Modified precipitated silica, its production and use

Abstract

The present invention relates to a modified precipitated silica (MPS) comprising precipitated silica particles, polyethylene glycol, and an antioxidant selected from certain hydroxyfuranone or phenol derivatives. The invention also relates to a method for producing the MPS, an elastomeric composition comprising the MPS, and its use for the production of semi-finished or finished products, such as tire components.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from European Patent Application Publication No. 22207337.1, filed on 14 / 11 / 2022, the entire contents of which are incorporated herein by reference for all purposes.

[0002] The present invention relates to modified precipitated silica, a method for preparing the same, and the use of the same in polymer compositions suitable for the manufacture of tire components. [Background technology]

[0003] Precipitated silica has long been used as a reinforcing filler in polymeric materials, especially elastomers. In the latter, it is known to use polyethylene glycol polymer (CAS No. 25322-68-3) to block the silica surface to prevent the adsorption of pre-reticulation components. However, mixing polyethylene glycol with silica and other components of the formulation is not practical, and this is also true when silica is used in other polymer compositions, such as paints and lacquers.

[0004] Canadian Patent No. 2,255,456 aims to solve this problem by providing a precipitated silica coated with polyethylene glycol. In Example 8, polyethylene glycol having a molecular weight of 1,000 is added to a liquefied silica filter cake. The applicant has observed that modified precipitated silicas such as those in Canadian Patent No. 2,255,456 exhibit improved dispersion in elastomer matrices, possibly resulting in an overall improved balance of mechanical properties. In particular, the applicant has found that tire rubber compositions filled with this precipitated silica achieve a better balance between abrasion resistance and rolling resistance. Unfortunately, as the applicant has also observed, such polyethylene glycol-modified precipitated silicas and rubber compositions formulated therewith suffer from poor thermal stability. Summary of the Invention [Problem to be solved by the invention]

[0005] There is a need for modified precipitated silicas that have significantly higher thermal stability than polyethylene glycol-modified silicas such as those of Canadian Patent No. 2,255,456, and desirably have thermal stability as close as possible to that of unmodified precipitated silica, while maintaining excellent dispersibility in an elastomeric matrix and still allowing the preparation of elastomeric compositions with an excellent balance of mechanical properties like the polyethylene glycol-modified silicas of Canadian Patent No. 2,255,456. In particular, there is a need for modified precipitated silicas that, when included in tire rubber compositions, provide said tire rubber compositions with a better balance between abrasion resistance and rolling resistance than that obtained with unmodified precipitated silica, while maintaining significantly higher thermal stability than that obtained with polyethylene glycol-modified precipitated silicas. [Means for solving the problem]

[0006] These and other requirements are met by the modified precipitated silica according to the present invention, i.e. - at least 70% by weight of precipitated silica particles, based on the total weight of the MPS; - at least 1.0% by weight, based on the total weight of the MPS, of at least one polyethylene glycol; - at least 0.0010% by weight, based on the total weight of the MPS, of at least one antioxidant; A modified precipitated silica (MPS) comprising: (i) Dehydroascorbic acid and its hydrate, hydroxyfuranone derivatives of formula (I) and hydroxyfuranone derivatives of formula (II) [ka] (In the formula, -R 7 is hydrogen or C1-C4 alkyl, -R 8 is selected from the group consisting of hydroxy, C1-C4 alkyl, C1-C4 alkoxy, C2-C4 alkenyl, and C2-C4 alkenyloxy; -R 9 is hydrogen, C1-C4 alkyl, C1-C4 hydroxyalkyl, C1-C4 dihydroxyalkyl, [ka] and [ka] and R c and R d are each independently selected from the group consisting of hydrogen and C1-C4 alkyl, and -R 10 is hydrogen or C1-C4 alkyl) and / or at least one hydroxyfuranone derivative selected from the group consisting of (ii) Formula (III) [ka] (In the formula, -R1 , R 3 and R 5 are each independently hydrogen or C1-C4 alkyl, -R 2 is hydroxy, C1-C4 alkyl, C1-C4 alkoxy, C1-C4 hydroxyalkyl, C2-C4 alkenyl, C2-C4 alkenyloxy, C2-C4 hydroxyalkenyl, -C(=O)H, -COOH, -COOMe (wherein Me is an alkali metal, in particular Na or K), -COOR f (where R f is C1-C4 alkanediyl or C2-C4 alkenediyl), -R f -COOH (where R f is C1-C4 alkanediyl or C2-C4 alkenediyl) and -R f -COOMe (where R f is C1-C4 alkanediyl or C2-C4 alkenediyl, and Me is an alkali metal, in particular Na or K; -R 4 is hydrogen, hydroxy, C1-C4 alkyl, C1-C4 alkoxy, C1-C4 hydroxyalkyl, C2-C4 alkenyl, C2-C4 alkenyloxy, C2-C4 hydroxyalkenyl, -C(=O)H, -COOH, -COOMe (wherein Me is an alkali metal, in particular Na or K), -COOR f (where R f is C1-C4 alkanediyl or C2-C4 alkenediyl), -R f -COOH (where R f is C1-C4 alkanediyl or C2-C4 alkenediyl), -R f -COOMe (where R f is selected from the group consisting of C1-C4 alkanediyl or C2-C4 alkenediyl, and Me is an alkali metal, in particular Na or K) and —SO3Me (wherein Me is an alkali metal, in particular Na or K); -R 6is hydrogen, hydroxy, C1-C4 alkyl, C1-C4 alkoxy, C1-C4 hydroxyalkyl, C2-C4 alkenyl, and -SO3Me (where Me is an alkali metal, in particular Na or K) Phenol derivatives of The filler is filled with modified precipitated silica (MPS). DETAILED DESCRIPTION OF THE INVENTION

