rubber composition

Abstract

The present invention provides a rubber composition comprising a diene rubber component and a filler system, the rubber component being surface functionalized by the introduction of one or more functional groups and having a BET specific surface area of ​​250 to 310 m. 2 / g and CTAB specific surface area of ​​230-285m 2 / g, and a first silica having a BET specific surface area of ​​60 to 120 m 2 / g and CTAB specific surface area of ​​55-105m 2 / g of a second silica. The rubber composition is particularly suitable for the manufacture of tire components, especially tire treads.

Description

[Technical Field]

[0001] The present invention relates to rubber compositions, methods for their preparation, and their use in the manufacture of vehicle tires and vehicle tire components. In particular, the present invention relates to the use of such compositions to manufacture tire treads. The present invention also relates to rubber articles and vehicle tires made from these rubber compositions.

[0002] More specifically, the present invention relates to rubber compositions containing a reinforcing filler system consisting of a combination of two different silica fillers, which, when used as a reinforcing filler in a diene rubber composition, provides an improved balance of wet performance, rolling resistance, and abrasion resistance properties. [Background technology]

[0003] The global movement to reduce carbon dioxide (CO2) emissions is driving increased demand for fuel-efficient vehicles. To meet this demand, tires must offer reduced rolling resistance. It is also important for tires to have excellent grip on both dry and wet roads, with wet grip performance being particularly important. High wear resistance is also a key factor in tire longevity. Wet performance ("WET"), rolling resistance ("RR"), and wear resistance ("WEAR") together constitute what is known as the "magic triangle" of viscoelastic properties. However, improving tire grip performance without adversely affecting rolling resistance and wear resistance is extremely difficult, necessitating the development of tires with a better balance of these properties.

[0004] The components of the rubber composition for tire manufacture can be modified to adjust its dynamic / mechanical properties, typically involving the use of modified rubbers, rubber mixtures, and / or the incorporation of reinforcing fillers into the rubber composition.

[0005] Diene rubbers, such as natural rubber, isoprene rubber, and butadiene rubber, contain repeating units derived from diolefins with conjugated carbon-carbon double bonds. The properties of synthetic diene rubbers can be tailored by copolymerizing diolefin monomers with other monomers, resulting in a wide range of applications. Diene rubbers include butadiene rubber (BR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR), epoxidized natural rubber (ENR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), isobutylene-isoprene rubber (IIR), styrene-isoprene-butadiene rubber (SIBR), and ethylene-propylene-diene rubber (EPDM). They are commonly used in the automotive industry, such as in the manufacture of tire treads and other tire components.

[0006] The mechanical properties of rubber compounds made from diene rubber are improved by incorporating reinforcing fillers such as silica and carbon black. Carbon black was the first material commonly used as a filler, but more recently, silica has increasingly replaced the traditional use of carbon black. The use of silica fillers improves rubber properties, such as reduced rolling resistance and improved traction, especially on wet roads.

[0007] Dispersion of any reinforcing filler and filler-rubber interactions are important in producing high-performance rubber compounds with the required mechanical properties. The presence of polar silanol groups on the silica surface makes the silica acidic and highly hygroscopic. This leads to silica agglomeration, poor dispersion in the rubber matrix, and increased viscosity and loss of reinforcing properties of the compound. Various in-situ treatments have been proposed to modify the silica surface chemistry, including the use of silanes as surface modifiers or "covering agents." Silane coupling agents are also used to form covalent bonds between silica and diene rubber chains during rubber compounding. Silane coupling agents improve filler dispersion in the diene rubber matrix and enhance the interaction between silica and rubber, reinforcing the rubber compound. Surface-modified silica gels for use as reinforcing agents in hydrocarbon rubbers are described, for example, in Patent Document 1 (WO 03 / 097737).

[0008] Generally, the use of highly reinforcing grade silica is known to improve the abrasion resistance of tire tread rubber, while low-reinforcing grade silica is known to improve wet performance and rolling resistance. To take advantage of these different properties, U.S. Patent No. 6,506,829 proposes blending highly reinforcing and low-reinforcing grade silicas characterized by different pore size distribution maxima ("PSD") and average specific surface areas ("SSA"). Z1165MP (a highly reinforcing grade silica sold by Rhodia, with a BET SSA of 175 m) is used. 2 / g, PSD 35 nm) and Z1115MP (a low reinforcing grade silica available from Rhodia, BET SSA 125 nm) 2 A rubber composition has been disclosed that is a 1:1 blend of 1,2-dimethyl-2,2-trimethylsilyl methyl acrylate / g, PSD 60 nm. This composition has high tensile strength and high hardness, resulting in beneficial handling properties and improved traction. A high rebound value at 100°C is beneficial for rolling resistance, and a low rebound value at 23°C is beneficial for wet grip properties.

[0009] In the search for alternative silica fillers for rubber compositions with improved dynamic properties, pre-functionalized precipitated silica has been proposed. For example, Patent Document 3 (WO 2015 / 121333) proposes a novel method for preparing precipitated silica using at least one polycarboxylic acid during or after the liquefaction of the precipitated silica.

[0010] An important contribution to energy dissipation in tire treads, and therefore rolling resistance, is due to free polymer chain ends and degradation of the filler network formed by the filler. The introduction of functional groups to the polymer chain ends allows the ends to be physically or chemically attached to the filler surface. For this reason, various end-group modifications of polymers using functional groups such as carboxyl groups and silanes have been proposed. The introduction of carboxyl groups using silanes is also described, for example, in Patent Document 4 (WO 2014 / 173706). [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 03 / 097737 Brochure [Patent Document 2] U.S. Patent No. 6,506,829 [Patent Document 3] International Publication No. 2015 / 121333 Brochure [Patent Document 4] International Publication No. 2014 / 173706 Brochure [Patent Document 5] European Patent No. 3725837 Summary of the Invention [Problem to be solved by the invention]

[0012] There is a continuing need in the art to provide tires with improved wet performance, rolling resistance, and wear resistance, and in particular to produce tires with an improved balance of WET / RR characteristics and WEAR performance.

[0013] The present inventors have discovered that diene rubber compositions containing specific blends of silica exhibit excellent abrasion resistance, rolling resistance, and wet performance, with an excellent balance of these properties. In particular, they have found that synergistic and / or interactive effects are observed with respect to the viscoelastic properties of rubber articles made from rubber compositions reinforced with filler systems consisting of a combination of surface-functionalized silica (i.e., "pre-functionalized" silica) and non-surface-functionalized silica (i.e., "non-functionalized" or "non-pre-functionalized" silica). These properties are improved compared to corresponding filler systems based on non-functionalized silica. Furthermore, the present inventors have surprisingly found that this effect is observed even when the total amount of reinforcing filler is reduced. [Means for solving the problem]

[0014] Accordingly, in one aspect, the present invention provides a rubber composition comprising: a diene rubber component, and A filler system comprising: Surface functionalized by the introduction of one or more functional groups, with a BET specific surface area of ​​250-310m 2 / g and CTAB specific surface area of ​​230-285m 2 / g, and No surface functionalization, BET specific surface area 60-120m 2 / g and CTAB specific surface area 55-105m 2 / g of a second silica the filler system comprising: Equipped with.

[0015] In another aspect, the present invention provides a process for making a rubber composition, comprising dispersing a filler system as defined herein in a diene rubber component.

[0016] In another aspect, the present invention provides a vulcanizable rubber composition comprising a diene rubber component having dispersed therein a filler system as defined herein.

[0017] In another aspect, the present invention provides vulcanized rubber compounds that are directly obtainable by crosslinking or that are obtainable by crosslinking the vulcanizable rubber compounds described herein.

[0018] In another aspect, the present invention provides a process for producing a vulcanized rubber compound, the process comprising the steps of introducing a silica filler system into a diene rubber component as defined herein, thereby producing a vulcanizable rubber composition, and vulcanizing the vulcanizable rubber composition by heating at a predetermined temperature and for a predetermined time.

[0019] In another aspect, the present invention provides the use of a rubber composition as described herein as a component of, or in the manufacture of, a component of a vehicle tire.

[0020] In another aspect, the present invention provides vehicle tire components made from the rubber compositions described herein.

[0021] In another aspect, the present invention provides a vehicle tire comprising the vehicle tire component described herein.

[0022] In another aspect, the present invention provides a silica filler system comprising: Surface functionalized by the introduction of one or more functional groups, with a BET specific surface area of ​​250-310m 2 / g and CTAB specific surface area of ​​230-285m 2 / g, and No surface functionalization, BET specific surface area 60-120m 2 / g and CTAB specific surface area 55-105m 2 / g, and a second silica having The silica filler system comprises:

[0023] [Detailed Description of the Invention] According to one aspect, the present invention provides a rubber composition comprising: a diene rubber component, and It is a filler system, Surface functionalized by the introduction of one or more functional groups, with a BET specific surface area of ​​250-310m 2 / g and CTAB specific surface area 230-285m 2 / g, and No surface functionalization, BET specific surface area 60-120m 2 / g and CTAB specific surface area 55-105m 2 / g of a second silica the filler system comprising: The rubber composition comprises:

[0024] As used herein, the term "rubber" is intended to include natural and synthetic rubber. The terms "rubber" and "elastomer" are used interchangeably herein unless otherwise specified. Unless otherwise specified, the terms "rubber composition," "compounded rubber," and "rubber compound" are used interchangeably herein to refer to rubber that has been blended or mixed (i.e., compounded) with various ingredients or materials, as such terms are well known and understood in the art.

[0025] The present invention relates to rubber compositions in both the raw state (ie, before curing or vulcanization) and the cured or vulcanized state (ie, after crosslinking or vulcanization).

[0026] In the rubber composition according to the present invention, the silica filler system described herein is dispersed in a diene rubber component and acts as a reinforcing filler. The term "diene rubber component" refers to an elastomeric matrix comprised of at least one diene rubber. As used herein, the term "diene rubber" refers to a rubber containing repeating units derived from at least one conjugated diolefin monomer. This includes homopolymers and copolymers having one or more additional units derived from a monomer copolymerizable with the diolefin monomer. The repeating units have carbon-carbon double bonds that may be present in the main chain and / or side chains of the polymer. The diene rubber may be natural or synthetic rubber.

[0027] The filler system for use in the compositions of the present invention consists of a first "functionalized" silica and a second "unfunctionalized" silica having specific surface area characteristics as defined herein. References herein to "silica" or "silica filler" refer to particulate silica. Any known type of particulate silica capable of reinforcing a diene rubber component can be used in the present invention. As will be appreciated, known silica materials typically contain some other components (e.g., as impurities), but the primary component is silicon dioxide, i.e., SiO2. The silicon dioxide content is generally at least 90% by weight, preferably at least 95% by weight, e.g., at least 97% by weight.

