MXPA97005947A - Rubber compositions charged with silice and the propagation of mis - Google Patents

Abstract

The present invention relates to rubber compositions loaded with silica and its processing method. The rubber compositions contain a mixture of 10 to 150 phr of a particulate precipitated silica having from 1 to 20 percent by weight dispersed therein, based on the weight of the silica, of a silica-modified elastomer.

Description

"COMPOSITIONS OF RUBBER LOADED WITH SILICA AND THE PROCESSING OF THE SAME" BACKGROUND OF THE INVENTION U.S. Patent Nos. 3,842,111, 3,873,489 and 3,978,103 disclose the preparation of various organosilicon compounds containing sulfur. Sulfur-containing organosilicon compounds are useful as reactive coupling agents between rubber and silica fillers or fillers providing improved physical properties. They are also useful as adhesion primers for glass substrates, metals and other substrates. U.S. Patent No. 5,409,969 relates to a tread rubber of a pneumatic tire, characterized by 10 to 150 parts by weight of a silica filler or filler and a silane modified polymer having a transition temperature of vitreous state not less than -50 ° C and obtained by reacting an active terminal of a living polymer resulting through the polymerization of 1,3-butadiene or the copolymerization of 1,3-butadiene and styrene, in an organic solvent inert, in the presence of an alkali metal initiator with a silane compound.

COMPENDIUM OF THE INVENTION The present invention relates to silica-loaded rubber compositions containing a precipitated silica in particles having dispersed therein an elastomer modified with its silane. The present invention also relates to an efficient method for processing silica-loaded rubber compositions.

DETAILED DESCRIPTION OF THE INVENTION A method for processing a silica loaded rubber composition comprising mixing (i) 100 parts by weight of at least one vulcanizable elastomer with sulfur selected from homopolymers and copolymers of conjugated diene and copolymers is disclosed. minus a conjugated diene and an aromatic vinyl compound; and (ii) from 10 to 150 phr of a particulate precipitated silica having from 1 to 20 weight percent dispersed therein, based on the weight of the silica, of a silane modified elastomer. Also disclosed is a silica-loaded rubber composition comprising a mixture of (i) 100 parts by weight of at least one sulfur vulcanizable elastomer selected from conjugated diene homopolymers and copolymers and copolymers of at least a conjugated diene and an aromatic vinyl compound; and (ii) from 10 to 150 phr of a particulate precipitated silica having from 1 to 20 percent by weight dispersed therein based on the weight of the silica of a silane-modified elastomer. Also disclosed is a method for reducing the energy required to mix the silica loaded rubber composition comprising mixing (i) 100 parts by weight of at least one vulcanizable elastomer with sulfur selected from homopolymers and copolymers of conjugated diene. and of copolymers of at least one conjugated diene and an aromatic vinyl compound; and (ii) from 10 to 150 phr of a precipitated silica in particles having therein dispersed from 1 percent to 20 weight percent, based on the weight of the silica, of a silane modified elastomer.

The present invention can be used to process vulcanizable elastomers or rubbers containing sulfur containing olefinic unsaturation. The phrase "rubber or elastomer containing olefinic unsaturation" is intended to include both natural rubber and its various raw and regenerated forms as well as the various synthetic rubbers. In the description of this invention, the terms "rubber" and "elastomer" can be used interchangeably, unless otherwise stated. The terms "rubber composition", "stirred or combined rubber" and "rubber compound" are used interchangeably to refer to rubber that has been blended or combined with different ingredients and materials and the terms are well known to those skilled in the art. the rubber mixing branch or rubber combination. Representative synthetic polymers are the homopolymerization products of butadiene and its homologs and derivatives, for example, methylbutadiene, dimethylbutadiene and pentadiene as well as copolymers such as those formed of butadiene or its homologs or derivatives with other unsaturated monomers. Among the latter are acetylenes, for example, acetylene vinyl; olefins, for example, isobutylene, which is copolymerized with isoprene to form the butyl rubber; vinyl compounds, for example, acrylic acid, acrylonitrile (which polymerizes with butadiene to form the NBR), methacrylic acid and styrene, the latter compound is polymerized with butadiene to form SBR, as well as vinyl esters and the various unsaturated aldehydes , ketones and ethers, e.g., acrolein, ethyl isopropenyl ketone and vinylethyl ether. Specific examples of synthetic rubbers include neoprene (polychloroprene), polybutadiene (including cis-1,4-polybutadiene), polyisoprene (including cis-1,4-polyisoprene), butyl rubber, halobutyl rubber such as chlorobutyl rubber or rubber. of bromobutyl, styrene / isoprene / butadiene rubber, copolymers of 1,3-butadiene or isoprene with monomers such as styrene, acrylonitrile and methyl methacrylate, as well as ethylene / propylene terpolymers, also known as ethylene / propylene monomer / diene (EPDM), and in particular, the ethylene / propylene / dicyclopentadiene terpolymers. The preferred rubber or elastomers are polybutadiene and SBR. In one aspect, the rubber composition purchased from at least two diene-based rubbers. For example, a combination of two or more rubbers such as cis-1,4-polyisoprene rubbers (natural or synthetic, even when natural is preferred), 3-4-polyisoprene rubber, styrene / isoprene rubber / butadiene, styrene / butadiene rubbers derived from emulsion and solution polymerization, cis-1, 4-polybutadiene rubbers and butadiene / acrylonitrile copolymers prepared by emulsion polymerization. In one aspect of this invention, a styrene / butadiene rubber (E-SBR) derived from emulsion polymerization, having a relatively conventional styrene content of from about 20 percent to about 28 percent styrene combined, or could be used, for some applications, an E-SBR having a combined medium to relatively high styrene content, namely, a combined styrene content of from about 30 percent to about 55 percent. The relatively high styrene content of about 30 percent to about 55 percent for the E-SBR can be considered beneficial for the purpose of improving the traction, or skid resistance, of the tire tread surface. The presence of E-SBR itself is considered beneficial for the purpose of improving the processability of the mixture of the uncured elastomeric composition especially compared to a use of an SBR (S-SBR) prepared by solution polymerization.

