature lower than a vulcanization temperature, the first mixture, a cure agent and an effective amount of sulfur to achieve a satisfactory cure.
  • the compound is cured at about 140°C to about 190°C for about 5 to about 120 minutes.
  • the initial (master batch) mixing step can include at least two substeps.
  • the initial mixing step can comprise the substeps of (i) mixing together at a temperature of 165°C to about 195°C, the diene elastomer, at least a portion of the silica, and at least a portion of the silica coupling agent; (ii) cooling the mixture below 165°C; and (iii) mixing the mixture obtained in step (ii) with the remainder of the silica, if any, and the remainder of the silica coupling agent, if any, at a temperature of 165°C to about 195°C.
  • the temperatures achieved by the at least two substeps can be the same or different from each other, within the temperature range. As disclosed above, the preferred temperature range is about 170°C to about 195°C, especially about 175°C to about 195°C.
  • the method can further include a remill step in which either no ingredients are added to the first mixture, or non-curing ingredients are added, in order to reduce the compound viscosity and improve the dispersion of the silica reinforcing filler.
  • the temperature of the remill step is typically about 130°C to about 165°C, especially about 145° to about 155°C.
  • the final step of the mixing process is the addition of cure agents to the mixture, including an effective amount of sulfur to achieve a satisfactory cure of the final compound.
  • the temperature at which the final mixture is mixed must be below the vulcanization temperature in order to avoid unwanted precure of the compound. Therefore, the temperature of the final mixing step must not exceed about 120°C and is typically about 40°C to about 120°C, preferably about 60DC to about 110°C and, especially, about 75°C to about 100°C.
  • the order of addition of the silica and silica coupling agent to the mixer in the initial mixing step is not critical.
  • the silica coupling agent can be added prior to or after the addition of the silica.
  • the silica and silica coupling agent are added simultaneously to the mixer.
  • the silica coupling agent can be partially or fully supported on the silica and/or the carbon black reinforcing filler.
  • the ratio of the amount of supported silica coupling agent to the filler is not critical. If the silica coupling agent is a liquid, a suitable ratio of supported coupling agent to filler is that which results in a suitably dry material for addition to the elastomer.
  • the ratio can be about 1/99 to about 70/30, about 20/80, about 60/40, about 50/50, and the like.
  • Suitable disulfide organosilane silica coupling agents for use in the method of the invention are bisftrialkoxysilylorgano) disulfides, including, but not limited to 3,3'-bis(triethoxysilylpropyl) disulfide, 3,3'-bis(trimethoxysilylpropyl) disulfide, 3,3'-bis(tributoxy-silylpropyl) disulfide, 3,3'-bis(tri-f-butoxysilylpropyl) disulfide, 3,3'- bisftrihexoxysilylpropyl) disulfide, 2,2'-bis(dimethyl-methoxysilylethyl) disulfide, 3,3'- bis(diphenylcyclohexoxy-silylpropyl) disulfide, 3,3'-bis(ethyl-di-sec-butoxysilylpropyl) disulfide, 3,3'-bis(propyldie
  • the disulfide organosilane silica coupling agent is present in the vulcanizable elastomeric composition in an amount of about 0.1% to about 20% by weight based on the weight of the silica .
  • the silica coupling agent is present in an amount of about 0.5% to about 15% by weight and, more preferably, in the amount of about 1 % to about 10% by weight based on the weight of the silica.
  • a disulfide organosilane coupling agent instead of a tetrasulfide organosilane coupling agent requires an appropriate adjustment in the amount of sulfur added to the elastomeric composition to achieve a satisfactory cure of the composition.
  • an effective amount of sulfur in an invention composition would provide a property of the cured compound that is approximately equal to the same property of a satisfactorily cured compound containing Si69 with a conventional amount of sulfur.
  • Exemplary cured compound properties for comparison include, but are not limited to, the value of the 300% Modulus (psi), the molecular weight between crosslinks (Mc g/mol), and the like, and other cured compound properties that are well known to those skilled in the art of rubber making.
  • the increased amount of sulfur to compensate for the reduced availability of sulfur from a sulfur-donating silica coupling agent will vary from composition to composition, depending on the amount of silica and the amount, if any, of a sulfur-donating silica coupling agent present in the formulation. Based on the disclosure contained herein, and in the examples of invention compositions described below, one skilled in the art of rubber compounding can easily determine the effective amount of sulfur required for a satisfactory cure of the compound without undue experimentation.
  • the additional sulfur can take any form, including soluble sulfur, insoluble sulfur, or any of the sulfur-donating compounds described as vulcanizing agents below, or mixtures of the foregoing.
  • disulfide organosilane silica coupling agent it can be desirable to employ one or more additional dispersing aids, such as an alkyl alkoxysilane, a fatty acid ester of hydrogenated or non-hydrogenated C 5 and C 6 sugars, and the polyoxyethylene derivatives thereof, or a mineral or non-mineral additional filler, as described below.
  • additional dispersing aids such as an alkyl alkoxysilane, a fatty acid ester of hydrogenated or non-hydrogenated C 5 and C 6 sugars, and the polyoxyethylene derivatives thereof, or a mineral or non-mineral additional filler, as described below.
  • Alkyl alkoxysilanes useful as an additional processing aid preferably have the formula R 1 pSi (OR 2 ) 4-p ' wherein the alkoxy groups are the same or different from each other, each R 1 independently comprises Ci to about C 20 aliphatic, about C 5 to about C 20 cycloaliphatic, or about C 6 to about C 20 aromatic, each R 2 independently comprises Ci to about C 6 , and p is an integer from 1 to 3.