[0028] The terms "functionalized silica" and "surface-functionalized silica" are used interchangeably herein and are intended to refer to particulate silica having a surface modified with at least one functional group. The terms "non-functionalized silica" and "silica which is not surface-functionalized" are used interchangeably herein and should be interpreted accordingly. References herein to the surface functionalization of silica, or the absence of surface functionalization of silica, refer to the nature of the particulate silica added to the diene rubber component in the preparation of a rubber composition. Thus, "surface-functionalized" silica refers to "pre-functionalized" silica. Similarly, "non-surface-functionalized silica" refers to particulate silica that is not "pre-functionalized." More specifically, "functionalized silica" for use in the present invention is particulate silica that has been surface-modified with one or more functional groups as described herein, such as one or more carboxyl groups. Similarly, a "non-surface-functionalized silica" is a particulate silica that does not have any of the functional groups described herein, such as carboxyl groups.

[0029] Silica materials for use in the present invention are well known in the art and include, among others, precipitated silica (an amorphous form of silica), pyrogenic (fumed) silica, wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Silica materials are used in the form of discrete particles, e.g., as highly disperse granules. Such materials may be monodisperse in size and uniform in shape. Alternatively, they may be provided in the form of branched or linear clusters. Precipitated silica materials are preferred for use in the present invention.

[0030] The filler system for use in the present invention comprises a first silica whose surface has been functionalized with one or more functional groups. This "first silica" is also referred to herein as "functionalized silica" or as a highly reinforcing grade of silica.

[0031] The first silica is 250-310m 2 The Brunauer-Emmett-Teller (BET) specific surface area is preferably 270-300 m / g. 2 / g, more preferably 280 to 290 m 2 / g, e.g., 280, 281, 282, 283, 284, 285, 286, 287, 288, 289 or 290m 2 / g. The first silica is 230 to 285 m 2 / g of surface area by cetyltrimethylammonium bromide (CTAB) adsorption. The surface area by cetyltrimethylammonium bromide (CTAB) adsorption is preferably 240 to 270 m 2 / g, more preferably 245 to 265 m 2 / g, more preferably 250 to 260m 2 / g, e.g., 250, 251, 252, 253, 254, 255, 256, 257, 258, 259 or 260m 2 / g.

[0032] The filler system also includes a second silica, which is a low reinforcing grade silica that is not surface functionalized.

[0033] The second silica is 60-120m 2 / g, preferably 70 to 110 m 2 / g, e.g., 80-100m 2 The second type of silica is characterized by a Brunauer-Emmett-Teller (BET) specific surface area in the range of 55-105 m / g. 2 / g of surface area by cetyltrimethylammonium bromide (CTAB) adsorption. The surface area by cetyltrimethylammonium bromide (CTAB) adsorption is preferably 60 to 100 m2 / g, more preferably 70 to 95m 2 / g, more preferably 80 to 90m 2 / g, e.g., 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90m 2 / g.

[0034] The average specific surface area is determined by nitrogen adsorption and cetyltrimethylammonium bromide (CTAB) adsorption using the Brunauer-Emmett-Teller (BET) method. The CTAB specific surface area is the external surface. The Brunauer-Emmett-Teller (BET) method is described in the Journal of the American Chemical Society (Vol. 60, p. 309, February 1938) and corresponds to NF ISO 5794-1, Appendix D (June 2010). The cetyltrimethylammonium bromide (CTAB) adsorption method corresponds to ASTM D6845.

[0035] In one embodiment, the BET surface area of ​​the first silica is at least 250 m 2 Preferably, the BET specific surface area of ​​the first silica differs from the BET specific surface area of ​​the second silica by at least 220 m 2 / g, more preferably at least 190m 2 / g, e.g., at least 175, 180, 185, 190, 195, 200 or 205 m 2 / g different.

[0036] In one embodiment, the CTAB specific surface area of ​​the first silica is at least 230 m 2 Preferably, the CTAB specific surface area of ​​the first silica differs from the CTAB specific surface area of ​​the second silica by at least 200 m 2 / g, more preferably at least 170m 2 / g, e.g., at least 155, 160, 165, 170, 175, 180 or 185 m 2 / g different.

[0037] The first silica is surface-modified by introducing one or more functional groups. Examples of functional groups include carboxyl groups, hydroxyl groups, and carbonyl groups. Where appropriate, any of these groups can exist in the form of a corresponding salt or derivative. The functional group is generally present as an organic compound, for example, as a substituent of a low-molecular-weight organic compound. Depending on the nature of the organic compound, the functional group can be effectively "linked" to the silica surface by an organic linking group. The organic compound can be selected to provide any desired linking group, for example, in terms of the chain length of the linking group.

[0038] In some embodiments, the first silica is surface-functionalized with an organic compound containing one or more functional groups selected from carboxyl, hydroxyl, carbonyl, and, optionally, their salts or derivatives. The compound may contain two, three, four, or more functional groups, e.g., a difunctional or trifunctional compound. The functional groups in the compound may be the same or different, but typically will be the same. The organic compound may be a linear or branched, saturated or unsaturated aliphatic compound containing 2 to 20 carbon atoms, or an aromatic compound. The aliphatic organic compound may contain heteroatoms, such as nitrogen or sulfur, in the main chain. The organic compound may be selected from the group consisting of linear, branched, saturated, unsaturated, aliphatic, and aromatic compounds containing 2 to 16 carbon atoms.

[0039] The aliphatic compounds may be linear, saturated or unsaturated and may contain 2 to 14 carbon atoms, for example 2 to 12 carbon atoms. The compounds may contain 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 carbon atoms. Advantageously, the compounds may contain 4, 5, 6, 7, 8, 9 or 10 carbon atoms, for example 4, 5, 6, 7 or 8 carbon atoms. The compounds may contain 4, 5 or 6 carbon atoms.

[0040] In one set of embodiments, the functionalized silica may comprise silica functionalized on its surface with one or more carboxyl groups, which may be present as carboxylic acids and / or as derivatives thereof, such as salts or esters.

[0041] The carboxyl groups of the functionalized silica may be derived from one or more carboxylic acids or derivatives thereof, such as one or more polycarboxylic acids. As used herein, the term "polycarboxylic acid" means a carboxylic acid containing at least two carboxylic acid functional groups (i.e., -COOH).

[0042] The one or more polycarboxylic acids may contain two, three, four, or more than four carboxylic acid functional groups. For example, the polycarboxylic acid may be a dicarboxylic acid or a tricarboxylic acid. The polycarboxylic acid may be a linear or branched, saturated or unsaturated, aliphatic polycarboxylic acid containing 2 to 20 carbon atoms, or an aromatic polycarboxylic acid. The polycarboxylic acid may optionally contain hydroxyl groups and / or halogen atoms. The aliphatic polycarboxylic acid may contain heteroatoms, such as nitrogen or sulfur, in the main chain. The polycarboxylic acid may be one or more selected from the group consisting of linear, branched, saturated, unsaturated, aliphatic polycarboxylic acids having 2 to 16 carbon atoms, and aromatic polycarboxylic acids.

[0043] The aliphatic polycarboxylic acid can be a linear saturated or unsaturated polycarboxylic acid containing 2 to 14 carbon atoms, for example, 2 to 12 carbon atoms. The polycarboxylic acid may contain 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms. Advantageously, the polycarboxylic acid may contain 4, 5, 6, 7, 8, 9, or 10 carbon atoms, for example, 4, 5, 6, 7, or 8 carbon atoms. For example, the polycarboxylic acid may contain 4, 5, or 6 carbon atoms.

[0044] Examples of linear aliphatic polycarboxylic acids that can be used include, but are not limited to, oxalic acid, malonic acid, tricarballylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and the like.

[0045] Examples of branched aliphatic polycarboxylic acids that can be used include, but are not limited to, methylsuccinic acid, ethylsuccinic acid, oxalosuccinic acid, methyladipic acid, methylglutaric acid, and dimethylglutaric acid. The term "methylglutaric acid" includes both 2- and 3-methylglutaric acid, as well as mixtures of these two isomers in any proportion. The term "2-methylglutaric acid" includes both the (S) and (R) forms of the compound, as well as any racemic mixtures.

[0046] Examples of unsaturated polycarboxylic acids that can be used include, but are not limited to, maleic acid, fumaric acid, itaconic acid, muconic acid, aconitic acid, traumatic acid, glutaconic acid, and the like.

[0047] Examples of polycarboxylic acids that also contain hydroxyl groups that can be used include, but are not limited to, malic acid, citric acid, isocitric acid, tartaric acid, and the like.

[0048] Examples of aromatic polycarboxylic acids that can be used include, but are not limited to, phthalic acid, orthophthalic acid, isophthalic acid, trimesic acid, trimellitic acid, and the like.

[0049] Preferably, the polycarboxylic acid is one or more selected from the group consisting of oxalic acid, malonic acid, tricarballylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, methylsuccinic acid, ethylsuccinic acid, methyladipic acid, methylglutaric acid, dimethylglutaric acid, malic acid, citric acid, isocitric acid, and tartaric acid. More preferably, the polycarboxylic acid is one or more selected from the group consisting of adipic acid, succinic acid, ethylsuccinic acid, glutaric acid, methylglutaric acid, oxalic acid, and citric acid.

[0050] In one embodiment, a single type of polycarboxylic acid may be employed, in which case the polycarboxylic acid is preferably methyl glutaric acid.

[0051] In another embodiment, a mixture of polycarboxylic acids is employed. In this case, the polycarboxylic acids in the mixture can be selected from dicarboxylic acids and / or tricarboxylic acids. For example, the polycarboxylic acids can be selected from adipic acid, succinic acid, ethylsuccinic acid, glutaric acid, methylglutaric acid, oxalic acid, and citric acid. As will be appreciated, the mixture of polycarboxylic acids can result from the process used to prepare them.

[0052] Some or all of the polycarboxylic acids for use in the present invention can be used in the form of their salts or derivatives. For example, they can be used in the form of esters, anhydrides, alkali, alkaline earth metal, or ammonium salts (i.e., carboxylates). Examples of salts include those formed with sodium, potassium, or calcium.

[0053] Further examples of types of polycarboxylic acids, their derivatives, and mixtures thereof for use in the present invention, along with methods for preparing functionalized silica incorporating these compounds, are described in WO 2015 / 121333.

[0054] The functionalized silica can have a carbon content of at least 0.10% by weight of the functionalized silica. The carbon content (referred to as (C)) is the carbon content of the organic compound (e.g., carboxylic acid and its corresponding salt or derivative), expressed as total carbon. The carbon content can be measured using a carbon-sulfur analyzer, such as the Horiba EMIA 320 V2 instrument, as described herein. The carbon content is preferably at least 0.15% by weight of the functionalized silica, more preferably at least 0.20% by weight, even more preferably at least 0.25% by weight, for example at least 0.30% by weight.

[0055] The functionalized silica can have an object size distribution width ratio (Ld) of at least 0.91. Ld is preferably at least 0.94. As used herein, object size distribution width ratio (Ld) is measured by X-ray disc centrifuge (XDC) particle size analysis after ultrasonic deagglomeration (in water), and corresponds to the ratio (d84-d16) / d50, where dn is the size of n% particles (mass ratio) smaller than this size (therefore, distribution width Ld is calculated on the cumulative particle size curve taken as a whole). After ultrasonic deagglomeration (in water), object size distribution width ratio Ld of less than 500nm is measured by XDC particle size analysis, and corresponds to the ratio (d84-d16) / d50, where dn is the size of n% particles (mass ratio) smaller than this size (the distribution width Ld is thus calculated on the cumulative particle size curve truncated above 500nm). As used herein, Ld is measured according to the method described in Patent Document 3 (WO 2015 / 121333).

