Precipitated silica and its manufacturing process

Abstract

To provide precipitated silica having large particle size for use in tire applications.SOLUTION: There are provided precipitated silica having a specific relation between a CTAB surface area and median particle size, an elastomer composition using the precipitated silica, a tire, and a tire component.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to precipitated silica for use as a reinforcing filler in an elastomer composition.

Background Art

[0002] The use of precipitated silica as a reinforcing filler in polymer compositions, particularly in elastomer compositions, is known. Such use is highly desirable, and the filler must be easily and efficiently mixed and dispersed in the elastomer matrix and typically enter into chemical bonding with the elastomer together with a coupling reagent to provide high and homogeneous reinforcement of the elastomer composition. Silica-filled elastomer compositions have particularly advantageous uses in tire formulations. So-called high-dispersibility silica-filled tire treads have made it possible to achieve a compromise of properties regarding rolling resistance, wear resistance, and grip that cannot be obtained with conventional carbon black for tires.

[0003] Typically precipitated silica having a large surface area exceeding 160 m 2 / g is known. For example, International Publication No. 03 / 016215A1 pamphlet discloses precipitated silica having a large surface area and a broad particle size distribution.

[0004] International Publication No. WO 2013 / 092745 A1 discloses a method for preparing precipitated silica, comprising: (i) preparing an aqueous stock solution having a pH of 2 to 5; (ii) simultaneously adding a silicate and an acid to the stock solution such that the pH of the reaction medium is maintained at 2 to 5; (iii) continuing the addition of the silicate to the reaction medium while stopping the addition of the acid until a pH value of the reaction medium of 7 to 10 is obtained; (iv) simultaneously adding a silicate and an acid to the reaction medium such that the pH of the reaction medium is maintained at 7 to 10; and (v) continuing the addition of the acid while stopping the addition of the silicate until a pH value of the reaction medium of less than 6 is obtained, wherein concentrated acid is used in at least part of step (ii). International Publication No. WO 2013 / 092745 A1 does not disclose the amount of silicate added to the reaction medium during step (ii) relative to the total amount of silicate required for the reaction. The amount that can be calculated from the method exemplified in International Publication No. WO 2013 / 092745 A1 is less than 50% of the total amount of silicate required for the reaction.

[0005] The advantage of using silica with a large surface area lies mainly in the possibility of increasing the binding number of silica with an elastomer, and thus the level of its reinforcement. Therefore, in a tire tread rubber composition, especially for improving the rolling resistance and wear resistance of a tire, it is considered advantageous to use silica with a large surface area at a lower addition amount compared to the addition amount conventionally used for silica having a surface area of about 160 m 2 / g.

[0006] However, this achievement of improving tread wear characteristics by using large surface area silica in rubber compositions often results in a decrease in wet grip performance. In fact, the use of large surface area silica with small particle size is expected to increase the filler network, which may result in lower hysteresis at low temperatures and lower wet grip performance. Therefore, there is always a need for precipitated silica as a reinforcing filler in polymer compositions that is effective in finding a balance between wet grip and rolling resistance performance without compromising the advantages of tread wear performance. [Overview of the project]

[0007] In this study, it was found that precipitated silica, which has a specific relationship between surface area and particle size, provides an excellent balance among the following properties of the elastomer composition: low hysteresis at high temperatures with high hysteresis and equivalent strengthening index (tensile properties), and processability of the compound.

[0008] The first object of the present invention is, - 160m 2 CTAB surface area of ​​≥ / g CTAB ; - Measured by centrifugal sedimentation |d50|>25000 / |S CTAB |(I) median particle size d50 (In the formula, |d50| represents the median particle size d50, expressed in nm, measured by centrifugal sedimentation, and |S CTAB | is m 2 CTAB surface area S expressed in units of / g CTAB Represents a numerical value; - Aluminum content not exceeding 4500 ppm; It is a precipitated silica characterized by the following:

[0009] In other parts of this specification, the terms "silica" and "precipitated silica" can be used interchangeably to mean precipitated silica. The term "particle" is used herein to refer to an aggregate of primary particles of silica.

[0010] CTAB surface area S CTAB is a measure of the external specific surface area determined by measuring the amount of N-hexadecyl-N,N,N-trimethylammonium bromide adsorbed on the silica surface at a given pH.

[0011] CTAB surface area S CTAB is preferably 180 m 2 / g or more. CTAB surface area S CTAB may be 200 m 2 / g or more.

[0012] The CTAB surface area does not exceed 400 m 2 / g and typically does not exceed 380 m 2 / g. CTAB surface area S CTAB can be lower than 350 m 2 / g.

[0013] In elastomer reinforcement applications, the advantageous range of CTAB surface area S CTAB is 160 - 400 m 2 / g, 180 - 400 m 2 / g, 180 - 380 m 2 / g, preferably 180 - 350 m 2 / g, 200 - 350 m 2 / g, and more preferably 220 - 330 m 2 / g.

[0014] An important feature of the silica of the present invention is a large median particle size (particle diameter) d50 for a given S CTAB value. In particular, the median particle size of the silica of the present invention at a given CTAB surface area S CTAB has been found to be larger than the value measured for precipitated silica of the prior art.

[0015] As used herein, the term "aggregate" refers to an aggregate of primary silica particles. The term "particle" is used to refer to the smallest aggregate of primary silica particles that can be broken by mechanical action. In other words, the term "particle" refers to an indivisible collection of primary particles.

[0016] The median particle size d50 and CTAB surface area S of the silica of the present invention CTAB It was found that the following is true: |d50|>25000 / |S CTAB |(I).

[0017] In equation (I), |S CTAB | is m 2 Surface area S of CTAB expressed in units of / g CTAB Represents the numerical value of |S CTAB | is a dimensionless number. For example, S CTAB The measured value is 200m 2 If / g, |S CTAB | is 200.

[0018] In equation (I), |d50| represents the median particle size d50, expressed in nm, as measured by centrifugal sedimentation. For example, if the value of d50 measured by centrifugal sedimentation is 100 nm, then |d50| is 100. d50 represents the diameter at which 50% of the total mass of the aggregate is found below (and above) it. Thus, d50 represents the median particle size of a given distribution, and the related term "size" must mean "diameter". |d50| is a dimensionless number.

[0019] 200-400m 2 CTAB surface area S in the range of / g CTAB In this context, the silica of the present invention is characterized by a median particle size d50 that is typically greater than 60 nm, and even greater than 80 nm. In some cases, d50 in the CTAB surface area range may exceed 90 nm.

[0020] The d50 value of the silica of the present invention typically does not exceed 250 nm, and more typically does not exceed 200 nm.

