MXPA97006817A - Composition of reinforced rubber with silice and its use in llan - Google Patents

Abstract

The present invention relates to a rubber composition containing a substantial reinforcement of silica and pneumatic tires having bearing surfaces formed with such a rubber composition. The rubber composition comprises an elastomeric reinforcement, substantially of silica, optionally a minor amount of carbon black reinforcement, and a copolymer of three blocks of terminal segments in hard styrene and internal elastomer segments based on hard styrene and internal segments elastomer based on die

Description

COMPOSITION OF REINFORCED RUBBER WITH SILICA AND ITS USE ON TIRE TIES FIELD OF THE INVENTION This invention relates to rubber compositions containing a quantitative amount of silica reinforcement and a minor amount, possibly, of carbon black reinforcement and tires having Rolling surfaces made with said composition. BACKGROUND OF THE INVENTION r For various applications employing rubber that require high strength and resistance to abrasion, especially in applications such as tires and various industrial products, sulfur-cured rubber containing substantial amounts of reinforcing reagents is employed. . Carbon black is commonly used for this purpose and usually provides good physical properties for sulfur-cured rubber or increases such physical properties. Silica in particulates is often also used for this purpose, especially when the silica is used in combination with a coupling agent. In some cases, a combination of silica and carbon black is used for reinforcement grinders for various rubber products, including tire bearing surfaces. Conventionally, the bearing surfaces for elastomer (s) tires based on reinforced diene (s) with re-lumber (s) are composed of a larger amount of precipitated silica and a smaller amount, if any, of black reinforcement. Carbon have a lower bearing wear to comparable rim bearing surfaces reinforced with carbon black with a lower amount, possibly of silica. This invention relates to the inclusion of thermoplastic materials in the rubber combination. In the description of this invention, the term "phr", when used herein, and in accordance with conventional practice, refers to "parts of a respective material per 100 parts by weight of rubber, or elastomer". In the description of this invention, the terms "rubber" and "elastomer", if used herein, may be used interchangeably, unless otherwise indicated. The terms "rubber composition", "composite rubber" and "rubber compound", if used herein, are used interchangeably to refer to a rubber that has been mixed with various ingredients and materials and such terms are well known to part of those skilled in the art in the technique of rubber mixing or rubber composition. A reference to an elastomer Tg refers to a glass transition temperature which can be conveniently determined by a differential scanning calorimeter at a heating rate of 10 * C per minute. COMPENDIUM AND PRACTICE OF THE INVENTION In accordance with one aspect of this invention, in the rubber composition comprises (A) 100 parts by weight (phr) of elastomers composed of (i) from about 50 to about 98, preferably from Approximately 70 to about 95, phr of at least one elastomer selected from among isoprene aprolytes or 1,3-butadiene, copolymers of isoprene and 1,3-butadiene and isoprene copolymers and / or 1, 3 butadiene and styrene or alpha-methyl styrene, preferably styrene, and, correspondingly, (ii) from about 2 to about 50, preferably from about 5 to about 30, phr of at least one three-block elastomer composed of terminal segments of hard irene polies and of an internal segment of soft dienna based elastomer and having the general configuration of: ABA; where A represents said terminal hard psystyrene segments and B represents said internal soft diene based elastomer segment and where component B is from about 20 to about 8% of said three block elastomer, < C) Approximately 20 to about 50, preferably about 25 to about 90, phr, of filler composed of precipitated silica, in particles, and carbon black, wherein said filler is composed of from about 10 to about 100, alternatively from about 20 to about 85, and as an additional alternative from about 50 to about 80, phr of said silica, and where the weight ratio between the silica and the carbon black is at least about 1/1, preferably as a majority of said filler and alternately within a range of about 1/1 to about 15/1, and (D) a coupler for said silica having a reactive portion with the surface of said silica and another interactive portion with said diene-based elastomer (s). In another aspect of the present invention, a rim is provided having a formed bearing surface of said rubber composition. In general, the three-block elastomer is represented by the formula ABA, wherein the terminal blocks, A, may be the same or different, preferably the same, and are thermoplastic homopolymers or teropolymer copolymers of a compound aromatic vinyl, such as styrene. The center block, B, is an elastomeric polymer derived from conjugated dienes selected from 1,3-butadiene and isarene. The ratio between segments A and B can vary widely. Frequently, the molecular weight of the central block, B, will be greater than the molecular weight of the terminal blocks, A. The molecular weight of the terminal block, A, can, for example, be within a range of about 2,000 to about 100,000, while the molecular weight