Rubber composition and tire

Abstract

To provide new elastomer compositions for tires which provide good stiffness, tear and rolling resistance properties.SOLUTION: A sulfur vulcanizable elastomer composition comprises: 50 phr to 100 phr of at least one partially saturated elastomer comprising repeat units, where at most 15% of all repeat units of the partially saturated elastomer comprise a double bond; 0 phr to 50 phr of at least one diene-based elastomer; and 40 phr to 200 phr of at least one filler, where the filler comprises predominantly silanized or pre-silanized silica.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to sulfur vulcanizable or vulcanizable elastomeric compositions, particularly for use in rubber components such as tires. The present invention is further directed to rubber components for tires or tires comprising such elastomeric compositions. [Background technology]

[0002] As tire performance continues to improve, tire manufacturers are constantly evaluating and testing new material combinations. In particular, many tire tread elastomer compositions present a difficult trade-off between hysteresis and tear properties. While some approaches may provide good tensile and / or tear properties and maintain high rolling resistance metrics, simultaneously achieving desirable stiffness properties can prove challenging. Summary of the Invention [Problem to be solved by the invention]

[0003] Therefore, there is a need to provide new elastomeric tire compositions that offer good stiffness, tear and rolling resistance properties. [Means for solving the problem]

[0004] The present invention relates to an elastomer composition according to claim 1 and a tire according to claim 10 .

[0005] The dependent claims refer to preferred embodiments of the invention.

[0006] A primary object of the present invention is to provide an elastomeric composition having desirable rolling resistance and / or hysteresis properties.

[0007] Another object of the present invention is to provide an elastomeric composition having good tensile properties.

[0008] Another object of the present invention is to provide an elastomeric composition having sufficient or high stiffness.

[0009] It is yet another object of the present invention to provide an elastomeric composition that exhibits a good balance of hysteresis properties, tensile properties and composite stiffness.

[0010] In a first aspect, the present invention is directed to a sulfur-vulcanizable (or vulcanizable) elastomer composition (i.e., rubber composition) comprising 50 to 100 phr of at least one partially saturated elastomer containing a repeating unit, wherein up to 15% of all repeating units of the partially saturated elastomer contain double bonds. The elastomer composition further comprises 0 to 50 phr of at least one diene-based elastomer and 40 to 200 phr of at least one filler, the filler consisting primarily of silanized silica, preferably pre-silanized silica. That is, the majority (by weight) of the filler is silanized or pre-silanized silica. DETAILED DESCRIPTION OF THE INVENTION

[0011] Surprisingly, the present inventors have found that the combination of a partially unsaturated elastomer having a limited number of double bonds with silanized or presilanized silica unexpectedly improves the stiffness of the compound. Generally, the use of such silica in combination with conventional elastomers has been found to adversely limit stiffness. However, the present inventors have found that the combination with an unsaturated polymer having a limited number of double bonds unexpectedly achieves the opposite effect.

[0012] In a preferred embodiment, the partially saturated elastomer has a glass transition temperature in the range of −20° C. to −65° C. Such a Tg range is suitable for use of the polymer in rubber compositions for, for example, car and truck tread applications.

[0013] In another preferred embodiment, the partially saturated elastomer has a weight average molecular weight, Mw, of 150,000 g / mol to 900,000 g / mol, preferably 200,000 g / mol to 500,000 g / mol, as measured by gel permeation chromatography (GPC) according to ASTM 5296-11 using polystyrene calibration standards or equivalent. This molecular weight range provides an appropriate balance of processability and hysteresis characteristics.

[0014] In another preferred embodiment, the partially saturated elastomer has a glass transition temperature in the range of -20°C to -45°C, preferably in the range of -25°C to -40°C.

[0015] In yet another preferred embodiment, the partially saturated elastomer has a glass transition temperature in the range of -45°C to -65°C, preferably in the range of -45°C to -60°C.

[0016] In yet another preferred embodiment, at most 11%, preferably at most 8%, of all repeating units have double bonds, and / or at least 4% of the repeating units have double bonds. It is particularly less preferred that the elastomer be completely free of double bonds or completely hydrogenated. In particular, some double bonds (typically from double bonds in monomer units) remain for the purpose of crosslinking, i.e., sulfur vulcanization. When counting double bonds herein, bonds in aromatic structures or groups, such as styrene repeating units, are not counted as double bonds. However, styrene units are still counted as repeating units when determining the total number of repeating units in a polymer or elastomer.

[0017] In yet another preferred embodiment, the partially saturated elastomer comprises repeating units formed by residues of monomers selected from ethylene, propylene, butadiene, isoprene, and styrene. These monomers are preferably used to produce or obtain the partially saturated elastomer. One or more of the residues may be hydrogenated, i.e., the double bonds of one or more of the residues may be hydrogenated.

[0018] In yet another preferred embodiment, the partially saturated elastomer is a hydrogenated styrene-butadiene rubber, preferably a hydrogenated solution-polymerized styrene-butadiene rubber (SSBR). Hydrogenated SSBR and its preparation are known to those skilled in the art and are described, for example, in U.S. Patent Application Publications US2018201065A1, US2018251576A1, and US20190062539A1.

[0019] In yet another preferred embodiment, the partially saturated elastomer comprises a styrene butadiene rubber, such as one or more of the partially saturated solution-polymerized styrene butadiene rubbers listed below in i) to iv). i) having less than 5% by weight of non-hydrogenated vinyl groups, based on the total number of vinyl groups in the hydrogenated styrene butadiene rubber; ii) the non-hydrogenated double bonds in the cis-1,4 and trans-1,4 butadiene repeat units are less than 20 wt. %, preferably less than 10 wt. %, or preferably less than 5 wt. %, based on the total number of cis-1,4 and trans-1,4 butadiene repeat units; iii) 80% to 99% by weight (preferably 85% to 90% by weight or 90% to 98% by weight) of hydrogenated double bonds; and iv) A bound styrene content ranging from 5% to 40% by weight, preferably from 20% to 35% by weight, and a butadiene content ranging from 50% to 95% by weight, or from 50% to 80% by weight.

