Patent Application
20130061998
This invention relates to pneumatic rubber tires having a carcass ply extending to and turning around a tire bead with an outside-in, turn-up configuration.
Vehicular tires are composed of complex constructions which conventionally include a circumferential tread, two sidewalls individually extending radially inward from a periphery of said tread to a pair of spaced apart relatively inextensible beads and an underlying carcass supporting said tread and sidewalls. The carcass contains at least one and usually several cord reinforced rubber plies extending from bead to bead through the crown region of the tire to promote dimensional and handling stability for the tire.
Carcass ply construction for pneumatic tires is typically provided in a form of an inside-out turn-up configuration with a cord reinforcement-containing rubber carcass ply extending radially inward from the inside of the tire carcass in the sidewall region to and around a bead of the tire with its turn-up end portion terminating radially outward and anchored in the tire's outer sidewall. Such carcass ply configuration might sometimes be referred to as an inside-out turn-up configuration, namely with its carcass ply extending from the inside of the tire and turning around a tire bead with the end of the ply turning up into the tire's outer sidewall portion. Such carcass ply configuration is well known to those having skill in such art.
Further, the construction of such tire may be accomplished, for example, by building the tire components on a building drum to result a shape similar to an open ended barrel with the tire bead portions on the outer ends of the barrel.
As the uncured barrel shaped tire construction is expanded and transformed to a somewhat donut shape, the aforesaid outside-in, turn-up ply configuration causes the carcass ply to be partially pulled around its associated bead which, in turn, pulls the end of the aforesaid turn-up ply in the outer sidewall region toward the bead portion of the tire before the tire assembly is cured and the tire assembly, including the carcass ply fixed in position for the resultant cured tire.
In contrast to such inside-out ply configuration, it is desired to provide a pneumatic tire with a reversed ply direction around the bead, namely, with an outside-in turn-up ply configuration where a cord reinforcement-containing rubber carcass ply extends from the outside of the bead to and around the bead of the tire with the carcass end portion terminating in the tire's inner tire carcass.
For such outside-in turn-up ply configuration, after the tire is built on a tire building drum to form the uncured tire having the aforesaid barrel-like configuration, the tire assembly is expanded to a donut shape and the aforesaid outside-in, turn-up ply configuration causes the carcass ply to be partially pulled around its associated bead which, in turn, pulls the end of the aforesaid turn-up ply in the inner carcass region of the tire toward the bead portion of the tire before the tire assembly is cured and the tire assembly, including the carcass ply fixed in position for the resultant cured tire.
To counteract and thereby reduce or eliminate such movement of the carcass ply around the bead during the shaping of the uncured tire, it has heretofore been proposed to divide the carcass ply into a form of a stress-relieving split ply construction in the crown region of the tire. In such manner, the carcass ply is provided with divided and separated carcass ply ends, which is might sometimes be referred to as split ply construction, in the crown region of the tire, to allow movement of the carcass ply split ends in the tire crown region instead of the tire's bead region during the aforesaid shaping of the uncured tire. For example, see U.S. Pat. No. 7,017,635.
An advantage of such outside-in, turn-up carcass configuration, according to the aforesaid U.S. Pat. No. 7,017,635 may be, for example, to provide a reduction in tire weight resulting from less needed rubber in the outer sidewall portion of the tire which would, in turn, enable an associated reduction in material cost for the tire. It is to be appreciated that even a small decrease in tire weight, with its associated small reduction in tire cost, can promote improved associated vehicular fuel economy, reduction in internal heat generation as the tire is being worked as well as a reduction in cost of manufacturing of the tire.
For this invention, it is desired to provide a novel outside-in, turn-up carcass ply configuration without such aforesaid split-ply construction.
In the description of this invention, the term “phr” relates to parts by weight per 100 parts by weight rubber (phr) unless otherwise indicated.