By means of E-SBR prepared by emulsion polymerization, it is meant that styrene and 1,3-butadiene are copolymerized as an aqueous emulsion. This is well known to those skilled in this art. The combined styrene content can vary, for example, from about 5 percent to about 50 percent. In one aspect, the E-SBR may also contain acrylonitrile to form a terpolymer rubber such as E-SBAR, in amounts, for example, from about 2 percent to about 20 percent by weight of acrylonitrile combined in the terpolymer. Styrene / butadiene / acrylonitrile copolymer rubbers prepared by emulsion polymerization containing from about 2 percent to about 40 weight percent of acrylonitrile combined in the copolymer are also proposed as diene-based rubbers for use in this invention . The SBR (S-SBR) prepared by solution polymerization typically has a combined styrene content within the range of about 5 percent to about 50 percent, preferably from about 9 percent to about 36 percent. The S-SBR can conveniently be prepared, for example, by catalysing organolithium in the presence of an organic hydrocarbon solvent. An object of using the S-SBR is due to its improved rim rolling resistance as a result of the lower hysteresis when used in a tread surface composition. The 3,4-polyisoprene (3,4-PI) rubber is considered beneficial for the purpose of improving the traction of the rim when it is used in a tread surface composition. 3,4-PI and the use thereof, are more fully described in U.S. Patent No. 5,087,668 which is incorporated herein by reference. The Tg refers to the glass transition temperature which can be conveniently determined by a differential scanning calorimeter at a heating rate of 10 ° C per minute. The rubber of cis-1,4-polybutadiene (BR) is considered to be beneficial for the purpose of improving wear of the running surface of the rim or duration of the running surface. This BR can also be prepared, for example, by polymerization by organic solution of 1,3-butadiene. The BR can be conveniently characterized, for example, having at least a cis-1,4 content of 90 percent. Cis-1, 4-polyisoprene and the natural rubber of cis-1,4-polyisoprene are well known to those skilled in the rubber art. The term "phr" as used herein, and in accordance with conventional practice, refers to "parts by weight of a respective material per 100 parts by weight of a rubber or elastomer". The rubber composition should contain a sufficient amount of pretreated silica (a term used interchangeably herein, to describe a precipitated silica in particles that has dispersed therein from 1 percent to 20 percent by weight, based on the weight of the silica , of a silane-modified elastomer described herein), and non-pretreated silica, if used to contribute to a reasonably high modulus and high breaking strength. The pretreated silica filler or filler material can be added in amounts ranging from 10 to 150 phr. Preferably, the pretreated silica is present in an amount ranging from 15 to 80 phr. If untreated silica is also present, the amount of unpretreated silica, if used, may vary. Generally speaking, the amount of non-pretreated silica will vary from 0 to 80 phr. Preferably, the amount of the non-pretreated silica will vary from 0 to 40 phr. When the rubber composition contains both pretreated silica and unpretreated silica, the weight ratio of the silica pretreated to the untreated silica can vary. For example, the weight ratio can be as low as 1: 5 with respect to a weight ratio of 30: 1 of a pretreated silica to a non-pretreated silica. Preferably, the weight ratio of the pretreated to the pretreated silica varies from 1: 3 to 5: 1. The combined weight of the pretreated silica and the unpretreated silica as mentioned herein may be as low as about 10 phr, but preferably is about 45 to about 90 phr. The precipitated siliceous pigments commonly used in rubber blending or combination applications can be used as the silica pretreated and not pretreated in this invention. The siliceous pigments preferably used in this invention are obtained by acidification of a soluble silicate, v.gr, sodium silicate. These silicas could be characterized, for example, by having a BET surface area as measured using nitrogen gas, preferably within the range of about 40 to about 600, and more usually within the range of about 50 to about 300 square meters. per gram. The BET method for measuring surface area is described in Journal of the American Chemical Society, Volume 60, page 304 (1930). The silica can also typically be characterized having an absorption value of dibutyl phthalate (DBP) within the range of from about 100 to about 400, and more usually from about 150 to about 300. The silica could be expected to have a final particle size average, for example, within the range of 0.01 to 0.05 micron as determined by an electron microscope, even though the silica particles may be of an even smaller, or possibly larger, size. The various silicas commercially obtainable for use in this invention may be considered such as, for example only and without limitation, the silicas commercially available from PPG Industries under the trademark Hi-Sil with designations 210, 243, etc.; the silicas obtainable from Rhone-Poulenc, with, for example, designations of Z1165MP, Z165GR and silicas obtainable from Degussa AG, for example, with designations VN2 and VN3, etc. As mentioned above, prior to mixing with an elastomer, the precipitated silica is pretreated or has a silane-modified elastomer dispersed thereon. The polymer to be dispersed on the surface of the silica is a silane-modified polymer having a glass transition temperature of not less than -50 ° C. Generally speaking, the vitreous state transition temperature ranges from about -50 ° C to -90 ° C, with a scale of about -60 ° C to -75 ° C being preferred. The silane-modified polymer per se can be prepared according to the teachings of U.S. Patent No. 5,409,969. Therefore, the polymer can be obtained by reacting an active terminal of a living polymer resulting through the polymerization of 1,3-butadiene or the copolymerization of 1,3-butadiene and styrene with an organic alkali metal initiator with a silane compound represented by the following general formula XyWySMOR1 ^ I wherein X is halogen selected from the group consisting of chlorine, bromine and iodine; W is an alkylene radical having from 1 to 8 carbon atoms; Y is 0 or 1, R1 is independently selected from the group consisting of alkyl radicals having from 1 to 8 carbon atoms and aryl radicals having from 6 to 24 carbon atoms; yz is 4 when y is 0 and z is 3 when y is 1. Preferably y is 0, R ^ - is an alkylene group having 2 carbon atoms and z is 4. The polymer used in the invention can be produced by the Well-known method using an organic alkali metal initiator. The production of this polymer is usually carried out in an inert organic solvent. As the inert organic solvent, pentane, hexane, cyclohexane, heptane, benzene, xylene, toluene, tetrahydrofuran, diethyl ether and the like can be used. First, the polymerization of 1,3-butadiene or the copolymerization of 1,3-butadiene and styrene is carried out in the presence of an organic alkali metal initiator. As the organic alkali metal initiator, examples include alkyl lithiums, such as n-butyl lithium, secondary butyl lithium, tertiary butyl lithium, butane 1-di-lithium, a butyl lithium reaction product and divinylbenzene and the like; alkylene di-lithium, phenyl-lithium, di-lithium stilbene. di-lithium diisopropylbenzene, sodium naphthalene, lithium naphthalene, etc.