[0020] In another preferred embodiment, the hydrogenated styrene-butadiene rubber has 90% to 98% hydrogenated double bonds, meaning that the remaining double bonds are not hydrogenated. As known to those skilled in the art, the number of double bonds can be determined by NMR, as well as partially saturated elastomers other than styrene-butadiene rubber.

[0021] In yet another preferred embodiment, the styrene-butadiene rubber will have a bound styrene content in the range of 10% to 40% by weight, as determined by NMR, and a bound butadiene content in the range of 60% to 90% by weight. The styrene-butadiene rubber will typically have a bound styrene content in the range of 20% to 35% and a bound butadiene content in the range of 65% to 80%.

[0022] In yet another preferred embodiment, the silica is 150 g / m 2 Smaller, preferably 120 g / m 2 less, and more preferably still less than 100 g / m 2 has a BET surface area of

[0023] In yet another preferred embodiment, the silica is 50 g / m 2 from 100g / m 2 The low surface area is believed herein to help provide better silica dispersion which helps to obtain low hysteresis.

[0024] Such BET surface area is measured herein by nitrogen adsorption according to ASTM D6556 or a method equivalent thereto, and the BET method for measuring surface area is described, for example, in the Journal of American Chemical Society, Volume 60.

[0025] In yet another preferred embodiment, the silanized or presilanized (preferably precipitated) silica is 130 ml 2 / g~210m 2 / g, optionally 130m 2 / g~150m 2 / g. The CTAB (cetyltrimethylammonium bromide) method for measuring silica surface area according to ASTM D6845 is known to those skilled in the art.

[0026] In another preferred embodiment, the silanized or presilanized (and optionally precipitated) silica utilized is hydrophobized prior to addition to the elastomeric composition by treatment with at least one silane. Suitable silanes include, but are not limited to, alkylsilanes, alkoxysilanes, organoalkoxysilyl polysulfides, and organomercaptoalkoxysilanes.

[0027] In yet another preferred embodiment, the presilanized silica is silica that has been pre-reacted with a sulfur-containing silane.

[0028] In another preferred embodiment, instead of reacting the silica with a silica coupling agent in situ within the elastomer composition, the presilanized silica may be pretreated with a silica coupling agent, such as an alkoxyorganomercaptoalkoxysilane or a combination of an alkoxysilane and an organomercaptoalkoxysilane, prior to blending with the elastomer. See, for example, U.S. Patent 7,214,731, which provides further details on the preparation of such presilanized silica.

[0029] In another preferred embodiment, the silanated or presilanated silica is a silica pre-reacted (optionally precipitated) with a silica coupler comprising bis(3-triethoxysilylpropyl) polysulfide or an alkoxyorganomercaptosilane containing an average of 1 to 5 linked sulfur atoms (preferably 2 to 4) in its polysulfidic bridge. The silane improves compatibility with the rubber material, dispersion, or rubber matrix and / or supports the curing process.

[0030] The amount of mercapto groups on the surface of the silica may range from 0.1 to 1% by weight, alternatively 0.4 to 1% by weight, or 0.4 to 0.6% by weight, where 100 is the (total) weight of the silica sample. Such mercapto group quantification is carried out by titration.

[0031] In addition to the mercapto groups attached to the silica, the silica may contain a compatibilizer, which is typically a (hydro)carbon chain material having multiple carbon atoms (e.g., at least four carbon atoms) along the chain. Such a compatibilizer can facilitate mixing of the composition. By way of example, the weight percent of carbon surface loading / functionalization may be between 2 and 10, or alternatively, between 3 and 8. Again, 100% is the total weight of the silica sample herein.

[0032] The silanized or presilanized silica can be optionally treated with a silica dispersing agent. Such silica dispersing agents can include glycols such as fatty acids, diethylene glycol, polyethylene glycol, hydrogenated or non-hydrogenated fatty acid esters of C5 or C6 sugars, and polyoxyethylene derivatives of hydrogenated or non-hydrogenated fatty acid esters of C5 or C6 sugars. Exemplary fatty acids include stearic acid, palmitic acid, and oleic acid. Exemplary fatty acid esters of hydrogenated and non-hydrogenated C5 and C6 sugars (e.g., sorbose, mannose, and arabinose) include, but are not limited to, sorbitan oleates, such as sorbitan monooleate, dioleate, trioleate, and sesquioleate, and sorbitan esters of laurate fatty acid, palmitate, and stearate fatty acid. Exemplary polyoxyethylene derivatives of hydrogenated and non-hydrogenated C5 and C6 sugar fatty acid esters include, but are not limited to, polysorbates and polyoxyethylene sorbitan esters, which are similar to the hydrogenated and non-hydrogenated sugar fatty acid esters described above except that an ethylene oxide group is placed in place of each of the hydroxyl groups.

[0033] The optional silica dispersing aid, when used, is present in an amount ranging from about 0.1% to about 25% by weight based on the weight of the silica, with from about 0.5 to about 20% by weight being preferred, and from about 1 to about 15% by weight based on the weight of the silica being preferred.

[0034] In another embodiment, the presilanized silica is pre-hydrophobized by treating the silica in its aqueous colloidal form with both the organomercaptosilane and the alkylsilane in a weight ratio ranging from 10 / 90 to 90 / 10, wherein the alkylsilane is of general formula (I).

[0035] [ka]

[0036] where R is an alkyl group having 1 to 18 carbon atoms, preferably 1 to 8 carbon atoms, such as methyl, ethyl, isopropyl, n-butyl and octadecyl groups, n is an integer from 1 to 3, X is a halogen, i.e., a group selected from chlorine or bromine, preferably a chlorine group, and an alkoxy group, preferably (R 1 O)-, where R 1 is an alkyl group having 1 to 3 carbon atoms, such as a methyl, ethyl, or isopropyl group, preferably a methyl or ethyl group, and the organic mercaptosilane is represented by general formula (II).

