Tires with dyed indicia

Abstract: This invention relates to a vulcanized rubber substrate such as, for example, a tire and a crosslinked, non-black rubber composition layer thereon such as, for example, a white sidewall. In one aspect, the invention relates to such a tire wherein said white sidewall is colored after its vulcanization with a contrasting colored dye. In another aspect, a dye solution is provided which is comprised of a dye dissolved in a hydrocarbon solvent which is characterized by having a solubility parameter of from about 12 to about 20 [J/m 3 ] 1/2 ·10 -3 according to the Polymer Handbook. Upon application of such dye solution to, for example, a crosslinked white portion of a tire sidewall, such dye solution penetrates and swells at least a portion of said white tire sidewall. Upon evaporation of the solvent, a dyed penetration layer is formed.

Description: Field of Invention The present invention relates to dyeing non-black solvent swellable elastomeric articles or products. More specifically, the present invention relates to a dye solution which is generally a hydrocarbon soluble dye dissolved in a hydrocarbon solvent, the dye solution being utilized to penetrate and dye a non-black swellable-hydrocarbon rubber. The non-black rubber may in general be integral or adhered to an elastomeric or thermoset substrate. An apparatus for applying the dye solution is provided as a dispenser comprised of a reservoir and an applicator such as a felt tip. The present invention is particularly directed to dyeing white sidewall portions or white lettering or indicia of pneumatic tires. Background Heretofore, colored vulcanized elastomers have often been prepared by mixing finely divided pigments with uncured rubber followed by vulcanizing the rubber composition. Such elastomers generally have a very uniform color which is resistant to abrasion in the sense that a pigment is dispersed throughout the rubber composition. U.S. Patent 3,577,261 provides a quick method for identifying uncured rubber stocks and rubber cements by the effect of a dye therein on an adherent layer applied thereto. The adherent layer includes particulate pigments and a solvent. The solvent picks up dye from the substrate of rubber stock or rubber cement and imparts the color of the dye to the adherent layer. It is implied that the color of the dye within the rubber stock or rubber cement is hard to visually perceive because of colored pigments (such as carbon black) in the substrate. White sidewalls and raised white letters on pneumatic tires are often composed of stain resistant elastomers, particularly elastomers having large amounts of isobutylene repeat units such as butyl rubber and halobutyl rubber, as well as EPDMs so that common contaminants on the roadways such as motor oils, salt, cinders, tars and also staining oils and vulcanization accelerators within the adjoining black elastomer portions of the tire do not readily stain or discolor the white regions. Summary of the Invention In accordance with this invention, a pneumatic tire , a process for dyeing a pneumatic tire and a rubber article are provided as recited in the claims. Detailed Description of the Invention The invention generally relates to any vulcanized rubber article, generally black because it contains carbon black therein, which has a non-black, solvent swellable, hydrocarbon rubber portion thereon or integral therewith. The present invention will be described with respect to a preferred embodiment of white tire sidewalls, the white sidewall region being a component in a toroidal-shaped pneumatic tire. It is to be understood that it can also be applied to numerous articles or products such as bumper strips, vehicle protection or trim strips, tennis shoes and the like. The white regions on a tire sidewall are generally prepared by assembling a white colored compounded rubber with the tire forming components during the assembly of a green (uncured) tire. The white colored rubber is desirably crosslinked in the mold with the other portions of the tire. The white colored component is formulated so that it is compatible with the other components and bonds well with the crosslinked elastomers of the tire. While a preferred embodiment of the disclosure of the invention relates to dyeing a white tire sidewall, it is to be understood that generally any non-black rubber can be dyed. By the term "non-black" it is meant any color or reflectivity which is greater than zero, on the CIE 1976 L* scale such as rubbers which have a CIE 1976 L* value, of at least 40, desirably at least 50, preferably at least 60, and more preferably at least 70, 80, or 85 before dyeing. A pure white color on the CIE 1976 L* scale has a value of 