MXPA98007238A - Rim surface surface with espacially defined tv elastomers - Google Patents

Abstract

The invention relates to a rim with a rolling surface. The running surface is composed of at least two defined elastomers that have Tv separated by at least 55 ° C for the exclusion of elastomers having Tv between -30 ° C and -85 ° C. The composition of the tread surface can be reinforced with carbon black or a combination of reinforcing filler materials and carbon black.

Description

RIM SURFACE SURFACE WITH SPACIOUSLY DEFINED TV ELASTOMERS.

FIELD This invention relates to a rim having a rubber tread surface which is composed of at least two elastomers defined with separate Tv. The tread rubber can be reinforced with carbon black or a combination of the reinforcing filler materials silica and carbon black, together with a coupler or coupler agent for the silica.

BACKGROUND Rubber pneumatic tires are conventionally prepared with a rubber tread surface which may be a combination of different rubbers which are usually reinforced with carbon black. In one aspect, the rubbers are evaluated, selected and mixed for purposes of achieving the desired properties for the tread surface of the rim and particularly an equilibrium of the characteristic properties of the tread surface of the rim, namely, traction, resistance to rolling and wear.

Typically, the rubber for the tread is reinforced with carbon black or a combination of the black carbon and silica materials. Silica is often used with a silica coupler to couple the silica to the elastomers for rubber reinforcement purposes. The use of carbon black and silica, including the use of silica couplers, is well known to those skilled in the art. Historically it is recognized that tires that have hitherto been suggested and / or have been prepared with tread rubber compositions are based on: (i) mixtures of elastomers having similar Tv or (ii) mixtures of elastomers with Tv completely separated by at least 30 ° C. For example, tires with rolling surfaces composed of a mixture of elastomers with glass transition temperatures (Tv) that differ by at least 30 ° C can be prepared with styrene / butadiene copolymer rubbers having a Tv in a range of about -35 ° C to about -50 ° C mixed with natural rubber having a Tv of about -60 to about -65 ° C and / or 1, 4-polybutadiene cis rubber having a Tv of about -85 to about -105 ° C to obtain compositions for the tread surface of the rim with acceptable traction on wet road surfaces or sometimes ice covered road surfaces. Also, a rim with tread compound composed of styrene / butadiene polymer rubber prepared by emulsion polymerization with a Tv in a range of about -35 to about -50 ° C with a natural rubber 1, 4-polyisoprene having a Tv of approximately -65 ° C can be used to operate in winter, such as traction on road surfaces covered with ice and / or could reduce the traction of the tread surface on a wet road surface. In this case it is desired to provide a tread surface for rim composed of elastomers with Tv substantially separated and defined for the exclusion of the specified intermediate Tv elastomers, to improve traction and / or wear of the tread surface. In the description of this invention, the term "pee" when used herein, and in accordance with conventional practice refers to "parts of a respective material per hundred parts by weight of rubber". The terms such as "compound rubber", "rubber compound" and "rubber composition" generally refer to "rubber that has been mixed with various rubber component ingredients". These terms are well known to those skilled in the art of rubber mixing, especially for tires. The terms "vulcanized", "vulcanized", "cured" and "cured", if used in the present, are used interchangeably to refer to "rubber vulcanization" and these terms are well known to those who have the skills in the rubber vulcanization technique. The term "Tv", when used herein refers to "the glass transition temperature of a specific elastomer". Glass transition temperatures are characterizations of well-known elastomers..

These, for example, can be determined in a suitable way by a CED instrument with a heating rate of 20 ° C per minute.