of the center elastomer block, B, can, for example, be within a range of about 25,000 to about 1,000,000. If desired, the three-block elastomer can be further processed to hydrogenate the rubber part of the three-block elastomer. Conventional hydrogenation methods can generally be employed. AB-type two-block thermoplastic elastomers, such as the polystyrene and polybutadiene or polyisoprene block compounds, are contemplated here as elastomers which could be used as a total or partial replacement of the three-block ABA elastomer described here. In one aspect, such rubber opposition can be provided cured with sulfur. Healing with sulfur is achieved in a conventional manner, that is, by curing under a condition of temperature and high pressure for a suitable period of time. In the practice of this invention, as indicated above, the rubber composition is formed of at least one elastomer based on diene, or rubber. Accordingly, it is considered that the elastomer is a sulfur-curable elastomer. Such a diene-based elastomer, or rubber, can be selected, for example from at least one of the following! rubber 1, 4-pol and cis isoprene (natural and / or synthetic, and preferably natural rubber) and, for example, synthetic polymers and synthetic copolymers of isoprep and butadiene and, for example, copal, non-conjugated dienes with aromatic vinyl compounds with, for example, styrene and fa-me i lest ireno. Representative elements of such elastomers are, for example, cis 1, 4-poly isoprene, cis 1,4-palibutane, vines Ipsl ibutadiene containing from about 35 to about 55/4 units of vinyl, 3,4 -poly isoprene, isoprene / butadiene copolymers, styrene / butadiene copolymer, styrene / isaprene capolimers, butadiene / acrylonitrile capyloides, styrene / butadiene / acri loni ri and terpoi terpolymers reno / isoprene / butadiene. It will be noted that the styrene / butadiene elastomers can be prepared by polymerization in organic solution or in aqueous emulsion. In one aspect of this invention, a styrene / butadiene (E-SBR) derivative of emulsion polymerization having a relatively conventional styrene content of approximately 20 to approximately 28% can be employed. of bound styrene or, in some applications, an E-SBR having a medium to relatively high bound styrene content, ie, a bound styrene content of approximately 30 to about 45 *;. The relatively high content of styrene of about 30 to approximately 45 for the E-SBR can be considered beneficial in order to increase the tensile strength or skidding of the bearing surface of the rim. The presence of E-SBR itself is considered beneficial for the purpose of increasing the processing capacity of the uncured elastomer composition mixture, especially as compared to the use of an SBR prepared by solution polymerization (S-SBR). By E-SBR prepared by emulsion polymerization, it is understood that styrene and 1,3-butadiene are copolymerized in an aqueous emulsion. Such methods are well known to those skilled in the art. The bound styrene content may vary, for example, from about 5 to 50%. In one aspect, the E-SBR may also contain acrylonitrile to form a rubber of terpolymers, known as E-SBAR, in amounts, for example, from about 2 to about Z% by weight of acrylate which is bound in the terpolymer The SBR prepared by emulsion polymerization (S-SBR) typically has a bound styrene content that ranges from about 5 to about 50, preferably from about 9 to about 36 '/. The S-SBR can be prepared conveniently, for example, by arganali catalysis in the presence of an organic hydrocarbon sol. One purpose of the use of S-SBR is to obtain an improved rolling resistance of the rims as a result of a lower hysteresis when used in a tire tread composition. The 3,4-poly isoprene rubber (3,4-PS) is considered beneficial for the purpose of increasing the tire's traction when used in a rolling surface composition of 1 lant. The elastomer of 3-polystyrene and the use thereof is described in greater detail in U.S. Patent No. 5,087,668 which is incorporated herein by reference. The cis 1,4-polybutadiene rubber is considered beneficial for the purpose of increasing the wear resistance by rolling. Such a polybutadiene elastomer can be prepared, for example, by polymerization in 1,3-butadiene organic solution or is well known to those skilled in the art. The polybutadiene elastomer can conveniently be characterized, for example, by having at least 90 '/ 1,4-cis content. The 1, 4-pal isoprene cis and natural rubber 1, 4-pol i iso reno cis san well known to those skilled in the rubber art. The vulcanized rubber composition must have a sufficient amount of silica, or carbon black if used, reinforcing filler (s) to contribute to a relatively high modulus and high wear resistance. The combined weight of the silica and carbon black, as indicated herein, may be from 20 parts per 100 parts in rubber, but is preferably from approximately 25 to approximately 90 parts by weight. While it is considered here that the customary siliceous pigments used in rubber composition applications can be employed as the silica in this invention, including siliceous (silica), pyrogenic pigments and precipitates precipitated silicas are preferred. The siliceous pigments, preferably used in this invention, are precipitated silicas such as, for example, those obtained by the acidification of a soluble silicate, for example, sodium silicate. Such precipitated silicas are well known to those skilled in the art.