  • alkyl alkoxysilanes include, but are not limited to, octyl triethoxysilane, octyl trimethoxysilane, trimethyl ethoxysilane, cyclohexyl triethoxysilane, /so-butyl triethoxysilane, ethyl trimethoxy silane, hexyl tributoxy silane, dimethyl diethoxysilane, methyl triethoxysilane, propyl triethoxysilane, hexyl triethoxysilane, heptyl triethoxysilane, nonyl triethoxysilane, octadecyl triethoxysilane, methyl octyl diethoxysilane, dimethyl dimethoxysilane, methyl trimethoxysilane, propyl trimethoxysilane, hexyl trimethoxysilane,
  • alkyl alkoxysilane processing aids are octyl triethoxysilane, octadecyl triethoxysilane, and nonyl triethoxysilane.
  • the alkyl alkoxysilane if used, can be present in an amount of about 0.1 % to about 50% by weight based on the weight of the silica.
  • the alkyl alkoxysilane can be present in an amount of about 0.1% to about 30% by weight and, more preferably, in an amount of about 0.1% to about 20% by weight based on the weight of the silica.
  • the alkyl alkoxysilane can be fully or partially supported by the reinforcing filler.
  • the ratio of the alkyl alkoxysilane to the reinforcing filler is not critical. For example, the ratio can be about 1/99 to about 70/30, about 20/80 about 60/40, about 50/50, and the like.
  • the addition of the alkyl alkoxysilane processing aid to the composition results in a further reduction in the compound Mooney viscosity, improved silica flocculation stability, and improved scorch time and cure rate.
  • Exemplary fatty acid esters of hydrogenated and non-hydrogenated C 5 and C 6 sugars that are useful as an additional processing aid include the sorbitan oleates, such as sorbitan monooleate, dioleate, trioleate and sesquioleate, as well as sorbitan esters of laurate, palmitate and stearate fatty acids.
  • Fatty acid esters of hydrogenated and non-hydrogenated C5 and C 6 sugars are commercially available from ICI Specialty Chemicals (Wilmington, DE) under the trade name SPAN ® .
  • Representative products include SPAN ® 60 (sorbitan stearate), SPAN ® 80 (sorbitan oleate), and SPAN ® 85 (sorbitan trioleate).
  • Other commercially available fatty acid esters of sorbitan are also available, such as the sorbitan monooleates known as Alkamul ® SMO; Capmul ® O; Glycomul ® O; Arlacel ® 80; Emsorb ® 2500; and S-Maz ® 80.
  • a useful amount of these additional processing aids is about 0.1% to about 60% by weight based on the weight of the silica, with about 0.5% to about 50% by weight being preferred, and about 1 % to about 30% by weight based on the weight of the silica being more preferred.
  • Esters of polyols including glycols such as polyhydroxy compounds and the like, in the same quantities, are also useful.
  • Exemplary polyoxyethylene derivatives of fatty acid esters of hydrogenated and non-hydrogenated C 5 and C 6 sugars include, but are not limited to, polysorbates and polyoxyethylene sorbitan esters, which are analogous to the fatty acid esters of hydrogenated and non-hydrogenated sugars noted above except that ethylene oxide groups are placed on each of the hydroxyl groups.
  • Representative examples of polyoxyethylene derivatives of sorbitan include POE ® (20) sorbitan monooleate, Polysorbate ® 80, Tween ® 80, Emsorb ® 6900, Liposorb ® O-20, T-Maz ® 80, and the like.
  • the Tween ® products are commercially available from ICI Specialty Chemicals.
  • a useful amount of these additional processing aids is about 0.1% to about 60% by weight based on the weight of the silica, with about 0.5% to about 50% by weight being preferred, and about 1% to about 30% by weight based on the weight of the silica being more preferred.
  • the fatty acid esters described above, and their polyoxyethylene derivatives, can be fully or partially supported by the reinforcing filler.
  • the ratio of the dispersing agent to the reinforcing filler is not critical. If the dispersing agent is a liquid, a suitable ratio of dispersing agent to filler is that which results in a suitably dry material for addition to the elastomer. For example, the ratio can be about 1/99 to about 70/30, about 20/80 about 60/40, about 50/50, and the like.
  • Additional fillers can be utilized according to the present invention as processing aids, including mineral fillers, such as clay (hydrous aluminum silicate), talc (hydrous magnesium silicate), aluminum hydrate [AI(OH) 3 ] and mica, as well as non-mineral fillers such as urea and sodium sulfate.
  • mineral fillers such as clay (hydrous aluminum silicate), talc (hydrous magnesium silicate), aluminum hydrate [AI(OH) 3 ] and mica
  • non-mineral fillers such as urea and sodium sulfate.
  • Preferred micas principally contain alumina and silica, although other known variants are also useful.
  • the foregoing additional fillers are optional and can be utilized in the amount of about 0.5 to about 40 phr, preferably in an amount of about one to about 20 phr and, more preferably in an amount of about one to about 10 phr.
  • additional fillers can also be used as non-reinforcing fillers to support the alkyl tin compound processing aids, as well as any of the optional additional processing aids described above.
  • the ratio of processing aid to non-reinforcing filler is not critical.
  • the ratio can be about 1/99 to about 70/30, about 20/80 about 60/40, about 50/50, and the like.