[0056] The functionalized silica may have a pore volume distribution ratio of at least 0.65. The pore volume distribution is preferably at least 0.66, more preferably at least 0.68. The pore volume and pore diameter are measured by mercury (Hg) porosimetry using a Micromeritics Autopore 9520 porosimeter and calculated using the Washburn equation, where the contact angle θ is equal to 140° and the γ surface tension is equal to 484 dynes / cm (standard DIN 66133). Each sample is prepared as follows: each sample is pre-dried in an oven at 200°C for 2 hours. The pore volume distribution ratio used herein is a pore volume distribution such that V(d5-d50) / V(d5-d100) is at least 0.65, preferably at least 0.66, and more preferably at least 0.68. V(d5-d50) represents the pore volume consisting of pores with diameters d5 to d50, V(d5-d100) represents the pore volume consisting of pores with diameters d5 to d100, and dn is the pore diameter where n% of the total surface area of ​​all pores is formed by pores with diameters larger than this diameter (the total surface area of ​​pores (S0) may be determined from a mercury intrusion curve). The pore volume distribution ratio used in this specification is measured according to the method described in Patent Document 3 (WO 2015 / 121333).

[0057] In one set of embodiments, the first silica for use in the present invention further has the following properties: a carbon content of at least 0.10% by weight relative to the weight of the functionalized silica, - an object size distribution width ratio (Ld) of at least 0.91, and - a pore volume distribution ratio of at least 0.65, It is characterized by one or more of the following:

[0058] In another series of embodiments, the first silica for use in the present invention further has the following characteristics: - a carbon content of at least 0.10% by weight relative to the weight of the functionalized silica, and - an object size distribution width ratio (Ld) of at least 0.91, and - Pore volume distribution ratio of at least 0.65 It is characterized by:

[0059] The functionalized silica may have a pH of 2.5 to 7, preferably 2.5 to 5, more preferably 3 to 4.5, for example 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, or 4.5. In particular, silica functionalized with one or more carboxyl groups, salts or derivatives thereof may have a pH of 2.5 to 7, preferably 2.5 to 5, more preferably 3 to 4.5, for example 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, or 4.5. The pH can be measured according to the method described in WO 2015 / 121333, which is derived from standard ISO 787 / 9 (pH of a 5% suspension in water).

[0060] The functionalized silica is known in the art or can be prepared using a method known in the art. The exact method depends on the nature of the functional group and can be easily selected by those skilled in the art. When the silica is functionalized with one or more carboxyl groups, the carboxyl groups can be derived by reacting the silica with one or more carboxylic acids to form the functionalized silica. Generally, this method can include a precipitation reaction to produce silica, i.e., the first silica will be precipitated silica. The precipitated silica can be in any physical state, for example, in the form of substantially spherical beads (e.g., microbeads), powder, or granules.

[0061] The synthesis of silica functionalized with one or more carboxyl groups is disclosed, for example, in Patent Document 3 (WO 2015 / 121333), the entire contents of which are incorporated herein by reference. Generally, functionalized silica is prepared by precipitation of a silicate, such as an alkali metal silicate (e.g., sodium silicate), with an acidifying agent (e.g., sulfuric acid), followed by filtration to separate the precipitated silica filter cake, liquefying the filter cake, and finally drying (typically by atomization). Silica can be precipitated by any method, including, in particular, adding the acidifying agent to the silicate feedstock, or adding the acidifying agent and silicate to water or the silicate feedstock simultaneously, either in whole or in part. The polycarboxylic acid is added to the filter cake during the liquefaction process or after the liquefaction process and before the drying step.

[0062] In one embodiment, the functionalized silica is prepared by the following steps: - reacting the silicate with an acidifying agent to obtain a suspension of precipitated silica; - filtering the suspension of precipitated silica to obtain a filter cake of precipitated silica; - liquefying the filter cake; and - drying the liquefied filter cake; and Here, an organic compound having one or more functional groups as defined herein (e.g., at least one polycarboxylic acid) is added to the filter cake either during liquefaction or after liquefaction but before drying.

[0063] The resulting precipitated silica is generally provided in the form of a dry powder. The precipitated silica has molecules of organic compounds, such as molecules of polycarboxylic acids or their salts or derivatives, on its surface. The presence of polycarboxylic acids, their salts or derivatives can be confirmed by known techniques such as surface infrared or diamond attenuated total reflection (ATR) infrared. Depending on the source of the starting materials used to produce the silica, the precipitated silica may contain additional elements such as aluminum.

[0064] The second silica for use in the filler systems described herein is non-functionalized. It can consist of any silica commonly known in the art, including precipitated amorphous silica, wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), pyrogenic (fumed) silica, calcium silicate, aluminum silicate, magnesium silicate (e.g., Mg2SiO4, MgSiO3), calcium magnesium silicate (CaMgSiO4), or calcium aluminum silicate (e.g., Al2O3·CaO2SiO2). Commercial grades of silica meeting the above requirements for BET and CTAB are widely available. Such silicas include those supplied by Solvay under the trade name Zeosil® 1085 GR. The BET specific surface area of ​​the silica is 90 m 2 / g±20m 2 / g, CTAB specific surface area is 80m 2 / g±15m 2 / g.

[0065] In some embodiments, the surface of the first and / or second silica may be surface treated to reduce interactions between fillers during compounding, thus improving dispersibility in the rubber component. Suitable coatings for this purpose are well known in the art and include, but are not limited to, monofunctional silanes such as hexadecyltrimethoxysilane or propyltriethoxysilane. As described herein, such coatings may be introduced during compounding of the various components to form the rubber composition.

[0066] The weight ratio of the second silica to the first silica (i.e., the weight of the second silica divided by the weight of the first silica) may vary. Advantageously, the weight ratio of the second silica to the first silica ranges from 0.15 to 0.60, preferably from 0.25 to 0.45. In some embodiments, the weight ratio may be 0.15, 0.31, 0.42, or 0.56.

[0067] The filler systems described herein form further aspects of the present invention. Thus, in another aspect, the present invention provides a filler system, the filler system comprising: Surface functionalized by the introduction of one or more functional groups, with a BET specific surface area of ​​250-310m 2 / g and CTAB specific surface area of ​​230-285m 2 / g, and No surface functionalization, BET specific surface area 60-120m 2 / g and CTAB specific surface area 55-105m 2 / g, and a second silica having Equipped with.

[0068] The silica system used in the present invention is dispersed in the diene rubber component. The amount of the silica system (i.e., the total weight of the first and second silicas) is not particularly limited and can be easily selected by those skilled in the art. However, generally, the filler system may be present in an amount of 90 to 130 phr, preferably 100 to 120 phr, and more preferably 100 to 115 phr, per 100 phr of the rubber composition.

[0069] The first silica may be present in an amount of 55 to 120 phr, preferably 55 to 100 phr, more preferably 65 to 90 phr, relative to 100 phr of the rubber composition.The second silica may be present in an amount of 10 to 40 phr, preferably 20 to 40 phr, more preferably 20 to 35 phr, relative to 100 phr of the rubber composition.

[0070] Any known diene rubber component can be used in the rubber composition according to the present invention, and those skilled in the art can easily select an appropriate rubber, taking into account the intended use of the composition. Diene rubbers are well known in the art and include both natural and synthetic rubbers. Non-limiting examples of such rubbers include butadiene rubber (BR), natural rubber (NR), isoprene rubber (IR), epoxidized natural rubber (ENR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), isobutylene-isoprene rubber (IIR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), and ethylene-propylene-diene rubber (EPDM).

[0071] In one embodiment, the diene rubber used in the present invention contains repeating units derived from butadiene. Examples of such rubbers include, but are not limited to, styrene-butadiene rubber (SBR) and butadiene rubber (BR). In one set of embodiments, the diene rubber used in the present invention is SBR. Styrene-butadiene rubber is well known in the art. As used herein, the term "styrene-butadiene rubber" or "SBR" is generally intended to refer to any synthetic rubber produced by the polymerization of styrene and butadiene monomers. It therefore refers to a styrene-butadiene copolymer. SBR is commonly used in the tire industry and can be produced by well-known methods, such as copolymerizing the corresponding monomers in emulsion, suspension, or solution. The styrene and butadiene monomers can be selected in appropriate ratios depending on the application and properties of the rubber compound. For example, styrene can be present in an amount of up to 80% by weight, more typically up to about 45% by weight, of the rubber tire tread compound (based on the total weight of the comonomers). In some embodiments, styrene may be present in an amount of 10 to 30 wt%, preferably 15 to 25 wt%, more preferably 21 to 24 wt%, e.g., 21 wt%, 22 wt%, 23 wt%, based on the weight of the SBR diene rubber. The diene component is generally present in an amount of at least 50 wt%, e.g., 50 to 75 wt%.

[0072] The diene rubber may be modified with one or more functional groups and such functionalized diene rubbers may be used in the present invention, or the diene rubbers used in the present invention may be unmodified (i.e., without functional groups).

[0073] When a diene rubber is functionalized, one or more functional groups may be attached to its polymer backbone, end groups, and / or side chains. These functional groups may be incorporated into the polymer material during its manufacture or may be subsequently grafted onto the polymer. The type and location of the functional groups vary for different grades of rubber known in the art. The choice of functionalized rubber depends on the intended use of the rubber compound described herein. Examples of functionalized diene rubbers include those having one or more reactive groups, such as groups capable of reacting with silica coupling agents, e.g., sulfur-containing organosilicon compounds. Representative functional groups include halogens such as Cl and Br; alkoxy groups such as methoxy; siloxy groups; and pseudohalogens such as -SCN. In one embodiment, the rubber may be a siloxy-terminated polymer, such as a siloxy-terminated styrene-butadiene copolymer. The functional groups may also include one or more interactive groups, e.g., amino groups. Interactive groups such as amino groups may, for example, form hydrogen bonds within the rubber matrix.

[0074] An important contribution to energy dissipation in tire treads, and therefore rolling resistance, comes from the presence of free polymer chain ends and degradation of the filler network formed by the silica filler used in the rubber composition. Advantageously, polymers with functional groups at the ends and / or beginnings of the polymer chains, which enable them to physically or chemically adhere to the filler surface, can be employed in the present invention. These polymers limit the mobility of the polymer, thus reducing energy dissipation under dynamic stress. They also improve filler dispersion in the rubber composition, leading to a strengthened filler network and further reducing rolling resistance.