Such precipitated silicas can be characterized, for example, because they have a BET surface area, in accordance with that measured using nitrogen gas, preferably within the range of approximately 40 to about 600, and more usually, within a range of about 50. to approximately 300 square meters per gram. The BET method for measuring surface area is described in the Journal to the American Chemical Society, Volume 60, page 304 (1930). Silica can also typically be characterized as having an absorption value of dibutylphthalate (DBP) within a range of about 100 to about 4O0, and more usually, within a range of about 150 to about 300. It should be expected that The silica has an average ultimate particle size, for example, within a range of 0.01 to 0.05 microns as determined by the electron microscope, even though the silica particles may be even smaller, or possibly larger, in terms of their size. Various commercially available silicas may be considered for use in this invention as, for example, and without limitation, silicas commercially available from PPG Industries under the trademark Hi-Sil with designations 210, 243, etc; silicas available from Rhone-Poulenc such as Zeosil 1165MP and silicas available from Degussa AG, for example, with designations VN2 and VN3, etc. Silica is conventionally used in combination with a silica coupler to connect the silica with the elastomer (s) and, therefore, to increase the reinforcing effect of the silica elastomer. Such coupling agents can, for example, be mixed before, with prior reaction, with the silica particles either added to the rubber mixture during rubber / silica processing, or mixed in stages. If the coupling agent and the silica are added separately to the rubber mixture during the mixing of the rubber / silica, or in the processing step, it is considered that the coupling agent is then combined in it with the silica. Particularly, such coupling agents are sometimes composed of a silane having a constituent component, or portion (the silane portion) capable of reacting with the silica surface, usually with ßilanol groups normally contained on the silica surface and, also , a constituent component, or portion, capable of reacting with the rubber, particularly a vulcanizable rubber with sulfur containing carbon-carbon double bonds, or unsaturation. In this way, the coupler consequently acts as a connection bridge between the silica and the rubber, thus the reinforcing aspect of the silica rubber increases. Numerous coupling agents are taught for use in the combination of silica and rubber such as, for example, wool-coupling agents containing a polysulphide component, or structure, as for example bis- (3-trietoxisi 1 and Ipropi 1 ) tetrasulfu.ro and / or polyester rubber together with a mixture of silica and carbon black, and silica is usually required to be a major component of the reinforcing filler constituted by silica / carbon black. In a practice of the invention, said silica coupler can be, for example, a bis- (3-triethyl isi 1 i lprapi 1) te rasul furo. It is easily understood by those skilled in the art that the rubber composition will be composed by generally karyotic methods in the rubber composition technique, such as for example the mixture of the various vulcanizable constituents with sulfur with various additive materials. employees with, for example, curing aids such as sulfur, activators, retarders and accelerators, processing additives, such as oils, resins including lime resins, silicas, and plastics, repellents, pigments, fatty acid, zinc oxide, waxes, antioxidants and aniosanantes, peptizing agents as well as reinforcing materials such as carbon black. As those skilled in the art know, according to the intended use of the vulcanizable material with sulfur and vulcanized with sulfur (rubber), the aforementioned additives are usually selected and used in conventional amounts. Typical amounts of carbon black (s) of reinforcing type, for this invention, if employed, are presented below. It will be noted that the silica coupler can be used in combination with a carbon black, ie, premixed with a carbon black prior to its addition to the rubber composition, and such carbon black must be included in the aforementioned amount of black of carbon for the formulation of the rubber composition. Typical amounts of ligand resins, if employed, comprise from about 0.5 to about 10 phr, usually from about 1 to about 5 phr. Typical amounts of processing aids comprise from approximately 1 to approximately 50 phr. Such processing aids may include, for example, aromatic, naphthenic, and / or paraffinic processing oils. Typical amounts of antioxidants comprise from approximately 1 to 5 phr. Representative antioxidants can be, for example, diphenyl-p-phenylenediamine and others such as those presented in The Vanderbilt Rubber Handboo (1978), pages 344-346. Typical amounts of anhydrants comprise from approximately 1 to about 5 phr. Typical amounts of fatty acids, if employed, may include stearic acid comprising from about 0.5 to about 3 phr. Typical amounts of zinc oxide comprise from about 1 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 can be, for example, pentaclarotiafenal and dibenzamidodi feni ldisul furo. The vulcanization is carried out in the presence of a sulfur vulcanization agent. Examples of suitable sulfur vulcanization agents include elemental sulfur (free sulfur) or sulfur donor vulcanization agents, for example amine disulfide adducts, polymeric pslisulfurs to good sulfide sulfur. Preferably, the sulfur vulcanization agent is elemental sulfur. As is known to those skilled in the art, sulfur vulcanization agents are employed in an amount ranging from approximately 0.05 to approximately 4 phr, or even, in some circumstances, up to approximately 8 phr, and a range from about 1.5 to about 2.5, sometimes from about 2 to about 2.5, is preferred. Accelerators are used to control the time and / or temperature required for vulcanization and to improve the properties of the vulcanized product. In one embodiment, a single accelerator system, ie, a primary accelerator, may be employed. Conventionally, and preferably, one to several primary accelerator (s) is employed in total amounts being within a range of about 0.5 to about 4, preferably about 0.8 to about 1.5 phr. In another embodiment, combinations of a primary accelerator and a secondary accelerator can be employed with the secondary accelerator being used in smaller amounts (from about 0.05 to about 3 phr) to activate and improve the properties of the vulcanized product. Combinations of these accelerators can produce a synergistic effect on the final properties and are to a certain extent better than those produced by the use of any of the accelerators alone. In addition, delayed action accelerators can be employed which are not affected by normal processing temperatures if they produce a satisfactory cure at ordinary vulcanization temperatures. Vulcanization retardants can also be used. Suitable types of accelerators that can be employed in the present invention are amines, disulfides, guanidines, thioureaß, thiazoles, thiurams, sulphenas, diacarbamates and xanthos. Preferably, the primary accelerator is a sulfenamide. If a second accelerator is used, the secondary accelerator is preferably a guanidine, di tiocarbamate or a thiura compound. The presence and relative amounts of the aforementioned rubber composition ingredients are not considered an aspect of this invention that is essentially focused on the use of said inclusion of three-block elastomers in a rubber composition quantitatively reinforced with silica, particularly for its use in rim bearing surface. The mixture of the rubber composition can be achieved by methods known to those skilled in the art. For example, the ingredients are typically mixed in at least two stages, that is, at least one non-productive stage followed by a productive mixing step. The final curing agents are typically mixed in the final stage which is conventionally called the "productive" mixing stage where the mixture typically occurs at a temperature or at a lower temperature, lower than that (s >).; mixing temperature (s) than in the preceding nonproductive mixing stage (s). The rubber, silica and silicon coupler, and carbon black, if used, are mixed in one or several non-productive mixing stages. The terms "non-productive" and "productive" mixing stages are well known to those skilled in the art of mixing the rubbers. The rubber composition of this invention can be used for various purposes. For example, it can be used for several tire compounds. Such tires can be constructed, shaped, molded and cured by various methods known and apparent to those skilled in the art. The invention will be better understood with reference to the following examples wherein the parts and percentages are indicated by weight unless otherwise indicated. EXAMPLE I In this example, a rubber composition containing a linear block A-B-A elastomer is prepared as a triple block elastomer S-B-S containing 31 *! of styrene (K aton D-1101). In practice, the three-block elastomer S-B-S was used as a replacement for an elastomeric capolimer prepared for emulsion polymerization of butadiene / styrene (SBR) containing 40 * /! of styrene. Two samples of control rubber are also included in this study. One contains 12.8 phr of coupling agent X50S (Control A) and the other contains 6.4 phr of coupling agent X50S (Control B). The rubber sample containing Kraton D-1101 (Experimental Sample C) also contains the lowest level of coupling agent that corresponds to the control rubber sample B. It was observed that the experimental sample C had an increased resistance to The abrasion compared to Control A q? e contained the highest level of coupling agent. It also shows a superior resistance to abrasion compared to Control B which contains an equivalent level of coupling agent. It was observed that the replacement of the emulsion copolymer SBR with the block type polymer S-B-S provides an improved abrasion resistance and also allows a reduction of the content of coupling agent in the rubber composition. The rubber compositions containing the materials presented in Table 1 were prepared in a Banbury BR mixer using two separate, sequential stages of addition (mixing), i.e., a non-productive mixing step and a final productive mixture at temperatures of 160 ° C. and 120 ° C and times of 7 minutes and 2 minutes, respectively. The physical properties of these compounds are compared in Table 2.