  • the vulcanizable elastomeric composition is preferably compounded with reinforcing fillers, such as silica, or a mixture of silica and carbon black.
  • silica fillers which can be used in the vulcanizable elastomeric composition of the invention include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and the like.
  • suitable fillers include aluminum silicate, magnesium silicate, and the like.
  • precipitated amorphous wet-process hydrated silicas are preferred. These silicas are so-called because they are produced by a chemical reaction in water, from which they are precipitated as ultrafine, spherical particles. These primary particles strongly associate into aggregates, which in turn combine less strongly into agglomerates. The surface area, as measured by the BET method gives the best measure of the reinforcing character of different silicas.
  • the surface area should be about 32 m 2 /g to about 400 m 2 /g, with the range of about 100 m 2 /g to about 250 m 2 /g being preferred, and the range of about 150 m 2 /g to about 220 m 2 /g being most preferred.
  • the pH of the silica filler is generally about 5.5 to about 7 or slightly over, preferably about 5.5 to about 6.8.
  • Silica can be employed in the amount of about one to about 100 parts per hundred parts of the elastomer, preferably in an amount of about five to about 80 phr and, more preferably, in an amount of about 30 to about 80 phr.
  • the useful upper range is limited by the high viscosity imparted by fillers of this type.
  • Some of the commercially available silicas which can be used include, but are not limited to, Hi- Sir* 190, Hi-Sil ® 210, Hi-Sil ® 215, Hi-Sil ® 233, Hi-Sil ® 243, and the like, produced by PPG Industries (Pittsburgh, PA).
  • a number of useful commercial grades of different silicas are also available from DeGussa Corporation (e.g., VN2, VN3), Rhone Poulenc (e.g., Zeosil ® 1165MP), and J.M. Huber Corporation.
  • the elastomers can be compounded with all forms of carbon black in a mixture with the silica.
  • the carbon black can be present in amounts ranging from about one to about 50 phr, with about five to about 35 phr being preferred.
  • the carbon blacks can include any of the commonly available, commercially-produced carbon blacks, but those having a surface area (EMSA) of at least 20 m 2 /g and, more preferably, at least 35 m 2 /g up to 200 m 2 /g or higher are preferred.
  • SMA surface area
  • Surface area values used in this application are determined by ASTM D-1765 using the cetyltrimethyl-ammonium bromide (CTAB) technique.
  • CTAB cetyltrimethyl-ammonium bromide
  • the useful carbon blacks are furnace black, channel blacks and lamp blacks.
  • examples of useful carbon blacks include super abrasion furnace (SAF) blacks, high abrasion furnace (HAF) blacks, fast extrusion furnace (FEF) blacks, fine furnace (FF) blacks, intermediate super abrasion furnace (ISAF) blacks, semi-reinforcing furnace (SRF) blacks, medium processing channel blacks, hard processing channel blacks and conducting channel blacks.
  • SAF super abrasion furnace
  • HAF high abrasion furnace
  • FEF fast extrusion furnace
  • FF fine furnace
  • IGF intermediate super abrasion furnace
  • SRF semi-reinforcing furnace
  • Typical suitable carbon blacks are N-110, N-220, N-339, N-330, N-351 , N-550, N-660, as designated by ASTM D- 1765-82a.
  • the carbon blacks utilized in the preparation of the vulcanizable elastomeric compositions of the invention can be in pelletized form or an unpelletized flocculent mass. Preferably, for more uniform mixing, unpelletized carbon black is preferred.
  • the present invention can be used in conjunction with any solution polymerizable or emulsion polymerizable elastomer.
  • Solution and emulsion polymerization techniques are well known to those of ordinary skill in the art.
  • conjugated diene monomers, monovinyl aromatic monomers, triene monomers, and the like can be anionically polymerized to form conjugated diene polymers, or copolymers or terpolymers of conjugated diene monomers and monovinyl aromatic monomers (e.g., styrene, alpha methyl styrene and the like) and triene monomers.
  • the elastomeric products can include diene homopolymers from monomer A and copolymers thereof with monovinyl aromatic monomers B.
  • Exemplary diene homopolymers are those prepared from diolefin monomers having from about four to about 12 carbon atoms.
  • Exemplary vinyl aromatic copolymers are those prepared from monomers having from about eight to about 20 carbon atoms. Copolymers can comprise from about 99 percent to about 50 percent by weight of diene units and from about one to about 50 percent by weight of monovinyl aromatic or triene units, totaling 100 percent.
  • the polymers, copolymers and terpolymers of the present invention can have 1 ,2-microstructure contents ranging from about 10 percent to about 80 percent, with the preferred polymers, copolymers or terpolymers having 1 ,2-microstructure content of from about 25 to 65 percent, based upon the diene content.
  • the elastomeric copolymers are preferably random copolymers which result from simultaneous copolymerization of the monomers A and B with randomizing agents, as is known in the art.
  • Preferred polymers for use in a vulcanized elastomeric compound of the invention include polyisoprene, polystyrene, polybutadiene, butadiene-isoprene copolymer, butadiene-isoprene-styrene terpolymer, isoprene-styrene copolymer, and styrene-butadiene copolymer.
  • Anionic polymerization initiators for use in polymerizing the anionically polymerizable monomers include, but are not limited to, organo-sodium, organo- potassium, organo-tin-lithium, organo-lithium, dialkylimido-lithium and cycloalkylimido- lithium initiators.