[0075] Thus, in some embodiments, the diene rubber component for use in the present invention comprises an end-group functionalized diene rubber compound that may have an interactive and / or synergistic effect on the properties of the rubber composition, resulting in advantageous properties. Specifically, the interaction between the end-group functionalized diene rubber compound and the functionalized silica may be synergistic, resulting in improved dispersion of the filler system (particularly the functionalized silica filler provided in the system) in the rubber composition and products made therefrom. "End-group functionalized" rubber may also be referred to as "end-modified" rubber. In one embodiment, the diene rubber component may be an end-group functionalized SBR, such as an end-group functionalized SSBR.

[0076] End-group functionalized rubbers are well known in the art, and any of these can be selected for use in the present invention. Examples of such rubbers include those described in WO 2014 / 173706 and EP 3 725 837, the entire contents of which are incorporated herein by reference.

[0077] The modifying functional group may be any functional group that has affinity with the silica filler. Preferably, it may contain at least one atom selected from nitrogen, silicon, oxygen, and tin atoms. From the viewpoint of its ability to strongly interact with the silica filler, those containing nitrogen, silicon, or oxygen atoms are preferred. The silicon-containing functional group is preferably one having a silicon-carbon bond, for example. Such a modifying functional group can be formed using an appropriate coupling agent, such as those described in Patent Document 5 (EP 3 725 837). Methods for introducing the modifying functional group into the rubber component are well known in the art and can be appropriately selected. These methods include the use of a functional group-containing polymerization initiator, copolymerization of a functional group-containing monomer with another compound, and reaction of the end group of the rubber component with a modifying functional group agent.

[0078] In some embodiments, the modifying functional group comprises a nitrogen atom. Examples thereof include a substituted amino group represented by the general formula (I) shown below ([Chemical Formula 1]) and a cyclic amino group represented by the general formula (II) shown below ([Chemical Formula 2]). [ka] (I)

[0079] Here, each R 1 may be the same or different and are alkyl groups, cycloalkyl groups, or aralkyl groups having 1 to 12 carbon atoms. Preferably, the alkyl group is a methyl group, an ethyl group, a butyl group, an octyl group, or an isobutyl group. The cycloalkyl group is preferably a cyclohexyl group, and the aralkyl group is preferably a 3-phenyl-1-propyl group. [ka] (II)

[0080] where R 2is an alkylene group, a substituted alkylene group, an oxyalkylene group, or an N-alkylaminoalkylene group having 3 to 16 methylene groups. The substituted alkylene group includes mono- to octa-substituted alkylene groups, and examples of the substituent include a linear or branched alkyl group, cycloalkyl group, bicycloalkyl group, aryl group, or aralkyl group having 1 to 12 carbon atoms. The alkylene group is preferably a trimethylene group, tetramethylene group, hexamethylene group, or dodecamethylene group. The substituted alkylene group is preferably a hexadecamethylene group. The oxyalkylene group is preferably an oxydiethylene group. The N-alkylaminoalkylene group is preferably an N-alkylazadiethylene group. Examples of the cyclic amino group represented by general formula (II) include 2-(2-ethylhexyl)pyrrolidine, 3-(2-propyl)pyrrolidine, 3,5-bis(2-ethylhexyl)piperidine, 4-phenylpiperidine, 7-decyl-1-azacyclotridecane, 3,3-dimethyl-1-azacyclotetradecane, 4-dodecyl-1-azacyclooctane, 4-(2-phenylbutyl)-1-azacyclooctane, 3-ethyl-5-cyclohexyl-1-azacycloheptane, 4-hexyl-1-azacycloheptane, 9-isoamyl-1-azacycloheptadecane, 2-methyl-1-azacycloheptadec-9-ene, Examples include 3-isobutyl-1-azacyclododecane, 2-methyl-7-t-butyl-1-azacyclododecane, 5-nonyl-1-azacyclododecane, 8-(4'-methylphenyl)-5-pentyl-3-azabicyclo[5.4.0]undecane, 1-butyl-6-azabicyclo[3.2.1]octane, 8-ethyl-3-azabicyclo[3.2.1]octane, 1-propyl-3-azabicyclo[3.2.2]nonane, 3-(t-butyl)-7-azabicyclo[4.3.0]nonane, and 1,5,5-trimethyl-3-azabicyclo[4.4.0]decane, which have had the hydrogen atom bonded to the nitrogen atom removed.

[0081] In some embodiments, the modifying functional group comprises a silicon atom, such as a group represented by the following general formula (III): (R3 ) a Z(R 4 ) b (III) Examples of the modified functional group include a silicon-carbon bond formed using a coupling agent represented by the formula:

[0082] where Z is silicon and each R 3 are independently selected from the group consisting of alkyl groups having 1 to 20 carbon atoms, cycloalkyl groups having 3 to 20 carbon atoms, aryl groups having 6 to 20 carbon atoms, and aralkyl groups having 7 to 20 carbon atoms; and each R 4 are independently chlorine or bromine, a is 0 to 3, b is 1 to 4, and a+b=4. The alkyl group is preferably a methyl group, an ethyl group, an n-butyl group, an n-octyl group, or a 2-ethylhexyl group, the cycloalkyl group is preferably a cyclohexyl group, the aryl group is preferably a phenyl group, and the aralkyl group is preferably a neopyr group.

[0083] Other modifying functional groups containing a silicon atom include those represented by the following general formula (III-1) and the following general formula (III-2) ([Chemical Formula 3]). R 1 a -Si-(OR 2 ) 4-a (III-1)

[0084] In the above general formula (III-1), R 1 and R 2 each independently represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, a is an integer of 0 to 2, and a plurality of OR 2 If groups are present, they may be the same or different and no active protons are present in the molecule.

[0085] Specific examples of the compound represented by the general formula (III-1) (i.e., the alkoxysilane compound) include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, methyltriisopropoxysilane, ethyltriethoxysilane, methyl ... Examples of suitable silanes include silane, ethyl tripropoxysilane, ethyl triisopropoxysilane, propyl trimethoxysilane, propyl triethoxysilane, propyl tripropoxysilane, propyl triisopropoxysilane, butyl trimethoxysilane, butyl triethoxysilane, phenyl trimethoxysilane, phenyl triethoxysilane, dimethoxydimethylsilane, methyl phenyl dimethoxysilane, dimethyl diethoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane, and divinyl diethoxysilane. Among these, tetraethoxysilane, methyl triethoxysilane, and dimethyl diethoxysilane are preferred. [ka] (III-2)

[0086] In the general formula (III-2) shown above ([Chemical Formula 3]), A 1 is a monovalent group having at least one functional group selected from the group consisting of an epoxy group, a glycidyloxy group, an isocyanate group, an imine group, a carboxylic acid group, a carboxylic anhydride group, a cyclic tertiary amine group, an acyclic tertiary amine group, a pyridine group, a silazane group, and a disulfide group, and R 3 is a single bond or a divalent hydrocarbon group, R 4 and R 5 are each independently a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, b is an integer of 0 to 2, and a plurality of OR 5If groups are present, they may be the same or different and no active protons are present in the molecule.

[0087] Specific examples of the compound represented by general formula (III-2) above ([Chemical Formula 3]) include epoxy group-containing alkoxysilane compounds, such as 2-glycidyloxyethyltrimethoxysilane, 2-glycidyloxyethyltriethoxysilane, (2-glycidyloxyethyl)methyldimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, (3-glycidyloxypropyl)methyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane. Of these, 3-glycidyloxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane are preferred.

[0088] Examples of silicon-containing coupling agents capable of forming a modifying functional group can be appropriately selected. Examples include hydrocarbyloxysilane compounds, SiCl4 (silicon tetrachloride), (R a )SiCl3, (R a )2SiCl2, and (R a ) 3SiCl, and each R a each independently represents an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms.

[0089] The modified functional groups formed from coupling agents that are hydrocarbyloxysilane compounds are preferred for use in the present invention because they have a particularly high affinity for silica. Suitable hydrocarbyloxysilane compounds can be selected by those skilled in the art. Examples include those represented by the general formula (IV) below ([Chemical Formula 4]). [ka] (IV)

[0090] Here, n1+n2+n3+n4=4, where n2 is an integer from 1 to 4, n1, n3, and n4 are each an integer from 0 to 3, and A 1 represents at least one functional group selected from a saturated cyclic tertiary amine compound residue, an unsaturated cyclic tertiary amine compound residue, a ketimine residue, a nitrile group, a (thio)isocyanate group (representing an isocyanate group or a thioisocyanate group), a (thio)epoxy group, a trihydrocarbyl isocyanurate group, a dihydrocarbyl carbonate group, a nitrile group, a pyridine group, a (thio)ketone group, a (thio)aldehyde group, an amide group, a (thio)carboxylate group, a (thio)carboxylic acid metal salt group, a carboxylic acid anhydride residue, a carboxylic acid halide residue, and a hydrolyzable group containing a primary or secondary amino group or a mercapto group. When n4 is 2 or more, each A 1 may be the same or different. 1 Alternatively, R may be a divalent group bonded to Si to form a ring structure. 21 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. When n1 is 2 or more, each R 21 may be the same or different. 23 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom (fluorine, chlorine, bromine, or iodine). When n3 is 2 or more, each R 23 may be the same or different. 22 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, optionally containing a nitrogen atom and / or a silicon atom. When n2 is 2 or more, each R 22 may be the same or different and may be bonded to each other to form a ring. 24represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. When n4 is 2 or more, each R 24 The hydrolyzable group in the primary or secondary amino group-containing hydrolyzable group or the mercapto group-containing hydrolyzable group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, more preferably a trimethylsilyl group.

[0091] In some embodiments, the hydrocarbyloxysilane compound represented by the general formula (IV) above ([Chemical Formula 4]) may be a compound represented by the general formula (V) below ([Chemical Formula 5]). [ka] (V)

[0092] where p1+p2+p3=2 (where p2 is an integer between 1 and 2, and p1 and p3 are each an integer between 0 and 1); A 2 is NR a (where R a represents a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group; the hydrolyzable group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, more preferably a trimethylsilyl group), or represents sulfur; R 25 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R 27 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom (fluorine, chlorine, bromine, iodine); R 26 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a nitrogen-containing organic group optionally containing a nitrogen atom and / or a silicon atom. When p2 is 2, each R 26may be the same or different and may be bonded to each other to form a ring. 28 represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms.

[0093] In some embodiments, the hydrocarbyloxysilane compound represented by the general formula (IV) above ([Chemical Formula 4]) may be a compound represented by the general formula (VI) below ([Chemical Formula 6]) or the general formula (VII) below ([Chemical Formula 7]). [ka] (VI)

[0094] where q1+q2=3 (where q1 is an integer from 0 to 2, and q2 is an integer from 1 to 3); R 31 represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R 32 and R 33 each independently represents a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R 34 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. When q1 is 2, each R 34 may be the same or different. 35 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. When q2 is 2 or more, each R 35 may be the same or different. [ka]

[0095] In formula (VII), r1+r2=3 (wherein r1 is an integer of 1 to 3, and r2 is an integer of 0 to 2); R 36 represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R 37 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and represents a dimethylaminomethyl group, a dimethylaminoethyl group, a diethylaminomethyl group, a diethylaminoethyl group, a methylsilyl(methyl)aminomethyl group, a methylsilyl(methyl)aminoethyl group, a methylsilyl(ethyl)aminomethyl group, a methylsilyl(ethyl)aminoethyl group, a dimethylsilylaminomethyl group, or a dimethylsilylaminoethyl group. When r1 is 2 or more, each R 37 may be the same or different. 38 represents a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. When r2 is 2, each R 38 may be the same or different.