100, while a black color has a value of 0. Reference to the CIE 1976 L* scale can be readily found in ASTM E 308-94a. A preferred method of forming the white regions of the sidewall is to extrude the white colored component to another (generally black) tire component. The extruded white colored compound has a thin skin of a compounded rubber that matches the composition and color of the tire and which covers the white rubber component. When this covered white component is cocured with the tire and thus adhered or chemically joined thereto, the entire tire sidewall appears to be one color irrespective of whether raised or depressed regions are present on the tire such as letters, or rings, logos, etc. The tire manufacturer can then expose the white component by grinding or abrading away the thin skin to remove the same and expose any desired regions of white rubber. Typically letters spelling a trade name, tire sizes, shape designation, etc. are raised letters (protrude above the rest of the sidewall) while rings around the tire can be raised or recessed. Pneumatic tires generally comprise a tread region which is designed to contact the road or path, two or more sidewalls which help contain the air and provide lateral support, and bead areas which make contact with a rim. The dyeable, non-black, solvent swellable, hydrocarbon elastomers or rubber compositions of the present invention are either substantially free or completely free of polar groups other than small amounts of halogens as in butyl rubber. Desirably, the one or more elastomers have an average of less than 10 weight percent, more desirably less than 5 weight percent, preferably less than 3 or 2 weight percent, and more preferably completely free (i.e, 0 percent) of polar groups. Such polar groups are carboxylic acids, sulfites, sulfates, alkali salts of carboxylic acids, esters, etc., and specifically include amine, sulfonyl, carbonyl, hydroxyl, nitrile, carboxyl, alcohol, ether linkages, and other groups. In calculating these weight percents, only the polar group is considered while attached alkyl or aromatic groups are excluded. Desirably excluded (i.e., substantially free or completely free of) from this embodiment or used in such small amounts to result in an elastomer blend having less than the above specified amounts of polar groups are butadiene-acrylonitrile polymers, acrylate polymers and other polar elastomers. Suitable dyeable elastomers include copolymers having at least 50, desirably at least 80 and preferably at least 90 weight percent repeat units from C 4 to C 7 isomonoolefins, lightly halogenated versions thereof (e.g., less than 5 percent by weight halogen), polydiene (i.e., C 4 to C 12 ) homopolymers or copolymers; copolymers of diene (C 4 to C 12 ) and vinyl aromatic monomers (C 8 to C 15 ); natural rubber, ethylene propylene rubbers, hydrogenated polymers or copolymers of (C 4 to C 12 ) dienes like. The lightly halogenated versions of the above polymers are used due to beneficial changes in cure behavior and are not considered as polar polymers. Preferable elastomer compositions for white sidewall portions comprise from 20 to 80 parts by weight of a copolymer having at least 50 weight percent repeat units from C 4 to C 7 isomonoolefin monomers (e.g., butyl rubber), more desirably from about 25 to about 65 parts by weight; optionally up to 30 parts by weight of an ethylene-propylene diene monomers rubber (EPDM), more desirably up to 25 parts by weight; and up to 80 parts by weight of a homopolymer or copolymer of one or more conjugated diene monomers and optionally with vinyl substituted aromatic monomers, more desirably from 15 to 75 parts by weight wherein all parts by weight are per 100 parts by weight (PHR) of total rubbers in the composition. The carbon black filled portion of a tire sidewall often contains antioxidants and other oil soluble components which tend to discolor or stain many white rubber compounds. Often the antioxidants and other oil soluble components give desirable properties to the tire which cannot be achieved with non-staining components. Therefore, tire sidewall portions which are to be white or light colored, are compounded with large amounts (e.g., greater than 30 PHR, more desirably greater than 40 PHR, and preferably greater than 50 PHR of rubbers having predominantly repeat units from one or more isomonoolefin (C 4 -C 7 ) monomers (e.g., butyl rubber). The non-permeable nature of polymers from isomonoolefin monomers such as isobucylene (e.g., butyl or halobutyl rubber) is the reason why these rubbers are used nearly exclusively (instead of natural rubber or styrenebutadiene rubber) for innertubes and tire innerliners. These isobutylene based rubbers as