In the case of copolymerization, a Lewis base can be used as a random agent and a regulating agent for the microstructure of the butadiene unit in the copolymer, if necessary. Examples of the Lewis base include ethers and tertiary amines, such as dimethoxybenzene, tetrahydrofuran, dimethoxyethane, dibutyl ether of diethylene glycol, dimethyl ether of diethylene glycol, triethylamine, pyridine, morpholine of N-methyl, ethylenediamine of N, N, N ', N'-tetramethyl, 1,2-dipiperidinoethane and the like. In addition, the content of the combined styrene in the copolymer can be controlled by varying the amount of the styrene monomer in the monomer mixture, while introducing a single styrene chain into the copolymer; that is, the placement of the chain of styrenes without sequence of the styrene chain unit can be controlled by the use of an organic potassium compound, such as potassium dodecylbenzene sulfonate or the like. In addition, the content of the 1,2-linkage in the butadiene unit of the copolymer molecule can be controlled by varying the polymerization temperature. Also, the living polymer can be produced by charging the monomers: that is, 1,3-butadiene or 1,3-butadiene and styrene, the inert organic solvent, the organic alkali metal initiator, and if necessary, the base Lewis in a reaction vessel purged with nitrogen gas, all at once, discontinuously or continuously. The polymerization temperature is usually -120 ° C to + 150 ° C, preferably from -88 ° C to + 120 ° C, and the polymerization time is usually from 5 minutes to 24 hours, preferably from 10 minutes to 10 hours. The polymerization temperature can be maintained at a constant value within the aforementioned scale or it can be raised or adiabatic. Also, the polymerization reaction can be carried out by an intermittent system or a continuous system. In addition, the concentration of the monomer in the solvent is usually from 5 percent to 50 percent by weight, preferably from 10 percent to 35 percent by weight. In the formation of the living polymer, it is necessary to prevent the incorporation of a compound exhibiting a deactivation function, such as a halogen compound, oxygen, water, carbon dioxide gas or the like in the polymerization system, as much as possible. possible in order to avoid the deactivation of the organic alkali metal initiator and the resulting living polymer. Representative examples of the silane of the formula I include, tetramethoxy silane, tetraethoxy silane, tetrapropoxy silane, tetrabutoxy silane, tetrahexoxy silane, tetraheptoxy silane, tetrabutoxy silane, tetra (2-ethylhexoxy) silane, tetrafenoxi, chloropropoxy silane, chloromethylpropoxy silane (mention all the others of importance). This silane-modified polymer is obtained by reacting the active terminal of the above-mentioned living polymer with the silane compound of the formula I. The amount of the silane compound that is used is not less than 0.7 molecule per active terminal of the living polymer. Preferably, the amount varies from 0.7 to 5.0 and, more specifically from 0.7 to 2.0. When the amount of the silane compound used is less than 0.7 molecule per active terminal of the living polymer, the production of the branched polymer becomes larger and the change in molecular weight distribution is large, and therefore, the control of the Molecular weight and molecular weight distribution is difficult, whereas when it exceeds 5.0 molecules per active terminal of the living polymer, the effect to improve wear resistance and fracture properties becomes saturated and becomes unfavorable in view of economic reasons . In the production of the silane-modified polymer, the addition of two steps wherein a small amount of the silane compound is first added to the active terminal of the living polymer can be used., in order to form a polymer having a branched structure and then another silane compound is added to the remaining active terminal. The reaction between the active terminal of the living polymer and the functional group of the silane compound is carried out by adding the silane compound to the solution in the living polymer system, or by adding the solution of the living polymer to an organic solvent solution which contains the silane compound. The reaction temperature is from -120 ° C to + 150 ° C, preferably from -80 ° C to + 120 ° C and the reaction time is from 1 minute to 5 hours, preferably from 5 minutes to 2 hours. After the completion of the reaction, the silane-modified polymer can be obtained by blowing steam into the polymer solution to remove the solvent or by adding a lean solvent, such as methanol or the like to solidify the resulting polymer modified with silane, then drying through cylinders. hot or under reduced pressure. Alternatively, the solvent can be removed directly from the polymer solution under reduced pressure to obtain a silane modified polymer. Even though the molecular weight of the silane-modified polymer can be varied across a wide scale, the Mooney viscosity (MLi + 4, 100 ° C) should preferably be within the slat from 10 to 150. When the Mooney viscosity is lower of 10, the wear resistance is deficient, while when it exceeds 150 the processability is deficient. Pretreatment of the silica precipitated with the silane-modified polymer is usually carried out in the presence of an appropriate solvent. The main criterion is to use a solvent that does not react with the starting materials or the final product. Representative organic solvents include chloroform, dichloromethane, carbon tetrachloride, hexane, heptane, cyclohexane, xylene, benzene, toluene, aliphatic and cycloaliphatic alcohols. Preferably, the water is avoided to prevent reaction with the reactable siloxy groups of the silane-modified polymers. The first step in the pretreatment step is to dissolve the silane-modified polymer in the solvent containing the silica. The silane-modified polymer should