[0021] The silica of the present invention is characterized not by aggregates of primary particles having multiple different primary particle sizes on average, but by aggregates of primary particles having the same size on average, i.e., a single median measured, for example, by electron microscopy (TEM) or small-angle X-ray scattering (SAXS). In other words, the precipitated silica of the present invention is characterized by a single population of primary particle sizes.

[0022] The precipitated silica of the present invention is further characterized by a broad particle size distribution. To characterize the particle size distribution width, the parameter Ld, determined by a disk centrifugal sedimentation machine detailed below, is used. Ld is defined as follows: Ld=(d84-d16) / d50 Here, dn is the diameter to which n% of the total measured mass is less than or equal to. Ld is a dimensionless number. The particle size distribution width Ld is calculated based on the cumulative particle size curve.

[0023] The particle size distribution width Ld is at least 1.2, typically at least 1.3, and preferably at least 1.4. The particle size distribution width Ld is 4.0 or less, typically 3.5 or less.

[0024] Advantageously, the particle size distribution width Ld of the silica of the present invention is in the range of 1.2 to 3.5, more preferably in the range of 1.3 to 3.2. The particle size distribution width Ld of the silica of the present invention can be in the range of 1.3 to 3.0, preferably 1.4 to 3.0, and more preferably 1.5 to 2.8.

[0025] The precipitated silica of the present invention contains less than 4500 ppm, typically less than 4000 ppm, of aluminum. The amount of aluminum is defined as the amount of aluminum metal relative to the weight of silica. The aluminum content in the silica of the present invention does not usually exceed 3800 ppm, preferably 3500 ppm. The aluminum content may be as low as about 100 ppm.

[0026] The precipitated silica of the present invention is typically characterized by a specific V (d5-d50) / V (d5-d100) It is characterized by a large pore volume distribution defined using, where V (d5-d50) V represents the pore volume formed by pores with diameters between d5 and d50. (d5-d100) d represents the pore volume formed by pores with diameters between d5 and d100, where dn is the pore diameter formed by pores with a larger diameter than the total surface area of ​​all pores, which is n% of the total surface area of ​​all pores.

[0027] The silica of the present invention typically has a specific V ratio of 0.60 or higher, preferably 0.65 or higher, and more preferably 0.70 or higher. (d5-d50) / V (d5-d100) It has. Ratio V (d5-d50) / V (d5-d100) Typically, it does not exceed 1.20.

[0028] The BET surface area S of silica in the present invention BET This is not particularly limited. BET surface area S BET It is usually at least 160m 2 / g, at least 170m 2 / g is the BET surface area S BET 400m 2 Approximately / g, and furthermore, 450m 2 It can be as large as / g.

[0029] The precipitated silica of the present invention is typically at least 30m 2 / g difference (S BET -S CTAB Characterized by the difference value (S BET -S CTAB ) is not restricted. Usually, the difference (SBET -S CTAB ) is 100m 2 It is less than / g.

[0030] The silica of the present invention has a pH of at least 4.0, and moreover, at least 4.5N. SiOH / nm2 1nm 2 Number of silanolSiOH per unit, N SiOH / nm2 It is characterized by:

[0031] A second object of the present invention is a method for preparing precipitated silica of the first object, the method being: (i) A step of providing a starting solution having a pH of 2.0 to 5.0, (ii) A step of simultaneously adding a silicate and an acid to the starting solution so that the pH of the reaction medium is maintained in the range of 2.0 to 5.0, (iii) Stopping the addition of the acid and silicate, and adding a base to the reaction medium to raise the pH of the reaction medium to a value of 7.0 to 10.0, (iv) A step of simultaneously adding silicate and acid to the reaction medium so that the pH of the reaction medium is maintained in the range of 7.0 to 10.0, (v) A step of obtaining a suspension of precipitated silica by stopping the addition of silicate while continuing to add acid to the reaction medium, and bringing the pH of the reaction medium to below 5.5. The amount of silicate added to the reaction medium during step (ii) exceeds 55% by weight of the total amount of silicate required for the reaction.

[0032] The total amount of silicate required to obtain a given final amount of silica can be determined by a person skilled in the art at the beginning of the process, according to generally accepted knowledge.

[0033] The term “base” as used herein means one or more bases that may be added in the course of the process of the present invention, and it includes the group consisting of silicates as defined below. Any base can be used in the process. Notable non-limiting examples of suitable bases in the addition of silicates are, for example, alkali metal hydroxides and ammonia.

[0034] The term "silicate" is used herein to refer to one or more silicates that may be added in the process of the present invention. Silicates are typically selected from the group consisting of alkali metal silicates. Silicates are advantageously selected from the group consisting of sodium silicate and potassium silicate. Silicates may be any known form, such as metasilicate or disilicate.

[0035] When sodium silicate is used, the latter generally has an SiO2 / Na2O weight ratio of 2.0 to 4.0, especially 2.4 to 3.9, for example 3.1 to 3.8.

[0036] Silicates can have concentrations (expressed with respect to SiO2) of 3.9% to 25.0% by weight, for example, 5.6% to 23.0% by weight, specifically 5.6% to 20.7% by weight.

[0037] The term "acid" is used herein to refer to one or more acids that may be added in the process of the present invention. Any acid can be used in the process. Generally, mineral acids such as sulfuric acid, nitric acid, phosphoric acid, or hydrochloric acid, or organic acids such as carboxylic acids, for example acetic acid, formic acid, or carbonic acid are used.

[0038] The acid can be metered into the reaction medium in a diluted or concentrated form. The same acid can be used at different stages of the process, but at different concentrations. Preferably, this acid is sulfuric acid.

[0039] In a preferred embodiment of the process, sulfuric acid and sodium silicate are used at all stages of the process. Preferably, the same sodium silicate, expressed as SiO2 and having the same concentration, is used at all stages of the process.

[0040] In step (i) of the process, a starting solution having a pH of 2.0 to 5.0 is provided into the reaction vessel. The starting solution is an aqueous solution, and the term "aqueous" indicates that the solvent is water.

[0041] Preferably, the starting solution has a pH of 2.5 to 5.0, particularly 2.8 to 4.4, for example, 3.0 to 4.0.

[0042] The starting solution can be obtained by adding an acid to water to achieve the above pH value.

[0043] Alternatively, the starting solution may contain silicates. In such cases, this can be achieved by adding an acid to a mixture of water and silicates to obtain a pH of 2.0 to 5.0.

[0044] The starting solution in step (i) may or may not contain an electrolyte. Preferably, the starting solution in step (i) contains an electrolyte.