[0096] In another embodiment, the hydrocarbyloxysilane compound represented by the general formula (IV) above ([Chemical Formula 4]) is a compound having two or more nitrogen atoms represented by the general formula (VIII) below ([Chemical Formula 8]) or the general formula (IX) below ([Chemical Formula 9]). [ka] (VIII)

[0097] where TMS represents a trimethylsilyl group; R 40 represents a trimethylsilyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R 41represents a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R 42 represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. [ka] (IX)

[0098] where TMS represents a trimethylsilyl group; R 43 and R 44 each independently represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R 45 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and each R 45 may be the same or different.

[0099] In another embodiment, the hydrocarbyloxysilane compound represented by the general formula (IV) above ([Chemical Formula 4]) is a hydrocarbyloxysilane compound represented by the general formula (X) below ([Chemical Formula 10]). [ka] (X)

[0100] where r1+r2=3 (where r1 is an integer of 0 to 2, and r2 is an integer of 1 to 3); TMS represents a trimethylsilyl group; R 46 represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R 47 and R 48each independently represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and two or more R 47 group or R 48 When groups are present, they may be the same or different.

[0101] In another embodiment, the hydrocarbyloxysilane compound represented by the general formula (IV) above ([Chemical Formula 4]) is a compound represented by the general formula (XI) below ([Chemical Formula 11]). [ka] (XI)

[0102] where Y represents a halogen atom; R 49 represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms; R 50 and R 51 each independently represents a hydrolyzable group, or a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or R 50 and R 51 are bonded to each other to form a divalent organic group; R 52 and R 53 are each independently a halogen atom, a hydrocarbyloxy group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 50 and R 51 are each a hydrolyzable group, and the hydrolyzable group is more preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, and even more preferably a trimethylsilyl group.

[0103] In one embodiment, the compound of formula (IV) may be N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane. In one embodiment, the diene rubber component for use in the present invention comprises SBR modified by reaction with a coupling agent of formula (IV), for example, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane.

[0104] In another embodiment, the modifying functional group comprises an oxygen atom, examples of which include alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy; alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl; alkoxyaryl groups such as methoxyphenyl and ethoxyphenyl; alkylene oxide groups such as epoxy and tetrahydrofuranyl; and trialkylsilyloxy groups such as trimethylsilyloxy, triethylsilyloxy, and t-butyldimethylsilyloxy.

[0105] In one embodiment, the diene rubber component comprises a styrene-butadiene copolymer end-functionalized by reaction with a hydrocarbyloxysilane compound, and the filler system comprises a first silica surface-functionalized with methylglutaric acid. In this embodiment, the hydrocarbyloxysilane compound may be a compound of general formula (IV) described herein, such as N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane.

[0106] In one set of embodiments, the diene rubbers used in the present invention are suitable for use in making rubber compositions that can be used as components of tires, such as tire treads. The diene rubbers used in the present invention can be, for example, functionalized or non-functionalized styrene butadiene rubber (SBR).

[0107] The average molecular weight (e.g., weight average, Mw) and / or average molar mass (e.g., number average, Mn) of the diene rubber can be selected to provide appropriate and / or desired physical properties. For example, it can be understood that the viscosity, and therefore processability, of a diene rubber compound increases (e.g., linearly or non-linearly) with increasing average molecular weight and / or average molar mass. Those skilled in the art will understand which diene rubber compounds have appropriate average molecular weights and / or average molar masses. In some embodiments, the diene rubber component for use in the present invention can have an average molar mass (number average, Mn) of 10,000 to 2,000,000 g / mol, preferably 100,000 to 1,000,000 g / mol.

[0108] In some embodiments, the diene rubber component may be an end-group functionalized SBR or SSBR having an average molar mass (number average, Mn) of 10,000 to 2,000,000 g / mol, preferably 100,000 to 1,000,000 g / mol.

[0109] The diene rubber component, for example, the end-group functionalized SSBR copolymer, can have a glass transition temperature of -110°C to +20°C, preferably -60°C to 0°C, preferably -40°C to -10°C, preferably -30°C to -15°C, more preferably -22°C to -26°C, for example, -22°C, -23°C, -24°C, -25°C, or -26°C.

[0110] The selected diene rubber can be used as 100% rubber in the compositions described herein or can be mixed with any elastomer or blend thereof conventionally used in rubber compounds, including both natural and synthetic rubbers. Blends of different diene rubbers may also be used. Suitable rubbers for use in any blend are well known to those skilled in the art and include natural rubber, synthetic polyisoprene rubber, styrene-isoprene rubber, styrene-butadiene rubber, styrene-isoprene-butadiene rubber, butadiene-isoprene rubber, polybutadiene, butyl rubber, neoprene, acrylonitrile-butadiene rubber (NBR), silicone rubber, fluoroelastomers, ethylene acrylic rubber, ethylene propylene rubber, ethylene propylene terpolymer (EPDM), ethylene vinyl acetate copolymer, epichlorohydrin rubber, chlorinated polyethylene-propylene rubber, chlorosulfonated polyethylene rubber, hydrogenated nitrile rubber, and tetrafluoroethylene-propylene rubber. The ratios of any polymer blends can be selected as needed, for example, based on the viscoelastic properties of the rubber composition. Those skilled in the art can readily determine which elastomers are suitable and the relative amounts of elastomers to provide the desired range of viscoelastic properties.

[0111] In one set of embodiments, the rubber component used in the present invention is a blend of at least two types of diene rubber. For example, it may be a blend of two or more such rubbers. In some embodiments, the diene rubber blend may be composed of at least two diene rubber components of the same type but having different (e.g., number-average or weight-average) molecular weights. In some embodiments, the diene rubber blend may be composed of at least two chemically different diene rubber components (e.g., two diene rubbers having different monomer units or repeat units). In some embodiments, the diene rubber blend may be composed of at least two diene rubber components of the same type but produced by different polymerization processes (e.g., solution polymerization or emulsion polymerization). For example, in one set of embodiments, the diene rubber may be composed of a combination of two types of styrene butadiene rubber, such as solution-polymerized styrene butadiene rubber (SSBR) and emulsion-polymerized styrene butadiene rubber (ESBR). "Emulsion-polymerized styrene butadiene rubber" means that styrene and 1,3-butadiene are copolymerized as an aqueous emulsion. Such methods are well known and understood by those skilled in the art.

[0112] The presence of ESBR is believed to be beneficial for enhancing the processability of the unvulcanized rubber composition. Emulsion-polymerized styrene-butadiene rubber (ESBR) can be used having a conventional styrene content of about 20 to about 29% bound styrene. However, in some cases, higher bound styrene contents, such as those in the range of about 30 to about 45%, can be used. A higher styrene content is beneficial for enhancing the traction of the tire tread. A non-limiting example of ESBR for use in the present invention is Europrene 1723 (Versalis, Italy).

[0113] Solution-polymerized SBR generally has a bound styrene content ranging from about 5 to about 50%, preferably from 5 to 40%, and more preferably from 5 to 20%. When used in tire tread compositions, SSBR reduces hysteresis and improves tire rolling resistance.

[0114] The silica filler systems described herein can be blended with a diene rubber component, and other rubber materials as desired, to provide rubber compositions according to the present invention.

[0115] The methods for preparing the rubber compositions described herein form a further aspect of the invention. Accordingly, in another aspect, the present invention provides a process for making a rubber composition, comprising dispersing a filler system as defined herein in a diene rubber component.

[0116] The amount of filler system and diene rubber component can be selected based on the desired physical properties of the resulting rubber composition, and may depend, for example, on the presence or absence of other fillers. Suitable amounts can be easily determined by one skilled in the art, but may range, for example, from 90 to 130 phr, preferably from 100 to 120 phr, and more preferably from 100 to 115 phr, per 100 phr of the rubber composition (where "phr" is parts per hundred parts of rubber).

[0117] The amount of the functionalized silica may be 55 to 120 phr, preferably 55 to 100 phr, more preferably 65 to 90 phr, based on 100 phr of the rubber composition. The amount of the second silica may be 10 to 40 phr, preferably 20 to 40 phr, more preferably 20 to 35 phr, based on 100 phr of the rubber composition.

[0118] Those skilled in the art will appreciate that the amount of diene rubber component, as well as the ratio of the diene rubber component to the filler system dispersed therein, can have a beneficial effect on the properties of the rubber composition. In some embodiments, the amount of diene rubber component is 10 to 150 phr, preferably 40 to 120 phr, preferably 50 to 110 phr, more preferably 70 to 110 phr, for example, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, or 110 phr, relative to 100 phr of the rubber composition.

[0119] In embodiments comprising a binary blend (e.g., a diene rubber composition comprising a first diene rubber compound and a second diene-based rubber compound), the relative amounts of the diene rubber compounds can be readily determined by one skilled in the art. In one embodiment, the binary blend can comprise a major component and a minor component. In such an embodiment, the amount of the major component diene rubber compound can be 50 to 140 phr, preferably 60 to 120 phr, more preferably 70 to 100 phr, e.g., 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100 phr, per 100 phr of the rubber composition. The amount of the diene rubber compound as a minor component may be 5 to 60 phr, preferably 10 to 50 phr, more preferably 20 to 40 phr, for example, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 phr, relative to 100 phr of the rubber composition. In a specific embodiment, the diene rubber compound as a major component is SSBR, and the diene rubber compound as a minor component is ESBR.

[0120] In some embodiments, the weight ratio of the diene rubber component to the filler system ranges from 0.50 to 1.20, preferably from 0.70 to 1.15, more preferably from 0.85 to 1.10, for example, from 0.90 to 1.10.

[0121] Rubber compositions having the filler systems described herein dispersed in a rubber matrix can be prepared using methods known in the art for preparing rubber compositions, such as compounding with other ingredients. These additional ingredients can include additional polymers, processing aids (such as oils, waxes, resins, and plasticizers), cure systems (such as vulcanizing agents, vulcanization accelerators, and vulcanization accelerator coagents), antidegradants (such as antioxidants or antiozonants), pigments, additional fillers, compatibilizers for fillers (such as silane coupling agents or coating agents), fibers, and the like. Those skilled in the art can readily select combinations of vulcanizable rubber compounds and the amounts of each compounded, followed by mixing and vulcanization, depending on the particular rubber product desired.

[0122] For example, in addition to the diene rubber matrix and silica filler system described herein, the vulcanizable composition may contain one or more of the following: processing aids (e.g., oils), vulcanization activators (e.g., zinc oxide, stearic acid), vulcanizing agents (e.g., sulfur or sulfur-donating compounds), vulcanization accelerators, antidegradants (e.g., antioxidants, antiozonants), pigments, additional fillers, compatibilizers, and silane coupling agents. Zinc oxide and stearic acid function as activators in the vulcanization process by shortening vulcanization time and influencing the length and number of crosslinks in the rubber matrix formed during cure or vulcanization. These additives can be selected and used in conventional amounts depending on the intended use of the sulfur vulcanizate.