be added in an amount ranging from about 2 percent to 30 percent by weight, based on the weight of the untreated silica. Preferably, the amount of the silane modified polymer is added in an amount ranging from 10 percent to 20 percent by weight. The reaction should be carried out at a temperature ranging from about 50 ° C to about 200 ° C. The reaction time may vary. In general, the reaction time varies from approximately 1 to 24 hours. The final step in the pretreatment procedure is to remove the pretreated silica from the solvent. This separation step can be achieved by well-known means such as filtration, drying of the heat and vacuum pre-treated silica and the like. Upon completion of the pretreatment step, a silica having dispersed in the same silane modified elastomer identified above is provided. The silane-modified elastomer is generally present at a level ranging from 1 percent to 20 percent by weight based on the weight of the silica. Preferably, the silane modified elastomer is present at a level ranging from 5 percent to 15 percent by weight, based on the weight of the silica. Although the pretreated silica contains suspended alkoxysilane residues, this pretreated silica loaded rubber composition may also contain known symmetrical sulfur-containing organosilicon compounds. Examples of suitable sulfur-containing organosilicon compounds are of the formula: Z-Alq-Sn-Alq-Z (II) where Z is selected from the group consisting of R3 R I -Si - R3 -Si - R4 -Si - R4 R4 R4 R4 wherein R3 is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl; R 4 is alkoxy of 1 to 8 carbon atoms or cycloalkoxy of 5 to 8 carbon atoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is an integer of 2 to 8. Specific examples of the sulfur-containing organosilicon compounds that can be used in accordance with the present invention include: 3, 3'-bis ( trimethoxysilylpropyl) disulfide, 3,3'-bis (triethoxysilylpropyl) tetrasulfide, 3,3'-bis (triethoxysilylpropyl) octasulfide, 3,3'-bis (trimethoxysilylpropyl) tetrasulfide, 2,2'-bis (triethoxysilylethyl) tetrasulfide, 3, 3'-bis (trimethoxysilylpropyl) trisulfide, 3,3'-bis (triethoxysilylpropyl) trisulfide, 3,3'-bis (tributoxysilylpropyl) disulfide, 3,3'-bis (trimethoxysilylpropyl) hexasulfide, 3,3'-bis (trimethoxysilylpropyl) ) octasulfide, 3,3'-bis (trioctoxysilylpropyl) tetrasulfide, 3,3'-bis (trihexoxysilylpropyl) disulfide, 3,3'-bis (tri-2"-ethylhexosilylpropyl) trisulfide, 3,3'-bis (triisooctoxysilylpropyl) tetrasulfide, 3, 3'-bis (tri-t-butoxysilylpropyl) disulfide, 2,2'-bis (methoxy diethoxy silylethyl) tetras ulfuro, 2,2'-bis (tripropoxysilylethyl) pentasulfide, 3,3'-bis (tricyclonexoxysilylpropyl) tetrasulfide, 3,3'-bis (tricyclopentoxysilylpropyl) trisulfide, 2,2'-bis (tri-2"-methylcyclohexoxysilylethyl) tetrasulfide , bis (trimethoxysilylmethyl) tetrasulfide, 3-methoxy ethoxy propoxysilyl 3'-diethoxybutoxy-silylpropyltetrasulfide, 2,2'-bis (dimethylmethoxysilyl) disulfide, 2,2'-bis (dimethyl sec.-butoxysilylethyl) trisulfide, 3'3'- bis (methyl butylethoxysilylpropyl) tetrasulfide, 3, 3'-bis (di t -butylmethoxysilylpropyl) tetrasulfide, 2,2'-bis (phenylmethylmethoxylethyl) trisulfide, 3,3'-bis (diphenyl isopropoxysilylpropyl) tetrasulfide, 3, 3 ' bis (diphenyl cyclohexoxysilylpropyl) disulfide, 3, 3'-bis (dimethyl ethylmercaptosilylpropyl) tetrasulfide, 2,2'-bis (methyl dimethoxysilylethyl) trisulfide, 2,2'-bis (methyl ethoxypropoxysilylethyl) tetrasulfide, 3, 3'-bis (diethylmethoxysilylpropyl) tetrasulfide, 3,3'-bis (ethyl di.sec-butoxysilylpropyl) disulfide, 3,3'-bis (propyl-diethoxysilylpropyl) disulfide, 3,3'-bis (butyl-dimethoxysilylpropyl) trisulfide , 3, 3'-bis (phenyl dimethoxysilylpropyl) tetrasulfide, 3-phenyl-ethoxybutoxysilyl-3'-trimethoxysilylpropyl tetrasulfide, 4,4'-bis (trimethoxysilylbutyl) tetrasulfide, 6,6'-bis (triethoxysilylhexyl) tetrasulfide, 12, 12 '- bis (triisopropoxysilyl dodecyl) disulfide, 18,18'-bis (trimethoxysilyloctadecyl) tetrasulfide, 18,18'-bis (tripropoxysilyloctadecenyl) tetrasulfide, 4, '-bis (trimethoxysilyl-buten-2-yl) tetrasulfide, 4,4' - bis (trimethoxysilylcyclohexylene) tetrasulfide, 5,5'-bis (dimethoxymethylsilylpentyl) trisulfide, 3,3 * -bis (trimethoxysilyl-2-methylpropyl) tetrasulfide, 3,3'-bis (dimethoxyphenylsilyl-2-methylpropyl) disulfide. Preferred sulfur-containing organosilicon compounds are the 3,3'-bis (trimethoxy or triethoxy silylpropyl) sulfides. The especially preferred compound is 3, 3'-bis (triethoxysilylpropyl) tetrasulfide. Therefore, as for formula II, preferably Z is - Si - R4 I R4 wherein R4 is an alkoxy of 2 to 4 carbon atoms, with the 2 carbon atoms being particularly preferred; Alk is a divalent hydrocarbon of 2 to 4 carbon atoms with 3 carbon atoms being particularly preferred; and n is an integer from 3 to 5, with 4 being particularly preferred. The amount of the sulfur-containing organosilicon compound of the formula II in a rubber composition will vary, depending on the level of the silica used. Generally speaking, the amount of the compound of the formula II will vary from .00 to 1.0 part by weight per part by weight of the silica. Preferably the amount will vary from .00 to 0.4 part by weight per part by weight of the silica. It will be readily understood by those skilled in the art that the rubber composition would be combined or stirred by methods generally known in the rubber combination branch., such as mixed with the various constituent rubbers vulcanizable with sulfur with various materials used as an additive, 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 or fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants and peptizing agents. As is known to those skilled in the art, depending on the use to which the material vulcanized with sulfur or vulcanized with sulfur (rubbers) is intended, the aforementioned additives are selected and commonly used in conventional amounts. Typical amounts of the