SUMMARY AND PRACTICE OF THE INVENTION According to this invention there is provided a pneumatic rim having a rolling surface of a rubber composition consisting of, based on one hundred parts by weight of rubber, and exclusive of elastomers having a Tv between -30 ° C and -85 ° C; (A) about 20 to about 50, alternatively about 30 to about 40 pee of at least one synthetic elastomer having a Tv in the range of -30 ° C to about + 10 ° C which is selected from high vinyl polybutadiene with a 1,2-vinyl content in a range of about 75 to about 95%; isoprene / butadiene copolymer with a content of about 10 to about 90 percent of isoprene-derived units; 3, 4-polyisoprene having a content of microstructures 3,4- of at least 60%; styrene / butadiene copolymer prepared by emulsion polymerization with from about 45 to about 65 percent of styrene units and a 1,2-vinyl content based on the butadiene component thereof in a range of about 8 to about of 15%; and the styrene / butadiene copolymer prepared by solution polymerization with from about 15 to about 40 percent of units derived from styrene and a content of vinyl 1,2-based on the butadiene component thereof in a range of about 15 to about 60%; and (B) about 50 to about 80, otherwise about 60 to about 70 pee of at least one synthetic elastomer having a Tv in a range of -85 ° C to about -110 ° C which is selected from isoprene copolymer / butadiene having about 10 to about 30% units derived from isoprene; cis 1, 4-polybutadiene rubber having about 90 to about 98% of cis 1,4- microstructures and a 1,2- vinyl content in a range of about 2 to about 10% with the remainder being mainly of a trans-1 microstructure ,4-; (C) about 40 to about 100, alternatively, about 60 to about 90 pee of particulate reinforcing filler material that is selected from: (1) carbon black, or (2) carbon black and silica, preferably precipitated silica , with a weight ratio of carbon black to silica in a range of about 1/20 to about 20/1, otherwise, about 1/5 to about 5/1; (D) at least one silica coupler for the silica, if silica is used, that has a reactive portion with the surface of the silica and another, based on sulfur, interactive portion with the elastomer. Typically, the silica coupler has a reactive silane moiety with the surface of the silica such as, for example, silanol groups therein, and another, based on polysulfide, interactive portion with the elastomers, usually in a ratio of silica to coupler weight from about 7/1 to about 15/1. For example, the coupler may be a bis- (trialkoxysilylalkyl) polysulfide having from 2 to about 8 sulfur atoms in its polysulfide bridge. Examples of this coupler can be a bis (3-triethoxysilylpropyl) polysulfide having an average of about 2 to about 5 sulfur atoms in its polysulfide bridge. It is important to note that it is necessary that the rubber composition for the tread surface contain an appreciable amount of elastomer (s) having a relatively high Tv in a range of -30 to about + 10 ° C. One purpose of using these high Tv elastomers is to improve traction, particularly wet traction. Also, it is important to note that, it is necessary that the rubber composition for the tread surface contain an appreciable amount of elastomer (s) having a relatively low Tv in a range of about -85 to about -110 ° C. One purpose of using elastomer (s) with low Tv is to reduce wear on the tread surface. It is also important to note, for the purpose of this invention, that elastomers having a Tv within a range of -35 to -85 ° C are proposed to be excluded. This is because these elastomers are considered hereinafter as unsuitable, or fully significant contributors to the traction and / or, as the case may be, for the wear of the reduced tread surface. Representative examples for these desired elastomers to be excluded are those such as, for example, 1,4-polyisoprene either natural or synthetic and styrene / butadiene elastomers prepared by emulsion polymerization.

(SBR) containing less than 45% units derived from styrene. Although it is possible that the mechanism is not completely understood, it is considered that it is the prescribed combination of elastomers with high and low spatially defined Tv that acts to favor the more optimized aspects of traction and wear of the tread surface, mentioned above of the Rubber composition for the tread surface of the rim. The various polybutadiene rubbers for use in this invention can be prepared by organic solution polymerization processes for the 1,3-butadiene monomer well known to those skilled in the art. The isoprene / butadiene copolymer elastomer prepared by polymerization in organic solution can be suitably prepared by copolymerization of isoprene and 1,3-butadiene in an organic solvent solution in the presence of a catalyst and suitable modifier. The preparation of this isoprene / butadiene copolymer elastomer is well known to those skilled in the art.