[0123] Processing aids improve the processability of the composition and include oils such as mineral oils, vegetable oils, synthetic oils, or mixtures thereof. These may be used in amounts of about 5 to 75 phr, preferably about 10 to 50 phr. Typical processing aids include oils such as aromatic oils. Examples of such oils include treated distillate aromatic extract (TDAE), residual aromatic extract (RAE), mild extract solvate (MES), and bio-based oilseed derivatives. The oil used in the rubber composition of the present invention is not particularly limited and may be any oil known to those skilled in the art. For example, the oil may be one or more selected from the group consisting of processing oils such as aromatic oils, naphthenic oils, and paraffinic oils, vegetable oils such as palm oil, synthetic oils such as alkylbenzene oils, castor oil, etc. Preferably, the oil is an aromatic oil, such as a residual aromatic extract.

[0124] The vulcanizing agent for the rubber composition is not particularly limited and may be any commonly known agent in the art. For example, the vulcanizing agent may be sulfur. The amount of vulcanizing agent is not particularly limited, and one skilled in the art can easily select an amount effective to achieve satisfactory vulcanization of the composition. The vulcanizing agent (e.g., sulfur) may be used in an amount ranging from about 0.1 to about 10 phr, preferably from about 0.1 to about 5 phr, for example, from about 1 to about 3 phr. For example, the rubber composition may contain 0.1 to 3 phr, preferably 0.5 to 2 phr, for example, 1 to 1.5 phr, of the vulcanizing agent.

[0125] The vulcanization accelerator used in the rubber composition is not particularly limited, and any accelerator generally known in the art may be used, including thiazoles, dithiocarbamates, thiurams, guanidines, sulfonamides, and the like. Examples of suitable vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (MBT), dibenzothiazyl disulfide (MBTS), N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), and N-tert-butyl-2-benzothiazolylsulfenamide (TBBS); guanidine-based vulcanization accelerators such as 1,3-diphenylguanidine (DPG); thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide, tetrabutylthiuram disulfide, tetradodecylthiuram disulfide, tetraoctylthiuram disulfide, and tetrabenzylthiuram disulfide; and dithiocarbamic acid compounds such as zinc dimethyldithiocarbamate; and other zinc dialkyldithiophosphates. Preferably, the vulcanization accelerator is a combination of dibenzothiazyl disulfide (MBTS), N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), and 1,3-diphenylguanidine (DPG). The amount of the vulcanization accelerator used in the composition is not particularly limited and may range, for example, from about 0.5 to about 10 phr, preferably from about 1 to about 8 phr, and more preferably from about 2 to about 6 phr. Preferably, the vulcanization accelerator comprises 1 to 2 phr of dibenzothiazyl disulfide (MBTS), 1 to 2 phr of N-cyclohexyl-2-benzothiazyl sulfenamide (CBS), and 2 to 3 phr of 1,3-diphenylguanidine (DPG).

[0126] The vulcanization accelerator used in the rubber composition is not particularly limited, and those known to those skilled in the art can be used. For example, the vulcanization accelerator may be zinc oxide (ZnO) and a fatty acid. The fatty acid may be any of saturated fatty acids, unsaturated fatty acids, straight-chain fatty acids, and branched fatty acids. The number of carbon atoms of the fatty acid is also not particularly limited, but may be 1 to 30 or 15 to 30. For example, the fatty acid may be one or more selected from the group consisting of saturated fatty acids such as cyclohexanoic acid (cyclohexanecarboxylic acid), naphthenic acids having side chains such as alkylcyclopentane, hexanoic acid, and octanoic acid, unsaturated fatty acids such as decanoic acid (including branched carboxylic acids such as neodecanoic acid), dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid (stearic acid), methacrylic acid, oleic acid, linoleic acid, and linolenic acid, and resin acids such as rosin, tall oil acid, and abietic acid. Preferably, the vulcanization accelerator of the present invention is zinc oxide (ZnO) and stearic acid. The total amount of the vulcanization accelerator aid is not particularly limited, but can be 1 to 10 phr, preferably 1.5 to 7 phr, for example, 2 to 5 phr. Zinc oxide can be used in an amount of about 1 to about 10 phr, preferably about 2 to about 5 phr, more preferably about 2 to about 3 phr. Stearic acid can be used in an amount of about 1 to about 5 phr, preferably about 2 to about 3 phr.

[0127] Additional reinforcing fillers, such as carbon black, carbon nanotubes, short carbon, polyamide, polyester, natural fiber, calcium carbonate, clay, alumina, aluminosilicate, etc., or any mixture thereof, may also be present in the rubber composition of the present invention. When present, carbon black may be furnace black, channel black, or lamp black. For example, the carbon black may be one or more selected from the group consisting of super abrasion furnace (SAF) black, high abrasion furnace (HAF) black, high speed extrusion furnace (FEF) black, fine furnace (FF) black, intermediate super abrasion furnace (ISAF) black, semi-reinforced furnace (SRF) black, medium processed channel black, hard processed channel black, and conductive channel black. Other carbon blacks include acetylene black. Carbon black may be in pelletized form or as unpelletized agglomerates. Specific examples of carbon blacks for use in the rubber composition of the present invention include CORAX® N234, supplied by Orion Engineered Carbons. The amount of carbon black that may be present is not particularly limited, but may be from 0.1 to 10 phr, such as from 0.5 to 5 phr, or from 1 to 4 phr, such as from 2 to 3 phr.

[0128] Advantageously, the only silica-based filler present in the rubber composition of the present invention is the filler system described herein, i.e., no additional silica is present. Thus, the silica system can constitute all of the silica filler in the composition. In some embodiments, the silica system can constitute all of the reinforcing filler in the rubber composition. However, the presence of additional silica-based fillers or additional non-silica-based fillers is not necessarily excluded. If additional silica is present, it can be selected from those known in the art, including, but not limited to, precipitated amorphous silica, wet-process silica (hydrated silicic acid), dry-process silica (anhydrous silicic acid), pyrogenic (fumed) silica, calcium silicate, aluminum silicate, magnesium silicate (e.g., MgSiO, MgSiO), calcium magnesium silicate (CaMgSiO), calcium aluminum silicate (e.g., AlO·CaOSiO), and the like.

[0129] The rubber composition may contain additional fillers known to those skilled in the art. For example, the rubber composition may contain aluminum hydroxide, talc, alumina (Al2O3), aluminum hydrate (Al2O3·H2O), aluminum hydroxide (Al(OH)3), aluminum carbonate (Al2(CO3)2), magnesium aluminum oxide (MgOAl2O3), pyrophyllite (Al2O3·4SiO2·H2O), bentonite (Al2O3·4SiO2.2H2O), mica, kaolin, glass balloons, glass beads, calcium oxide (CaO), calcium hydroxide (Ca The composition may include one or more additional fillers selected from the group consisting of calcium carbonate (CaCO), magnesium carbonate, magnesium hydroxide (Mg(OH)), magnesium oxide (MgO), magnesium carbonate (MgCO), potassium titanate, barium sulfate, zirconium oxide (ZrO), zirconium hydroxide (Zr(OH)nH0), zirconium carbonate (Zr(CO), crystalline aluminosilicates, and reinforcing grades of zinc oxide (i.e., reinforcing zinc oxide). The amount of additional filler can be 5 to 200 phr, e.g., 10 to 150 phr or 25 to 100 phr.

[0130] The antidegradant used in the rubber composition of the present invention is not particularly limited and may be any known to those skilled in the art. The antidegradant may be an antioxidant and / or an antiozonant. For example, the antidegradant may be one or more selected from the group consisting of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ). Preferably, the antidegradant is a combination of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ). The amount of each antidegradant is 0.1 to 3 phr, preferably 0.2 to 2 phr. The total amount of antidegradants is 0.1 to 5 phr, preferably 1 to 3 phr.

[0131] A coating agent can be used to suppress the formation of silica aggregates during compounding. When present, the coating agent can be used in an amount of up to 5 phr, preferably about 1 to about 3 phr. In one embodiment, no additional coating agent is used. The coating agent is not particularly limited and can be any known in the art. Suitable silica-based coating agents include silanes such as alkylalkoxysilanes, e.g., hexadecyltrimethoxysilane, octyltriethoxysilane, and hexyltrimethoxysilane. In one embodiment, the coating agent can be pre-grafted onto the polymer. The coating agent can be used in a free state (i.e., not pre-grafted) or grafted onto the surface of the silica.

[0132] A coupling agent may be present to bond to the silanol groups of the silica to inhibit silica aggregation and to covalently bond the silica filler to the diene rubber matrix. The appropriate amount of coupling agent can be determined by one skilled in the art, taking into account factors such as the molecular weight, the number of functional groups contained, and reactivity. Most coupling agents can be used in an equimolar amount based on the amount of silica. The coupling agent used in the rubber composition of the present invention is not particularly limited, and any known to those skilled in the art may be used. In one embodiment, the coupling agent may be pre-grafted onto the polymer. It may also be used in a free state (i.e., not pre-grafted) or grafted onto the surface of the silica.

[0133] Generally, the coupling agent is a silane coupling agent, such as a bifunctional silane. For example, the silane coupling agent may be bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthio The silane coupling agent may be one or more selected from the group consisting of carbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide. Preferably, the silane coupling agent is bis(3-triethoxysilylpropyl)tetrasulfide. A specific example of the silane coupling agent used in the present invention is Si 69 (registered trademark) from Evonik Industries AG. The amount of the silane coupling agent is not particularly limited, but can be set to 2 to 20 phr, preferably 5 to 18 phr, more preferably 7 to 16 phr, for example 10 to 16 phr.

[0134] The rubber compositions according to the present invention can be prepared by methods known in the art, including mixing (i.e., compounding) the diene rubber component, the filler system described herein, and any other ingredients described herein to produce a rubber composition for subsequent vulcanization. According to a further aspect, the present invention provides a method for producing a rubber compound by compounding the rubber composition described herein.

[0135] According to a further aspect, the present invention provides a method for producing a rubber article, comprising the steps of: compounding a rubber composition described herein to form a rubber compound; shaping (e.g., molding) the rubber compound into a desired shape; and vulcanizing the rubber compound.

[0136] In preparing the rubber compound of the present invention, the method of compounding each component is not particularly limited, and any method known in the art can be used. To mold the rubber composition into any desired shape, known molding machines such as an extruder or a press molding machine can be used.

[0137] The mixing of the components is usually carried out in stages where the components can be added. To optimize the dispersion of the silica filler system, a multi-stage mixing process is generally preferred and may involve the use of multiple mixers, for example, different mixers arranged in series. For example, when mixing a tire tread compound, the mixing process may include an initial mixing stage to produce a masterbatch, followed by one or more additional non-direct production mixing stages, and finally a productive mixing stage to add the curatives (i.e., sulfur or sulfur donors and accelerator(s)). Mixers that can be used are well known in the art and include, for example, open mills or Banbury-type mixers with tangential or intermeshing rotors.