The present invention relates to a pneumatic rubber tire, particularly a passenger tire, comprised of a circumferential tread, two sidewalls individually extending radially inward from a periphery of said tread to a pair of spaced apart relatively inextensible beads and an underlying carcass supporting said tread and sidewalls, wherein said carcass contains at least one cord reinforced rubber ply extending from bead to bead through the crown region of the tire,
wherein said cord reinforced carcass ply extends from the outside of said bead to and around said bead and where the end portion of said ply terminates in the tire's inner tire carcass,
wherein a self lubricating rubber layer is positioned between said carcass ply and its associated bead to facilitate movement of the carcass ply around said bead during shaping of the uncured rubber tire.
Said tire carcass ply construction is referred to herein as an outside-in, turn-up configuration.
Said tire carcass ply construction is not configured with and is therefore exclusive of a carcass split ply construction.
Said bead of the tire is typically comprised of a plurality of metal filaments which are typically twisted, or cabled together.
In particular, such combination of outside-in turn up carcass ply configuration and said intermediate self lubricating rubber layer is provided to enable movement of said configured carcass ply around said bead component during shaping of the uncured, or green, rubber tire without necessitating a split ply construction in the crown region of the tire.
Historically, a self lubricating rubber layer has heretofore been suggested for positioning on an outer portion of a tire bead component to enable movement of the bead against an associated rigid tire rim of a vehicular wheel. For example, see U.S. Pat. No. 7,231,951.
In practice, said self lubricating rubber layer is comprised of a self lubricating rubber composition containing at least one diene-based elastomer and from about 1 to about 20, alternately from about 2 to about 10, phr of at least one additive comprised of at least one of alcohols of formula (I), esters of formula (II) and amides of formula (III):
wherein R1 and R2 are independently selected from alkyl radicals having from 12 to 36 carbon atoms, alkenyl radicals having from 12 to 36 carbon atoms and alkadienyl radicals having 12 to 36 carbon atoms, so long as said additive promotes a self lubricating quality for said uncured rubber composition of said intermediate rubber layer.
In one embodiment, said alcohol of formula (I) may be comprised of, for example, 1-dodecanol (lauryl alcohol), 1-tetradecanol (myristyl alcohol), 1-hexadecanol (cetyl alcohol), 1-octadecanol (stearyl alcohol), 1-eicosanol (arachidyl alcohol), 1-docosanol (behenyl alcohol), 1-tetracosanol, 1-hexacosanol, 1-octaconsanol, 1-triacontanol (melissyl alcohol), 1-dotriacontanol, 1-tetratriacontanol and mixtures thereof.
In one embodiment, the alcohol of formula (I) comprises 1-octadecanol.
An exemplary octadecanol for the alcohol of formula (I) may be comprised of, for example, CO-1895 Stearyl Alcohol from Procter & Gamble Chemicals. Such product reportedly has a melting point of about 58° C. and a distribution (percent by weight), determined by gas chromatography, of about 0.1 percent C14, about 1.3 percent C16, about 95.5 percent C18, 95.5 percent; and about 0.9 percent C20.
In one embodiment, it is envisioned that the ester of formula (II) may be comprised of for example, a product of esterification of C12-C36 fatty acids with C12-C36 alcohols according to procedures known to those having skill in such art. For example, it is envisioned that such ester may be formed by reaction of the C12-C36 fatty acid with an aliphatic alcohol having from about 12 to about 36 carbon atoms under esterification conditions. For example, it is also envisioned that such ester may be formed by reaction of a C12-C36 fatty acid with a dihydric or polyhydric alcohol, for example, glycerin, ethylene glycol, propylene glycol, pentaerythritol, and polyethylene glycol, and the like.
In one embodiment, it is envisioned that the ester may be comprised of at least one of a fatty acid ester of an aliphatic alcohol including dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, nonadecyl alcohol, eicosyl alcohol, heneicosyl alcohol, docosyl alcohol or mixtures thereof.
In one embodiment, it is envisioned that the ester may be comprised of any of dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, or docosyl esters of any of stearic, oleic, palmitic, 9,12-linoleic, 9,11-linoleic (conjugated linoleic), pinolenic, eicosenoic, palmitoleic, magaric, octadecadienoic, or octadectrienoic acids. For example, in one embodiment, it is envisioned that the ester is comprised of a fatty acid ester of dodecyl alcohol, hexadecyl alcohol or octadecyl alcohol.