[0037] [ka]

[0038] where X is a group selected from halogen, such as chlorine or bromine, preferably a chlorine group, and alkyl groups having 1 to 16 carbon atoms, preferably methyl, ethyl, n-propyl, and n-butyl groups. 2 is an alkyl group having 1 to 16 carbon atoms, preferably 1 to 4 carbon atoms, and is preferably selected from methyl and ethyl groups; R 3is an alkylene group having 1 to 16 carbon atoms, preferably 1 to 4 carbon atoms, preferably a propylene group; where n represents an integer from 0 to 3, and n is preferably zero.

[0039] Representative alkylsilanes of formula (I) include, for example, trichloromethylsilane, dichlorodimethylsilane, chlorotrimethylsilane, trimethoxymethylsilane, dimethoxydimethylsilane, methoxytrimethylsilane, trimethoxypropylsilane, trimethoxyoctylsilane, trimethoxyhexadecylsilane, dimethoxydipropylsilane, triethoxymethylsilane, triethoxypropylsilane, triethoxyoctylsilane, diethoxydimethylsilane, and the like.

[0040] Representative organomercaptosilanes of formula (II) include, for example, triethoxymercaptopropylsilane, trimethoxymercaptopropylsilane, methyldimethoxymercaptopropylsilane, methyldiethoxymercaptopropylsilane, dimethylmethoxymercaptopropylsilane, triethoxymercaptoethylsilane, and tripropoxymercaptopropylsilane.

[0041] Examples of pre-silanized silicas suitable for use in the practice of the present invention include, but are not limited to, mercaptosilane pre-treated Ciptane® 255 LD and Ciptane® LP (PPG Industries) silicas, as well as Coupsil® 8113 (Degussa), which is a reaction product of organosilane bis(triethoxysilylpropyl) polide (Si69) with Ultrasil® VN3 silica, Coupsil® 6508, PPG Industries Agilon® 400 silica, PPG Industries Agilon® 454 silica, and PPG Industries Agilon® 458 silica.

[0042] In an embodiment, the elastomeric composition is free of non-presilanized silica or consists of less than 10 phr, preferably less than 5 phr, of non-presilanized silica.

[0043] Generally, as used herein, presilanized silica is preferably, but not necessarily, presilanized precipitated silica.

[0044] In embodiments, the elastomeric composition may also include silica, which is optionally a precipitated silica (non-presilanized). Such conventional silicas are characterized by having a BET surface area, as measured, for example, using nitrogen gas. In one embodiment, the BET surface area may range from 40 to 600 square meters per gram. In another embodiment, the BET surface area may range from 80 to 300 square meters per gram. Conventional silicas may also be characterized by a dibutyl phthalate (DBP) absorption value ranging from 100 to 400, or alternatively, from 150 to 300. Conventional silicas are expected to have an average ultimate particle size, as measured by electron microscopy, ranging, for example, from 0.01 to 0.05 microns, although silica particles may be smaller or even larger. Various commercially available silicas can be used, including, by way of example only and not limitation, silicas commercially available under the Hi-Sil trademark from PPG Industries under designations such as 210, 315G, EZ160G, etc.; silicas available from Solvay under designations such as Z1165MP and Premium200MP; and silicas available from Evonik AG under designations such as VN2 and Ultrasil 6000GR, 9100GR, etc.

[0045] In one embodiment, when the elastomeric composition includes added / non-presilanated silica (in addition to the presilanated silica), the elastomeric composition includes an added silica coupler (a silica coupler added to the elastomeric composition) that has a moiety that interacts with hydroxyl groups (e.g., silanol groups) on the silica and the presilanated silica and an additional moiety that interacts with the elastomer of the elastomeric composition. In one embodiment, the silica coupler added to the elastomeric composition is comprised of a bis(3-triethoxysilylpropyl) polysulfide having an average of about 2 to about 4 connecting sulfur atoms in its polysulfidic bridge.

[0046] Representative examples of silica couplers (or silica coupling agents) having one site reactive with the presilanized silica and the hydroxyl groups on the silica and another site interacting with the elastomer include: (A) bis(3-trialkoxysilylalkyl) polysulfides containing an average of about 2 to about 4, or about 2 to about 2.6, or about 3.2 to about 3.8 sulfur atoms in the crosslinking bridges; (B) alkoxyorganomercaptosilanes; or (C) combinations thereof. Representative examples of such bis(3-trialkoxysilylalkyl) polysulfides include bis(3-triethoxysilylpropyl) polysulfides. As indicated, in the case of presilanized precipitated silicas, the silica coupler may desirably be an alkoxyorganomercaptosilane. For non-presilanized silicas, the silica coupler desirably comprises bis(3-triethoxysilylpropyl) polysulfide.

[0047] In one embodiment, the elastomeric composition can include conventional sulfur-containing organosilicon compounds or silanes. Examples of suitable sulfur-containing organosilicon compounds include those of the formula:

[0048] [ka]

[0049] wherein Z is selected from the group consisting of:

[0050] [ka]

[0051] where R 1 is an alkyl group of 1 to 4 carbon atoms, cyclohexyl, or phenyl, and R 2 is an alkoxy of 1 to 8 carbon atoms or a 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. In one embodiment, the sulfur-containing organosilicon compound is a 3,3'-bis(trimethoxy or triethoxysilylpropyl) polysulfide. In one embodiment, the sulfur-containing organosilicon compound is a 3,3'-bis(triethoxysilylpropyl) disulfide and / or a 3,3'-(triethoxysilylpropyl) tetrasulfide. Thus, for Formula I, Z can be:

[0052] [ka]

[0053] where R 2is an alkoxy of 2 to 4 carbon atoms, alternatively 2 carbon atoms; Alk is a divalent hydrocarbon of 2 to 4 carbon atoms, alternatively 3 carbon atoms; and n is an integer of 2 to 5, alternatively 2 or 4. In another embodiment, suitable sulfur-containing organosilicon compounds include those disclosed in U.S. Patent No. 6,608,125. In one embodiment, the sulfur-containing organosilicon compound is 3-(octanoylthio)-1-propyltriethoxysilane, CH3(CH2)6C(=O)-S-CH2CH2Si(OCH2CH3)3, commercially available as NXT from Momentive Performance Materials. In another embodiment, suitable sulfur-containing organosilicon compounds include those disclosed in U.S. Patent Publication No. 2003 / 0130535. In one embodiment, the sulfur-containing organosilicon compound is Si-363 manufactured by Degussa. The amount of sulfur-containing organosilicon compound in the elastomeric composition can vary depending on the level of other additives used. Generally, the amount of compound ranges from 0.5 phr to 20 phr. In one embodiment, the amount ranges from 1 phr to 10 phr.