[0138] Typically, rubber, silica filler system, processing aids, zinc oxide, stearic acid, antidegradants (antioxidants, antiozonants, etc.), pigments, additional fillers, compatibilizers, and coupling agents (if present) are mixed to produce an initial masterbatch. This initial masterbatch may be followed by another masterbatch that adds additional fillers and additives, or by a non-direct manufacturing mixing stage that does not add additional ingredients. Non-direct manufacturing mixing stages may also be used to further disperse ingredients (such as fillers) within the rubber or to reduce the viscosity of the mixed rubber compound.

[0139] During mixing, the temperature is maintained below a predetermined level to avoid premature crosslinking of the composition. Generally, the temperature can be maintained below 150°C, preferably below 140°C. When preparing the initial masterbatch, mixing can be carried out at temperatures ranging from about 80 to about 110°C, e.g., about 100°C. For mixing stages not directly related to production, the temperature can be increased, e.g., up to about 150°C, e.g., about 130°C. If additional compatibilizers are added during mixing, higher temperatures may be required to ensure that these compatibilizers react with the silica surface. Mixing times can vary, but those skilled in the art can easily determine the appropriate mixing time based on the composition of the mixture and the type of mixer used. Generally, a mixing time of at least 1 minute, preferably 2 to 30 minutes, is sufficient to obtain the desired homogeneous composition.

[0140] The final mix stage involves the addition of curatives such as accelerators, antidegradants, etc. The temperature at this stage is generally low, for example, in the range of about 40° C. to about 60° C., e.g., about 50° C. This final mix may be followed by other mix stages not directly related to manufacturing, in which no ingredients are added.

[0141] The most appropriate type of mixing can be easily selected to obtain a vulcanizable rubber compound. The mixing speed can be easily determined, but may be, for example, about 20 to about 100 rpm, for example, about 30 to about 80 rpm, preferably about 50 rpm.

[0142] Vulcanizable rubber compounds can be supplied as uncured (so-called "green") tire components for final vulcanization to cure the composition. Curing to crosslink the rubber component can be carried out by known methods. For example, in the tire industry, uncured rubber (so-called "green body") is produced, followed by crosslinking the rubber component and vulcanization in a press mold to form the final tire. Vulcanization cures the rubber primarily through sulfur crosslinking. Vulcanization methods and conditions for curing rubber compositions are well known to those skilled in the art. Suitable vulcanization conditions typically include heating at a temperature in the range of 120 to 200°C, e.g., 140 to 180°C, for 5 to 180 minutes, e.g., 5 to 120 minutes.

[0143] Vulcanizable rubber compositions form a further aspect of the present invention. In another aspect, the present invention provides a vulcanizable rubber composition comprising a diene rubber component having dispersed therein a filler system as defined herein.

[0144] Vulcanized rubber compounds obtained, obtained directly, or obtainable by crosslinking the vulcanizable rubber compositions described herein are also part of this invention.

[0145] Methods for producing vulcanized rubber compositions also form part of the present invention. Accordingly, in another aspect, the present invention provides a process for producing a vulcanized rubber composition, comprising the steps of: introducing a silica filler system, as defined herein, into a diene rubber component, thereby producing a vulcanizable rubber composition; and vulcanizing the vulcanizable rubber composition by heating at a predetermined temperature and for a predetermined time.

[0146] The rubber compositions described herein find use in the manufacture of vehicle tires, particularly in the manufacture of tire components such as tire treads. Tire treads may be used in any vehicle tire, but are particularly used in the manufacture of tire treads for automobiles. Other uses for the rubber compounds include vibration dampers, sidewall rubber, innerliner rubber, bead filler rubber, body ply rubber, skim shock rubber, and tread rubber.

[0147] In another aspect, the present invention provides the use of a rubber composition as described herein as a component of, or in the manufacture of, a component of a vehicle tire.

[0148] In another aspect, the present invention provides a vehicle tire component, such as a tire tread, made from the rubber composition as described herein. Vehicle tires comprising the vehicle tire component also form part of the present invention.

[0149] Methods for assembling and manufacturing tire components are well known in the art. Following assembly of the "green" tire, it is compression molded in a suitable mold where it is vulcanized to produce the final tire.

[0150] The rubber compounds according to the present invention may also be used in applications other than tires, such as in the manufacture of hoses and seals.

[0151] In the present invention, by replacing conventional fillers with the silica filler system described herein, rubber compositions are obtained that have excellent abrasion resistance, rolling resistance, and wet performance, and an excellent balance of these properties, for use as tire tread rubber compounds.

[0152] The present invention is further illustrated by the following non-limiting examples and accompanying drawings: [Brief explanation of the drawings]

[0153] [Figure 1] tan δ curves showing tan δ as a function of temperature for a rubber composition E1 according to the invention and for a reference composition CE1; [Figure 2] tan δ curves showing tan δ as a function of temperature for a rubber composition E2 according to the invention and for a reference composition CE2; [Figure 3] tan δ curves showing tan δ as a function of temperature for a rubber composition E3 according to the invention and for a reference composition CE3; [Figure 4]tan δ curves showing tan δ as a function of temperature for a rubber composition E4 according to the invention and for a reference composition CE4; [Figure 5] Graph showing bound rubber wear index (%) as a function of WET / RR index by tan δ@peak / tan δ@60° C. for rubber compositions E1 to E4 according to the invention and for reference rubber compositions CE1 to CE4. [Example]

[0154] [Test method]

[0155] <Brunauer-Emmett-Teller (BET) specific surface area> The specific surface area of ​​the functionalized silica was measured by the BET method according to the method described in Journal of the American Chemical Society, Vol. 60, page 309, February 1938, which corresponds to the NF ISO 5794-1, Appendix D standard (June 2010).

[0156] <Cetyltrimethylammonium bromide (CTAB) adsorption method> The surface area of ​​the functionalized silica was measured by the CTAB method according to ASTM D6845.

[0157] <Carbon content (C) of carboxylic acids and corresponding carboxylates> The content (C) of carboxylic acid and the corresponding carboxylate is expressed as total carbon and can be measured using a carbon / sulfur analyzer such as the Horiba EMIA 320 V2 apparatus. The principle of the carbon / sulfur analyzer is based on the combustion of a solid sample in an oxygen stream in an induction furnace (adjusted to about 170 mA) in the presence of combustion promoters (about 2 g of tungsten (especially Lecocel 763-266) and about 1 g of iron). The analysis time is about 1 minute. Carbon (with a mass of about 0.2 g) contained in the sample to be analyzed combines with oxygen to generate CO2 and CO, and these decomposition gases are analyzed with an infrared detector. To prevent interference with infrared measurement, moisture from the sample and moisture generated by these oxidation reactions are removed by passing through a cartridge containing a dehydrating agent (magnesium perchlorate). The results are expressed as the mass percentage of elemental carbon.

[0158] <Ratio of object size distribution width (Ld)> The ratio of object size distribution width is the ratio of object size distribution width Ld ((d84 - d16) / d50) measured by XDC particle size analysis after ultrasonic deaggregation according to the method described in Patent Document 3 (WO 2015 / 121333).

[0159] <Pore volume distribution> The pore volume distribution is the ratio of pore volume distribution V(d5 - d50) / V(d5 - d100) measured according to the method described in Patent Document 3 (WO 2015 / 121333).

[0160] <pH of functionalized silica> The pH of the functionalized silica was measured according to the method described in Patent Document 3 (WO 2015 / 121333) derived from ISO 787 / 9.

[0161] <WET / RR index determined by the maximum value of the tanδ@ curve / tanδ at 60 °C (i.e., tanδ@ peak / tanδ at 60 °C)> Loss factor (tangent delta, or tanδ) at different temperatures is used to evaluate rolling resistance and wet traction. Tanδ at low temperatures is an indicator of wet traction. Compared to a control compound, an increase in tanδ at low temperatures correlates with improved wet traction of the tread compound. When developing a rubber composition for a tire tread to improve rolling resistance, the loss tangent (tanδ) at around 60°C is generally considered as an indicator. Using a rubber composition with a low tanδ at around 60°C for the tread rubber can suppress heat generation within the tire, reduce rolling resistance, and improve tire fuel economy. Therefore, tanδ at 60°C is an indicator of rolling resistance (RR). A lower result compared to a control compound indicates reduced rolling resistance. The WET / RR index is calculated by the ratio of the maximum value (i.e., low-temperature region) of the tanδ curve (tanδ@peak) to tanδ at 60°C (tanδ@60°C). Dynamic physical testing to measure tanδ was performed according to ISO 4664.

[0162] <Pain Effect (%)> The Payne effect provides an index of the degree of filler network, i.e., filler dispersion. The Payne effect was calculated from the dynamic properties of the compound measured according to the ISO 4664 standard in a stress / strain test at room temperature. The Payne effect can predict filler dispersion in a rubber composition from the ratio (expressed as a percentage) of ΔE' / E' (0.1% strain), where ΔE' is the difference between E' (0.1% strain) and E' (4% strain). The lower the Payne effect, the better the filler dispersion in the rubber composition.

[0163] <Bound rubber (%)> The "bound rubber" is an indicator of filler reinforcement. The so-called "bound rubber" test allows the determination of the proportion of elastomer in an unvulcanized composition that is intimately bound to the reinforcing filler, making this proportion insoluble in common organic solvents. Knowing the proportion of this insoluble rubber bound to the reinforcing filler during mixing quantitatively indicates the reinforcing activity of the filler in the rubber composition. Quantifying the proportion of rubber bound to the filler allows the prediction of the abrasion resistance of the rubber compound. The higher the bound rubber, the higher the abrasion resistance of the rubber compound. This test, well known to those skilled in the art for characterizing the quality of reinforcement provided by reinforcing fillers, is described in the following non-patent literature: Plastics, Rubber and Composites Processing and Applications, Vol. 25, No. 7, p. 327 (1996); and Rubber Chemistry and Technology, Vol. 69, p. 325 (1996). In the examples herein, the extent of non-extractable elastomer in cyclohexane is determined by swelling a sample of the rubber composition (typically 100-200 mg) in this solvent (e.g., in 20-40 ml of cyclohexane) for 2 days, followed by a drying step at room temperature for 24 hours before weighing the rubber composition thus treated. Preferably, the swelling step is carried out at room temperature (20°C) and away from light. The "bound rubber" content (wt%) is calculated in known manner by the difference between the initial and final weights of the rubber composition sample, after taking into account and excluding the proportion of essentially insoluble components other than the elastomer initially present in the rubber composition.

[0164] [Silica filler] Surface-functionalized silica (referred to herein as "VHSA-functionalized silica") was prepared according to Example 6 of WO 2015 / 121333, where the amount of methyl glutaric acid (MGA) added was 0.40 wt% (expressed as MGA mixture / SiO2 weight ratio) and the pH was adjusted to between 3 and 3.7. The properties of the functionalized silica are shown in Table 1 below.