[0045] The term “electrolyte” is used herein in its generally accepted sense, that is, to identify any ionic or molecular substance that, when in solution, decomposes or dissociates to form ions or charged particles. The term “electrolyte” is used herein to indicate that one or more electrolytes may be present. Examples of electrolytes include salts of alkali metals and alkaline earth metals. Advantageously, the electrolyte used in the starting solution is a salt of the metal and acid of the starting silicate used in the process. Notable examples are, for example, sodium chloride in the case of the reaction of sodium silicate with hydrochloric acid, or preferably sodium sulfate in the case of the reaction of sodium silicate with sulfuric acid. Electrolytes do not contain aluminum.

[0046] Preferably, when sodium sulfate is used as the electrolyte in step (i), its concentration in the starting solution is 8 to 40 g / L, particularly 10 to 35 g / L, for example, 10 to 30 g / L.

[0047] Step (ii) of the process involves the simultaneous addition of an acid and a silicate to the starting solution. The rate at which the acid and silicate are added during step (ii) is controlled so that the pH of the reaction medium is maintained in the range of 2.0 to 5.0. Preferably, the pH of the reaction medium is maintained in the range of 2.5 to 5.0, particularly 2.8 to 5.0, for example, 2.8 to 4.5.

[0048] The method of the present invention is characterized by the fact that the amount of silicate added during step (ii) is at least 55%, preferably at least 65%, of the total amount of silicate required for the reaction.

[0049] Although not bound by theory, it is thought that adding at least 55% of the required total amount of silicate to the reaction mixture during step (ii) has the effect of increasing the median particle size d50 of the silica aggregates.

[0050] Preferably, step (ii) consists of the simultaneous addition of the acid and silicate, as detailed above.

[0051] In one embodiment of the process of the present invention, the intermediate step (ii') may be carried out between step (i) and step (ii), wherein a silicate and an acid are added to the starting solution so that the pH of the reaction medium is maintained in the range of 2.0 to 9.5. The addition of the silicate and the acid may be simultaneous for all or part of step (ii'). Step (ii') is typically extended by 1 to 10 minutes, preferably 2 to 8 minutes, before step (ii) is started.

[0052] Next, in step (iii), the addition of the acid and silicate is stopped, and the base is added to the reaction medium. The addition of the base is stopped when the pH of the reaction medium reaches a value of 7.0 to 10.0, preferably 7.5 to 9.5.

[0053] In the first embodiment of the process, the base is a silicate. Thus, in step (iii), the addition of the silicate to the reaction medium is continued while the addition of the acid is stopped until a pH of 7.0 to 10.0, preferably 7.5 to 9.5, is achieved.

[0054] In a second embodiment of the process, the base is different from a silicate and is selected from the group consisting of alkali metal hydroxides, preferably sodium or potassium hydroxide. When sodium silicate is used in the process, the preferred base may be sodium hydroxide.

[0055] Thus, in this second embodiment of the process, in step (iii), the addition of the acid and silicate is stopped until a pH of 7.0 to 10.0, preferably 7.5 to 9.5, is reached, and a base different from the silicate is added to the reaction medium.

[0056] It may be advantageous to perform a reaction medium maturation step at the end of step (iii), after stopping the addition of base. This step is preferably performed at the pH obtained at the end of step (iii). The maturation step may be performed while stirring the reaction medium. The maturation step is preferably performed for a period of 2 to 45 minutes, specifically 5 to 25 minutes, while stirring the reaction medium. The maturation step preferably does not involve the addition of any acid or silicate.

[0057] After step (iii) and an optional maturation step, the acid and silicate are added simultaneously so that the pH of the reaction medium is maintained in the range of 7.0 to 10.0, preferably 7.5 to 9.5.

[0058] The simultaneous addition of the acid and silicate (step (iv)) is typically carried out so that the pH of the reaction medium is maintained at the same level as the pH reached at the end of the preceding step, step (iii) (to within ±0.2 pH units).

[0059] It should be noted that the process of the present invention may include further steps. For example, an acid may be added to the reaction medium between step (iii) and step (iv), particularly between an optional maturation step after step (iii) and step (iv). The pH of the reaction medium after this addition of the acid should remain in the range of 7.0 to 9.5, preferably 7.5 to 9.5.

[0060] In step (v), the addition of silicate is stopped while the addition of acid to the reaction medium is continued in order to obtain a pH value of less than 5.5, preferably 3.0 to 5.5, and especially 3.0 to 5.0 in the reaction medium. A suspension of precipitated silica is obtained in the reaction vessel.

[0061] At the end of step (v), and therefore after the addition of acid to the reaction medium has been stopped, a maturation step can be advantageously carried out. This maturation step may be carried out at the same pH obtained at the end of step (v) and under the same time conditions as described above for a maturation step that may be optionally carried out between steps (iii) and (iv) of the process.

[0062] The total amount of silicate required for the reaction includes silicate that may be present in the starting solution (step (i)), step (ii), step (ii'), and, if present, silicate added to the reaction medium during steps (iv) and (iii) (if the base used to raise the pH in this step is silicate).

[0063] The reaction vessel in which the entire reaction between silicates and acids takes place is usually equipped with appropriate stirring and heating devices.

[0064] The entire reaction between the silicate and the acid (steps (i) to (v)) is generally carried out at a temperature of 40 to 97°C, particularly 60 to 95°C, preferably 80 to 95°C, and more preferably 85 to 95°C.

[0065] According to one variant of the present invention, the overall reaction between the silicate and the acid is usually carried out at a constant temperature of 40-97°C, specifically 80-95°C, and even more specifically 85-95°C.

[0066] According to another variation of the present invention, the temperature at the end of the reaction is higher than the temperature at the start of the reaction: therefore, the temperature at the start of the reaction (e.g., between steps (i) and (iii)) is preferably maintained at 40-85°C, and then the temperature is preferably raised to a value in the range of 80-95°C, and even further to a value in the range of 85-95°C, at which value it is maintained until the end of the reaction (e.g., between steps (iv) and (v)).

[0067] At the end of the process described above, a suspension of precipitated silica is obtained, which is subsequently separated (liquid / solid separation). The process typically includes a further step (vi) of filtering the suspension and drying the precipitated silica.

[0068] The separations performed in the preparation method according to the present invention typically involve filtration, followed by washing if necessary. This filtration is carried out according to any preferred method, for example, by a belt filter, a rotary filter (e.g., a vacuum filter), or preferably by a filter press.

[0069] Next, the filtration cake is subjected to a liquefaction procedure, during which a mineral acid is added to the filtration cake. The acid is selected from the group consisting of sulfuric acid, hydrochloric acid, phosphoric acid, and nitric acid. The acid is preferably sulfuric acid. The amount of mineral acid added to the filtration cake during the liquefaction process is such that the pH of the final product, precipitated silica, is less than 5.5, preferably less than 4.5. The pH may be even lower than 3.5, but it is generally 3.0 or higher.