[0054] In one embodiment, the elastomeric composition excludes a separate silica coupler, i.e., a silica coupler added separately to the rubber composition.

[0055] In yet another embodiment, the filler comprises at least 50 phr of silica, preferably 50 phr to 160 phr of silica, wherein the silica is predominantly presilanized silica (all by weight).

[0056] In yet another embodiment, the filler comprises 45 phr to 150 phr of pre-silanized silica. In a preferred embodiment, the filler comprises 60 phr to 150 phr of pre-silanized silica.

[0057] In yet another embodiment, the filler comprises 25 phr to 60 phr of pre-silanized silica, such a range being of particular interest for truck tires.

[0058] In yet another embodiment, the filler comprises less than 25 phr of carbon black, preferably less than 10 phr of carbon black, or more preferably less than 5 phr of carbon black.

[0059] In another preferred embodiment, the elastomeric composition comprises at most 10 phr of a liquid plasticizer, preferably at most 10 phr of an oil. By liquid plasticizer is meant herein a plasticizer that is liquid at 23°C.

[0060] In another preferred embodiment, the elastomeric composition contains less than 50 phr of oil, preferably less than 30 phr of oil, more preferably less than 10 phr of oil, or even more preferably less than 7 phr of oil, and may contain less than 5 phr of oil or may be essentially or completely oil-free.

[0061] In yet another embodiment, the elastomeric composition further comprises 3 phr to 20 phr (preferably 5 phr to 15 phr) of polyoctenamer. The addition of polyoctenamer further improves tensile properties and also aids in co-curability with other diene-based elastomer compounds. Furthermore, the presence of polyoctenamer helps improve rolling resistance in combination with partially saturated elastomers such as hydrogenated SSBR.

[0062] In another preferred embodiment, the polyoctenamer has one or more of the following: a glass transition temperature in the range of −50° C. to −80° C., as determined in accordance with ASTM D3418, as referred to herein; a weight average molecular weight MW in the range of 80,000 g / mol to 100,000 g / mol, as determined by gel permeation chromatography (GPC) according to ASTM 5296-11 or an equivalent method using polystyrene calibration standards; and a melting point in the range of 45° C. to 55° C., as measured on the second heat of a DSC according to ASTM D3418 or an equivalent method.

[0063] In yet another preferred embodiment, the polyoctenamer has at least 65% and at most 85% trans double bonds of all double bonds in the polyoctenamer.

[0064] In another embodiment, the elastomer composition comprises 75 phr (preferably 80 phr) to 100 phr of a partially saturated elastomer and / or 0 phr to 25 phr (preferably 20 phr) of one or more of polybutadiene rubber, polyisoprene, and natural rubber. In particular, a high content of the partially saturated elastomer is considered to be most preferred.

[0065] In yet another embodiment, the polybutadiene rubber is a (high) cis-polybutadiene rubber having a glass transition temperature in the range of -90°C to -115°C and / or having a cis-microstructure content of at least 95%.

[0066] In another embodiment, the composition can include one or more hydrogenated plasticizers selected from one or more of hydrogenated liquid plasticizers and hydrogenated hydrocarbon resins. In particular, the hydrogenated liquid plasticizer can include hydrogenated oils and / or hydrogenated liquid polymers, preferably hydrogenated liquid diene-based polymers. Such hydrogenated liquids and diene-based polymers preferably have an average molecular weight (Mw) of less than 50,000 g / mol, where Mw is measured by gel permeation chromatography (GPC) using polystyrene calibration standards according to ASTM 5296-11 or an equivalent method. Liquid diene-based polymers include liquid styrene-butadiene rubber, butadiene rubber, isoprene rubber, styrene-isoprene rubber, isoprene-butadiene rubber, and styrene-isoprene-butadiene rubber, or combinations thereof.

[0067] In embodiments, the hydrogenated hydrocarbon resin is selected from a fully or partially hydrogenated C9 resin, a fully or partially hydrogenated C5 resin, a fully or partially hydrogenated alpha-methylstyrene resin, a fully or partially hydrogenated terpene resin, a fully or partially hydrogenated rosin resin, or a mixture thereof, and the resin may be modified with one or more aliphatic or aromatic groups.

[0068] In another embodiment, the hydrogenated hydrocarbon resin is selected from the group consisting of fully or partially hydrogenated (especially aliphatic) C5 resins, fully or partially hydrogenated cyclopentadiene resins, fully or partially hydrogenated dicyclopentadiene resins, and combinations thereof. The resin may also be modified with one or more aliphatic or aromatic groups. However, the majority of the monomer residues of the resin are preferably partially or fully hydrogenated cyclopentadiene, fully or partially hydrogenated dicyclopentadiene, and combinations thereof.

[0069] In yet another embodiment, the hydrogenated hydrocarbon resin has no double bonds. Such highly hydrogenated hydrocarbon resins are more compatible with the rubber matrix according to the present invention.

[0070] In another embodiment, the hydrogenated hydrocarbon resin is a fully or partially hydrogenated cyclopentadiene resin, a fully or partially hydrogenated dicyclopentadiene resin, or a combination thereof.