a cured layer slow the diffusion of pressurized air from inside the tire to a negligible rate. Similarly, polymers from isomonoolefins such as isobutylene slow the diffusion of staining ingredients such as oils, thus preventing undesirable staining of white sidewalls. The effect of polymers from isomonoolefins of preventing dye migration into the rubber is minimized in this application by applying the dye with a solvent that swells the rubber and facilitates migration of dye into the rubber. Desirably, the copolymer of at least 50 weight percent isomonoolefin is a copolymer of at least 50 weight percent isobutylene or halogenated isobutylene. Desirably, the copolymer having at least 50 weight percent of a isomonoolefin comprises butyl rubber (typically a polymer with from 95 to 99 weight percent isobutylene repeat units and from 1 to 5 weight percent of diolefin repeat units) or chlorinated or brominated butyl rubber (having from 0.25 to 2.5 weight percent halogen, more desirably from 0.5 to 1.75 weight percent halogen). Other desired copolymers having at least 50 weight percent of isomonoolefins are derived from polymerizations of C 4 to C 7 isomonoolefins with p-alkylstyrenes having from 80 to 99 weight percent, more desirably from 85 to 98 weight percent isomonoolefin repeat units and from 1 to 20 weight percent, and more desirably from 2 to 15 weight percent of p-alkylstyrenes. These polymers of isomonoolefins and p-alkylstyrenes are made by Exxon. A preferred copolymer is a brominated copolymer with up to 5 weight percent bromine, more desirably from 0.2 to 1.5 or 2.5 weight percent bromine, and from 85 to 98 weight percent isobutylene repeat units and from 2 to 15 weight percent p-methylstyrene. The predominate site of bromination is the p-methyl group. Desirably the ethylene propylene diene monomer (EPDM) copolymer comprises repeat units of from 20 to 90 weight percent, and more desirably from 30 to 85 weight percent ethylene, from 10 to 80 weight percent, more desirably from 15 to 70 weight percent of at least one alpha olefin having from 3 to 16 carbon atoms (usually mostly propylene) based on the total of ethylene and alpha olefins having from 3 to 16 carbon atoms, and from 0.1 to 0.8 moles of one or more nonconjugated dienes having from 6 to 12 carbon atoms per kilogram of EPDM polymer. Desirably the homopolymer or copolymer of a conjugated diene monomer is natural rubber or a synthetic polymer comprised of at least 50 and usually at least 70 weight percent repeat units derived from one or more conjugated diene monomers having from 4 to 8 or 12 carbon atoms. Natural rubber (comprising repeat units of isoprene) is preferred. A desirable comonomer for the residual of the copolymer is vinyl aromatic monomers of from 8 to 12 carbon atoms such as styrene. Preferred polymers include polybutadiene and polyisobutylene. Polar monomers such as acrylates, acrylics, itaconic acid, etc., if utilized at all, are only used in amounts so the total amount of polar groups do not exceed the specified percentages. Other non-polar monomers can also be used in the polymers or copolymers of this elastomer. The solvent swellable rubber compositions of the present invention are not dyed until they are cured (vulcanized or crosslinked). The crosslink density is generally measured by volume swelling capacity with a good solvent. Lower crosslink density is associated with fewer crosslinking occurrences per polymer chain, and low crosslink density results in greater swelling capacity of the cured rubber in a good solvent. Suitable swelling by percent volume in cyclohexane solvent is at least 50 percent, desirably at least 75 percent, 100 percent, or 125 percent, and preferably at least 150 percent or 175 percent by volume of the solvent swellable rubber after soaking overnight at room temperature, i.e., 24 hours at 25°C. Only after the solvent swellable hydrocarbon rubbers such as an elastomeric tire sidewall has been shaped and crosslinked into a final article or end product is the dye applied thereto. This is in distinct contrast to the occasional use of pigments in rubber compounds wherein the pigment was always dispersed in the rubber before crosslinking or-vulcanization occurs. Known crosslinking agents (also known as curatives) which can be used include sulfur, sulfur accelerators, peroxides, other non sulfur curatives, sulfur donor compounds, etc. Sulfur accelerators include guanidines, thiurams, dithiocarbamates, thioureas, thiazoles, sulfenamides and xanthates. Peroxides include dialkyl peroxides, peresters, hydroperoxides, peroxydicarbonates, etc. Crosslinking agents also include zinc oxide, etc. The use of these crosslinking agents, their effective amounts, etc., are well