In one embodiment, the ester comprises octadecyl octadecanoate (also known as stearyl stearate).
In one embodiment, it is envisioned that the amide of the formula (III) is comprised of for example, be an amide of a saturated or unsaturated monovalent amine, or saturated or unsaturated polyvalent amine, for example, caprylamine, laurylamine, palmitylamine, stearylamine, oleylamine, myristylamine, methylenediamine, ethylenediamine, hexamethylenediamine, and ammonia, and the like. For example, it is envisioned that the amide may be caprylamide, laurylamide, palmitylamide, stearylamide, oleamide, myristylamide, and the like.
In the accompanying drawings:
In the drawings, in general, some of the same numbers are used for the same components or items in the several views.
With reference to
The carcass 8 is comprised at least one cord reinforced rubber carcass ply 8 extending from said bead portion 3 to bead portion 3 through the crown region of the tire 1.
The bead portions 3 contain relatively inextensible metal cords, or bundle of metal filaments and may optionally contain a protective layer, such as for example a nylon layer, wrapped around said bundle of filaments.
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In one embodiment, the rubber to be combined with the additive selected from alcohols of formula I, esters of formula II, and amides of formula III is at least one conjugated diene-based elastomer comprised of at last one polymer selected from polymers of at least one of isoprene and 1,3-butadiene and polymers of styrene and at least one of isoprene and 1,3-butadiene. In one embodiment, rubber may be a blend of two or more of such elastomers.
Representative of such elastomers are, for example, c is 1,4-polyisoprene, c is 1,4-polybutadene, styrene/butadiene copolymers and styrene/isoprene/butadiene terpolymers.
For example, such styrene/butadiene copolymers may be emulsion polymerization prepared (E-SBR) where styrene and 1,3-butadiene are copolymerized as an aqueous emulsion of may be prepared by organic solution copolymerization (S-SBR). Such are well known to those skilled in such art. The bound styrene content can vary, for example, from about 5 to about 50 percent. In one aspect, the E-SBR may also contain acrylonitrile to form a terpolymer rubber, as E-SBAR, in amounts, for example, of about 2 to about 30 weight percent bound acrylonitrile in the terpolymer.
The solution polymerization prepared SBR (S-SBR) typically has a bound styrene content in a range of about 5 to about 50, alternatively about 9 to about 36, percent. The S-SBR can be conveniently prepared, for example, by organo lithium catalyzation in the presence of an organic hydrocarbon solvent.
The cis 1,4-polybutadiene rubber (BR) is often considered to be beneficial for a purpose of enhancing the tire wear. Such BR can be prepared, for example, by organic solution polymerization of 1,3-butadiene. The BR may be conveniently characterized, for example, by having at least a 90 percent cis 1,4-content.
Conventional reinforcing fillers such as for example rubber reinforcing carbon black and rubber reinforcing amorphous synthetic silica such as, for example, precipitated silica may be also present. The amount of such reinforcing fillers may range from 10 to 250 phr. In one embodiment, the filler is present in an amount ranging from 20 to 100 phr.
The commonly employed amorphous synthetic silica may include conventional pyrogenic and precipitated siliceous pigments (silica). In one embodiment precipitated silica is used. The conventional siliceous pigments that may be employed in this invention are in one embodiment precipitated silicas such as, for example, those obtained by the acidification of a soluble silicate, e.g., sodium silicate.
Such conventional silicas might be characterized, for example, by having a BET surface area, as measured using nitrogen gas, in one embodiment in the range of about 40 to about 600, and in another embodiment in a range of about 50 to about 300 square meters per gram. The BET method of measuring surface area is described in the Journal of the American Chemical Society, Volume 60, Page 304 (1930).
The conventional silica may also be typically characterized by having a dibutylphthalate (DBP) absorption value in a range of about 100 to about 400, and more usually about 150 to about 300 cc/100 g.