[0071] In another embodiment, the elastomeric composition may include at least one resin, preferably a hydrocarbon resin, more preferably a plasticized hydrocarbon resin (e.g., a hydrogenated hydrocarbon resin as described herein above). The resin may be present in a range of from 5 phr to 80 phr, preferably from 10 phr to 75 phr, more preferably from 20 phr to 70 phr.

[0072] In another embodiment, the glass transition temperature of the resin is within the range of 30° C. to 80° C., preferably within the range of 40° C. to 80° C., and more preferably within the range of 40° C. to 70° C. In this specification, the glass transition temperature of the resin is determined as the peak midpoint at a heating rate of 10° C. per minute using a differential scanning calorimeter (DSC) according to ASTM D6604 or a method equivalent thereto.

[0073] In another embodiment, the resin has a softening point, as determined according to ASTM E28 or an equivalent method (sometimes referred to as the Ring and Ball Softening Point Determination Method), of at least 95°C. Preferably, the softening point is at most 140°C, more preferably at most 120°C, and even more preferably at most 110°C.

[0074] In yet another embodiment, the resin has a polydispersity index in the range of 1 to 5, preferably 1 to 2, and more preferably 1.5 to 1.8.

[0075] In yet another embodiment, the resin has an average molecular weight Mw of 150 g / mol to 1500 g / mol, preferably 400 g / mol to 1000 g / mol, more preferably 500 g / mol to 900 g / mol, and even more preferably 600 g / mol to less than 700 g / mol, as measured by gel permeation chromatography (GPC) using polystyrene calibration standards according to ASTM 5296-11 or equivalent.

[0076] In yet another embodiment, the elastomeric composition further contains at least 0.2 phr of a vulcanizing agent, preferably elemental sulfur. For example, the composition contains 0.4 phr to 15 phr of a vulcanizing agent, which may include, but is not limited to, elemental sulfur or a sulfur-containing silane.

[0077] In another embodiment, the elastomeric composition includes 0.3 to 3 phr of at least one vulcanization accelerator selected from dithiocarbamate and / or thiuram accelerators. Such accelerators are known as high-speed accelerators and are considered herein to be particularly beneficial in view of utilizing the limited amount of double bonds in the elastomer and / or hydrogenated resin. The composition may also include additional accelerators.

[0078] In yet another embodiment, the vulcanization accelerator is tetrabenzyl thiuram disulfide, which has been found to be preferable in combination with partially saturated polymers.

[0079] In embodiments, the elastomeric composition may contain at least one and / or one additional diene-based rubber. Representative synthetic polymers include homopolymers of butadiene and its homologs and derivatives, such as methylbutadiene, dimethylbutadiene, and pentadiene, as well as copolymers formed from butadiene or its homologs or derivatives with other unsaturated monomers. Among the latter are acetylenes, such as vinyl acetylene; olefins, such as isobutylene, which copolymerizes with isoprene to form butyl rubber; vinyl compounds, such as acrylic acid, acrylonitrile (which polymerizes with butadiene to form NBR), methacrylic acid, and styrene, the latter of which polymerizes with butadiene to form SBR; vinyl esters; and various unsaturated aldehydes, ketones, and ethers, such as acrolein, methyl isopropenyl ketone, and vinyl ethyl ether. Specific examples of synthetic rubbers include neoprene (polychloroprene), polybutadiene (including cis-1,4-polybutadiene), polyisoprene (including cis-1,4-polyisoprene), butyl rubber, halobutyl rubbers such as chlorobutyl rubber and bromobutyl rubber, and styrene / isoprene / butadiene rubber. These include 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 / diene monomer (EPDM), particularly ethylene / propylene / dicylopentadiene terpolymers. Additional examples of usable rubbers include alkoxysilyl-end-functionalized solution-polymerized polymers (SBR, PBR, IBR, and SIBR), silicon-coupled and tin-coupled star-branched polymers. Preferred rubbers or elastomers are generally natural rubber, synthetic polyisoprene, polybutadiene, and SBR, including SSBR. One or more of these rubbers may be functionalized for coupling with silica.

[0080] In another embodiment, the composition can include at least two diene-based rubbers. For example, a combination of two or more rubbers is preferred, such as cis-1,4-polyisoprene rubber (natural or synthetic, but preferably natural), 3,4-polyisoprene rubber, styrene / isoprene / butadiene rubber, emulsion-solution polymerization-derived styrene / butadiene rubber, cis-1,4-polybutadiene rubber, emulsion polymerization-prepared butadiene / acrylonitrile copolymer, etc. In some embodiments, the partially saturated elastomer can also be a diene-based polymer, but is not necessarily diene-based.

[0081] In another embodiment, emulsion polymerization-derived styrene / butadiene (ESBR) having a bound styrene content of 20 to 35% is used, and in some applications, ESBR with a moderate to relatively high bound styrene content, i.e., 30 to 45%, is used. Emulsion polymerization-prepared ESBR may refer to copolymerization of styrene and 1,3-butadiene as an aqueous emulsion. Such is well known to those familiar with such technology. The bound styrene content may vary, for example, from 5 to 50%. In one aspect, ESBR may also contain acrylonitrile in the form of a terpolymer rubber, e.g., in an amount of 2 to 30% by weight of bound acrylonitrile in the terpolymer. Emulsion polymerization-prepared styrene / butadiene / acrylonitrile copolymer rubber having 2 to 40% by weight of bound acrylonitrile in the copolymer may also be considered as a diene-based rubber.

[0082] In another embodiment, solution polymerization-prepared SBR (SSBR) can be used. Such SSBR can have a bound styrene content ranging, for example, from 5 to 50%, preferably from 9 to 36%. SSBR can be conveniently prepared, for example, by anionic polymerization in an inert organic solvent. Specifically, it can be synthesized by copolymerizing styrene and 1,3-butadiene monomers in a hydrocarbon solvent using an organolithium compound as an initiator. As mentioned above, such rubbers can also be functionalized for coupling with silica.