known to the art. Vulcanization is a subset of the crosslinking process. Crosslinking agents are also known as curatives. Crosslinking is often called curing in the art of rubber processing. Fillers can be added to the non-black, solvent swellable rubber composition. Fillers generally are particulate material added to either reduce the total cost or to enhance the stiffness and/or chemical resistance of a composition. Reinforcing fillers tend to enhance the strength of a composition. While carbon black can be utilized, it is not desirable in non-black articles and hence is used in low amounts such as less than 2 PHR, more desirably less than 1.5 or 1 PHR, and preferably less than 0.5 or 0.25 PHR such that the composition would not be black and would be capable of reflecting some colored light as a result of dyeing. Preferably, the dyed elastomers of the present invention are substantially free if not completely free, that is zero parts of carbon black per 100 parts of rubber. Rubber compositions with more than these amounts are generally referred to as black surfaces while those with less than these amounts are generally referred to as non-black. Suitable and desired fillers include talc, clay, silica, calcium carbonate, etc. These may function in addition as pigments -or pigment extenders but their principal function is as fillers. Pigments are desirably added to the composition. Desirably only white pigments are added since white can be dyed to any other color. Thus, any white or non-black pigments which reflect light can be used in these rubber formulations. Desirably, the pigments used have good color retention during aging and resistance to discoloring or degrading on U.V. exposure or they are formulated with age resistors or U. V. protectors to provide color integrity in the final product. The pigments desirably are insoluble in the elastomer component and are consequently dispersed in particulate form. Desirable pigments include titanium dioxide, zinc oxide, white lead and antimony oxide, as well as precipitated silica, calcium silicate, calcium carbonate, treated clays, talc, and whiting. Other additives added to the solvent swellable hydrocarbon composition can include processing aids which generally enhance a composition's speed and ease of processing. They may function by reducing an elastomer's molecular weight or by lubricating the elastomer's surface. Age resistors and U.V. protectors may be added to the composition. Waxes are desirably used because they tend to bloom to the surface and protect the elastomer immediately below the waxy surface. The additives may absorb or neutralize harmful materials or energy or they function to block a mechanism of aging or degradation. While processing oils are often used in rather large amounts in tires and other molded or shaped elastomer articles, if utilized in the non-black, solvent swellable rubber, they are desirably utilized in small amounts. To enhance the compatibility of the elastomer with the dye, the oil generally has the same solubility parameter as the elastomer and/or the solvent for the dye and thus are compatible therewith. Small amounts of oils are from 1 or to 15 PHR and desirably from 2 to 10 PHR. The process oils can include non-staining oils such as naphthenic and paraffinic oils. The hydrocarbon solvents which can be utilized to swell the non-black hydrocarbon rubber compositions generally have a solubility parameter of from 12 to 20, desirably from 13 to 18, and preferably from 14 to 17.5 [J/m 3 ] 1/2 · 10 -3 · Such solvents can be identified in the Polymer Handbook, Second Edition, edited by J. Brandrup and E. H. Immergut, John Wiley and Sons, New York, NY (1975), pages IV-337-347. If a blend of two or more different solvents is utilized, the solubility parameter of the overall blend generally lies within the above-noted ranges. Generally, but not always, solvents which have such suitable solubility parameters can be classified as terpene based solvents such as KNI Solvent-2000; various naphtha solvents such as high flash naphthas, petroleum naphtha, mineral spirits ; various fuel oils such as kerosene, fuel oil no. 2, fuel oil no. 4 ; various alkanes including halogenated alkanes such as cyclohexane, hexane, heptane, octene, decane, dodecane, methylene chloride, chloroform ; and various aromatic solvents including halogenated aromatics such as toluene, various Tolusols generally containing C 7 hydrocarbons and significant amounts of aromatic compounds therein, xylene, dichlorobenzene. Another, but not highly desired class of solvents include the various ethers, desirably those having a high molecular weight such as diphenyl ether. A highly preferred solvent is RE-ENTRY® KNI Solvent-2000, a