The conventional silica might be expected to have an average ultimate particle size, for example, in the range of 0.01 to 0.05 micron as determined by the electron microscope, although the silica particles may be even smaller, or possibly larger, in size.
Various commercially available silicas may be used, such as, only for example herein, and without limitation, silicas commercially available from PPG Industries under the Hi-Sil trademark with designations 210, 243, etc; silicas available from Rhone-Poulenc, with, for example, designations of Z1165MP and Z165GR and silicas available from Degussa AG with, for example, designations VN2 and VN3, etc.
Commonly employed rubber reinforcing carbon blacks might be used, representative of which may include those ASTM referenced as N110, N115, N121, N134, N220, N231, N234, N242, N293, N299, N315, N326, N330, M332, N339, N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N774, N787, N907, N908, N990 and N991. Such rubber reinforcing carbon blacks generally have iodine absorption values ranging from 9 to 170 g/kg and DBP number values ranging from 34 to 150 cc/100 g.
In one embodiment the rubber composition for use in the tire component may additionally contain silica coupling agent having a moiety reactive with hydroxyl groups (e.g. silanol groups) on said amorphous synthetic silica (e.g. precipitated silica) and another different moiety interactive with said conjungated diene based elastomer(s).
For example, said coupling agent may comprise a bis(3-trialkoxysilylalkyl)polysulfide having an average of from about 2 to about 4, alternately from about 2 to about 2.6, or alternately from about 3.2 to about 3.8, connecting sulfur atoms in its polysulfidic bridge or an organoalkoxymercaptosilane.
Representative of such silica coupler is comprised of a bis(3-triethoxysilylpropyl)polysulfide.
It is readily understood by those having skill in the art that the rubber composition 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 such as, for example, sulfur donors, curing aids, such as activators and retarders and processing additives, such as oils, resins including tackifying resins and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants and peptizing agents. 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. Representative examples of sulfur donors include elemental sulfur (free sulfur), an amine disulfide, polymeric polysulfide and sulfur olefin adducts. In one embodiment, the sulfur vulcanizing agent is elemental sulfur. The sulfur vulcanizing agent may be used in an amount ranging from 0.5 to 8 phr, with a range of from 1.5 to 6 phr being used in one embodiment. Typical amounts of tackifier resins, if used, comprise about 0.5 to about 10 phr, usually about 1 to about 5 phr. Typical amounts of processing aids comprise about 1 to about 50 phr. Such processing aids can include, for example, aromatic, naphthenic, and/or paraffinic processing oils. Typical amounts of antioxidants comprise about 1 to about 5 phr. Representative antioxidants may be, for example, diphenyl-p-phenylenediamine and others, such as, for example, those disclosed in The Vanderbilt Rubber Handbook (1978), Pages 344 through 346. Typical amounts of antiozonants comprise about 1 to 5 phr. Typical amounts of fatty acids, if used, which can include stearic acid comprise about 0.5 to about 3 phr. Typical amounts of zinc oxide comprise about 2 to about 5 phr. Typical amounts of waxes comprise about 1 to about 5 phr. Often microcrystalline waxes are used. Typical amounts of peptizers comprise about 0.1 to about 1 phr. Typical peptizers may be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide.
Accelerators are used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate. In one embodiment, a single accelerator system may be used, i.e., primary accelerator. The primary accelerator(s) may be used in total amounts ranging from about 0.5 to about 4, in another embodiment about 0.8 to about 1.5, phr. In another embodiment, combinations of a primary and a secondary accelerator might be used with the secondary accelerator being used in smaller amounts, such as from about 0.05 to about 3 phr, in order to activate and to improve the properties of the vulcanizate. Combinations of these accelerators might be expected to produce a synergistic effect on the final properties and are somewhat better than those produced by use of either accelerator alone. In addition, delayed action accelerators may be used which are not affected by normal processing temperatures but produce a satisfactory cure at ordinary 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. In one embodiment, the primary accelerator is a sulfenamide. If a second accelerator is used, the secondary accelerator is in one embodiment a guanidine, dithiocarbamate or thiuram compound.