  • organo-lithium compounds useful in the polymerization of 1 ,3-diene monomers are hydrocarbyl lithium compounds having the formula RLi, where R represents a hydrocarbyl group containing from one to about 20 carbon atoms, and preferably from about 2 to about 8 carbon atoms.
  • hydrocarbyl group is preferably an aliphatic group
  • the hydrocarbyl group can also be cycloaliphatic or aromatic.
  • the aliphatic group can be a primary, secondary, or tertiary group, although the primary and secondary groups are preferred.
  • aliphatic hydrocarbyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, f-butyl, n-amyl, sec-amyl, n-hexyl, sec-hexyl, n-heptyl, n- octyl, n-nonyl, n-dodecyl, and octadecyl.
  • the aliphatic group can contain some unsaturation, such as allyl, 2-butenyl, and the like.
  • Cycloalkyl groups are exemplified by cyclohexyl, methylcyclohexyl, ethylcyclohexyl, cycloheptyl, cyclopentylmethyl, and methylcyclopentylethyl.
  • aromatic hydrocarbyl groups include phenyl, tolyl, phenylethyl, benzyl, naphthyl, phenyl cyclohexyl, and the like.
  • organo-lithium compounds which are useful as anionic initiators in the polymerization of the monomers listed above, especially conjugated dienes include, but are not limited to, n-butyl lithium, n-propyl lithium, isobutyl lithium, ferf-butyl lithium, tributyl tin lithium (described in co-owned U.S. Patent No. 5,268,439), amyl-lithium, cyclohexyl lithium, and the like.
  • Other suitable organo- lithium compounds for use as anionic initiators are well known to those skilled in the art. A mixture of different lithium initiator compounds also can be employed.
  • the preferred organo-lithium initiators are n-butyl lithium, tributyl tin lithium and "in situ" produced lithium hexamethyleneimide initiator prepared by reacting hexamethyleneimine and n-butyl lithium (described in co-owned U.S. Patent No. 5,496,940).
  • the amount of initiator required to effect the desired polymerization can be varied over a wide range depending upon a number of factors, such as the desired polymer molecular weight, the desired 1 ,2- and 1 ,4-content of the polydiene, and the desired physical properties for the polymer produced. In general, the amount of initiator utilized can vary from as little as 0.2 millimoles (mM) of lithium per 100 grams of monomers up to about 100 mM of lithium per 100 grams of monomers, depending upon the desired polymer molecular weight.
  • mM millimoles
  • Polymerization is usually conducted in a conventional solvent for anionic polymerizations, such as hexane, cyclohexane, benzene and the like.
  • anionic polymerizations such as hexane, cyclohexane, benzene and the like.
  • Various techniques for polymerization such as semi-batch and continuous polymerization can be employed.
  • a polar coordinator can optionally be added to the polymerization ingredients. Amounts range between about one to about 90 or more equivalents per equivalent of lithium. The amount depends upon the type of polar coordinator that is employed, the amount of vinyl desired, the level of styrene employed and the temperature of the polymerizations, as well as the selected initiator.
  • Compounds useful as polar coordinators are organic and include tetrahydrofuran, linear and cyclic oligomeric oxolanyl alkanes such as 2-2D-di(tetrahydrofuryl) propane, dipiperidyl ethane, hexamethyl phosphoramide, ⁇ /- ⁇ /G-dimethyl piperazine, diazabicyclo octane, dimethyl ether, diethyl ether, tributyl amine and the like.
  • the linear and cyclic oligomeric oxolanyl alkane polar coordinators are described in U.S. Patent No. 4,429,091.
  • polar coordinators include those having an oxygen or nitrogen hetero-atom and a non-bonded pair of electrons. Examples include dialkyl ethers of mono and oligo alkylene glycols; "crown" ethers; and tertiary amines, such as tetramethylethylene diamine (TMEDA).
  • TMDA tetramethylethylene diamine
  • Polymerization is begun by charging a blend of the monomer(s) and solvent to a suitable reaction vessel, followed by the addition of the polar coordinator and the initiator previously described. The procedure is carried out under anhydrous, anaerobic conditions. Often, it is conducted under a dry, inert gas atmosphere. The polymerization can be carried out at any convenient temperature, such as about 0 °C to about 150 °C.
  • the peak temperature is maintained at from about 50 °C to about 150°C and, more preferably, from about 60 °C to about 100 °C.
  • Polymerization is allowed to continue under agitation for about 0.15 hours to 24 hours.
  • the product is terminated by a quenching agent, an endcapping agent and/or a coupling agent, as described herein below.
  • the terminating agent is added to the reaction vessel, and the vessel is agitated for about 0.1 hours to about 4.0 hours. Quenching is usually conducted by stirring the polymer and quenching agent for about 0.01 hours to about 1.0 hour at temperatures of from about 20 °C to about 120 °C to ensure a complete reaction.
  • Polymers terminated with a functional group as discussed herein below, are subsequently treated with alcohol or other quenching agent.
  • the solvent is removed from the polymer by conventional techniques such as drum drying, extruder drying, vacuum drying or the like, which can be combined with coagulation with water, alcohol or steam. If coagulation with water or steam is used, oven drying can be desirable.
  • One way to terminate the polymerization reaction is to employ a protic quenching agent to give a monofunctional polymer chain. Quenching can be conducted in water, steam or an alcohol such as isopropanol, or any other suitable method. Quenching can also be conducted with a functional terminating agent, resulting in a difunctional polymer. Any compounds providing terminal functionality (i.e., endcapping) that are reactive with the polymer bound carbon-lithium moiety can be selected to provide a desired functional group.