terpene based solvent from Envirosolv Inc., also d.b.a. Environmental Solvents Corporation of Jacksonville, Florida. The hydrocarbon solvents with the exception of halogenated solvents are generally substantially free or completely free of polar atoms and/or groups. That is, the weight of the total number of any polar atoms and/or groups therein is generally less than 10 percent by weight, desirably less than 5 percent by weight, more desirably less than 3 or 2 percent by weight, and preferably nil, that is, zero percent by weight based upon the total weight of the solvent. Polar atoms include oxygen, nitrogen, sulfur, and the like. Polar groups are defined with respect to the hydrocarbon elastomers. Although halogenated solvents are suitable even though they are polar, they are generally not desired due to environmental reasons. The desired non-polar solvents are generally poorly hydrogen bonded except for the ethers which are moderately hydrogen bonded. Otherwise, moderately hydrogen bonded and strongly hydrogen bonded solvents are avoided and thus are not within the scope of the present invention inasmuch as they generally do not effectively swell non-black rubber compositions. Moderately hydrogen bonded solvents which are avoided, generally include various esters, ketones, glycol monoethers, and the like. Strongly hydrogen bonded solvents include various alcohols, amines, acids, amides, aldehydes, and the like. Numerous examples of solvents having the above noted solubility parameters as well as being characterized as poorly, moderately, or highly hydrogen bonded are set forth in the Polymer Handbook. Another desired attribute of the hydrocarbon solvents of the present invention is that they have a flash point of at least 100°F, (38°C) more desirably at least 125°F (52°C), and preferably at least 140°F (60°C); have no health- effects at the typical exposure levels; and not be hazardous to the environment (desirably biodegradable). Desirably, the solvent has low ratings such as a total rating of 5 or less, and desirably 3 or less based upon the National Fire Protection Association's classification on labelling and properties of flammable liquids (health, flammability, and reactivity ratings). Dyes are generally defined as compounds which contain groups that confer color, generally called chromophores. More information on dyes in general is available in "The Chemistry of Synthetic Dyes," volumes I and II by K. Venkaktaraman, 1952, published by Academic Press, Inc., New York, and in "Organic Chemistry," by W. T. Caldwell, 1943, published by Houghton Mifflin Company in its chapter entitled "Synthetic Dyes," pages 702-725. The dyes desirably are soluble in the low polarity or non-polar hydrocarbon solvents and/or soluble in the poorly hydrogen bonded solvents and are generally free of pigments. Desirably these dyes are soluble to the extent of from 0.0001 to 1.0, desirably from 0.001g to 0.9, and preferably from 0.01 to 0.08 grams per 1.0 gram of solvent when the solvent has a solubility parameter of from 12 to 20, etc., with the solvent being further characterized as being generally a non-polar and/or a poorly hydrogen bonded solvent. Suitable dyes desirably include azo, diazo, quinoline, anthraquinone, indo, ketone imine/methine dyes or derivatives thereof, as well as combinations thereof. Preferred dyes include the azo and quinoline dyes. The synthetic dyes can also be derivatives of aromatic hydrocarbons such as benzene, toluene, naphthalene, and anthracene. Preferred dyes are Akrodye™ oil violet IRS E-705 solvent violet 13 (9,10-anthracenedione)-; 1-hydroxy-4-[(4-methylphenyl)amino], Akrodye™ oil orange #3 E-7174 solvent yellow 14, and Akrodye™ oil brown E-8855 solvent red 2 available from Akrochem Corp. in Akron, Ohio. Other dyes that can be used include Morplas yellow 33, a quinoline type (2(2-quinolylmethylene) phthalide); Morplas red 46, an anthraquinone dye (9,10-anthracenedione, 1-(alkylamino)-; Automates yellow 126, an azo dye, also known as solvent yellow (1-phenyl-3-methyl-4-(alkylphenylazo)-5-pyrazolone; Automates red B, a diazo dye also known as solvent red 164 (2-naphthalenol[(2-naphthalenol[ (phenylazo)phenyllazo alkyl derivatives); Akrodye™ oil yellow #6, solvent yellow 56, a mono azo dye; Akrodye™ oil red #1, solvent red 26, a diazo dye; Akrodye™ oil green #1, solvent green, an azo anthraquinone dye; Ceres™ red; Akrodye™ E8855 brown powder; Pylakrome™ Red LX-1903 (diazo, solvent red 24, 26) (aka CAS# 85-83-6 and CAS# 447-7-79-6); Pylakrome™ Yellow LX-1913A (monoazo, solvent yellow 29 and 56) (aka CAS# 6706-82-7 and CAS# 2481-94-9); Pylam™ blue LX-7270 (anthraquinone, solvent blue 36 and 58) (aka CAS# 14233-37-5 and CAS# 2987-08-9); and Akrodye™ oil blue #8, solvent blue 59, an anthraquinone dye. The present invention relates to dyeing generally any type of the above-noted non-black, solvent. swellable, rubber compositions, including those contained on a crosslinked substrate such as vehicle bumpers or trim, shoes, e.g., tennis shoes, and the like. The crosslinked substrate can also be a tire, for example, e.g., pneumatic tires as used on vehicles (cars, trucks, etc.) construction equipment tires, agricultural equipment tires, cart tires, wheelbarrow tires, recreation equipment tires (all terrain vehicles, motorcycles) and bicycles tires. Other uses of the dyed portion of non-black rubber compositions include the identification or origin of goods, the identification of trademarks or tradenames, the selective application of the dye for identifying marks (such as lot number, batch type, customer, supplier, and part number). Goods can also be customized or further colored by use of dyeing thereby enhancing their desirability and marketability. EXAMPLES The following examples illustrate how the organic - soluble dye can be transferred into swellable elastomeric compositions and especially white sidewalls. Table I shows a typical formulation for a white tire sidewall. A 6x"x6"x0.094" (15,2 x 15,2 x 0,23 cm 3 ) cured sheet of the white sidewall compound of Table I was prepared by molding in a bladder mold for 28 minutes/300°F/100 psi (28 mm/149°C/0,7MPa) bladder pressure/30 tons platen pressure. Then 1"x1"x0.094" (2.54x2.54x0.23cm 3 ) test pieces were clicked out from a bigger sheet for dyeing experiments. Material Parts Natural Rubber 35 Chlorobutyl Rubber 60 EPDM 5 Clay 55 TiO 2 45 Processing Aids 7.5 Fatty Acid Mix well in an intensive mixer such as two roll mill, Banbury, or Brabender 1 Sulfur 1.2 Sulfur Accelerators 2.0 Zinc Oxide 5 Antidegradant Further Mix in an Intensive Mixer 1 Total: 217.7 A 1"x1"x0.094" (2,54x2,54x0,23 cm 3 ) test piece of the white tire sidewall compounds disclosed in Table I was dipped into a solution of a mono azo dye, i.e., Akrodye™ oil yellow #6 (E-6089) (2 g per 100 g solvent) at 40°C in a terpene based KNI Solvent-2000 for 5 minutes. The sample was then removed, dried, and a cross-section cut was made to determine the extent of penetration. The dye penetration under these conditions was total, i.e., about 47 mils (1.19mm). The above mentioned dyeing experiments were repeated using Akrodye™ oil red #1 (E-5883) in a variety of solvents for overnight soaking. As soon as test pieces were taken out from the solvent, swollen lengths were determined using Vernier Calipers and from which the % volume swell were calculated and are reported in Table II. The solubility parameters and the hydrogen bonding capacity of different solvents were taken from the Polymer Handbook whenever available and are also reported in Table II. The dye penetration whenever needed was measured using Vernier Calipers. Solvent Solubility Parameter 3 (J/m 3 ) 1/2 ·10 -3 Hydrogen Bonding Dye Penetration (Mil) Volume % Swell Cyclohexane 16.8 p Total 141.4 m-Xylene 18 p Total 137.4 Toluene 18.2 p Total 129.5 KNI-2000 17.2 p Total 108.7 Decane 13.5 p Total 102.2 Mineral Spirit Total 97 n-Hexane 14.9 p Total 96.7 n-Heptane 15.1 p Total 90.4 Methylene Chloride 19.8 p Total 81.6 Dodecane 16.2 p Total 68.1 Diethyl Ether 15.1 m Total 57.3 Pyridine 21:9 s 0.0625 14.3 1,4-Dioxane 20.5 m 0.09 mil 14.0 Acetone 20.3 m 0.066 0.75 Isobutyl Alcohol 21.5 s Surface -2.0 Methanol 29.7 s Surface -3.4 Isopropanol 24 s Surface -3.6 Perfluoro-alkane 70 12.0 p None -4.9 As apparent from Table II, the hydrocarbon solvents of the present invention having solubility parameters between 13 and 18 as well as low amounts of polar groups and generally poor hydrogen bonding resulted in good penetration of the dye as well as good volume swell of the non-black rubber. In contrast, polar containing compounds such as alcohols, ketones, nitrogen containing compounds, and the like, resulted in poor dye penetration and low volume swell. Four samples of cured rubber having dimensions of 1"x1"x 0.1" (2.54x2.54x0.254cm) were prepared according to the formulations in Table III. Samples B, C, and D had 2, 4, and 6 times the curative concentration of Sample A. This resulted in higher crosslink densities in samples B, C, and D, which restricted their ability to swell with toluene solvent as shown in the volume percent swell test. The reduced swelling of samples B, C, and D resulted in a slower rate of dye penetration and shallower dye penetration as shown by the dye penetration values. Materials A B C D Natural rubber 70.00 70.00 70.00 70.00 SBR-1502 30.00 30.00 30.00 30.00 Silane treated clay 27.5 27.5 27.5 27.5 Titanium dioxide 37.00 37.00 37.00 37.00 