carbon black (s) of the reinforcing type for this invention, if used, are noted herein. Representative examples of sulfur donors include elemental sulfur (free sulfur) an amine disulfide, polymeric polysulfide and sulfur olefin adducts. Preferably the sulfur vulcanization agent is elemental sulfur. The sulfur vulcanization agent can be used in an amount ranging from 0.5 to 8 phr, with a scale of 1.5 to 6 phr being preferred. Typical amounts of the tackifying resins if used comprise from 0.5 to about 10 phr, usually from about 1 to about 5 phr. Typical amounts of processing aids comprise from about 1 to about 50 phr. These processing aids may include, for example, aromatic, naphthenic and / or paraffinic oils. Typical amounts of antioxidants comprise from about 1 to about 5 phr. Representative antioxidants, for example may be diphenyl-p-phenylenediamine and others, such as for example those disclosed in Vanderbilt Rubber Handbook (1978), pages 344 to 346. Typical amounts of antiozonants comprise from about 1 to about 5 phr. Typical amounts of fatty acids if used, which may include stearic acid comprise from about 0.5 to about 5 phr. Typical amounts of zinc oxide comprise from about 2 to about 5 phr. Typical amounts of waxes comprise from about 1 to about 5 phr. Microcrystalline waxes are frequently used. Typical amounts of peptizers comprise from about 0.1 to about 1 phr. Typical peptizers, for example, may be pentachlorothiophenol disulfide and dibenzamidodiphenyl disulfide. In one aspect of the present invention, the rubber composition vulcanizable with sulfur is then cured with sulfur or vulcanized with sulfur. Accelerators are used to control the time and / or temperature that are required for vulcanization and to improve the properties of the vulcanized material. In one embodiment, a single accelerator system, ie, a primary accelerator, can be used. The primary accelerator (s) can be used in total amounts ranging from about 0.5 to about 4, preferably from about 0.8 to about 2.5 phr. In another embodiment, combinations of a primary accelerator and a secondary accelerator could be used, with the secondary accelerator being used in amounts ranging from about 0.05 to about 3 phr, in order to activate and improve the properties of the vulcanized material. The combinations of these accelerators could be expected to produce a synergistic effect on the final properties and are somewhat better than those produced by the use of any single accelerator. In addition, delayed action accelerators which are not affected by normal processing temperatures can be used, but produce a satisfactory cure at regular vulcanization temperatures. Vulcanization retarders could also be used. The appropriate types of accelerators that can be used in the present invention are amines, disulfides, guanidines, thioureas, thiazoles, thiouramyls, sulfenamides, dithiocarbamates and xanthates. Preferably, the primary accelerator is a sulfenamide. If a secondary accelerator is used, the secondary accelerator is preferably a guanidine, dithiocarbamate or a thiouramyl compound. The mixing of the rubber composition can be achieved by methods known to those skilled in the rubber mixing field. For example, the ingredients are typically mixed in at least two stages, namely at least one non-productive step followed by a productive mixing step. The final curing agents, including sulfur vulcanization agents, are typically mixed in the final stage which is conventionally called the "productive" mixing step, in which mixing typically occurs at a temperature or final temperature lower than the temperature (s) of the mixture, than in the previous nonproductive mixing stage (s). Rubber, pretreated silica, and carbon black, if used, are mixed in one or more non-productive mixing stages. The terms "non-productive" and "productive" mixing stages are also known to those skilled in the field of rubber mixing. The sulfur vulcanizable rubber composition containing the vulcanizable rubber and generally at least part of the pretreated silica, as well as any optional sulfur-containing organosilicon compound, if used, must be subjected to a thermomechanical mixing step. The thermomechanical mixing step, generally, comprises a mechanical treatment in a mixer or extrusion apparatus for an appropriate period of time in order to produce a rubber temperature of between 140 ° C and 190 ° C. The proper duration of the thermomechanical treatment varies as a function of the operating conditions and the volume and nature of the components. For example, the thermomechanical treatment can be from 1 to 20 minutes. The vulcanization of the rubber composition of the present invention is, in general, carried out at conventional temperatures ranging from about 100 ° C to 200 ° C. Preferably, the vulcanization is carried out at temperatures ranging from about 110 ° C to 180 ° C. Any of the usual vulcanization processes such as heating in a press or mold, heating with superheated steam or hot air or in a salt bath can be used. During the vulcanization of the composition vulcanized with sulfur, the rubber composition of this invention can be used for various purposes. For example, the rubber composition vulcanized with sulfur can be in the form of a rim, a belt or a hose. In case of a tire, it can be used for different rim components. These rims can be made, shaped, molded and cured by different methods that are known and will be readily apparent to those skilled in this art. Preferably, the rubber composition is used on the running surface of a rim. As will be appreciated, the rim can be a rim for passenger cars, a tire for airplanes or a tire for trucks and the like. Preferably the rim is a rim for passenger cars. The rim can also be a radial or skewed rim, with the radial rim being preferred. Even though certain embodiments and representative details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