[0070] In this specification, the term "liquefaction" is intended to refer to the process by which a solid, i.e., the filtration cake, is converted into a fluid-like mass. After the liquefaction process, the filtration cake is in a fluid-like state with fluidity, and the precipitated silica is in a suspended state.

[0071] The liquefaction process may include mechanical treatment that reduces the particle size distribution of the suspended silica. This mechanical treatment can be carried out by passing the filtered cake through a high-shear mixer, a colloidal mill, or a ball mill.

[0072] During the liquefaction process, an aluminum compound can be added to the filtration cake provided that the pH of the final product, precipitated silica, is less than 8.0, preferably less than 7.0, and the total amount of aluminum in the precipitated silica does not exceed 4500 ppm.

[0073] The suspension of precipitated silica obtained after the liquefaction process is preferably subsequently dried.

[0074] Drying can be carried out according to methods known in the art. Preferably, drying is carried out by spraying. For this purpose, any type of suitable sprayer, in particular turbine, nozzle, liquid pressure, or two-fluid sprayer can be used. Generally, when filtration is carried out using a filter press, a nozzle sprayer is used, and when filtration is carried out using a vacuum filter, a turbine sprayer is used.

[0075] When the drying operation is carried out using a nozzle-type sprayer, the precipitated silica obtained is usually in the form of substantially spherical beads. After this drying operation, the recovered product can optionally be subjected to a grinding or pulverization process, and the precipitated silica obtained is generally in the form of a powder.

[0076] When the drying operation is carried out using a turbine-type sprayer, the precipitated silica obtained may be in the form of a powder.

[0077] Finally, as described above, the dried, pulverized, or pulverized product may optionally be subjected to an agglomeration process, which may consist of, for example, direct compression, wet granulation (i.e., using a binder such as water or silica suspension), extrusion, or preferably dry compaction.

[0078] The precipitated silica obtained through this agglomeration process is generally in the form of granules.

[0079] Precipitated silica obtained according to the present invention or by the method described above can be used in many applications.

[0080] The precipitated silica of the present invention can be used, for example, as a catalyst support. It can be used as an absorbent for active materials, such as liquids, particularly used in food, such as vitamins (vitamin E) or choline chloride. It can be used as a viscous agent, texture improver or anti-solidification agent, as a component of battery separators, or as an additive for toothpaste, concrete, or paper.

[0081] However, the precipitated silica of the present invention finds particularly advantageous applications in strengthening natural or synthetic polymers and their polymer blends.

[0082] The silica-containing elastomer composition of the present invention has been found to have excellent potential in tire tread compositions, particularly in significantly improving rolling resistance and wet grip performance while maintaining a high level of tire handling and wear performance compared to prior art compositions containing precipitated silica.

[0083] Therefore, a further object of the present invention is a composition comprising the silica of the present invention as defined above and at least one polymer. When referring to polymers in a composition, the phrase "at least one" is used herein to indicate that one or more polymers of each type may be present in the composition.

[0084] In this specification, the terms "copolymer" and "terpolymer" are used to refer to polymers that contain repeating units derived from two and three monomer units, respectively, of different properties.

[0085] At least one polymer can be selected from thermosetting polymers and thermoplastic polymers. Notable non-limiting examples of thermosetting polymers include epoxy resins, unsaturated polyester resins, vinyl ester resins, phenolic resins, epoxy acrylate resins, urethane acrylate resins, phenoxy resins, alkyd resins, urethane resins, maleimide resins, and cyanate resins.

[0086] Notable non-limiting examples of suitable thermoplastic polymers include styrene-based polymers such as polystyrene, (meth)acrylic acid ester / styrene copolymer, acrylonitrile / styrene copolymer, styrene / maleic anhydride copolymer, and ABS; acrylic polymers such as polymethyl methacrylate; polyesters such as polycarbonate, polyamide, polyethylene terephthalate, and polybutylene terephthalate; polyphenylene ether, polysulfone, polyaryl ether ketone, polyphenylene sulfide, thermoplastic polyurethane, polyethylene, polypropylene, polybutene, poly-4-methylpentene, polyolefins such as ethylene / propylene copolymer and ethylene / α-olefin copolymer; copolymers of α-olefins with various monomers, such as ethylene / vinyl acetate copolymer, ethylene / (meth)acrylic acid ester copolymer, ethylene / maleic anhydride copolymer, ethylene / acrylic acid copolymer, polylactic acid, polycaprolactone, and aliphatic polyesters such as aliphatic glycol / aliphatic dicarboxylic acid copolymer.

[0087] The silica of the present invention can be advantageously used as a reinforcing filler in elastomer compositions. Therefore, a preferred object of the present invention is a composition comprising the silica of the present invention and one or more elastomers exhibiting at least one glass transition temperature of -150°C to +300°C, for example, -150°C to +20°C.

[0088] Notable non-limiting examples of suitable elastomers are diene elastomers. For example, elastomers derived from aliphatic or aromatic monomers containing at least one unsaturated group, such as ethylene, propylene, butadiene, isoprene, styrene, acrylonitrile, isobutylene or vinyl acetate, polybutyl acrylate or mixtures thereof, can be used. Also, functionalized elastomers and halogenated polymers can be mentioned, which are elastomers functionalized by chemical groups located along and / or at one or more ends of the polymer chain (e.g., by functional groups that can or cannot chemically react with the surface of silica). Examples include polyamides, ethylene homo and copolymers, and propylene homo and copolymers.

[0089] Examples of diene elastomers include polybutadiene (BR), polyisoprene (IR), butadiene copolymers, isoprene copolymers, or mixtures thereof, particularly styrene / butadiene copolymers (SBR, especially ESBR (emulsion) or SSBR (solution)), isoprene / butadiene copolymers (BIR), isoprene / styrene copolymers (SIR), isoprene / butadiene / styrene copolymers (SBIR), ethylene / propylene / diene terrapolymers (EPDM), acrylonitrile copolymers or terrapolymers, and further related functionalized polymers (e.g., those exhibiting pendant polar groups or polar groups at chain ends that can interact with silica).

[0090] Furthermore, natural rubber (NR) and epoxidized natural rubber (ENR) can also be mentioned.

[0091] The polymer composition can be vulcanized with sulfur, or in particular, crosslinked with a peroxide or other crosslinking system (e.g., diamine or phenolic resin).

[0092] Generally, the polymer composition further comprises at least one coupling agent and / or at least one coating agent, which may further, among other things, include an antioxidant.

[0093] As coupling agents, non-limiting examples include "symmetrical" or "asymmetrical" silane polysulfides; more specifically, bis((C1-C4)alkoxyl(C1-C4)alkylsilyl(C1-C4)alkyl) polysulfides (especially disulfides, trisulfides, or tetrasulfides), such as bis(3-(trimethoxysilyl)propyl) polysulfide or bis(3-(triethoxysilyl)propyl) polysulfide, for example, triethoxysilylpropyl tetrasulfide. Also, monoethoxydimethylsilylpropyl tetrasulfide can be mentioned. Furthermore, silanes containing masked or free thiol functional groups can be mentioned.