The mixing of the rubber composition can be accomplished by methods known to those having skill in the rubber mixing art. For example the ingredients are typically mixed in at least two stages, namely at least one non-productive stage followed by a productive mix stage. The final curatives including sulfur vulcanizing agents are typically mixed in the final stage which is conventionally called the “productive” mix stage in which the mixing typically occurs at a temperature, or ultimate temperature, lower than the mix temperature(s) than the preceding non-productive mix stage(s). The rubber and compound is mixed in one or more non-productive mix stages. The terms “non-productive” and “productive” mix stages are well known to those having skill in the rubber mixing art. If the rubber composition contains a sulfur-containing organosilicon compound (silica coupling agent), one may subject the rubber composition to a thermomechanical mixing step. The thermomechanical mixing step generally comprises a mechanical working in a mixer or extruder for a period of time suitable in order to produce a rubber temperature between 140° C. and 190° C. The appropriate duration of the thermomechanical working varies as a function of the operating conditions and the volume and nature of the components. For example, the thermomechanical working may be from 1 to 20 minutes.
Vulcanization (curing) of the tire is generally carried out at conventional temperatures ranging from about 100° C. to 200° C. In one embodiment, the vulcanization is conducted at temperatures ranging from about 110° C. to 180° C. Any of the usual vulcanization processes may be used such as heating in a press or mold, heating with superheated steam or hot air.
In this Example, an alcohol of formula I (octadecanol) and an ester (stearyl stearate) of formula II were evaluated in a rubber composition containing reinforcing filler as rubber reinforcing carbon black.
Rubber compositions containing the materials illustrated in Table 1 were prepared using four individual, sequential mixing stages; namely three non-productive mix stages (without sulfur curative) followed by one productive mix stage (where sulfur curative is added). The non-productive stages were individually mixed for about four minutes to a rubber temperature of about 160° C. The productive stage was mixed for about two minutes, and the drop temperature (temperature of removal from the internal rubber mixer) for the productive mix stage was about 115° C., there the rubber composition was allowed to cool to below 40° C. between mix stages.
The rubber compositions are identified as rubber Samples A through H. Samples A, D, E and H are considered as controls due to the absence of the alcohol or ester.
Rubber Samples B, C, F and G contained the alcohol or ester with Samples B and C containing the ester and Samples F and G containing the alcohol.
Table 2 illustrates various physical properties of the cured rubber Samples A through H.
Where appropriate, the Samples were cured at about 150° C. for about 32 minutes.
The coefficient of friction (COF) test is done according to ASTM D-1894 on a Model SP-2000 Slip/Peel Tester from IMASS Inc. Samples are tested at 6 inches per minute using a 200 g sled. The COF is measured against a polished aluminum surface.
It can be seen from Table 2 that use of stearyl stearate or octadecanol resulted in reduced coefficient of friction.
In this Example, two amides of formula III, namely stearamide and oleamide, were evaluated in a rubber composition containing carbon black.
Rubber compositions containing the materials illustrated in Table 3 were prepared using four separate sequential stages of addition (mixing); namely three non-productive mix stages followed by one productive mix stage. The non-productive stages were mixed for about four minutes to a rubber temperature of about 160° C. The productive stage was mixed for about two minutes, and the drop temperature for the productive mix stage was about 115° C.
The rubber compositions are identified as rubber Samples I through P. Samples I, L, M and P are considered as controls due to the absence of the amide. Experimental rubber Samples J, K, N and O contained the amide, with Samples J and O containing the stearamide and Samples K and N containing the oleamide.
Table 4 illustrates various physical properties of the cured Samples I through P.
The coefficient of friction (COF) test is done according to ASTM D-1894 on a Model SP-2000 Slip/Peel Tester from IMASS Inc. Samples are tested at 6 inches per minute using a 200 g sled. The COF is measured against a polished aluminum surface.
It can be seen from Table 4 that use of stearamide or oleamide resulted in reduced coefficient of friction.
While certain representative embodiments and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in this art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.