Example 1 Preparation of Pretreated Silica In a meticulously dry stirred reactor with a capacity of 3.79 liters, 2,000 grams of a dried butadiene-hexane mixture (15 weight percent / 85 weight percent) and 3 millimole of n-butyllithium were charged. The reactor was heated at 60 ° C for 4 hours. Two millimoles of tetrahydroxysilane (Li / Si = 1) were added and heating continued for another hour. The batch was stopped with an excess of methanol. Six grams of 2,6-di-t-butyl-p-cresol was added to the solution, and the polymer was isolated by removing the hexane. Five hundred grams of silica Zeosil 1165MP were loaded into a 4 liter beaker together with 306 grams of silylated polymer cement (50 grams of dry polymer and 256 grams of hexane) the slurry was stirred followed by removal of the hexane at 70 ° C under reduced pressure in a vacuum oven. The amount of the polymer functionalized on the silica was calcined to be 10 weight percent.

Example 2 Preparation of Pretreated Silica In a meticulously dry stirred reactor with a capacity of 3.79 liters, 2,000 grams of a mixture of dry butadiene / hexane (15 weight percent / 85 weight percent) and 3 millimole of n-butyllithium were charged. The reactor was heated at 60 ° C for 4 hours. 2 millimoles of chloropropyltriethoxysilane (Li / Si = 1) were added and heating was continued for another hour. The batch was stopped with an excess of methanol. Six grams of 2,6-di-t-butyl-p-crucible was added to the solution, and the polymer was isolated by removing the hexane. Five hundred grams of silica Zeosil 1165MP was charged into a 4 liter beaker together with 306 grams of silylated polymer cement (50 grams of dry polymer and 256 grams of hexane). The slurry was stirred followed by evasion of hexane at 70 ° C under reduced pressure in a vacuum oven. The amount of functionalized polymer in the silica was calculated as being 10 percent.