[0094] The coupling agent can be pre-grafted onto a polymer. It can also be used in a free state or grafted onto the surface of silica. The coupling agent can be optionally combined with a suitable "coupling activator," i.e., a compound that is mixed with the coupling agent to increase its effectiveness.

[0095] The weight ratio of silica of the present invention in the polymer composition can vary over a fairly wide range. It typically corresponds to 10% to 200% by weight, particularly 20% to 150% by weight, especially 20% to 80% by weight, for example, 30% to 70% by weight. Alternatively, the weight ratio of silica of the present invention in the polymer composition may be 40% to 120% by weight of the polymer, for example, 60% to 110% by weight.

[0096] The silica of the present invention can, advantageously, constitute all of the reinforcing inorganic fillers and even all of the reinforcing fillers for polymer compositions.

[0097] The silica according to the present invention can be optionally combined with at least one other reinforcing filler, for example, in particular commercial highly dispersible silica, such as Zeosil® 1165MP, Zeosil® 1115MP, or Zeosil® 1085MP (commercially available from Solvay), or another inorganic reinforcing filler, such as alumina, or in fact, even more organic reinforcing fillers, particularly carbon black (optionally coated with an inorganic layer of silica). The silica according to the present invention then preferably constitutes at least 50% by weight, and indeed at least 80% by weight, of the total amount of the reinforcing filler.

[0098] Compositions containing precipitated silica of the present invention can be used for the manufacture of many articles. Non-limiting examples of articles containing the silica of the present invention or the polymer composition described above include, for example, shoe soles, flooring materials, gas barriers, flame retardant materials, and also engineering components such as cableway rollers, household appliance seals, liquid or gas pipe seals, brake system seals, pipes, coatings, especially cable coatings, cables, engine supports, battery separators, conveyor belts, transmission belts, or dampers. Advantageously, the silica of the present invention can be used particularly in the manufacture of tires, especially tire treads, for light or heavy-duty vehicles.

[0099] If any disclosure of a patent, patent application, or publication incorporated herein by reference conflicts with the description of this application to such an extent that it could obscure the terminology, the description herein shall prevail.

[0100] The present invention will now be described in more detail with reference to the following examples, but these are merely illustrative and not intended to limit the scope of the invention.

[0101] Analysis method The physicochemical properties of the precipitated silica of the present invention were determined using the method described below.

[0102] Measurement of CTAB surface area CTAB surface area (SCTAB The values ​​were determined according to the internal specifications obtained from Annex G of the standard NF ISO 5794-1.

[0103] BET surface area measurement BET surface area S BET The particulate pressure P / P was determined according to the Brunauer-Emmett-Teller method detailed in standard NF ISO 5794-1, Appendix E (June 2010), and the following adjustments were made: the sample was pre-dried at 200°C ± 10°C and the partial pressure P / P used for the measurement was determined. 0 The values ​​ranged from 0.05 to 0.3.

[0104] Measurement of particle size distribution and particle size by centrifugal sedimentation using a separation plate type centrifugal sedimentation machine (CPS). The values ​​of d50, d16, d84, and Ld were measured by centrifugal sedimentation using a separator-type centrifugal sedimentation machine with the "CPSDC24000UHR" centrifugal optical sedimentation velocometer, commercially available from CPS Instruments company. This instrument is equipped with operating software (operating software version 11g) supplied by the device.

[0105] Instruments used: For the measurement requirements, the following materials and products were used: Ultrasonic device: 1500W generator type Sonics Vibracell VC1500 / VCX1500 with 19mm probe (converter: CV154 + booster (part number: BHNVC21) + 19mm probe (part number: 630-0208)).

[0106] Chemical balance with 0.1 mg accuracy (e.g., Mettler AE260); syringes: 1.0 ml and 2.0 ml, 20 ga needle; 50 ml tall glass beaker (SCHOTT DURAN: 38 mm diameter, 78 mm height); magnetic stirrer with 2 cm stirring bar; container for ice bath during sonication.

[0107] Chemicals: Deionized water; 96% ethanol; 99% sucrose; dodecane, all manufactured by Merck; PVC reference standard manufactured by CPS Instrument Inc.; The peak value of the reference standard used should be between 200 and 600 nm (e.g., 237 nm).

[0108] Preparation of a separation plate type centrifugal sedimentation machine The following parameters were set for the measurement. For the calibration standard parameters, information on the PVC standard provided by the supplier was used.

[0109] TIFF0007829620000001.tif96170

[0110] Device configuration The measurement wavelength was set to 405 nm. The following runtime option parameters were set.

[0111] TIFF0007829620000002.tif37170

[0112] All other software options were left as they were set by the instrument manufacturer.

[0113] Preparation of a separation plate type centrifugal sedimentation machine The centrifugal disk is rotated at 24,000 rpm for 30 minutes. The sucrose density gradient (CASn°57-50-1) is prepared as follows.

[0114] Prepare a 24 wt% aqueous solution of sucrose in a 50 mL beaker. Prepare an 8 wt% aqueous solution of sucrose in a 50 mL beaker. Once these two solutions are homogenized separately, take a sample from each solution using a 2 mL syringe and inject it into the rotating disk in the following order. Sample 1: 1.8 mL of 24 wt% solution Sample 2: 1.6 mL of 24 wt% solution + 0.2 mL of 8 wt% solution Sample 3: 1.4 mL of 24 wt% solution + 0.4 mL of 8 wt% solution Sample 4: 1.2 mL of 24 wt% solution + 0.6 mL of 8 wt% solution Sample 5: 1.0 mL of 24 wt% solution + 0.8 mL of 8 wt% solution Sample 6: 0.8 mL of 24 wt% solution + 1.0 mL of 8 wt% solution Sample 7: 0.6 mL of 24 wt% solution + 1.2 mL of 8 wt% solution Sample 8: 0.4 mL of 24 wt% solution + 1.4 mL of 8 wt% solution Sample 9: 0.2 mL of 24 wt% solution + 1.6 mL of 8 wt% solution Sample 10: 1.8 mL of 8 wt% solution

[0115] Before injecting each solution into the disc, add approximately 0.2 mL of air, then homogenize the two solutions in the syringe by performing a brief, manual agitation for a few seconds, taking care not to lose any liquid.

[0116] These injections, with a total volume of 18 mL, aim to create a density gradient useful for eliminating certain instabilities that may occur during the injection of the sample to be measured. To protect the density gradient from evaporation, 1 mL of dodecane is added to the rotating disk using a 2 mL syringe. The disk is then rotated at 24,000 rpm for 60 minutes before any first measurement.

