Patent Application
20080093003
Figures (
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In
wherein the first central rubber layer (7A) overlays the radially outer surfaces of said split carcass ply elements (4) and (5) and split carcass ply ends (4A) and (5A) and
wherein the second central rubber layer (7B) underlays the radially inner surfaces of said split carcass ply elements (4) and (5) and split carcass ply ends (4A) and (5A).
In
In particular,
In particular,
The preparation of a tire carcass ply, including said split carcass plies, may be accomplished by conventional means such as, for example, by calendering procedures which are well known to those having skill in such art or by other procedures as may be appropriate.
It is readily understood by those having skill in the pertinent art that the rubber composition for the various tire components, including said split carcass plies and abridging rubber layer which spans the gap between said split carcass ply ends, would be compounded by methods generally known in the rubber compounding art, such as mixing the various sulfur-vulcanizable constituent rubbers with various commonly used additive materials, as herein before discussed, such as, for example, curing aids such as sulfur, activators, retarders and accelerators, processing additives, such as rubber processing oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, microcrystalline waxes, antioxidants and antiozonants, peptizing agents and reinforcing materials such as, for example, carbon black. As known to those skilled in the art, depending on the intended use of the sulfur vulcanizable and sulfur vulcanized material (rubbers), the additives mentioned above are selected and commonly used in conventional amounts.
The vulcanization is conducted in the presence of a sulfur vulcanizing agent. Examples of suitable sulfur vulcanizing agents may include, for example, elemental sulfur (free sulfur) or sulfur donating vulcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin adducts. Preferably, the sulfur vulcanizing agent is elemental sulfur. As known to those skilled in the art, sulfur vulcanizing agents might be used in an amount ranging from, for example, about 0.5 to about 4 phr, more typically from about, for example, about 2 to about 2.5 phr.
Vulcanization accelerators are used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate. Sometimes a single accelerator system may be used, i.e., primary accelerator. More typically, various combinations of primary and secondary accelerators might be used with the secondary accelerator being used in smaller amounts (of about 0.05 to about 3 phr) in order to activate and to improve the properties of the vulcanizate. Combinations of these accelerators might produce a synergistic effect on the final properties and are thereby usually somewhat better than those produced by use of either accelerator alone. In addition, delayed action accelerators may be used which are not particularly affected by normal processing temperatures but produce a more satisfactory cure at higher vulcanization temperatures. Vulcanization retarders might also be used. Suitable types of accelerators that may be used in the present invention are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates. The primary accelerator may often be a sulfenamide. If a second accelerator is used, the secondary accelerator is usually preferably a guanidine, dithiocarbamate or thiuram compound.
The mixing of the rubber composition can be accomplished by a sequential mixing process comprised of at least one non-productive mixing step followed by a productive mixing step. For example, the ingredients may be mixed in two or more (sometimes at least three mixing stages), namely, at least one non-productive (preparatory) stage followed by a productive (final) mix stage. The final curatives are typically mixed in the final stage which is conventionally called the “productive” or “final” mix stage in which the mixing typically occurs at a temperature, or ultimate temperature, lower than the mix temperature(s) of the preceding non-productive mix stage(s). The terms “non-productive” and “productive” mix stages are well known to those having skill in the rubber mixing art.
The following Examples are presented to further illustrate the invention. The parts and percentages are by weight unless otherwise indicated.
Rubber samples of rubber compositions which contain a micro reinforcement for use for an abridging rubber layer for the split ply tire carcass of this invention (to span the gap between split carcass ply ends in the crown portion of the tire) is prepared and identified herein as Control Sample A and experimental Samples B and C which contain UHMWPE micro reinforcement as reported in Table 2.
The basic formulation for the rubber Samples in this and following Examples is presented in the following Table 1.