[0083] In one embodiment, synthetic or natural polyisoprene rubber can be used. Synthetic cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber are well known to those skilled in the rubber art. In particular, the cis 1,4-content can be at least 90%, optionally at least 95%.

[0084] In one embodiment, cis-1,4-polybutadiene rubber (BR or PBD) is used. Suitable polybutadiene rubbers can be prepared, for example, by organic solution polymerization of 1,3-butadiene. BR can be conveniently characterized, for example, by having a cis-1,4-content of at least 90% ("high cis" content) and a glass transition temperature, Tg, in the range of 95°C to -110°C. Suitable polybutadiene rubbers are commercially available, for example, from The Goodyear Tire & Rubber Company, such as Budené® 1207, Budené® 1208, Budené® 1223, or Budené® 1280. These high cis-1,4-polybutadiene rubbers can be synthesized using a nickel catalyst system comprising a mixture of (1) an organonickel compound, (2) an organoaluminum compound, and (3) a fluorine-containing compound, as described, for example, in U.S. Patent Nos. 5,698,643 and 5,451,646.

[0085] The glass transition temperature (Tg) of an elastomer or rubber refers to the glass transition temperature (S) of the respective elastomer or rubber in the uncured state. The glass transition temperature (Tg) of an elastomer or rubber composition refers to the glass transition temperature of the respective elastomer or rubber composition in the cured state. Tg is determined by differential scanning calorimetry (DSC) at the midpoint of the peak at a heating rate of 20°C per minute according to ASTM D3418.

[0086] As used herein, the term "phr" refers, according to conventional practice, to "parts by weight of a respective material per 100 parts by weight of rubber or elastomer." Generally, using this convention, an elastomeric composition comprises 100 parts by weight of rubber / elastomer. A claimed composition may contain rubbers / elastomers other than those explicitly recited in the claims, provided that the phr values ​​of the claimed rubbers / elastomers comply with the claimed phr ranges and the amounts of all rubbers / elastomers in the composition total 100 parts rubber. In one example, the composition may further comprise 1 phr to 10 phr, optionally 1 phr to 5 phr, of one or more additional diene-based rubbers, such as SBR, SSBR, ESBR, PBD / BR, NR, and / or synthetic polyisoprene. In another example, the composition may contain less than 5, preferably less than 3, frames of additional diene-based rubbers, or may be essentially free of such additional diene-based rubbers. In this specification, the terms "compound" and "composition" may be used interchangeably unless otherwise noted. Also, the terms "rubber" and "elastomer" may be used interchangeably herein unless otherwise indicated.

[0087] In embodiments, the elastomer composition may also contain an oil, particularly a processing oil. The processing oil may be included in the elastomer composition as an extension oil, typically used for elastomer extension. Alternatively, the processing oil may be added directly to the elastomer composition during rubber compounding. The processing oil used may include both extension oils present in the elastomer and processing oils added during compounding. Suitable processing oils may include various oils known in the art, including aromatic, paraffinic, naphthenic, vegetable, and low PCA oils, such as MES, TDAE, SRAE, and heavy naphthenic oils. Suitable low PCA oils include those having a polycyclic aromatics content of less than 3% by weight, as determined by the IP346 method. The IP346 method procedure is described in Standard Methods for Analysis & Testing Petroleum and Related Products and British Standard 2000 Parts, 003, 62nd edition, published by the Institute of Petroleum, United Kingdom.

[0088] In an embodiment, the elastomer composition may also contain carbon black as one of the fillers. A preferred amount herein is 0.5 to 25 phr, preferably 0.5 to 10 phr or 0.5 to 5 phr. Representative examples of such carbon black include N110, N121, N134, N220, N231, N234, N242, N293, N299, N315, N326, N330, N332, N339, N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N683, N754, N762, N765, N774, N787, N907, N908, N990, and N991 grades. These carbon blacks have an iodine adsorption capacity of 9 g / kg to 145 g / kg and a DBP number of 34 cm 3 / 100g to 150cm 3 / 100g range.

[0089] In another embodiment, other fillers may be used in the elastomeric composition, including, but not limited to, particulate fillers including ultra-high molecular weight polyethylene (UHMWPE); crosslinked particulate polymer gels, including, but not limited to, those disclosed in U.S. Patent No. 6,242,534; U.S. Patent No. 6,242,534; U.S. Patent No. 6,207,757; U.S. Patent No. 6,133,364; U.S. Patent No. 6,372,857; U.S. Patent No. 5,395,891; or U.S. Patent No. 6,127,488; and composite fillers of plasticized starch, including, but not limited to, those disclosed in U.S. Patent No. 5,672,639. Such other fillers may be used in amounts ranging from 1 phr to 10 phr.

[0090] Those skilled in the art will readily understand that the elastomer composition can be compounded by methods commonly known in the rubber compounding art, such as mixing various sulfur-vulcanizable constituent rubbers with various commonly used additive materials. These additives include curing aids such as sulfur donors, activators, and retarders, as well as processing additives such as oils, resins including tackifying resins and plasticizers, fillers, pigments, fatty acids, zinc oxide, waxes, antioxidants, anti-ozonants, and peptizing agents. As known to those skilled in the art, the additives are selected and commonly used in conventional amounts depending on the intended use of the sulfur-vulcanizable and sulfur-vulcanized materials (rubbers). Representative examples of sulfur donors include elemental sulfur (free sulfur), amine disulfides, polymeric polysulfides, sulfur-olefin adducts, and the like. In one embodiment, the sulfur-vulcanizing agent is elemental sulfur. The sulfur-vulcanizing agent can be used in an amount ranging from 0.5 phr to 8 phr, or alternatively, from 1.5 phr to 6 phr. A typical amount of tackifying resin, if used, is, for example, 0.5 phr to 10 phr, usually 1 phr to 5 phr. A typical amount of processing aid, if used, is, for example, 1 phr to 50 phr (this may particularly consist of oil). A typical amount of antioxidant, if used, can be, for example, 1 phr to 5 phr. Representative antioxidants include, for example, diphenyl-p-phenylenediamine, and examples thereof include those disclosed in The Vanderbilt Rubber Handbook (1978), pages 344-346. A typical amount of antiozonant, if used, can be, for example, 1 phr to 5 phr. A typical amount of fatty acid, which may include stearic acid, if used, can be, for example, 0.5 phr to 3 phr. A typical amount of wax, if used, can be, for example, 1 phr to 5 phr. Microcrystalline wax is often used. A typical amount of peptizer, if used, can be, for example, 0.1 phr to 1 phr. Representative peptizers include, for example, pentachlorothiophenol, dibenzamidodiphenyl disulfide, and the like.