TABLE 1 read. NON-PRODUCTIVE STAGE itrol A Control B Exp C E-SBR (1) 25 25 0 BR (2> 20 20 20 Natural rubber 10 10 1 IBP. (2) 45 45 45 Kraton D-1101 (4) 0 0 25 X50S (5) 12.8 6.4 6.4 Silica (6) 80 80 80 Processing aids (7) 3 300 30 30 An iazanante (8) PRODUCTION MIXING STAGE Sulfur 1.4 1.4 1.4 Zinc Oxide 2.5 2.5 2.5 Anti-oxidants (9) 1 1 1 Accelerators (10) 3.7 3.7 3.7 1) SBR prepared with emulsion polymerization obtainable from The Goodyear Tire & Rubber Company, which has 40 * /. of styrene and about 37.5 parts by weight of aromatic oil per 100 parts of the elastomer. However, the amount of this material appears in Table 1 with a dry weight without the aforementioned oil. 2) Rubber 1,4-polybutadiene rubber obtained as Budene (r) 1254 in The Goodyear Ti e S-t Rubber Company. 3) An isoprene / butadiene copal elastomer obtained at The Goodyear Tire & Rubber Company has an isaprene content of approximately 50 * 4 and a Tg of approximately -45 ° C. 4) A three-block elastomer S-B-S (styrene-butadiene-styrene) available from Shell Chemical Company having a polystyrene content of about 31% and, consequently, a polybutadiene content of about 69%. 5) Here a mixture of bis-3- (triethoxysi 1 i lprop 1) tetrasulfide and carbon black is distributed in a 50/50 ratio and available as X50S in Degussa A.6. 6) A silica obtained as Zeosil 1165MP in Rhone-Poulenc. 7) Oil processing oil conforming approximately 26.5 parts of the E-SBR and approximately 5 parts in the PBd, where the quantities of E-SBR and PBd are reported above in dry weight and in addition, they added approximately 17 parts of processing oil , plas ificantes, resins and additional waxes. 8) Santaflez 6PPD of the company Monsanto. 9) Wingstay (r) 100, from The Goodyear Tire Z > . Rubber Ca pany.