  • Examples of such compounds are alcohols, substituted aldimines, substituted ketimines, Michler's ketone, 1 ,3-dimethyl- 2-imidazolidinone, 1 -alkyl substituted pyrrolidinones, 1-aryl substituted pyrrolidinones, tin tetrachloride, tributyl tin chloride, carbon dioxide, and mixtures thereof.
  • Further examples of reactive compounds include the terminators described in co-owned U.S. Patents Nos. 5,521 ,309 and 5,066,729.
  • Other useful terminating agents can include those of the structural formula (R) a ZX b , where Z is tin or silicon. It is preferred that Z is tin.
  • R is an alkyl having from about 1 to about 20 carbon atoms; a cycloalkyl having from about 3 to about 20 carbon atoms; an aryl having from about 6 to about 20 carbon atoms, or an aralkyl having from about 7 to about 20 carbon atoms.
  • R can include methyl, ethyl, n-butyl, neophyl, phenyl, cyclohexyl or the like.
  • terminating agents examples include tin tetrachloride, tributyl tin chloride, butyl tin trichloride, butyl silicon trichloride, as well as tetraethoxysilane (Si(OEt) ), and methyl triphenoxysilane (MeSi(OPh) 3 ).
  • the practice of the present invention is not limited solely to these terminators, since other compounds that are reactive with the polymer bound carbon-lithium moiety can be selected to provide a desired functional group.
  • the polymers for use in the vulcanizable elastomeric compositions according to the present invention have at least about 40 percent tin coupling. That is, about 40 percent of the polymer mass after coupling is of higher molecular weight than the polymer before coupling as measured, for example, by gel permeation chromatography.
  • the polydispersity (the ratio of the weight average molecular weight to the number average molecular weight) of polymers which can be controlled over a wide range, is from about one to about 5, preferably one to about 2 and, more preferably, one to about 1.5.
  • Vulcanized elastomeric compounds of the invention are prepared by the method described above, by mixing an elastomer with silica, or a mixture of silica and carbon black, the disulfide organosilane silica coupling agent and, optionally, at least one additional processing aid such as alkyl alkoxysilanes, fatty acid esters or their polyoxyethylene derivatives, as described above, or polyol esters, in addition to other conventional rubber additives including, for example, other fillers, plasticizers, antioxidants, cure agents and the like, using standard rubber mixing equipment and procedures.
  • Such elastomeric compositions when vulcanized using conventional rubber vulcanization conditions, exhibit reduced hysteresis, which means a product having increased rebound, decreased rolling resistance and lessened heat build-up when subjected to mechanical stress. Products including tires, power belts and the like are envisioned. Decreased rolling resistance is, of course, a useful property for pneumatic tires, both radial as well as bias ply types and thus, the vulcanizable elastomeric compositions of the present invention can be utilized to form treadstocks for such tires.
  • Pneumatic tires can be made according to the constructions disclosed in U.S. Patent Numbers 5,866,171 ; 5,876,527; 5,931,211 ; and 5,971 ,046.
  • the composition can also be used to form other elastomeric tire components such as subtreads, black sidewails, body ply skims, bead fillers and the like.
  • the preferred conjugated diene polymers, or copolymers or terpolymers of conjugated diene monomers and monovinyl aromatic monomers can be utilized as 100 parts of the rubber in the treadstock compound, or they can be blended with any conventionally employed treadstock rubber which includes natural rubber, synthetic rubber and blends thereof.
  • Such rubbers are well known to those skilled in the art and include synthetic polyisoprene rubber, styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber, styrene-isoprene rubber, butadiene- isoprene rubber, polybutadiene, butyl rubber, neoprene, ethylene-propylene rubber, ethylene-propylene-diene rubber (EPDM), acrylonitrile-butadiene rubber (NBR), silicone rubber, the fluoroelastomers, ethylene acrylic rubber, ethylene vinyl acetate copolymer (EVA), epichlorohydrin rubbers, chlorinated polyethylene rubbers, chlorosulfonated polyethylene rubbers, hydrogenated nitriie rubber, tetrafluoroethylene-propylene rubber and the like.
  • SBR styrene-butadiene rubber
  • EVA acrylonitrile-buta
  • the rubber composition would be compounded by methods generally known in the rubber compounding art, such as mixing the various vulcanizable polymer(s) with various commonly used additive materials such as, for example, curing agents, activators, retarders and accelerators, processing additives, such as oils, resins, including tackifying resins, plasticizers, pigments, additional fillers, fatty acid, zinc oxide, waxes, antioxidants, anti-ozonants, and peptizing agents.
  • additives mentioned above are selected and commonly used in conventional amounts.
  • Typical amounts of tackifier resins comprise about 0.5 to about 10 phr, usually about one to about 5 phr.
  • Typical amounts of compounding aids comprise about one to about 50 phr.
  • Such compounding aids can include, for example, aromatic, naphthenic, and/or paraffinic processing oils.
  • Typical amounts of antioxidants comprise about 0.1 to about 5 phr. Suitable antioxidants, such as diphenyl-p-phenylenediamine, are known to those skilled in the art.
  • Typical amounts of anti-ozonants comprise about 0.1 to about 5 phr.
  • Typical amounts of fatty acids can include stearic acid, palmitic acid, linoleic acid or a mixture of one or more fatty acids, can comprise about 0.5 to about 3 phr.
  • Typical amounts of zinc oxide comprise about one to about 5 phr.