[0165] [Table 1]

[0166] The unmodified silica (herein referred to as "VHSA silica") has a BET specific surface area of ​​260 m 2 / g, CTAB specific surface area 250m 2 / g, and carbon content 0, was obtained from Solvay under the trade name Premium Super Wear (Premium SW).

[0167] Low reinforcing grade silica (herein referred to as "VLSA silica") has a BET specific surface area of ​​90 m 2 / g±20m 2 / g and CTAB specific surface area 80m 2 / g±15m 2 The silica gel was obtained from Solvay under the trade name Zeosil® 1085 GR, with a saturation of 1000 saturates / g.

[0168] [Rubber composition] <Material>: Rubber: Functionalized SSBR: See preparation method below Non-functionalized ESBR: Europrene 1723 (Versalis, Italy) Carbon black: Corax® N234 (Orion Engineered Carbons, Luxembourg) Silane Coupling Agent - Si69 (Registered Trademark) Aliphatic resin - Impera E1780 (Eastman, Netherlands) Low Tg Oil - 2-Ethylhexyl Oleate: Permavis T (Traquisa) N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) 1,3-diphenylguanidine (DPG) sulfur Dibenzothiazyl disulfide (MBTS) N-Cyclohexyl-2-benzothiazylsulfenamide (CBS) stearic acid 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMQ) Zinc oxide (ZnO)

[0169] Functionalized SSBR was prepared according to the following method described in Patent Document 5 (EP 3 725 837): 1,3-butadiene cyclohexane solution and styrene cyclohexane solution were dried and placed in a nitrogen-purged, 800 mL pressure-sealed glass vessel so that the amounts of 1,3-butadiene and styrene were 67.5 g and 7.5 g, respectively. 0.6 mmol of 2,2-ditetrahydrofurylpropane and 0.8 mmol of n-butyllithium were added, and polymerization was carried out at 50 °C for 1.5 hours. After the polymerization system reached nearly 100% conversion, 0.72 mmol of the modifying agent, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, was added, and the modification reaction was carried out at 50 °C for 30 minutes. Subsequently, 2 mL of a 5 wt% solution of the antioxidant 2,6-di-t-butyl-4-cresol (BHT) in isopropanol was added to terminate the polymerization, and the resulting material was dried to obtain functionalized SSBR. The microstructure (vinyl bond content) of this functionalized SSBR was measured by the Morello method. The bound styrene content was 10 wt% and the vinyl bond content in butadiene was 40 wt%.

[0170] [Examples E1 to E4] Rubber compositions E1 to E4 according to the present invention were prepared by blending the components shown in Table 4. The values ​​in Table 4 are in parts by weight (PHR) based on 100 parts by weight of the rubber composition. As can be seen from Table 4, the total amount of silica filler system decreases from E1 to E4 with an increase in the weight ratio of VLSA silica to VHSA functionalized silica.

[0171] [Table 2]

[0172] The ingredients were formulated according to the following general procedure. Mixing stage not directly related to manufacturing: All ingredients except the vulcanization system were added to a Banbury mixer and mixed with the polymer base. During mixing, the temperature was initially maintained between 110°C and 130°C, and then increased to between 150°C and 160°C to allow for silanization. <Productive mixing stage>: The mixture produced in the mixing stage not directly related to manufacturing was mixed with the vulcanization system at 90 to 110°C to vulcanize the rubber composition.

[0173] [Comparative examples CE1~CE4] Rubber compositions CE1 to CE4 were prepared by compounding the ingredients shown in Table 5 using the same method as for the rubber compositions of Examples E1 to E4 described above. The values ​​in Table 5 are in parts by weight (PHR) based on 100 parts by weight of rubber composition. In these compositions, the functionalized silica of compositions E1 to E4 is replaced with a non-functionalized silica filler having the same specific surface area.

[0174] [Table 3]

[0175] [Rubber composition testing] The rubber compositions were subjected to the test methods described herein. Tan δ was measured over a temperature range of about -45°C to about +65°C. Figures 1-4 show tan δ as a function of temperature for each rubber composition according to the present invention and the corresponding reference rubber compositions (i.e., E1:CE1, E2:CE2, E3:CE3, and E4:CE4). The tan δ and temperature axes in each of Figures 1-4 have the same scale.

[0176] 1 to 4, it can be seen that as the weight ratio of low surface area (VLSA) filler to high surface area (VHSA) silica filler increases (by increasing the amount of VLSA filler and decreasing the amount of VHSA filler), the peak tan δ value increases and the tan δ value at 60°C decreases. As described above, a rubber composition with a low tan δ at around 60°C can suppress heat buildup in a tire tread and reduce rolling resistance. This effect is observed when the total amount of silica filler is reduced. This effect is enhanced in the composition according to the present invention compared to the reference rubber composition.

[0177] Table 6 shows the results of filler dispersion, WET / RR index, and WEAR index for rubber compositions E1 to E4 and CE1 to CE4. Figure 5 shows a graph of the relationship between the wear index (%) with bound rubber and the WET / RR index (tan δ @ peak / tan δ @ 60°C (%)) for all compositions.

[0178] [Table 4]

[0179] Comparing each rubber composition according to the present invention with the corresponding reference rubber composition, it can be seen that the WET / RR index (%) is higher, and likewise, the WEAR index (%) with bound rubber is improved for each rubber composition according to the present invention compared with the corresponding reference composition.

[0180] Surprisingly, increasing the "VLSA" improves the wear performance of the compositions according to the invention compared to the reference composition. Without wishing to be bound by theory, the different trends observed for the "functionalized VHSA" silica compared to the "VHSA" suggest that the presence of carboxyl groups on the modified silica surface aids in more homogeneous packing of the small silica ("VHSA") particles within the larger ("VLSA") particles. This results in a rubber composition in which the non-reinforced rubber domains are absent (or at least reduced), resulting in improved wear performance. This behavior is evident at all tested weight ratios of silica filler, with an optimum at a weight ratio of 0.31.

Claims

1. A rubber composition comprising: a diene rubber component, and It is a filler system, Surface functionalized by the introduction of one or more carboxylic acid groups, or their salts or esters, and having a BET specific surface area of ​​250 to 310 m ２ / g and CTAB specific surface area of ​​230 to 285 m ２ / g, and No surface functionalization, BET specific surface area 60-120m ２ / g and CTAB specific surface area of ​​55 to 105 m ２ / g, Including, wherein the BET specific surface area is measured according to NF ISO 5794-1 standard, Appendix D (June 2010), and the CTAB specific surface area is measured according to ASTM D6845; A rubber composition comprising:

2. 2. The rubber composition according to claim 1, wherein a weight ratio of the second silica to the first silica is 0.15 to 0.

60.

3. 3. The rubber composition of claim 1, wherein the filler system is present in the range of 90 to 130 phr per 100 phr of the rubber composition.

4. In the rubber composition according to claim 1 or claim 2, the first silica is present in a range of 55 to 120 phr per 100 phr of the rubber composition, and / or A rubber composition, wherein the second silica is present in an amount ranging from 10 to 40 phr per 100 phr of the rubber composition.

5. 3. The rubber composition according to claim 1, wherein the first silica is surface-functionalized with one or more polycarboxylic acids.

6. 6. The rubber composition according to claim 5, wherein the one or more polycarboxylic acids are one or more selected from the group consisting of adipic acid, succinic acid, ethylsuccinic acid, glutaric acid, methylglutaric acid, oxalic acid, and citric acid.

7. In the rubber composition according to claim 1 or claim 2, the first silica has the following properties: the carbon content of the functionalized silica is at least 0.10% by weight; - the object size distribution width ratio (Ld) is at least 0.91; - a pore volume distribution ratio of at least 0.65; The rubber composition is further characterized by one or more of:

8. 3. The rubber composition according to claim 1, wherein the first silica has a pH of 2.5 to 7.

9. 3. The rubber composition according to claim 1, wherein the diene rubber component comprises at least one styrene-butadiene copolymer (SBR).

10. 3. The rubber composition according to claim 1, wherein the diene rubber component comprises at least one solution-polymerized styrene-butadiene copolymer (SSBR).

11. 10. The rubber composition according to claim 9, wherein the styrene-butadiene copolymer is SSBR end-functionalized with a hydrocarbyloxysilane compound.

12. The rubber composition according to claim 11, wherein the end-group functionalized SSBR has a Tg in the range of -65 to -15°C.

13. The rubber composition of claim 9, wherein the diene rubber component further comprises at least one additional diene rubber polymer.

14. 14. The rubber composition according to claim 13, wherein the diene rubber component comprises additional styrene-butadiene rubber (SBR), butadiene rubber (BR), natural rubber (NR), or isobutylene-isoprene rubber (IIR).

15. 15. The rubber composition of claim 14, wherein the diene rubber component comprises a blend of solution-polymerized styrene-butadiene rubber copolymer (SSBR) and emulsion-polymerized styrene-butadiene rubber copolymer (ESBR).

16. 3. The rubber composition according to claim 1, wherein the first silica is surface-functionalized with methylglutaric acid, and the diene rubber component comprises a styrene-butadiene copolymer end-functionalized with a hydrocarbyloxysilane compound.

17. 17. The rubber composition according to claim 16, wherein the hydrocarbyloxysilane compound is represented by the following general formula (IV) [Chemical Formula 1]: 【Chemical 1】 is a compound of wherein n1+n2+n3+n4=4, where n2 is an integer from 1 to 4, and n1, n3, and n4 are each an integer from 0 to 3; A １ represents at least one functional group selected from a saturated cyclic tertiary amine compound residue, an unsaturated cyclic tertiary amine compound residue, a ketimine residue, a nitrile group, a (thio)isocyanate group (representing an isocyanate group or a thioisocyanate group), a (thio)epoxy group, a trihydrocarbyl isocyanurate group, a dihydrocarbyl carbonate group, a nitrile group, a pyridine group, a (thio)ketone group, a (thio)aldehyde group, an amide group, a (thio)carboxylate group, a (thio)carboxylate metal base, a carboxylic acid anhydride residue, a carboxylic acid halide residue, and a hydrolyzable group containing a primary or secondary amino group or a mercapto group; If n4 is 2 or more, each A １ may be the same or different, or A １ is a divalent group that can bond to Si to form a cyclic structure, R ２１ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms; When n1 is 2 or more, each R ２１ may be the same or different, R ２３ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom; When n3 is 2 or more, each R ２３ may be the same or different, R ２２ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, optionally containing a nitrogen atom and / or a silicon atom; When n2 is 2 or more, each R ２２ may be the same or different or may be joined together to form a ring, R ２４ represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms; When n4 is 2 or more, each R ２４ can be the same or different, Rubber composition.

18. 12. The rubber composition according to claim 11, wherein the solution polymerized styrene-butadiene rubber copolymer (SSBR) is present in an amount ranging from 60 to 100 phr per 100 phr of the rubber composition.

19. The rubber composition according to claim 1 or 2, wherein the rubber composition is vulcanized.

20. A tire comprising tire components made from the rubber composition of claim 1 or claim 2.

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