1Natural cis 1,4-polyisoprene rubber (SMR-20)
2Copolymer of butadiene and styrene rubber as Plioflex ™ 1778 from the Goodyear Tire & Rubber Company
3Rubber reinforcing carbon black as N299, an ASTM designation
4Rubber processing oil
5Quinoline type
6Polyoctenamer as Vestenamer 8012 from the Degussa Company
7Ultra high molecular weight polyethylene (UHMWPE) as GUR4120 from the Ticona company having an average molecular weight of about 5,000,000 mol/g.
8Cellulose in a form of surface treated fiber as Santoweb D ™ from the Flexsys Company.
9Polyaramid pulp in a form of a natural rubber masterbatch as GF 722 from the DuPont Company
10Accelerators as sulfenamide types
The rubber Samples were prepared by mixing the elastomers(s) together with reinforcing fillers and other rubber compounding ingredients in a first non-productive mixing stage (NP-1) in an internal rubber mixer for about 4 minutes to a temperature of about 160° C. The resulting rubber composition is then mixed in a productive mixing stage (PR) in an internal rubber mixer with sulfur curatives for about 2 minutes to a temperature of about 110° C. The rubber composition is sheeted out and cooled to below 40° C. between the non-productive mixing and the productive mixing steps.
The following Table 2 illustrates cure behavior and various physical properties of the rubber Samples. Where a cured rubber sample was evaluated, such as for the stress-strain, rebound, hardness, tear strength and abrasion measurements, the rubber sample was cured for about 23 minutes at a temperature of about 170° C.
1Data obtained according to Moving Die Rheometer instrument, model MDR-2000 by Alpha Technologies, used for determining cure characteristics of elastomeric materials, such as for example Torque, T90 etc.
2Data obtained according to Automated Testing System instrument by the Instron Corporation which incorporates six tests in one system. Such instrument may determine ultimate tensile, ultimate elongation, moduli, etc.
3Data according to Rubber Process Analyzer as RPA 2000 ™ instrument by Alpha Technologies, formerly the Flexsys Company and formerly the Monsanto Company
4Data according to stress-strain analysis of uncured rubber composition.
5Data obtained according to a tear strength (peal adhesion) test to determine interfacial adhesion between two samples of a rubber composition. In particular, such interfacial adhesion is determined by pulling one rubber composition away from the other at a right angle to the untorn test specimen with the two ends of the rubber compositions being pulled apart at a 180° angle to each other using an Instron instrument at 95° C. and reported as Newtons force.
From Tables 2 it can be seen that the compound Shore A hardness and stiffness (100% and 300% moduli) of Samples B and C were significantly enhanced, as compared to Control Sample A, from the introduction of ultrahigh molecular weight polyethylene into the compound (rubber composition).
This is considered herein to be significant in a sense that ultrahigh molecular weight polyethylene provided some reinforcement to the rubber compound as a rubber layer of Samples B and C spanning the gap between split ply ends of a split ply carcass in the crown portion of a tire and overlaying and/or underlaying the split ply ends.
From Tables 2 it can be seen that hysteretic properties (e.g. tan delta at 100° C.) of the compound (Samples B and C) were similar to those of Control Sample A and therefore considered herein as not being significantly affected from the addition of ultrahigh molecular weight polyethylene into the compound.
This is considered herein to be significant in a sense that maintaining the hysteretic properties of the rubber composition would substantially maintain the heat build up property (e.g. not significantly increase the heat built up during the running of the tire) of the rubber composition as well as the rolling resistance performance, of a tire containing an rubber layer of Samples B and C spanning the gap between split ply ends of a split ply carcass in the crown portion of a tire and overlaying and/or underlaying the split ply ends.
Rubber samples of rubber compositions which contain a macro reinforcement for use for an abridging rubber layer for the split carcass ply of this invention (to span the gap between the carcass split ply ends) is prepared and identified herein as Control Sample D and experimental Samples E, F and G which contain cellulose macro reinforcement as reported in Table 3.
The basic formulation for the rubber Samples is presented in Table 1 of Example I.
From Tables 3 it can be seen that the compound Shore A hardness and stiffness (100% and 300% moduli) were significantly enhanced from the introduction of cellulose fiber into the compound.