  • Typical amounts of waxes comprise about one to about 2 phr. Often microcrystalline waxes are used.
  • Typical amounts of peptizers, if used, comprise about 0.1 to about 1 phr.
  • Typical peptizers can be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide.
  • the reinforced rubber compounds can be cured in a conventional manner with known vulcanizing agents at about 0.1 to 10 phr.
  • suitable vulcanizing agents one can refer to Kirk-Othmer, Encyclopedia of Chemical Technology. 3rd ed., Wiley Interscience, N.Y. 1982, Vol. 20, pp. 365 to 468, particularly "Vulcanization Agents and Auxiliary Materials," pp. 390 to 402. Vulcanizing agents can be used alone or in combination.
  • the vulcanization is conducted in the presence of a sulfur vulcanizing agent.
  • suitable sulfur vulcanizing agents include "rubbermaker's" soluble sulfur; sulfur donating vulcanizing agents, such as an amine disulfide, polymeric polysulfide or sulfur olefin adducts; and insoluble polymeric sulfur.
  • the sulfur vulcanizing agent is soluble sulfur or a mixture of soluble and insoluble polymeric sulfur.
  • the sulfur vulcanizing agents are used in an amount ranging from about 0.1 to about 10 phr, more preferably about 1.5 to about 7.5 phr, with a range of about 1.5 to about 5 phr being most preferred.
  • Accelerators are used to control the time and/or temperature required for vulcanization and to improve properties of the vulcanizate.
  • the vulcanization accelerators used in the present invention are not particularly limited. Examples include thiazol vulcanization accelerators, such as 2-mercaptobenzothiazol, dibenzothiazyl disulfide, N-cyclohexyl-2-benzothiazyl-sulfenamide (CBS), N-terf-butyl- 2-benzothiazyl sulfenamide (TBBS), and the like; and guanidine vulcanization accelerators, such as diphenylguanidine (DPG) and the like.
  • the amount of the vulcanization accelerator used is about 0.1 to about 5 phr, preferably about 0.2 to about 3 phr.
  • the invention is not limited to the specified mixing times or temperatures, or to the stage in which the particular ingredients are added to the mixer, except that the disulfide organosilane silica coupling agent in the invention compounds is always mixed with the silica at a temperature of about 165°C to about 195°C.
  • the examples have been provided merely to demonstrate the practice of the subject invention and do not constitute limitations of the invention. Thus, it is believed that any of the variables disclosed herein can readily be determined and controlled without departing from the scope of the invention herein disclosed and described.
  • Example 1 In order to demonstrate the methods of preparation and properties of the vulcanizable elastomeric compositions of the invention, three stocks of rubbers were prepared using the compounding formulation and mixing conditions shown in Tables 1, 2 and 3.
  • the disulfide organosilane silica coupling agent employed was Silquest ® A1589 (Witco), and is hereinafter designated "DS".
  • "DS/master batch” stock is a compound in which the disulfane coupling agent, is mixed with the other ingredients in the master batch stage to a drop temperature of 175°C to 180°C.
  • the ingredients in the master batch stage were natural rubber, solution styrene-butadiene rubber (SBR), carbon black, silica, DS silica coupling agent, oil, wax and antioxidant.
  • SBR solution styrene-butadiene rubber
  • the "Si69/remiH” stock contains the same ingredients as the DS/master batch stock, except that the tetrasulfide organosilane silica coupling agent, Si69, was used instead of DS, and added in the remill stage to a drop temperature of 155°C because of the instability of Si69 at temperatures above 160DC.
  • a second control, "DS/remiH” stock was prepared with the same ingredients as the DS/master batch stock, except that the DS was added in the remill stage instead of in the master batch stage, and mixed to a drop temperature of 155°C. The amount of Si69 and DS employed was adjusted to provide equivalent molar content of ethoxysilanes.
  • the total sulfur content of stocks containing DS was adjusted to compensate for the reduction in the amount of sulfur in comparison with that donated from the tetrasulfide silica coupling agent (Si69).
  • the final stocks were sheeted and subsequently annealed at 171 °C for 15 minutes.
  • the green stock i.e., the stock obtained after the final stage, prior to curing
  • a reduced compound Mooney viscosity is advantageous because it provides better processability and handling, especially during the extrusion process.
  • a high compound Mooney viscosity can cause subsequent tire build problems, for example, difficulties in filling the tire mold during the cure step, and can result in modulated inner belts in the tires.
  • the Mooney viscosity measurement was conducted at 130°C using a large rotor, and was recorded as the torque when rotor had rotated for 4 minutes. The sample was preheated at 130°C for 1 minute before the rotor was started.
  • ts is the time required for the viscosity to increase by five Mooney units during a Mooney-scorch measurement. It is used as an index to predict how fast the compound viscosity will increase during processing (e.g., during extrusion).
  • ts 2 and tgo are the times taken for a torque increase of 2 % and 90 %, respectively, of the total torque increase during the cure characterization test. These values are useful in predicting the speed of the viscosity increase (ts 2 ) and the cure rate during the cure process (t 90 ).
  • Silica Coupling Agent* varied (Si69 or Disulfane)
  • the results of the testing are illustrated in Table 4.
  • the results show that the DS/remill stock showed in a reduction in the compound Mooney viscosity compared to the Si69/remill stock.
  • the DS/master batch stock showed a compound Mooney viscosity higher than that of the DS/remill stock, but was comparable to the S ⁇ 69/remill stock.