Naphthenic/paraffinic medium process oil 1.00 1.00 1.00 1.00 Stearic acid 1.5 1.5 1.5 1.5 Diphenyl guanidine 0.15 0.3 0.6 0.9 Benzothiazyl disulfide 1.5 3.0 6.0 9.0 Zinc oxide 20 20 20 20 Polymeric hindered phenol 1.5 3.0 6.0 9.0 Insoluble sulfur 2.75 5.5 11.0 16.5 Dye penetration 0.038" 0.037" 0.028" 0.011" Volume percent swell 174 152 118 75 The volume percent swell test was conducted by soaking a 1"x1"x 0.1" (2.54x2.54x0.254cm) sample in toluene overnight and then measuring the increase in the largest dimension of the sample. The increase in the dimension was cubed to give volume percent swell. The dye penetration was conducted by dipping a 1"x1"x 0.1" (2.54x2.54x0.254 cm) sample in a solution of Akrodye™ oil red #1 in KNI Solvent-2000 for 20 minutes. The dye concentration was 2 grams per 100 ml of solvent. After the sample was removed, the solvent was allowed to evaporate and the dyed sample was cut in half. The dye penetration was then measured using Vernier Calipers after drying at room temperature. Utilizing the general white rubber formulations set forth in Table IV with the specific rubbers set forth in Table V, other non-black cured rubber (1"x1"x0.076") examples were made and dyed utilizing 2 g of Akrodye™ oil red #1 in 100 g of KNI Solvent-2000. The dye was applied by dipping the test piece for 20 minutes at room temperature. The results are set forth in Table V. Material Parts First Mix Polymers (see E, F, G, & H) 100 Clays 27.5 TiO 2 37 Processing Oil 1 Fatty Acid 1.5 Second Mix Benzothiazyl disulfide 1.5 Diphenylquanidine 0.15 Antioxidant 1.5 Sulfur (80%) 2.75 Zinc Oxide 20 Total: 192.9 DYEABILITY OF WHITE COMPOUNDS BASED ON DIFFERENT RUBBERS All Compounds Exposed to Red dyeing solution for 20'@ RT Sample Thickness = 0.076" Example E F Rubbers Natural/EPDM Natural/SBR Natural 50 parts by weight 70 parts by weight Cl Butyl EPDM 50 parts by weight SBR 30 parts by weight Dyeable Yes Yes Penetration Depth >0.038" >0.038" Example G H Rubbers Natural Natural/Chlorobutyl Natural 100 parts by weight 50 parts by weight Cl Butyl 50 parts by weight EPDM SBR Dyeable Yes Yes Penetration Depth >0.038" >0.038" As apparent from the Table V where the dye penetrated >0.038" from both sides of the samples to dye the entire sample (0.076"), various types of cured elastomers were readily dyeable throughout the total thickness of the rubber. The recipe set forth in Table I was modified by adding various amounts of carbon black thereto. 6"x6"x0.094" cured test panels were dyed by dipping in a solution of Akrodye™ red #1 (E-5883) in KNI Solvent-2000 (2 g dye in 100 ml solvent). Colors were compared before and after dyeing and also their L* values were measured using a Hunter Ultascan equipment and the results are reported in Table VI. Effect of carbon black content in tire white sidewall compound on dyeability as measured by ASTM E 308, Commission Internationale de l'Eclairage CIE publication No. 15.2 (CIE) indices (L*) % Carbon Black Dyeing L* Visual Color 0 Before 87.53 White 0 After 69.49 Pink 0 % Diff 20.61 High 0.5 Before 56.49 Med Gray 0.5 After 52.03 Gray-Purple 0.5 % Diff 7.90 Medium 2.0 Before 40.07 Slate Gray 2.0 After 39.69 Dark Slate 2.0 % Diff 0.95 Low As apparent from Table VI, the amounts of carbon black within the rubber are kept very low so that L* values before are at least 40. Otherwise, the rubber is simply not defined as a non-black rubber. Table VII relates to dyes that were in accordance with the concepts of the present invention and dyes that did not work. Approximately 2 grams of dye were dissolved/dispersed in 200 ml of KNI Solvent-2000. To this was added the 1"x1"x 0.14" of cured control white sidewall test pieces (prepared from 35 natural/65 Cl Butyl + EPDM), i.e., Table I. It was taken out after overnight soaking and then cut into two pieces to examine dye penetration. The dye is said to have worked if it penetrated totally, otherwise it did not work. Just surface coating and penetration less than total on overnight soaking is considered as non-dyeing. Dyes that worked and that did not work are tabulated below. Dyes That Worked Dyes/Pigments That Did Not Work Akrodye™ Oil Yellow #6, E-6089 Akrodye™ Oil Black #4 (E-8540) Akrodye™ Oil Red #1, E-5883 Ceres™ Yellow Akrodye™ Oil Green #1 Akrochem 626 Blue Powder Akrodye™ E-8855 Brown Powder Akrosperse E-98 Blue Paste Akrodye™ Oil Orange #3 Intrasperse Yellow GBA Extra Akrodye™ Oil Violet IRS Intralan Yellow NW 250% Morplas™ Red 46 Aluminum Paste Automate™ Yellow 126 2B-Extra Concentrate Blue Dye Automate™ Red B Precipitated Azo Pigment Ceres™ Red Red Iron Oxide Morplas™ Yellow 33 Pylakrome™ Red LX-1903 Pylakrome™ Yellow LX-1913A Pylam™ Blue LX-7270 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.