[0117] Sample preparation 3.2 g of silica was weighed into a 50 mL tall glass beaker (SCHOTT DURAN: 38 mm diameter, 78 mm height), and 40 mL of deionized water was added to obtain an 8 wt% silica suspension. The suspension was stirred with an electromagnetic stirrer (for a minimum of 20 seconds) before placing the beaker in a crystallization dish filled with ice and cold water. The electromagnetic stirrer was removed, and the crystallization dish was placed under an ultrasonic probe positioned 1 cm from the bottom of the beaker. The ultrasonic probe was set to 56% of its maximum amplitude and activated for 8 minutes. At the end of the sonication, the beaker was placed again on an electromagnetic stirrer with a 2 cm magnetic stirring rod, stirring at a minimum of 500 rpm until after sample extraction.

[0118] The ultrasound probe must be placed under appropriate operating conditions. The following tests must be performed, and if the results are negative, a new probe should be used: Visual inspection of the physical integrity of the probe end (roughness depth less than 2 mm measured with a precision caliper): The measured d50 of commercially available silica Zeosil® 1165MP should be 93 nm ± 3 nm.

[0119] analysis Before analyzing each sample, the calibration standard was recorded. In each case, 0.1 mL of a PVC standard, provided by the CPS instrument and with its characteristics pre-programmed into the software, was injected. It is important to start the measurement in the software simultaneously with this initial injection of the PVC standard. To ensure that the measurement starts simultaneously with the injection, the instrument must be checked before injecting 100 μL of pre-sonicated sample.

[0120] These injections were performed using two clean 1 mL syringes.

[0121] At the end of the measurement, when the time required to settle all relatively small diameter particles (composed of 0.02 μm in the software) was reached, the ratio of each diameter class was obtained. The resulting curve is called the aggregate size distribution.

[0122] Results: The values ​​d50, d16, d84, and Ld are based on the distribution drawn on a ruler. Integrating the particle size distribution function with respect to diameter allows us to obtain the "cumulative" distribution, i.e., the total mass of particles between the minimum diameter and the desired diameter. d50: 50% of the population's mass has a diameter less than or greater than d50. d50 is called the median size, or diameter, of silica aggregates. d84: This is the diameter below which 84% of the total mass of the aggregate is measured. d16: This is the diameter below which 16% of the total mass of the aggregate is measured. Ld:Equation:Ld=(d84-d16) / d50 It is calculated according to [the formula].

[0123] Measurement of pore volume and size by mercury porosimetry Pore ​​volume and pore size distribution were determined using a Micromeritics AutoPore® IV9520 porosimeter; they were calculated using the Washburn relation with a contact angle theta equal to 140° and a surface tension gamma equal to 485 dynes / cm. Each sample was dried in a furnace at 200°C for 2 hours at atmospheric pressure before measurement. For good reproducibility of the measurements, the starting weight of silica placed in a Type 10 penetrometer with an accuracy of 0.001 g was selected so that the "stem volume used," i.e., the percentage of mercury (Hg) volume consumed for filling the penetrometer, was between 40% and 80%. The penetrometer was then slowly degassed to 50 μm Hg and maintained at this pressure for 5 minutes.

[0124] The AutoPore® instrument was operated using software version IV1.09. No modifications were made to the raw data. The measurement range was 3.59 kPa (0.52 psi) to 413685 kPa (60000 psi), and at least 100 measurement points were used (19 measurement points from 3.59 kPa (0.52 psi) to 193 kPa (28 psi) with a 10-second equilibrium time, followed by 81 points from 1.93 kPa (0.28 psi) to 413685 kPa (60000 psi) with a 20-second equilibrium time). Where appropriate, the software introduced additional measurement points if the gradually increasing intrusion volume was >0.5 mL / g. The intrusion curve was smoothed using the instrument's software's "smooth derivative" function.

[0125] Log differential intrusion (mL / g) was analyzed for pore diameter data in the pore diameter range of 3.5 nm to 5 μm.

[0126] Measurement of aluminum content The amount of aluminum was measured using XRF wavelength-dispersive X-ray fluorescence spectroscopy (using a WDXRF Panalytical analyzer). Sample analysis was performed in a 4 cm diameter cell under helium conditions using silica powder contained in a cell covered with a thin Prolene film (4 μm Chemplex®). Al and Si fluorescence were measured using the following parameters: Al Kα angle 2θ = 144,9468° (20 s), background signal angle 2θ = -1,2030° (4 s), Si Kα angle 2θ = 109,1152° (10 s), tube power 4 kW (32 kV, 125 mA), PE002 crystal and 550 μm collimator, gas flux detector.

[0127] Number of silanols / nm 2 Measurement Number of silanols / nm 2 The surface area was measured by grafting methanol onto the surface of silica. First, 1 gram of silica was suspended in 10 mL of methanol in a stirred autoclave. The hermetically sealed and heat-insulated autoclave was heated to 200°C (40 bar) for 4 hours. Next, the autoclave was cooled in a chilled water bath. The grafted silica was recovered by sedimentation, and the residual methanol was evaporated in a nitrogen stream. The grafted silica was vacuum-dried at 130°C for 12 hours. The carbon content was quantified by elemental analysis. Silanol count / nm 2 It is calculated using the following formula: N SiOH / nm2 =[(%Cg-%Cr)×6.023×10 23 ] / [S BET ×10 18 [×12×100] (In the formula, %Cg is the mass percentage of carbon present on the grafted silica, and %Cr is the percentage mass of carbon present on the raw silica.) [Examples]

[0128] Example 1 928 liters of industrial water were placed in a 2500-liter reactor and heated to 90°C. While stirring, 14.7 kg of solid sodium sulfate was added to the reactor, followed by sulfuric acid (concentration: 96% by weight) until the pH reached 4.2.

[0129] A sodium silicate solution (SiO2 / Na2O weight ratio: 3.43, density: 1.230 kg / L) was added to the reactor at a flow rate of 352 L / h over 50 minutes, simultaneously with sulfuric acid (concentration: 7.7 wt%). The acid flow rate was adjusted to maintain the pH of the reaction medium at 4.2. The amount of silicate added to the reaction medium was 79% of the total amount.

[0130] After 50 minutes, the introduction of the acid was stopped, and the addition of silicate was continued until the pH reached 8.0. During this time, the temperature rose to 94°C. Subsequently, a further simultaneous addition was carried out for 7 minutes at a flow rate of 577 L / h of sodium silicate (the same sodium silicate as in the initial simultaneous addition), with a flow rate of sulfuric acid (concentration: 7.7 wt%) adjusted to maintain the pH of the reaction medium at 8.0.