Example 3 Preparation of Pretreated Silica In a meticulously dry reactor with a capacity of 3.79 liters, 2,000 grams of a dry mixture of styrene / butadiene / hexane (1.5 weight percent / 13.5 weight percent / 85 weight percent) were charged, 1.0 millimole of tetraethylethylene diamine and 3 millimole of n-butyl lithium. The reactor was heated at 60 ° C for 4 hours. 2 millimoles of teratoxysilane (Li / Si = 1) were added and heating continued for another hour. The batch was stopped with excess methanol. 6 grams of 2,6-di-t-butyl-p-crucible was added to the solution and the polymer isolated by removing the hexane. Five hundred grams of the silica Zeosil 1165MP was charged into a beaker of 4 liters capacity together with 306 grams of silylated polymer cement (50 grams of dry polymer and 256 grams of hexane). The slurry was stirred followed by removal of the hexane at 70 ° C under reduced pressure in a vacuum oven.

Example 4 Preparation of Pretreated Silica To a meticulously dry stirred reactor with a capacity of 3.79 liters, 2,000 grams of a dry mixture of styrene / butadiene / hexane (3.75 weight percent / 11.25 weight percent / 85 weight percent), 1.0 millimole of tetraethylethylenediamine and 3 mmol of n-butyl-lithium. The reactor was heated at 60 ° C for 4 hours. 2 millimoles of teratoxysilane (Li / Si = 1) were added and the heating was continued for another hour. The batch was stopped with excess methanol. To the solution were added 6 grams of 2,6-di-t-butyl-p-pot and the polymer was isolated by removing the hexane. Five hundred grams of the silica Zeosil 1165MP was charged into a beaker of 4 liters capacity together with 306 grams of silylated polymer cement (50 grams of dry polymer and 256 grams of hexane). The slurry was stirred followed by removal of the hexane at 70 ° C under reduced pressure in a vacuum oven.

Example 5 Table I below shows the basic rubber compound that was used in this example. The rubber materials were prepared in order to compare the effects of using precipitated silicas on pretreated particles that were prepared in Examples 1 and 2 versus the control compound that does not contain these pretreated silicas, but that have modified polymers and silica added separately .

The combination or stirring procedure involved mixing the non-productive ingredients at 60 revolutions per minute until a rubber temperature of 160 ° C was achieved, followed by a reduction in the revolutions per minute to maintain a temperature of 160 ° C for a certain period. of time. The total mixing times for the non-productive stages are shown in Table II. All the mixing of the productive stage was 2 minutes. The physical data for each sample is also shown in Table II. Table I Ctrl Ctrl Ctrl Displays 1 2 4 Non-productive Natural rubber 25 25 25 10 IBRJ 30 30 30 30 30 E-SBR2 61. 88 61. 88 61. 88 61. 88 61.88 Si693 11.0 11.0 11.0 11.0 11.0 Aromatic Oil 10.0 10.0 10.0 10.0 10.0 Wax 3.5 3.5 3.5 3.5 3.5 Stearic Acid 2 2 2 2 2 Antidegradants of Amine 2 2 2 2 2 Silica4 70 70 0 70 0 Modified PBD of Example l5 Silica of Example 1 (77 Modified PBD of Example 27 Silica of Example 2 0 0 0 0 77 Productive Cyclobenzylsulfenamide 1.7 1.7 1.7 1.7 1.7 Diphenylguanidine 2.0 2.0 2.0 2.0 2.0 Sulfur 1.4 1.4 1.4 1.4 1.4 Zinc Oxide 3.5 3.5 3.5 3.5 3.5 1 Isoprene-butadiene rubber polymerized by solution having a Tg of -45 ° C. 2 Styrene-butadiene rubber emulsion polymerized having 40 weight percent styrene combined. It was added as 61.88 phr of rubber diluted with oil (45 phr of rubber and 16.88 phr of oil). 3 A composition of bis (3-triethoxysilylpropyl) tetrasulfide and carbon black N330 (weight ratio of 50/50, and therefore was considered to be 50 percent active) that can be obtained commercially as X50S from Degussa Ag. 4 A silica obtained as Zeosil ™ 1165MP from Rhone Poulenc Company and, supposedly has a BET surface area of about 165 and a DBP absorption value of about 260-280. 5 As prepared in Example 1. 6 As prepared in Example 1. 7 As prepared in Example 1. 8 As prepared in Example 2.