  • a compound Mooney viscosity of about 60 is not expected to cause difficulties in the extrusion, tire build and curing process in the tire plant.
  • the scorch time (t 5 scorch) and t s2 of the DS/master batch stock were longer than those of both the DS/remill and the Si69/remill stocks.
  • the DS/master batch stock affords a larger processing time window, especially during extrusion, giving the stock adequate time to flow and better fill the mold.
  • EtOSi ethoxysilane
  • the concentration of the residual EtOSi was determined by treating a portion of the stock with a siloxane hydrolysis reagent containing 0.2N toluenesulfonic acid, 0.24N water, 15% n-butanol, 85% toluene, and determining the ethanol content by headspace/gas chromography. About 0.6 grams of the stock was cut into small pieces, placed into a 10 ml. vial, and weighed to an accuracy of ⁇ 0.1 mg. Twelve ml of the siloxane hydrolysis reagent was added and the vial sealed with a Teflon ® lined septum and crimp seal.
  • the vial and contents were then placed in a heated ultrasonic bath at 50°C to 60°C for 60 minutes, followed by shaking on a shaker for 30 to 60 minutes. After cooling to room temperature, the vial and contents were tared and 5 to 10 mg (measured to an accuracy of 4 significant figures) of n-propanol was added to the sample. The n-propanol serves as an internal standard for quantitative gas chromographic analysis. The vial and contents were then placed in an unheated ultrasonic bath for an additional 30 minutes followed by shaking on the shaker for 30 minutes. The total extraction time, including ultrasonic treatment and shaking, was no less than 3 hours. After cooling to room temperature, a 2.0 ml aliquot was transferred to a 22 ml.
  • the vial was securely sealed with a Teflon ® -lined septum and crimp seal.
  • the vial containing the treated sample was loaded into a Varian Genesis headspace autosampler and the ethanol content determined by standard headspace/gas chromatographic techniques.
  • the results of the ethanol analysis of the remill stocks and the final stocks is illustrated in Tables 5 and 6.
  • the DS/master batch stock has 30% less residual EtOSi after remilling, and 33% less residual EtOSi in the final stocks, compared to the DS/remill stock and the Si69/remill stock. Therefore, the DS/master batch stock will have less problem with porosity and blisters.
  • a good silica coupling and dispersing agent should disperse the silica during compounding and stabilize the filler morphology during storage and curing of the compounds.
  • the three stocks prepared in Example 1 were examined for filler flocculation (the Payne effect) before and after they were annealed at 171°C for 15 minutes, as described above.
  • the Payne effects of the green stocks were measured using the Rubber Process Analyzer (RPA) 2000 viscometer (Alpha Technologies).
  • the comparison of the stocks before and after annealing is expressed as the change in the ⁇ G' values ( ⁇ ( ⁇ G')).
  • the annealing conditions employed are similar to conventional curing conditions.
  • the stocks do not contain curatives, therefore an increase in ⁇ G' cannot be attributed to sulfur crosslinking. This comparison illustrates the degree to which the filler flocculates prior to cure.
  • the ⁇ ( ⁇ G') of the DS/master batch stock is lower than both the DS/remill and Si69/remill stocks. Therefore, mixing of the silica and DS at high temperature (175°C) results in better control of the filler morphology in the green stock, and a reduction in filler flocculation after curing.
  • the strain sweep data for the uncured stocks are shown in Figure 1.
  • the G' of the DS/master batch stock is lowest at the lower strain region, but it is higher than the DS/remill as the applied strain level reaches higher than 9%. This indicates that, after annealing, the DS/master batch stock has the lowest filler structure but has more resistance to deformation at higher applied strains compared to the DS/remill stock.
  • the more connections between the polymer and the silica filler through the organosilane coupling agent can contribute to the higher resistance.
  • the Si69/remill stock has a higher G' at all strain levels. It is not clear that the resistance to deformation in this stock is due to the connections between the silica filler and the polymer, or to a higher silica structure.
  • the Payne effect ( ⁇ G') and tan ⁇ at 7% strain are illustrated in the data of Table 8.
  • the Payne effect of the DS/remill stock is much higher than the Si69/remill stock and the DS/master batch stock. This can indicate that mixing DS at 155°C does not effectively prevent the reagglomeration of the silica filler during the curing process.
  • the tan ⁇ at 7% strain also indicates lower hysteresis in the DS/master batch and Si69 remill stocks than in the DS/remill stock. Therefore, the micro-dispersion of the silica in the DS/master batch stock is improved /over both the DS/remill and Si69/remill stocks.
  • the DS/master batch stock exhibits a 50% decrease in the Payne Effect ( ⁇ G'), compared to the DS/remill stock and a 30% decrease in ⁇ G' compared to the Si69/remill stock, indicating improved wear resistance.
  • the DS/master batch stock also exhibits reduced hysteresis, as measured by the tan ⁇ at 7% strain at 65°C in the strain sweep test, i.e., the tan ⁇ of the DS/master batch stock is 11% lower and 21% lower than the Si69/remill stock and the DS/remill stock, respectively.
  • both the DS/master batch and the DS/remill stocks showed a higher tan ⁇ at 0DC compared to the Si69/remill stock, indicating an improvement in tire wet traction.
  • the DS/master batch stock showed a lower value than the DS/remill stock. The lower value indicates better snow traction.
  • the DS/master batch stock showed a lower tan ⁇ at 50°C than the DS/remill stock, and a comparable value to the Si69/remill stock, indicating improved rolling resistance over the DS/remill stock.