[0007] The term "precipitated silica particles" is used herein to refer to synthetic amorphous silica (silicon dioxide, SiO2) particles obtained by the process of reacting silicate with acid to precipitate SiO2.

[0008] For the avoidance of doubt, the weight of precipitated silica particles contained in the MPS provided herein does not include the weight of by-products and other impurities that may result from the precipitation process to form said precipitated silica particles. In other words, the weight of precipitated silica particles represents the weight of silica and the weight of silica only.

[0009] The precipitated silica particles are preferably present in the MPS in an amount of at least 75% by weight, more preferably at least 80% by weight, and even more preferably at least 82% by weight, based on the total weight of the MPS, and typically in an amount of up to 95% by weight, preferably up to 90% by weight, and more preferably up to 88% by weight, based on the total weight of the MPS.

[0010] MPS can be characterized by a CTAB surface area and a BET surface area, which typically reflect the CTAB surface area and BET surface area, respectively, of the precipitated silica particles contained in the MPS, since the MPS typically does not contain any particles other than precipitated silica particles.

[0011] CTAB surface area is a measure of the external specific surface area of ​​precipitated silica particles, determined by measuring the amount of N-hexadecyl-N,N,N-trimethylammonium bromide adsorbed onto the silica surface at a given pH. CTAB surface area can be determined according to standard NF ISO 5794-1, Appendix G (June 2010). The CTAB surface area of ​​MPS and the CTAB surface area of ​​precipitated silica particles are typically between 50 and 350 m. 2 / g, in most cases 70-300m 2 / g, often 100-250m 2 / g range. In some cases, these are 2 / g or more 200m 2 / g, and in other cases 200-250m 2 / g range.

[0012] The BET surface area of ​​MPS and the BET surface area of ​​precipitated silica particles are typically between 40 and 450 m 2 / g, in most cases 60-350m 2 / g, often 80-300m 2 / g range. In some cases, these are 2 / g or more 150m 2 / g or less, 150m 2 / g or more 200m 2 / g or less, 200m 2 / g or more 250m 2 / g or less than 250m 2 / g or more 300m 2 / g. The BET surface area is determined according to the Brunauer-Emmett-Teller method described in The Journal of the American Chemical Society, Vol. 60, page 309, February 1938, and corresponds to standard NF ISO 5794-1, Appendix D (June 2010).

[0013] Polyethylene glycol is preferably contained in the MPS in an amount of at least 2.0 wt.%, more preferably at least 4.0 wt.%, and even more preferably at least 6.0 wt.%, based on the total weight of the MPS, and is typically contained in the MPS in an amount of up to 20 wt.%, preferably up to 15 wt.%, and even more preferably up to 10 wt.%, based on the total weight of the MPS.

[0014] Similarly, the weight of polyethylene glycol may be expressed relative to the weight of the precipitated silica particles. The weight of polyethylene glycol based on the weight of the precipitated silica particles is advantageously in the range of 1.0% to 20% by weight. Preferably, it is at least 2.0% by weight, more preferably at least 4.0% by weight, and even more preferably at least 6.0% by weight, based on the weight of the precipitated silica particles. Furthermore, it is preferably at most 15% by weight, more preferably at most 10% by weight, based on the weight of the precipitated silica particles.