Table II Ctrl Ctrl Ctrl Sample 1 2 3 4 5 Silica 70 70 0 70 0 Modified PBD of Example 1 0 7 0 0 0 Silica of Example 1 0 0 77 0 0 Modified PBD of Example 2 0 0 0 7 0 Silica of Example 2 0 0 0 0 77 Mixing Treatment (MJ / m3) 2009 1681 1676 1909 1703 Effort-Deformation - 18 * / 150 ° C Module at 100% ((MPa) 2.08 1.95 1.98 1.89 2.01 Module at 330% (MPa) 8.36 8.14 8.4 7.91 8.63 M / 300 / M100 4.02 4.17 4.24 4.19 4.29 Resistance to breakage, (MPa) 18. 67 19.26 20. 38 18. 56 19. fifteen Elongation at break (%) 621 631 648 625 600 Shore Hardness A Ambient Temperature 66.4 63.9 64.1 63.1 63.4 100 ° C 59.4 57.9 57.9 56.4 57.7 Reboiling Ambient Temperature 35.9 39.3 39.8 39.3 40.2 100 ° C 60.1 61.7 61.4 59.7 62.9 Abrasion of DIN (ce) 122 100 105 114 107 Both treated silicas of the present invention (Examples 3 and 5) show a reduced working input required during mixing, a higher modulus ratio (M300 / M100), higher bounce and better DIN abrasion (lower) compared to control 1. These properties indicate an improved energy construction, improved interaction of the filler or polymer charge, better fuel economy of the rim and longer duration tires. The silica of Example 2 (Sample 5) shows a clear advantage with respect to Sample 4 (Control) in the required mixing treatment, higher modules, higher tensile strength, higher rebore and lower DIN abrasion. The lower DIN abrasion values indicate better abrasion resistance which correlates with longer lasting rubber when used as a tread surface. This indicates that it is advantageous to pretreat the silica before mixing.

Claims (10)

R E I V I N D I C A C I O N E S:

1. A method for processing a silica loaded rubber composition which is characterized by mixing (i) 100 parts by weight of at least one vulcanizable elastomer with sulfur which is selected from homopolymers and copolymers of conjugated diene and copolymers of at least one conjugated diene and an aromatic vinyl compound; and (ii) from 10 to 150 phr of precipitated particulate silica having from 1 to 20 weight percent dispersed therein based on the weight of the silica, of a silane modified elastomer.

The method according to claim 1, characterized in that the precipitated silica before having dispersed the silane-modified elastomer thereon has a BET surface area within the range of 40 to 600 square meters per gram; an absorption value of dibutyl phthalate (DBP) within the range of 100 to about 400; and an average final particle size within the range of 0.01 to 0.05 micron.

3. The method according to claim 1, characterized in that the particulate precipitated silica having the silane-modified elastomer dispersed thereon is obtained by reacting the silica in an inert organic solvent in the presence of a silane-modified elastomer.

The method according to claim 1, characterized in that the silane modified elastomer is obtained by reacting an active terminal of a living polymer resulting through the polymerization of 1,3-butadiene or the copolymerization of 1,3-butadiene and styrene in an inert organic solvent, in the presence of an organic alkali initiator with a silane compound of the formula XyWySMOR1 ^ wherein X is a halogen selected from the group consisting of chlorine, bromine and iodine; W is an alkylene radical having from 1 to 8 carbon atoms; And it is 0 or 1; R1 is independently selected from the group consisting of alkyl radicals having from 1 to 8 carbon atoms and aryl radicals having from 6 to 24 carbon atoms; yz is 4 when y is 0 and z is 3 when y is 1.

5. A silica-loaded rubber composition that is prepared by the process characterized by mixing (i) 100 parts by weight of at least one vulcanizable elastomer with sulfur that is selected from homopolymers and copolymers of conjugated diene and copolymers of at least one conjugated diene and an aromatic vinyl compound; and (ii) from 10 to 150 phr of a particulate precipitated silica having from 1 to 20 weight percent dispersed thereon, based on the weight of the silica, of a silane modified elastomer.

The composition according to claim 5, characterized in that the silica precipitated before having the silane-modified elastomer dispersed thereon has a BET surface area within the range of 40 to 600 square meters per gram; an absorption value of dibutyl phthalate (DBP) within the range of 100 to about 400; and an average final particle size within the range of 0.01 to 0.05 micron.

The composition according to claim 5, characterized in that the particulate precipitated silica having the silane modified elastomer dispersed thereon is obtained by reacting the silica in an inert organic solvent in the presence of the silane modified elastomer.

8. The composition according to claim 5, characterized in that the silane modified elastomer is obtained by reacting an active terminal of the resulting living polymer through the polymerization of 1,3-butadiene or the copolymerization of 1,3-butadiene and styrene in an inert organic solvent, in the presence of an organic alkaline initiator with a silane compound of the formula XyWySITOR1 ^ wherein X is a halogen selected from the group consisting of chlorine, bromine and iodine; W is an alkylene radical having from 1 to 8 carbon atoms; and is 0 or 1; RI is independently selected from the group consisting of alkyl radicals having from 1 to 8 carbon atoms and aryl radicals having from 6 to 24 carbon atoms; and z is 4 when y is 0 and z is 3 when y is 1.

9. The composition according to claim 5, characterized in that it is in the form of a pneumatic tire, belt or hose.

10. The composition according to claim 9, characterized in that it is in the form of a pneumatic tire.