[0091] Accelerators are preferred, but not required, for controlling the time and / or temperature required for vulcanization and improving the properties of the vulcanizate. In one embodiment, a single accelerator system, i.e., a primary accelerator, may be used. The primary accelerator(s) may be used in total amounts ranging from 0.5 phr to 4 phr, or alternatively, from 0.8 phr to 1.5 phr. In another embodiment, a combination of a primary accelerator and a secondary accelerator may be used, with the secondary accelerator being used in a smaller amount, such as 0.05 phr to 3 phr, to activate the vulcanizate and improve its properties. Combining these accelerators may have a synergistic effect on the final properties, resulting in properties that are somewhat superior to those achieved by either accelerator alone. In addition, delayed-action accelerators may be used, which are not affected by normal processing temperatures and provide sufficient cure at normal vulcanization temperatures. Vulcanization retarders may also be used. Suitable types of accelerators that can be used in the present invention include, for example, amines, disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides, dithiocarbamates, and xanthates. In one embodiment, the primary accelerator is a sulfenamide. If a secondary accelerator is used, the secondary accelerator may be, for example, a guanidine, a dithiocarbamic acid, or a thiuram compound. Suitable guanidines include diphenylguanidine, etc. Suitable thiurams include tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabenzylthiuram disulfide, etc.

[0092] Mixing of the elastomeric composition can be accomplished by methods known to those skilled in the rubber mixing art. For example, the components are typically mixed in at least two stages, i.e., at least one non-productive stage followed by a productive mix stage. The final curative, including the sulfur vulcanizing agent, can be mixed in the final stage, commonly referred to as the "productive" mix stage, which is typically performed at a temperature lower than the mixing temperature(s) of the preceding non-productive mix stage(s), i.e., the final temperature. The terms "non-productive" and "productive" mix stages are familiar to those skilled in the rubber mixing art. In one embodiment, the elastomeric composition is subjected to a thermomechanical mixing step. The thermomechanical mixing step generally involves mechanical manipulation in a mixer or extruder for a time suitable to generate a rubber temperature, e.g., in the range of 140°C to 190°C. The appropriate duration of the thermomechanical processing varies as a function of the conditions of use and the quantity and nature of the parts. For example, the thermomechanical processing can be on the order of 1 to 20 minutes.

[0093] The elastomer composition can be incorporated into various rubber components, such as tires (or other terms, tire components). For example, the rubber component can be a tread (including a tread cap and a tread base), a sidewall, an apex, a chafer, a sidewall insert, a wire coat, or an innerliner. Preferred applications of the present invention include tread rubber applications.

[0094] In a second aspect of the present invention, there is provided a vulcanized elastomeric composition based on an elastomeric composition according to the first aspect of the present invention, i.e. the vulcanized elastomeric composition is the vulcanized product of the sulfur vulcanizable elastomeric composition according to the first aspect and / or embodiments thereof.

[0095] In a third aspect of the present invention, there is provided a rubber component, preferably a rubber component for a tire, in particular comprising an elastomer composition according to the first aspect of the present invention or an elastomer composition according to the second aspect of the present invention, and / or one or more of their embodiments. The tire may thus be an unvulcanized tire or a vulcanized tire, i.e. a vulcanized tire.

[0096] In a fourth aspect of the present invention, there is provided a tire comprising a rubber composition according to the first or second aspect of the present invention, or having a rubber component according to the third aspect of the present invention.

[0097] In a preferred embodiment, the tire includes a tread, preferably a tread cap, made of the elastomeric composition. In another embodiment, the tire has a radially outer tread cap layer, made of the elastomeric composition, intended to come into contact with the road during travel.

[0098] The tire of the present invention may be, for example, a pneumatic or non-pneumatic tire, a racing tire, a passenger tire, an aircraft tire, an agricultural tire, an earthmover tire, an off-the-road (OTR) tire, a truck tire, or a motorcycle tire, and the tire may be a radial or bias tire.

[0099] Vulcanization of pneumatic tires can be carried out at conventional temperatures, for example, within the range of 100°C to 200°C. In one embodiment, vulcanization is carried out at a temperature within the range of 110°C to 180°C. Vulcanization can be any conventional vulcanization process, such as heating in a press or mold, heating with superheated steam or hot air, etc. Such tires can be built, shaped, molded, and cured by a variety of methods that are known and readily apparent to those skilled in such art.

[0100] Additionally, in a fifth aspect, the present invention is directed to a method for producing an elastomeric composition (e.g., an elastomeric composition described in the previous aspect), the method comprising one or more of the following steps: i) Silica is silanized with at least one silane to obtain silanized (or alternatively pre-silanized) silica. ii) Adding silanized silica to partially saturated elastomers and / or diene-based elastomers. iii) Mixing the silanized silica with a partially saturated elastomer and / or a diene-based elastomer. iv) Addition of one or more of plasticizers (such as resins and / or oils), processing aids, antidegradants, waxes, etc. v) adding sulfur and optionally at least one (sulfur cure) accelerator;

[0101] In a sixth aspect, the present invention is directed to a method for manufacturing a tire, preferably manufactured using a composition according to the previous aspect and / or using a method for manufacturing an elastomeric composition according to the fifth aspect, the method comprising: a) A vulcanizable elastomeric composition forms at least a portion of the rubber component (or rubber components). b) Assembling a tire including rubber components. c) curing the tire having the rubber component to obtain a cured tire.