It should be understood herein that it is well known to those skilled in the art of tread surface for tires to use various combinations of elastomers for compositions for the tread surface of the rim. However, an important feature of this invention is that the specific elastomers are used in specific amounts as a basic rubber composition, in the substantial absence of other elastomers, together with the black reinforcing filler material or with the material of reinforcement load composed of carbon black and silica. In the present it is considered that this specific combination of elastomers for use on the running surface of the rubber rim is novel and inventive. Hereby it is contemplated that wet running (traction, or braking) and rolling resistance of the rim can further be improved by replacing part of the carbon black reinforcement with silica plus a silica coupler, as described herein. previous. In the practice of this invention, the rubber composition for the basic, balanced rolling surface, as a combination of elastomers with high and low spatially defined Tv is provided, which depends on the carbon black or a combination of carbon black and silica, together with a silica coupler to reinforce the rubber. The silica, in turn, depends on the use of a silica coupler for the reporter effect of the silica in the rubber mixture. It is recognized that various carbon blacks reinforcing elastomers can be used in the practice of this invention for the rubber composition for the tread surface of the rim as is well known to those skilled in the art. For example, relatively high reinforcing carbon blacks are contemplated as having an iodine number in a range of about 80 to about 150 and a DBP (dibutyl phthalate) value in a range of about 90 to about 150 as is exemplified in The Vanderbilt Rubber Handbook (1990), p. 417. For example, the carbon blacks N121, N234, N330 and N375 could be considered. The siliceous pigments commonly used in rubber blending applications can be used as the silica of this invention, including pyrogenic siliceous pigments and precipitates (silica), although precipitated silicas are preferred. The siliceous pigments which are 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. The BET surface area of the silica, measured using nitrogen gas, may be in the range of about 100 to about 25, preferably about 120 to about 200 square meters per gram (m2 / g). The BET method for measuring surface area is described in The Journal of the American Chemical Society, volume 60, p. 304 (1930). The silica also can usually have an absorption value of dibutyl phthalate (DPB) in a range of about 100 to about 400, and usually about 150 to about 300 ml / lOOg. The various commercially available silicas can be considered for use in this invention as can be, for example only and without limitation, the silicas available commercially from PPG Industries under the trademark Hi-Sil with the designations 210, 243, etcetera.; available silicas of Rhone-Poulenc with designations of Zeosil 1165MP, silicas available from Degussa AG under the designations VN2 and VN3, and BV3370GR and from JM Huber, such as for example Zeopol 8745. Those skilled in the art can readily understand that the rubber composition The rubber for the running surface will be composed by the methods generally known in the rubber mixing art, such as the mixing of the different constituent rubbers vulcanizable by sulfur with different commonly used additive materials such as, for example, curing auxiliaries, such as can be sulfur, activators, retarders and accelerators, processing additives such as oils, resins including thickener resins, silicas and plasticizers, fillers, pigments, fatty acids, zinc oxide, waxes, antioxidants and antiozonants, peptizing agents and reinforcing materials as for example, carbon black. As is known to those skilled in the art, depending on the proposed use of the vulcanizable material by sulfur and vulcanized by sulfur (rubbers), the aforementioned additives are selected and commonly used in conventional amounts. Commonly, additions of carbon black for this invention are set forth in the foregoing. Common amounts of thickener resins, if used, comprise about 0.5 to about 10 pee, usually about 1 to about 5 pee. The common amounts of processing aids comprise from about 1 to about 50 pee. These processing aids may include, for example, aromatic, naphthonic and / or paraffinic processing oils. Common amounts of antioxidants comprise about 1 to about 5 pee. Representative antioxidants may be, for example, diphenyl-p-phenylenediamine and others, such as, for example, those described in The Vanderbilt Rubber Handbook (1978), p. 344-346. Common amounts of antioxidants comprise from about 1 to about 5 pee. Common amounts of fatty acids, if used, which may include stearic acid comprise about 0.5 to about 5 pee. The common amounts of zinc oxide comprise about 2 to about 5 pee. The common amounts of waxes comprise about 1 to about 5 pee. Microcrystalline waxes are often used. The common amounts of peptizers comprise about 0.1 to about 1 pee. Common peptizers can be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulfide. The vulcanization is carried out in the presence of a vulcanizing agent by sulfur. Examples of suitable sulfur vulcanizing agents include elemental sulfur (free sulfur) or sulfur donating vulcanizing agents, for example, an amine disulfide, polymeric polysulfide or sulfur olefin addition products. Preferably, the sulfur vulcanizing agent is elemental sulfur. As is known to those skilled in the art, sulfur vulcanizing agents are used in the amount in the range of from about 0.5 to about 4 pee, with a range from about 0.5 to about 2.5 being sometimes preferred.