) Combination of tyrant guanidine and sulfenamide accelerators. The following Table 2 illustrates the amounts of the triple block elastomer introduced in each of the experiments, other than the control experiment A as well as various physical properties of the cured samples. The samples have been cured at a temperature of approximately 150 ° C for approximately 18 minutes.

TABLE 2 Sample Control A Control B E? P C REOMETER (150ßC) Maximum torque moment 43.5 45.8 48.8 Moment of minimum torque 12.2 23. 26.5 T90, minutes 17.0 14.0 18.0 TENSION-DEFORMATION Tension resistance, MPa 15.6 16.8 16.3 Elongation at break, *! 398 566 603 Module 100%, MPa 2.5 1 .5 2. 3 Module 300%, MPa 12.1 7. 2 8. 1 HARDNESS Shore A, 23ßC 64 59 70 Share A, 100ßC 62 56 REBOUND 23ßC,% 45 41 100'C,% 66 59 53 DIN Abrasion (loss of 90 117 84 volume in c) In particular, this example shows that the inclusion of the ABA three-block elastomer, Kratan (r) D-1101, in the experimental rubber composition C provides significant improvements in abrasion resistance compared to controls A and B that do not contain the stomer of three blocks. This is considered important for the use of the rubber composition in a rim bearing surface due to an improved wear resistance. While some embodiments and representative details were shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications of ions can be made without departing from the spirit or scope of the invention.

Claims (4)

1. CLAIMS i. In a rubber composition characterized in that it comprises (A) 100 parts by weight (phr) of elastomeric compounds of (i) about 50 to about 98 phr of at least one elastomer selected from among isoprene opal isomers at 1, 3 -butadi not, polymers of isoprene and 1,3-butadiene and copolymers of isaprene and / or 1,3-butadiene and styrene to al-methyl-urethane, and, correspondingly, (ii) from about 2 to about 50 phr of at least one three-block elastomer composed of terminal segments of hard iesti rein and inner segment of soft diene-based elastomer and having the general configuration of: ABA; where A represents said end segments of hard polystyrene and B represents said inner segment of soft diene-based elastomer and wherein component B represents from about 20 to about 80% of said three-block elastomer, (C) from about 20 to about 150 phr of filler composed of precipitated, particulate, and carbon black, where said filler consists of approximately 10 to about 100 phr of said silica, and wherein the weight ratio between the silica and the carbon black is at least about 1/1, and (D) a coupler for said silica having a portion that reacts with the surface of said silica and another interactive portion with said elastomer (s) based on diene.
2. 2. The rubber composition of claim 1, characterized in that said diene-derived inner elastomer for said three-block elastomer ABA is an elastomer of a conjugated diene selected from at least one of 1,3-butadiene and isoprene,
3. 3. The composition of rubber of any of the preceding claims, characterized in that said silica coupler is a bis- (3-trialco isi 1 i lp api 1) pal isul fura.
4. 4. A pneumatic tire having a rubber bearing surface characterized in that it comprises a rubber composition of any of the preceding claims.