[0102] Features of the aspects and embodiments described herein may be combined with each other. [Example]

[0103] Table 1 below shows two comparative elastomer compositions not according to the present invention. Comparative Example 1 is an elastomer composition with the same diene-based rubber matrix as Comparative Example 2. The compositions share most of the same components. However, Comparative Example 1 contains 80 phr of conventional silica and 7 phr of Silane 1, while Comparative Example 2 contains 90 phr of pre-silanized silica. Furthermore, Comparative Example 1 contains 10 phr of oil, while Comparative Example 2 contains 5 phr of oil. For example, these two comparative examples demonstrate that using pre-silanized silica in place of an equivalent amount of conventional, i.e., non-pre-silanized, silica typically reduces the stiffness of the compound. This effect is shown in Table 2 below.

[0104] [Table 1]

[0105] [Table 2]

[0106] The stiffness of Comparative Example 2 was confirmed to be significantly less than that of Comparative Example 1, as evidenced by a reduction in G' of approximately 32%. The reduction in stiffness is even more pronounced because the composition of Comparative Example 2 already has an increased silica content (10 phr); more filler generally increases the stiffness of a composition. Additionally, Comparative Example 2 contains 5 phr less oil than Comparative Example 1, which also typically increases the stiffness of a compound. Silica prior to silanization disperses well in the elastomer composition, resulting in reduced stiffness at low strains.

[0107] As shown in Table 2, the tangent delta is improved by approximately 14% with the use of pre-silane silica. Tangent delta can be considered a hysteresis index, and a decrease in tangent delta indicates a decrease in rolling resistance when the same elastomer composition is used in a tire. Tensile strength remains relatively low for both Comparative Example 1 and Comparative Example 2.

[0108] While the above-described improvement in tangent delta is desirable, a significant reduction in stiffness, for example, would be undesirable for many performance-critical tire applications.

[0109] In accordance with an embodiment of the present invention, the inventors have discovered Examples 1 and 2, as shown in Table 3 below. Examples 1 and 2 are listed along with Comparative Examples 3 and 4, which are not in accordance with the present invention. All of the examples in Table 3 include a partially saturated elastomer in the form of a hydrogenated solution-polymerized styrene-butadiene rubber. Furthermore, Examples 1 and 2 are comprised of pre-silanized silica, whereas Comparative Examples 3 and 4, like Comparative Examples 1 and 2, are comprised of conventional silica. Comparative Example 3 and Example 1 each comprise a high Tg hydrogenated solution-polymerized styrene-butadiene rubber. Comparative Example 4 and Example 2 each comprise a low Tg hydrogenated solution-polymerized styrene-butadiene rubber.

[0110] [Table 3]

[0111] For the examples in Table 3, the stiffness, tangent delta, and tensile strength were measured and are shown in Table 4 below.

[0112] [Table 4]

[0113] As shown in Table 4, Example 1 has substantially higher stiffness than its related Comparative Example 3. This surprising and unexpected effect is completely different from that observed when combining conventional diene rubber with pre-silanated silica. This typical behavior is demonstrated, for example, by Comparative Examples 1 and 2 in Table 2, which show that replacing conventional silica with pre-silanated silica has the opposite effect of reducing stiffness. However, when this silica is used in combination with a partially saturated elastomer (here, hydrogenated solution-polymerized styrene-butadiene rubber), the stiffness is even higher than when replacing conventional silica with pre-silanated silica. Similar behavior is also observed when comparing the stiffness values ​​of Comparative Example 4 and Inventive Example 2, as shown in Table 4. Tangent delta values, which are an indicator of hysteresis and rolling resistance, are significantly improved when pre-silanized silica is used compared to conventional silica. Comparative Examples 3 and 4 and Examples 1 and 2 also exhibit good tensile strength.

[0114] Overall, Examples 1 and 2 have high stiffness, good rolling resistance index, and at the same time good tensile properties.

Claims

1. At least one partially saturated elastomer characterized by repeating units of 50 phr to 100 phr, wherein up to 15% of all repeating units of the partially saturated elastomer contain double bonds. At least one diene-based elastomer ranging from 0 phr to 50 phr; and At least one filler ranging from 40 phr to 200 phr, characterized in that the filler mainly comprises silica silane or silica presilane. A sulfur-curable elastomer composition characterized by containing the following:

2. The elastomer composition according to claim 1, characterized in that the partially saturated elastomer has a glass transition temperature in the range of -20°C to -65°C; and / or, characterized in that the partially saturated elastomer has a weight-average molecular weight Mw of 200,000 g / mol to 500,000 g / mol.

3. The elastomer composition according to claim 1, characterized in that the elastomer composition contains 0 phr to 10 phr of liquid plasticizer or 2 phr to 10 phr of liquid plasticizer.

4. The elastomer composition according to claim 1, characterized in that the silane silica or presilane silica has a BET surface area less than 120 g / m2.

5. The elastomer composition according to claim 1, characterized in that the presilanized silica is silica that has been pre-reacted with a sulfur-containing silane; or, characterized in that the silanized silica is silica that has been reacted with a sulfur-containing silane.

6. The elastomer composition according to claim 1, characterized in that the filler contains 45 phr to 150 phr of silica; and / or the filler contains less than 5 phr of carbon black.

7. The elastomer composition according to claim 1, characterized in that up to 11% of the total repeating units have double bonds; and / or, at least 4% of the repeating units have double bonds.

8. The elastomer composition according to claim 1, further characterized by containing 3 phr to 20 phr of polyoctenomer.

9. The elastomer composition according to claim 1, further characterized by containing 0.1 phr to 3 phr of a vulcanization accelerator selected from one or more dithiocarbamate-based accelerators and thiram-based accelerators.

10. A tire having a rubber member such as a tread characterized by an elastomer composition described in any one of the preceding claims, wherein the elastomer composition is vulcanized.