Accelerators are used to control the time and / or temperatures necessary for vulcanization and to improve the vulcanization properties. Retarders are also used to control the speed of vulcanization. In one mode it is possible to use a single accelerator system, that is, the primary accelerator. Conventionally and preferably, a primary accelerator (s) is used in total amounts in the range of about 0.5 to about 4, alternatively about 1.2 to about 2.0 pee. In another embodiment, it is possible to use combinations of a primary and a secondary accelerator, with the secondary accelerator being used in amounts of about 0.05 to about 3 pee, for example, to activate and improve the properties of the vulcanizate. It could be expected that the combinations of these accelerators produce a synergistic effect on the final properties and are somewhat better than those produced by the use of a single accelerator. In addition, it is possible to use accelerators for the delayed action that are not affected by normal processing temperatures but produce a satisfactory cure at ordinary vulcanization temperatures. The types of suitable accelerators which can be used in the present invention are amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates and xanthates. Preferably, the primary accelerator is a sulfenamide. If a secondary accelerator is used, preferably the secondary accelerator is a guanidine, dithiocarbamate or thiuram compound. The presence and relative amounts of the aforementioned additives are not considered an aspect of the present invention which is primarily directed to the use of the specified mixture of synthetic elastomers with relatively high Tv and relatively low spatially defined Tv, all with an exclusion of the elastomers with specifically defined intermediate Tv. The rim can be constructed, shaped, molded and cured by the various methods that are readily apparent to those who have the skills in the art. The invention can be better understood by referring to the following examples in which parts and percentages are by weight unless otherwise indicated.

EXAMPLE I Compositions of rubber (compound rubber) are prepared as mixtures of high and low spatially defined Tv elastomers, mentioned herein as Ex. B-D, as well as a control rubber composition containing natural rubber (cis 1,4-polyisoprene) identified herein as control-A. The rubber compositions are prepared by mixing the ingredients in several stages, namely, two stages of sequential internal mixing without the curatives (commonly referred to as the "non-productive mixing stage") and a final internal mixing step to add the curatives (usually referred to as a "productive mix stage"). Then, the resulting composition is molded and cured under the conditions of elevated temperature and pressure. This mixing of the rubber compositions is well known to those who have the skills in the art. The rubber compositions are composed of the ingredients illustrated in Table 1. The amounts of the materials are presented in terms of pee or parts by weight of the material per 100 parts by weight of the dry rubber.

Elastomer of the styrene / butadiene copolymer prepared by solution polymerization as SLF1216 from Goodyear Tire & Rubber Company with a content of approximately 12% styrene, with a Tv of approximately -40 ° C and a Mooney viscosity (ML / 4) at 100 ° C of approximately 85. Natural rubber cis 1,4-polyisoprene.

. Cis 1, 4-polybutadiene rubber as BUDENE ® 1208 from Goodyear Tire & Rubber Company with a Tv of approximately -103 ° C. . Vinyl polybutadiene elevated Goodyear Tire & Rubber Company with a vinyl content of approximately 80% and a Tv of approximately -25 ° C and a Mooney viscosity (ML / 4) at 100 ° C of about 82.. Rubber 3, 4-polyisoprene obtained from Goodyear Tire & Rubber Company with a content of 3.4- of about 60-705, a Tv of about -16 ° C and a Mooney viscosity (ML / 4) at 100 ° C of about 70. 6. The processing aids were composed of oil for rubber processing, fatty acid (mainly stearic acid) and microcrystalline waxes. 7. Antidegradants of the amine type. 8. Silica as Hi-Sil-210 from PPG company. 9. Silica coupler obtained as X50S from Degussa company as a 50/50 blend of carbon black and bis (triethoxysilylpropyl) polysulfide with an average of about 3.5 to about 4 sulfur atoms in the polysulphide bridge. 10. Accelerator (s) of the sulfenamide type.