[0131] Following this simultaneous addition, sulfuric acid (concentration: 7.7 wt%) was added to adjust the pH of the reaction medium to 4.8, obtaining a suspension of precipitated silica. The suspension was filtered and washed with a filter press to obtain a precipitated silica cake with a solid content of 20.7 wt%. Subsequently, the obtained silica cake was subjected to a liquefaction step in a reactor with continuous and vigorous stirring after adding 1360 grams of sulfuric acid solution (concentration: 7.7 wt%). The resulting slurry was dried using a nozzle-type spray dryer to obtain precipitated silica S1. The properties of precipitated silica S1 are reported in Table 1.

[0132] Example 2 927 liters of industrial water were placed in a 2500-liter reactor and heated to 90°C. 14.7 kg of solid sodium sulfate was introduced into the reactor while stirring, followed by the addition of sulfuric acid (concentration: 96% by weight) until the pH reached 4.1.

[0133] A sodium silicate solution (SiO2 / Na2O weight ratio: 3.43, density: 1.230 kg / L) was added to the reactor at a flow rate of 352 L / h over 50 minutes, simultaneously with sulfuric acid (concentration: 7.7 wt%). The acid flow rate was adjusted to maintain the pH of the reaction medium at 4.1. The amount of silicate added to the reaction medium was 78% of the total amount.

[0134] After 50 minutes, the introduction of the acid was stopped, and the addition of silicates was continued until the pH reached 8.0. During this time, the temperature rose to 94°C. Subsequently, further simultaneous additions were made over 7 minutes at a flow rate of 577 L / h of sodium silicate (the same sodium silicate as in the initial simultaneous addition), and at a flow rate of sulfuric acid (concentration: 7.7 wt%) adjusted to maintain the pH of the reaction medium at 8.0.

[0135] After this second simultaneous addition, sulfuric acid (concentration: 7.7 wt%) was added to adjust the pH of the reaction medium to 4.7, obtaining a suspension of precipitated silica. The suspension was filtered and washed with a filter press to obtain a precipitated silica cake with a solid content of 19.5 wt%. Subsequently, the obtained silica cake was subjected to a liquefaction step in a reactor with continuous and vigorous stirring, with 1751 grams of sodium aluminate solution (Al2O3 content 22.5 wt%) added to the cake. The resulting slurry was dried using a nozzle-type spray dryer to obtain precipitated silica S2. The properties of precipitated silica S2 are reported in Table 1.

[0136] Comparative Example 1 960 liters of water were placed in a 2500-liter reactor and heated to 90°C. 15 kg of solid sodium sulfate was added to the reactor under stirring. Then, sulfuric acid (concentration: 96 wt%) was added until the pH reached 3.7.

[0137] A sodium silicate solution (SiO2 / Na2O weight ratio: 3.41, density: 1.231 kg / L) was added to the reactor at a flow rate of 370 L / h over 25 minutes, simultaneously with sulfuric acid (concentration: 7.7 wt%). The acid flow rate was adjusted to maintain the pH of the reaction medium at 3.7. The amount of silicate added to the reaction medium was less than 50% of the total amount of silicate required for the reaction.

[0138] After 25 minutes of simultaneous addition at 90°C, the introduction of the acid was stopped, and the pH of the reaction medium was brought to 8.0. During this time, the temperature rose to 94°C. Subsequently, a further simultaneous addition was carried out for 18 minutes at a flow rate of 600 L / h of sodium silicate (the same sodium silicate as in the initial simultaneous addition), with a flow rate of sulfuric acid (concentration: 7.7 wt%) adjusted to maintain the pH of the reaction medium at 8.0.

[0139] After this simultaneous addition, the pH of the reaction medium was adjusted to 4.5 by adding sulfuric acid (concentration: 7.7 wt%) to obtain a suspension of precipitated silica. The suspension was filtered and washed with a filter press to obtain a precipitated silica cake with a solid content of 19.2 wt%. The silica cake was simultaneously added to a cake of sulfuric acid (concentration: 7.7 wt%) and sodium aluminate solution (Al / SiO2 ratio: 0.30 wt%) and subjected to a liquefaction process in a reactor that was continuously and vigorously stirred.

[0140] The liquefied cake was then spray-dried using a nozzle atomizer to obtain silica CS1. The properties of silica CS1 are shown in Table 1.

[0141] TIFF0007829620000003.tif36170

[0142] Examples 3-5 - Comparative Example 2 The control composition CE2 contains silica CS1. Compositions E3 to E5 according to the present invention contain silica S1 and S2.

[0143] The compositions were prepared according to the following recipes shown in Table 2 (components are expressed in parts by weight (phr) per 100 parts of elastomer).

[0144] TIFF0007829620000004.tif144170

[0145] Preparation of Rubber Composition: The process for preparing the rubber composition was carried out in three consecutive stages. The first and second mixing stages (non-manufacturing stages, NP1 and NP2) consisted of thermomechanical work at high temperatures, followed by a third mechanical work stage (production stage, P3) at a temperature below 110°C. The latter allowed for the introduction of the vulcanization system. The first and second stages were performed using a Brabender internal mixer (net chamber capacity: 380 mL) with filling ratios of 0.62 and 0.60, respectively. The initial rotor temperature and speed were fixed in each cycle to reach a mixing temperature drop of approximately 140–170°C. The duration of the first mixing stage was 2–10 minutes. After the mixture cooled (to a temperature below 100°C), the second mixing stage allowed for the introduction of the vulcanization system (sulfur and accelerator). This was carried out in an open double-roll mill preheated to 50°C. The duration of this stage was 2–6 minutes. Next, the final rubber composition was calendered into sheets with a thickness of 2-3 mm. The rheological properties of the uncured compound were evaluated first to monitor the processability. After determining the vulcanization properties, the uncured compound was vulcanized at optimal vulcanization (t98), and its mechanical and dynamic properties were measured.

[0146] Viscosity of the uncured composition Mooney viscosity was measured at 100°C using an MV2000 rheometer according to the NF ISO289 standard. After preheating for 1 minute, the torque value was read at 4 minutes (ML(1+4)-100°C). Complementarily, strain sweep measurements of 0.9–50% were performed at 100°C and a frequency of 1 Hz using a D-MDR3000 rheometer according to the DIN 53529 standard. The results obtained by these two methods are shown in Table 3.

[0147] TIFF0007829620000005.tif48170

[0148] As can be seen in Table 3, the uncured compositions according to the present invention exhibit a lower (improved) Payne effect ΔG' (0.9–50%) and a lower (improved) Mooney viscosity ML (1+4) compared to silica CS1 from symmetrical CE2 at equivalent CTAB values. Uncured composition E4 exhibits an equivalent Payne effect value ΔG' (0.9–50%), reflecting the equivalent processability of the uncured compound, although it has a slightly higher Mooney viscosity value due to the larger CTAB surface area of ​​silica S2. It can be concluded that the processability of the unvulcanized rubber mixtures containing silica according to the present invention is equivalent to that shown by compositions containing larger surface area silica from the prior art having the same CTAB surface area.