Claims: A pneumatic tire, comprising; a toroidal shaped carbon black filled vulcanized rubber composition having integral therewith, a crosslinked non-black rubber composition comprising at least one hydrocarbon rubber having less than 10 weight percent of polar groups therein and other than small amounts of halogens, a white pigment, characterized by having a hydrocarbon soluble dye absorbed into at least a portion of said crosslinked non-black rubber composition, said non-black rubber composition having an exposed surface with a CIE 1976 L* value of at least 40. A pneumatic tire according to claim 1, characterized in that the said crosslinked non-black hydrocarbon rubber composition comprises from 20 to 80 parts by weight of a copolymer per 100 parts by weight of said total hydrocarbon rubber, said copolymer containing at least 50 weight percent of repeat units derived from one or more C 4 to C 7 isomonoolefin monomers, and wherein said toroidal shaped vulcanized composition has a tread region and two sidewall regions. A pneumatic tire according to claim 2, characterized in that the said white pigment comprises titanium dioxide, wherein said portion having absorbed dye of said non-black rubber composition is one or more selective exterior layers, and wherein said crosslinked non-black rubber composition has swelling capacity of at least 75 volume percent in a hydrocarbon solvent. A pneumatic tire according to claim 3, characterized in that the said non-black rubber composition comprises: from 25 to 65 parts by weight of a copolymer being at least 50 weight percent repeat units from one or more C 4 to C 7 isomonoolefin monomers; up to 30 parts by weight of EPDM rubber, and from 15 to 75 parts by weight of natural rubber or a synthetic polymer or combinations thereof, said synthetic polymer having at least 50 weight percent of repeat units derived from a C 4 to C 12 conjugated diene monomer, said parts by weight based upon 100 parts by weight total rubbers of said non-black rubber composition. A pneumatic tire according to claim 1, characterized in that the said hydrocarbon soluble dye has a solubility in a hydrocarbon solvent of at least 0.001 gram per one gram of said hydrocarbon solvent, said hydrocarbon solvent having a solubility parameter of from 12 to 20, and wherein said crosslinked non-black hydrocarbon rubber has less than 3 percent by weight of polar groups therein. A pneumatic tire according to claim 5, characterized in that the said dye is an azo, diazo dye, an anthraquinone dye, a quinoline dye, an aromatic hydrocarbon dye, an indo dye, or a ketone imine/methine dye, or derivatives thereof, or combinations thereof. A pneumatic tire according to claim 4, characterized in that the said hydrocarbon soluble dye has a solubility in a hydrocarbon solvent of at least 0.001 gram per one gram of said hydrocarbon solvent having a solubility parameter of from 12 to 20, and wherein said crosslinked non-black hydrocarbon rubber has less than 2 percent by weight of polar groups therein. A pneumatic tire according to claim 7, characterized in that the said dye is an azo, diazo dye, an anthraquinone dye, a quinoline dye, an aromatic hydrocarbon dye, an indo dye, or a ketone imine/methine dye, or derivatives thereof, or combinations thereof. A process for dyeing a pneumatic tire, characterized by comprising the steps of; applying a dye solution to at least one selective external surface of a crosslinked non-black rubber composition integral with said pneumatic tire, said dye solution being comprised of a dye and a hydrocarbon solvent having a solubility parameter of from 12 to 20 [J/m 3 ] 1/2 ·10 -3 and a flash point of at least 38°C, said solvent containing less than 10 percent by weight of polar atoms other than halogens based upon the total weight of said solvent, said dye being soluble in said hydrocarbon solvent, forming a dye penetration layer in said non-black rubber composition at said selective surface, and evaporating said hydrocarbon solvent. A process according to claim 9, characterized in that the said crosslinked non-black surface of said pneumatic tire is one or more sidewall surfaces, wherein said dye penetration layer is up to 100 mils (2,5 mm) deep in said one or more non-black rubber composition sidewall surfaces, and wherein said hydrocarbon solvent contains less than 5 percent by weight of polar atoms. A process according to claim 10, characterized in that the said non-black sidewall surface has a CIE 1976 L* value before dyeing of at least 50 according to method ASTM E 308, and wherein said hydrocarbon solvent has a solubility parameter of from 13 to 18. A process according to claim 11, characterized in that the said penetration layer is from 10 to 80 mils (0,25 to 2 mm) deep, wherein said hydrocarbon solvent contains less than 2 percent by weight of polar atoms, wherein said non-black rubber composition has a swelling capacity of at least 75 percent in a hydrocarbon solvent, and wherein said CIE 1976 L* value is at least 80. A process according to claim 12, characterized in that the said penetration layer has a dye gradient therein. A rubber article, comprising; a crosslinked substrate and an adhered crosslinked non-black rubber composition layer thereon having a swelling capacity in a hydrocarbon solvent of at least 75 percent, characterized by having a penetration layer located in the exterior portion of said non-black rubber composition layer up to the thickness thereof, and said penetration layer containing a dye therein. A rubber article according to claim 14, characterized in that the said non-black rubber has a non-dyed CIE 1976 L* value of at least 40 according to method ASTM E 308, wherein said dye is a hydrocarbon soluble dye, and wherein said penetration layer extends up to 80 mils (2 mm) deep. A rubber article according to claim 15, characterized in that the said substrate is a pneumatic tire and wherein said swellable non-black rubber layer is a white tire sidewall, and wherein said dye is an azo dye, a diazo dye, a quinoline dye, an anthraquinone dye, an aromatic hydrocarbon dye, an indo dye, or a ketone imine/methine dye, or derivatives thereof, or combinations thereof.

Inventors: MAJUMDAR RAMENDRA NATH, WHITE JOHN RICHARD, MAJUMDAR, RAMENDRA NATH, WHITE, JOHN RICHARD
Applicants: GOODYEAR TIRE & RUBBER, THE GOODYEAR TIRE & RUBBER COMPANY
Application year: 1996
Main classification: B60C13
IPC codes: B60C13