Classifications

• • 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
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L7/00—Compositions of natural rubber
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L9/00—Compositions of homopolymers or copolymers of conjugated diene hydrocarbons
  • C08L9/06—Copolymers with styrene

Definitions

• the present invention relates to tires and belts which have improved properties as compared to standard tire and belt compositions.
• the inventors have found that tire and belt compositions having a reduced heat buildup exhibit improved properties, especially when subjected to environments which lead to ageing of the rubber compositions.
• European Patent application 0314271 discloses the use of an improved processing aid to improve handling, durability and rolling resistance of tires, as well as reducing heat buildup.
• European Patent application 0451 603 relates to the use of an anionic polymerization initiator for curing elastomers to improve their hysteresis. Improved hysteresis leads to tires having a lower rolling resistance. One aspect of hysteresis is heat buildup.
• PCT patent application WO 91/05821 discloses a tire sidewall composition comprising a particular polymer which leads to sidewalls having a desirable reduced internal heat buildup and improved adhesion to adjacent rubber carcass and tread portions of the tire.
• publication, "Natural Rubber Compounds for Truck Tires," NR Technology, Vol. 16, Part 1 (1985) suggests the use of additional stearic acid activator in order to reduce the heat generation, among other properties, in truck tires.
• the present invention relates, in one aspect to a tire wherein at least one of the tread, steel-cord skim stock, sidewall and carcass portions contains a rubber composition formed by curing a blend of at least: 50-100 weight percent of natural rubber, polyisoprene or a mixture thereof,
• the present invention relates to a belt which contains a rubber composition formed by curing a blend of at least:
• the low heat buildup rubber compositions of the present invention can be used in tire treads for truck tires and off-the-road tires, in particular, for sidewalls, for tire carcasses and for steel-cord skim stocks.
• the rubber compositions of the present invention are particularly useful for conveyor belts and V-belts which are subjected to high loading and abrasion in service.
• a typical truck tire tread composition in accordance with the present invention comprises the cured product of a blend containing:
• truck tire treads may contain other conventional additives such as 0-20 phr silica, 2-10 phr tackifier, 5-50 phr of processing oil, 1-5 phr waxes, 1-5 phr antioxidant and 1-5 phr antiozonants.
• Important properties for truck tire treads include abrasion resistance, rolling resistance, resistance to cracking, thermal and oxidative stability and durability.
• a typical steel-cord skim stock composition in accordance with the present invention is the cured product of a blend comprising:
• These steel-cord skim stocks may also contain 0-20 phr silica, 0-2.0 phr of a cobalt salt and 1-3 phr of antidegradants. Adhesion to steel is an important property for this portion of the tire.
• a typical carcass portion of a tire in accordance with the present invention is the cured product of a blend comprising: 50-80 weight percent of natural rubber, polyisoprene or a mixture thereof,
• carcass portions may also contain 1-3 phr antioxidant and 2-8 phr processing oil, if desired. Important properties for the carcass portion are the thermal resistance and the rebound resilience.
• a typical sidewall portion of a tire in accordance with the present invention is the cured product of a blend comprising:
• a typical off-the-road tire tread in accordance with the present invention is the cured product of a blend which comprises:
• Off-the-road tire treads may also include 5-50 phr of processing oil, 0-5 phr of resin, 0-2 phr wax, 1-4 phr antiozonants and 0.5-2.0 phr antioxidants.
• Important properties for off-the-road tire treads are tread wear, cutting and chipping resistance and hysteresis.
• a typical conveyor belt in accordance with the present invention is the cured product of a blend comprising:
• a typical V-belt in accordance with the present invention is the cured product of a blend comprising:
• V-belts are fatigue resistance and service life.
• sulfur examples include various types of sulfur such as powdered sulfur, precipitated sulfur and insoluble sulfur.
• sulfur donors may be used in place of, or in addition to sulfur in order to provide the required level of sulfur during the vulcanization process.
• sulfur donors include, but are not limited to, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, dipentamethylene thiuram hexasulfide, dipentamethylene thiuram tetrasulfide, dithiodimorpholine, caprolactam disulfide and mixtures thereof.
• references to sulfur shall include sulfur donors and mixtures of sulfur and sulfur donors. Further, references to the quantity of sulfur employed in the vulcanization, when appl ied to sulfur donors, refer to a quantity of sulfur donor which is required to provide the equivalent amount of sulfur that is specified.
• a vulcanization accelerator in the rubber compound.
• Conventional , known vulcanization accelerators may be employed.
• the preferred vulcanization accelerators include mercaptobenzothiazole, 2,2'-mercaptobenzothiazole disulfide, sulfenamide accelerators including
• 2-(morpholinothio)benzothiazole 2-(morpholinothio)benzothiazole; thiophosphoric acid derivative accelerators, thiurams, dithiocarbamates, diphenyl guanidine, diorthotolyl guanidine, dithiocarbamyl sulfenamides, xanthates, triazine accelerators and mixtures thereof.
• Other rubber additives may also be employed in their usual amounts.
• reinforcing agents such as carbon black, silica, clay, whiting and other mineral fillers, as wel l as mixtures of fillers, may be included in the rubber composition.