[0149] Mechanical properties of the cured composition The Shore A hardness of the cured composition was measured according to the ASTM D2240 standard (vulcanization time t98 at 170°C). The value was measured after 3 seconds.

[0150] Uniaxial tensile tests were performed using an INSTRON5564 at a speed of 500 mm / min with H2 specimens, according to the NF ISO37 standard. The modulus of elasticity M100 and M300 (obtained at 100% and 300% strain, respectively) and tensile strength are expressed in MPa, and the elongation at fracture is expressed in %. The reinforcing index (RI), defined as the ratio between the modulus of elasticity obtained at 300% strain and the modulus of elasticity obtained at 100% strain, was calculated. The measured properties are summarized in Table 4.

[0151] TIFF0007829620000006.tif62170

[0152] The results in Table 4 show that using silica S1 and S2 at the same addition amounts as silica CS1 yields a compound with a lower Shore A hardness, a higher modulus of elasticity M300, and a higher strengthening index RI than composition CE2.

[0153] Increasing the amount of S1 (composition E5) added to achieve the same Shore A hardness as composition CE2 yielded the same results regarding the improved strengthening potential of the silica of the present invention.

[0154] Dynamic properties of cured composition Dynamic properties were measured using a viscometer (Metravib DMA+1000) according to ASTM D5992.

[0155] Dynamic response of cured compound under strain sweep conditions

[0156] Parallelepiped test specimen (8mm cross-section) 2 The sample (7 mm in height) was subjected to sinusoidal deformation by alternating biplane shear at a temperature of 40°C and a frequency of 10 Hz, with the forward cycle ranging from 0.1% to 50% and the return cycle ranging from 50% to 0.1%. The values ​​for maximum dielectric loss (tan δmax), shear storage modulus (G'0.1%, G'12%), and Payne effect (G'0.1% to G'50%) were recorded during the return cycle. These results are shown in Table 5.

[0157] TIFF0007829620000007.tif57170

[0158] The compositions E3 and E4 of the present invention exhibit a lower tanδ max value and a lower Pain effect (G') compared to composition CE2. 0,1% ~G' 50% Based on this, it exhibits dramatically improved hysteresis properties at high temperatures (40°C). Despite the higher silica S1 content in composition E5, the tanδ max value remains significantly lower than that of the prior art composition CE2. These indicators support the excellent potential of compositions E3-E5 to improve rolling resistance without compromising tire tread composition, particularly tire handling (steering) performance (G*12%).

[0159] Dynamic response of cured compound under temperature sweep conditions The dynamic response of the vulcanized rubber composition was measured on a parallelepiped specimen (cross-sectional area 8 mm²) under a temperature sweep from -45°C to +45°C (temperature rise rate of +5°C / min) at a frequency of 10 Hz and under 1% alternating biplane shear sinusoidal deformation. 2The measurement is performed by determining the height (7 mm). Then, the maximum loss coefficient (tanδ max) is observed. The results are summarized in Table 6.

[0160] TIFF0007829620000008.tif40170

[0161] The compositions E3 and E4 of the present invention exhibit dramatically improved hysteresis properties at low temperatures, with a significantly increased maximum loss factor (tanδ max) compared to composition CE2. Despite the larger amount of silica S1 added in composition E5, the tanδ max value is improved compared to the prior art composition CE2.

[0162] The investigation of the properties described above demonstrates that the silica S1 and S2-containing compositions of the present invention have excellent potential in tire tread compositions, particularly in significantly improving rolling resistance and wet grip at an equivalent level of tire handling, and without degrading the performance of wear performance and processability.

Claims

1. - 160m ２ CTAB surface area S of 1 / g or more ＣＴＡＢ ; - Particle size distribution width Ld of 1.2 to 4.0 as measured by centrifugal sedimentation; - Measured by centrifugal sedimentation |d50|>25000 / |S ＣＴＡＢ |(I) A median particle size d50, where d50 does not exceed 250 nm. (In the formula, |d50| represents the median particle size d50, measured by centrifugal sedimentation and expressed in nm, |S ＣＴＡＢ | is m ２ CTAB surface area S expressed in units of / g ＣＴＡＢ (represents the numerical value of); and - Aluminum content not exceeding 4500 ppm; Precipitated silica characterized by...

2. The CTAB surface area S ＣＴＡＢ 180-400m ２ The precipitated silica according to claim 1, wherein the value is in the range of / g.

3. The settled silica according to claim 1 or 2, wherein the particle size distribution width Ld measured by centrifugal sedimentation is 1.2 to 3.

5.

4. The settled silica according to claim 3, wherein the particle size distribution width Ld measured by centrifugal sedimentation is 1.4 to 3.

0.

5. The settled silica according to claim 1, wherein the particle size distribution width Ld measured by centrifugal sedimentation is 1.5 to 4.

0.

6. The settled silica according to claim 5, wherein the particle size distribution width Ld measured by centrifugal sedimentation is 1.5 to 2.

8.

7. BET specific surface area S ＢＥＴ is 170 m ２ / g or more, the precipitated silica according to any one of claims 1 to 6.

8. BET surface area S ＢＥＴ and the CTAB surface area S ＣＴＡＢ The difference between the two is at least 30m ２ Precipitated silica according to any one of claims 1 to 7, wherein the amount is / g.

9. - The CTAB surface area S ＣＴＡＢ However, 200-350m ２ It is within the range of / g, - The particle size distribution width Ld measured by centrifugal sedimentation is in the range of 1.5 to 2.

8. - The median particle size d50 measured by centrifugal sedimentation is |d50|>25000 / |S ＣＴＡＢ |(I) It does not exceed 250 nm, and - The precipitated silica according to any one of claims 1 to 8, wherein the aluminum content does not exceed 4,500 ppm.

10. The CTAB surface area S ＣＴＡＢ 220-330m ２ Precipitated silica according to any one of claims 1 to 9, wherein the amount is in the range of / g.

11. The precipitated silica according to any one of claims 1 to 10, wherein the aluminum content is less than 3,500 ppm.

12. A composition comprising precipitated silica according to any one of claims 1 to 11 and at least one polymer.

13. The composition according to claim 12, wherein the polymer is an elastomer.

14. The composition according to claim 13, wherein the elastomer is a diene elastomer.

15. An article comprising precipitated silica according to any one of claims 1 to 11 or a composition according to any one of claims 12 to 14.

16. The article according to claim 15, in the form of a tire or a tire component.

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