This is considered herein to be significant in a sense that cellulose fiber provided some reinforcement to the rubber compound.
From Tables 3 it can be seen that hysteretic properties (e.g. tan delta at 100° C.) of the Samples E, F and G, as compared to Control Sample D, were not significantly affected by the addition of cellulose fiber into the compound.
This is considered herein to be significant in a sense that maintaining the hysteretic properties of the rubber composition would substantially maintain the heat build up property (e.g. not significantly increase the heat built up during the running of the tire) of the rubber composition as well as the rolling resistance performance, of a tire containing an rubber layer of Samples E, F and G spanning the gap between split ply ends of a split ply carcass in the crown portion of a tire and overlaying and/or underlaying the split ply ends.
From Table 3 it also can be seen that the green strength of the compound was significantly enhanced for Samples E, F and G, as compared to Control Sample D, by the addition of cellulose fiber into the compound.
This is considered herein to be significant in a sense that the increased green strength would improve the tire building process for the green, uncured tire prior to the shaping and curing step for the tire.
Rubber samples of rubber compositions which contain micro and macro reinforcements for use in the abridging rubber layer for the split carcass ply of this invention (to span the gap between the carcass split ply ends in the crown portion of the tire) is prepared and identified herein as Control Sample H and experimental Samples I and J for polyoctenamaer micro reinforcement and K and L for aramid macro reinforcement as reported in Table 4.
The basic formulation for the rubber Samples is presented in Table 1 of Example I.
From Tables 4 it can be seen that the compound Shore A hardness and stiffness (100% and 300% moduli) were significantly enhanced from the introduction of aramid fiber into the compound.
This is considered herein to be significant in a sense that aramid fiber provided some reinforcement to the rubber compound.
From Tables 4 it can be seen that hysteretic properties (e.g. tan delta at 100° C.) of Samples I, J, K and L, as compared to Control Sample H, were not significantly affected by the addition of polyoctenamer or aramid fiber into the respective rubber Samples.
This is considered herein to be significant in a sense that maintaining the hysteretic properties of the rubber composition would substantially maintain the heat build up property (e.g. not significantly increase the heat built up during the running of the tire) of the rubber composition as well as the rolling resistance performance, of a tire containing an rubber layer of Samples I, J, K and L spanning the gap between split ply ends of a split ply carcass in the crown portion of a tire and overlaying and/or underlaying the split ply ends.
From Table 4 it also can be seen that the green strength of the compound was significantly enhanced from the addition of polyoctenamer and aramid fiber into the compound for Samples I, J, K and L, as compared to Control Sample H.
This is considered herein to be significant in a sense that increased green strength would improve the tire building process for the green, uncured tire prior to the shaping and curing step for the tire.
Rubber samples of rubber compositions which contain micro and macro reinforcement for use in an abridging rubber layer for the split ply tire carcass of this invention (to span the gap between the carcass split ply ends) is prepared and identified in this Example as Control Sample M (with a combination of natural rubber and emulsion SBR) and Control Sample N (with natural rubber) and experimental Samples O and P (corresponding to Control Samples M and N, respectively) which contain cellulose macro reinforcement as reported in Table 6.
The basic formulation for the rubber samples is presented in the following Table 5.
6Data obtained by measuring force in Newtons for a cord pull-out test of the cords embedded in the cured rubber composition.
From Table 6 it can be seen that the combination of all-NR and macro cellulose reinforcement for Sample P, as compared to the rubber blend and macro cellulose reinforcement for Sample O, led to a significant enhancement of the tear strength of the compound.
From Table 6 it also can be seen that the 23° C. cord adhesion of the Samples O and P, as compared to Control Samples M and N, respectively, was maintained or improved by the incorporation of the macro cellulose fiber into the rubber compound.
This is considered herein to be significant in a sense that the macro cellulose-containing compound can be used in combination with fiber cords for further enhancement of the strength of the rubber layer composed of Samples O and M spanning the gap between split ply ends of a split ply carcass in the crown portion of a tire and overlaying and/or underlaying the split ply ends.
While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention.