The physical properties of the rubber compositions are shown in the following Table 2. The results reported in Table 2 illustrate the advantage of using elastomers with high and low spatially defined Tv in a rubber composition for running surface of a rim in terms of rolling resistance, tensile strength and abrasion. In particular, the rubber composition for control A is illustrated as that which could be considered an example or a conventional good criterion for a rubber composition for the tread surface of the rim, although it is recognized that many other rubber compositions for The rolling surface of the rim have been suggested and used. The samples of Examples B-D illustrate the rubber compositions of this invention which are composed of elastomers of high and low spatially defined Tv rubbers. The most drastic demonstrative effect is the DIN abrasion values in which the lower values represent less wear due to abrasion for the abrasion test. Another significant aspect of the comparative properties is the rebound value at room temperature (23 ° C) which is predictive of rolling resistance of the rim when a rim of respective rubber composition is used. In this case, the higher values are considered better. Examples B-D demonstrated higher bounce values than control A, which is considered significant in the present because the rolling resistance must be improved. Also of importance are the Tan. Delta comparative values that are considered comparatively indicative of wet traction. Examples B-D show tan values. Delta equal to or greater than 0 ° C and, thus, are predictive of wet traction equal to or greater than control A. These properties, as a whole, suggest drastic improvements in the wear of the tread surface (wear of the reduced rolling surface) and slight to moderate improvements in rolling resistance (reduced rolling resistance of the rim) and wet traction (greater traction of the tread surface of the rim on the wet road). Although certain representative embodiments and details have been shown for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications may be made herein without departing from the spirit or scope of the invention.

Claims (7)

1. A pneumatic tire having a rolling surface of a rubber composition is characterized as being composed of, based on 100 parts by weight of rubber, and excludes elastomers having a Tv between -30 ° C and -85 ° C; (A) about 20 to about 50 pee of at least one synthetic elastomer having a Tv in the range of -30 ° C to about + 10 ° C which is selected from high vinyl polybutadiene with a content of vinyl 1,2- in a range from about 75 to about 95%; isoprene / butadiene copolymer with a content of about 10 to about 90% isoprene-derived units; 3, 4-polyisoprene having a content of the 3,4- microstructure of at least 60%; styrene / butadiene copolymer prepared by emulsion polymerization having from about 45 to about 65% of units derived from styrene and a content of vinyl 1,2-based on the butadiene component thereof, in a range of about 8 to about fifteen%; and styrene / butadiene copolymer prepared by solution polymerization having from about 15 to about 40% units derived from styrene and a vinyl 1,2-content based on the butadiene component thereof, in a range from about 15 to approximately 60%; and (B) about 50 to about 80 pee of at least one synthetic elastomer having a Tv in a range of -85 ° C to about 10 -. 10 -110 ° C which is selected from the isoprene / butadiene copolymer having about 10 to about 30% isoprene-derived units; cis 1, 4-polybutadiene rubber having about 90 to about 98% of the 15 cis 1,4- microstructure, and a 1,2- vinyl content in a range of about 2 to about 10%, the remainder being mainly of a trans 1,4- microstructure; (C) about 40 to about 20 100 pee of a particulate reinforcing filler material that is selected from: (1) carbon black or (2) carbon black and silica with a weight ratio of carbon black to silica in a range of about 1/20 to about 20/1; (D) at least one silica coupler for the silica, if silica is used, which has a reactive portion with the surface of the silica and another, based on sulfur, interactive portion with the elastomer.

2. The rim of claim 1 is characterized in that, for the running surface, the elastomers for the rubber composition consists essentially of: (A) about 30 to about 40 pee of at least one synthetic elastomer having a Tv in a range from -30 ° C to about + 10 ° C, and (B) about 60 to about 70 pee of at least one of the synthetic elastomers having a Tv in a range of -85 ° C to about -110 ° C.

3. The rim of any of the preceding claims is characterized in that, for the running surface, the particulate reinforcing agent consists essentially of carbon black and excludes the silica coupler.

4. The rim of any of claims 1 and 2 is characterized in that, for the running surface, the reinforcing agent consists of carbon black and precipitated silica.

5. The rim of claim 4 is characterized in that, for the running surface, the silica coupler has a silane reactive portion with silanol groups on the surface of the silica and another portion interacting with the elastomers. The rim of any one of the preceding claims 1, 2, 4 and 5 is characterized in that, for the running surface, the coupler is a bis (trialkoxysilylalkyl) poolisulfide having an average from about 2 to about 5 sulfur in its polysulfidic bridge. 7. The rim of any of claims 1, 2, 5 and 6 is characterized in that, for the running surface, the coupler is a bis (triethoxysilylpropyl) polysulfide.