• scorch retarders such as phthalic anhydride, pyromellitic anhydride, benzene hexacarboxylic trianhydride, 4-methylphthalic anhydride, trimellitic anhydride, 4-chlorophthalic anhydride, N- cyclohexyl-thiophthalimide, salicylic acid, benzoic acid, maleic anhydride and N-nitrosodiphenylamine may also be included in the rubber composition in conventional, known amounts.
• steel-cord adhesion promoters such as cobalt salts and dithiosulfates in conventional, known quantities.
• the process of curing the blends of the present invention is preferably carried out at a temperature of 110-220°C over a period of up to 24 hours. More preferably, the process is carried out at a temperature of 120-190°C over a period of up to 8 hours. All of the additives mentioned above with respect to the rubber composition may also be present during the vulcanization process. In a more preferred embodiment of the vulcanization process, the vulcanization is carried out at a temperature of 120-190°C over a period of up to 8 hours and in the presence of at least one vulcanization accelerator. The best heat buildup in accordance with the present invention is found when vulcanization is carried out at a temperature above 160°C and/or for a period exceeding t 90 .
• the tire and belt products of the present invention have reduced heat buildup. With respect to the tire products, they exhibit a heat buildup of 20-35°C whereas the belt products exhibit a heat buildup of from 10-35°C.
• Heat buildup for the purposes of the present specification, was measured using ASTM 623 A at a starting temperature of 100°C. The actual heat buildup is the temperature rise from 100°C to the temperature at which equilibrium was reached. Equilibrium temperature is when the temperature stabilizes and does not rise any further. Note that for some prior art products, the temperature never stabilizes.
• One way to produce products in accordance with the present invention is to carry out the curing of the blend in the presence of 0.1-5.0 parts by weight of a coagent represented by the general formula A:
• Ql-D-(Q 2 )n (A); wherein D, optionally containing one or more heteroatoms or groups selected from nitrogen, oxygen, silicon, phosphorus, boron, sulphone and sulphoxy, is a monomeric or oligomeric divalent, trivalent or tetravalent group, n is an integer selected from 1, 2 or 3, Q 1 and Q 2 are independently selected from the formulas I and II:
• R 1 , R 2 and R 3 are i ndependently selected from hydrogen, C 1 -C 18 al kyl groups, C 3 -C 18 cycloal kyl groups, C 6 -C 18 aryl groups, C 7 -C 30 aral kyl groups and C 7 -C 30 al karyl groups and R 2 and R 3 may combine to form a ring when R 1 is hydrogen; B and B 1 are independently selected from the fol lowing hetero atoms: oxygen and sulfur.
• These imides are, in general, known compounds and may be prepared by the methods disclosed in, "The synthesis of Biscitraconimides and Polybiscitraconimides," Galanti, A.V. and Scola, D.A., Journ. of Poly.
• Base compounds were mixed in a Farrel Bridge BR 1.6 liter Banbury type internal mixer (preheating at 50°C, rotor speed 77 rpm, mixing time 6 min with full cooling).
• Optimum cure time (t 90 ) is the time to 90% of delta torque above minimum
• reversion time (t r 2) is the time to 2% of delta torque below maximum torque
• Final torque (Tf) is the torque measured after the overcure time.
• Sheets and test specimens were vulcanized by compression molding in a Fontyne TP-400 press.
• Compression set was determined after 24 h at 70°C or 72 h at 23°C according to ASTM D 395-89.
• Heat build-up temperature rise and compression set after dynamic loading were determined using a Goodrich Flexometer (load 1 MPa, stroke 0.445 cm, frequency 30 Hz, start temperature 100°C, running time 30 min; ASTM D 623-78). Blow out time was determined according to ASTM D 623-78 (load 2 MPa, stroke 0.645 cm, frequency 30 Hz, start temperature 100°C).
• Abrasion was determined using a Zwick abrasion tester as volume loss per 40 m path travelled (DIN 53516).
• Examples 1-3 and Comparative Example A are formulations for truck tire treads.
• the components of each formulation are given in Table 1 and the physical and mechanical properties for different curing conditions are given in Tables 2a-2d.
• the heat buildup and permanent set are given for different curing conditions in Tables 3a-3b.
• Example 4 and Comparative Example B are also formulations for truck tire treads.
• the components of each formulation are given in Table 4 and the physical and mechanical properties for different curing conditions are given in Tables 5a-5b.
• the heat buildup and permanent set are given for different curing conditions in Tables 6a-6b.
• Examples 5-7 and Comparative Examples C-D are formulations for off- the-road tire treads.
• the components of each formulation are given in Table 7 and the physical and mechanical properties for different curing conditions are given in Tables 8a-8d.
• the heat buildup and permanent set are given for different curing conditions in Tables 9-10.
• Example 8 and Comparative Examples E-F are formulations for conveyor belts.
• the components of each formulation are given in Table 11 and the physical and mechanical properties for different curing conditions are given in Tables 12a-12b.
• the heat buildup and permanent set are given for different curing conditions in Table 13.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Compositions Of Macromolecular Compounds (AREA)

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Publications (1)

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• 1992
  • 1992-05-07 SK SK496-94A patent/SK49694A3/sk unknown
  • 1992-05-07 WO PCT/EP1992/001030 patent/WO1993009178A1/en not_active Application Discontinuation
  • 1992-05-07 BR BR9206688A patent/BR9206688A/pt not_active Application Discontinuation
  • 1992-05-07 CA CA002122347A patent/CA2122347A1/en not_active Abandoned
  • 1992-05-07 CZ CZ941047A patent/CZ104794A3/cs unknown
  • 1992-05-07 JP JP4508553A patent/JPH07500616A/ja active Pending
  • 1992-05-07 EP EP92909444A patent/EP0610197A1/en not_active Withdrawn
• 1994
  • 1994-04-28 FI FI941968A patent/FI941968A0/fi unknown

Non-Patent Citations (1)

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