  • the temperature spread around the T g peak is wider for the DS/master batch stock and the S ⁇ ' 69/remill stock than for the DS/remill stock, suggesting that more polymer chains are immobilized around the silica particle surfaces.
  • the wider tan ⁇ peak indicates higher hysteresis that could produce the benefit in the tire of better wet traction.
  • This data is further illustrated in Table 8 as the tan ⁇ at -15°C, wherein the values are higher for both the DS/master batch and the Si69/remill stocks than for the DS/remill stock.
  • the tensile properties and Lambourn abrasion indices for the three stocks were measured using the standard procedure described in ASTM-D 412 at 25°C.
  • the tensile test specimens were round rings with a diameter of 0.05 (0.13 cm) inches and a thickness of 0.075 inches (0.19 cm).
  • a gauge length of 1.0 inches (2.54 cm) was used for the tensile test.
  • the wear resistance of the samples was evaluated by weighing the amount of wear using the Lambourn test. The wear index was obtained from the ratio of the weight loss of the control to that of the tested sample. Samples with higher wear indices have better wear resistance properties.
  • Samples used for Lambourn testing were toroidal (donut-shaped) with an approximate inside and outside diameter of 0.9 inches (2.3 cm) and 1.9 inches (4.8 cm), respectively, and a thickness of approximately 0.195 inches (0.495 cm). Test specimens were placed on an axle and run at a slip ratio of 65% against a driven abrasive surface. As illustrated by the results of the tensile and abrasion tests in Table 9, the DS/master batch stock showed superior tensile strength, elongation at break, and a higher wear index compared to the DS/remill stock, and equivalent properties to the Si69/remill stock.
  • the stock produced by mixing DS in the master batch at high temperatures showed surprisingly superior physical properties in comparison with a stock produced by mixing DS at the lower temperature.

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Abstract

L'invention concerne des composés élastomères vulcanisés améliorés contenant une charge de silice de renforcement et un agent de couplage de silice et de disulfane organosilane. Les composés selon l'invention sont obtenus par mélange de polymère, de silice, et de l'agent de couplage de disulfane dans une étape initiale (mélange monté) ou dans une étape de remalaxage à une température élevée de 165 °C à 195 °C. Lesdits composés présentent une dispersion de silice améliorée et une floculation de silice réduite après formulation, des durées de grillage réduites, des vitesses de cuisson réduites, et une diminution de l'évolution d'éthanol durant le stockage, l'extrusion, la cuisson, et la fabrication des pneumatiques. Les produits vulcanisés présentent des propriétés de viscoélasticité améliorées servant généralement à déterminer les performances des pneumatiques dans le domaine de la traction sur neige et sur glace, de la traction sur voie humide, de la résistance au roulement, et de l'hystérésis.
PCT/US2001/024152 2000-07-31 2001-07-31 Proprietes a temperatures de melange elevee de composes caoutchouc charges de silice comportant des agents de couplage de silice et de disulfane Ceased WO2002010271A2 (fr)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2005008639A (ja) * 2003-06-20 2005-01-13 Degussa Ag オルガノ珪素化合物
US7503364B2 (en) * 2003-06-17 2009-03-17 The Yokohama Rubber Co., Ltd. Pneumatic tire with sheet-like auxiliary filler
US7546863B2 (en) * 2003-06-17 2009-06-16 The Yokohama Rubber Co., Ltd. Pneumatic tire with reinforcement rubber layer
US10179479B2 (en) 2015-05-19 2019-01-15 Bridgestone Americas Tire Operations, Llc Plant oil-containing rubber compositions, tread thereof and race tires containing the tread
US10526475B2 (en) 2014-09-24 2020-01-07 Bridgestone Americas Tire Operations, Llc Silica-containing rubber compositions containing specified coupling agents and related methods

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5580919A (en) * 1995-03-14 1996-12-03 The Goodyear Tire & Rubber Company Silica reinforced rubber composition and use in tires
ES2184929T3 (es) * 1996-07-18 2003-04-16 Degussa Mezclas de organo-polisulfanos y procedimiento para la preparacion de mezclas de caucho que los contienen.
US6221943B1 (en) * 1997-07-11 2001-04-24 Bridgestone Corporation Processability of silica-filled rubber stocks
CA2282629A1 (fr) * 1998-10-15 2000-04-15 The Goodyear Tire & Rubber Company Preparation de caoutchouc renforce et utilisation dans les pneus

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7503364B2 (en) * 2003-06-17 2009-03-17 The Yokohama Rubber Co., Ltd. Pneumatic tire with sheet-like auxiliary filler
US7546863B2 (en) * 2003-06-17 2009-06-16 The Yokohama Rubber Co., Ltd. Pneumatic tire with reinforcement rubber layer
JP2005008639A (ja) * 2003-06-20 2005-01-13 Degussa Ag オルガノ珪素化合物
US10526475B2 (en) 2014-09-24 2020-01-07 Bridgestone Americas Tire Operations, Llc Silica-containing rubber compositions containing specified coupling agents and related methods
US11028256B2 (en) 2014-09-24 2021-06-08 Bridgestone Americas Tire Operations, Llc Silica-containing rubber compositions containing specified coupling agents and related methods
US10179479B2 (en) 2015-05-19 2019-01-15 Bridgestone Americas Tire Operations, Llc Plant oil-containing rubber compositions, tread thereof and race tires containing the tread

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