[0015] Advantageously, at least a portion, preferably more than half, and more preferably substantially all, of the weight of polyethylene glycol contained in the MPS forms a coating on and / or is adsorbed onto the surface of the precipitated silica particles.

[0016] In some embodiments, it may be useful to express the weight of polyethylene glycol relative to the CTAB surface area of ​​the MPS or precipitated silica particles. The weight of polyethylene glycol based on the CTAB surface area of ​​the MPS or precipitated silica particles is advantageously between 0.030 and 5.0 mg / m 2 Preferably, this is at least 0.075 mg / m based on the CTAB surface area of ​​the MPS or precipitated silica particles. 2 , more preferably at least 0.15 mg / m 2 , more preferably at least 0.30 mg / m 2 Further, preferably, this is up to 3.0 mg / m based on the CTAB surface area of ​​the MPS or precipitated silica particles. 2 , more preferably up to 1.5 mg / m 2 , more preferably up to 0.70 mg / m2 0.20 to 1.00 mg / m based on the CTAB surface area of ​​the MPS or precipitated silica particles. 2 , especially 0.30 to 0.70 mg / m 2 Good results have been obtained with polyethylene glycol weights in the range of 1000 ppm.

[0017] The weight-average molecular weight Mw of polyethylene glycol, measured by gel permeation chromatography (GPC) / size exclusion chromatography (SEC) using polystyrene calibration standards, is usually in the range of 100 to 10,000 g / mol. Preferably, it is at least 200 g / mol, more preferably at least 300 g / mol, and even more preferably at least 400 g / mol. Furthermore, it is preferably at most 5,000 g / mol, more preferably at most 2,000 g / mol, even more preferably at most 1,000 g / mol, and even more preferably at most 800 g / mol. Good results have been obtained with polyethylene glycols having weight-average molecular weights Mw in the range of 400 to 800 g / mol, especially 500 to 700 g / mol.

[0018] The melting point of polyethylene glycol depends to a large extent on the molecular weight. It is usually in the range of -60°C to +60°C. Preferably, it is higher than 0°C, more preferably at least 10°C, even more preferably at least 15°C. Furthermore, it is preferably at most 50°C, more preferably at most 40°C, even more preferably at most 30°C. Good results have been obtained with polyethylene glycols having melting points between 15°C and 30°C, especially between 20°C and 25°C.

[0019] An exemplary polyethylene glycol according to the present invention is PEG400 (where PEG stands for "polyethylene glycol" and M w M is about 400, and usually has a melting point of 2 to 10°C, often 4 to 8°C), PEG600 (where M wis about 600 and usually has a melting point of 17 to 25°C, often 19 to 24°C), PEG 1000 (usually has a melting point of 32 to 40°C), and PEG 1500 (usually has a melting point of 42 to 50°C, often 44 to 48°C).

[0020] The antioxidant is preferably present in the MPS in an amount of at least 0.0030 wt.%, more preferably at least 0.010 wt.%, even more preferably at least 0.030 wt.%, and even more preferably at least 0.050 wt.%, based on the total weight of the MPS, and is typically present in the MPS in an amount of up to 3.0 wt.%, preferably up to 1.0 wt.%, more preferably up to 0.30 wt.%, and even more preferably up to 0.10 wt.%, based on the total weight of the MPS.

[0021] Advantageously, at least a portion, preferably more than half, and even more preferably essentially the entire amount by weight of the antioxidant contained in the MPS is uniformly dispersed, or at least substantially uniformly dispersed, in the coating formed by the polyethylene glycol on the surface of the precipitated silica particles and / or throughout the polyethylene glycol adsorbed on the surface of said precipitated silica particles.

[0022] In some embodiments, it may be useful to express the weight of antioxidant relative to the weight of polyethylene glycol. The weight of antioxidant typically ranges from 0.10% to 10.0% by weight, based on the weight of polyethylene glycol. It is preferably at least 0.25%, more preferably at least 0.50%, and even more preferably at least 0.75% by weight. Furthermore, it is preferably at most 5.0%, more preferably at most 2.5%, and even more preferably at most 1.5% by weight. Good results have been obtained with a weight of antioxidant in the range of 0.75% to 1.5% by weight, based on the weight of polyethylene glycol.

[0023] In many embodiments, the antioxidant is a solid at standard ambient temperature and pressure conditions (25° C.=298.15 K, 1 atm=101.325 kPa, hereafter "SATP").

[0024] In some embodiments, the antioxidant is s It is solid at atmospheric pressure (1 atm = 101.325 kPa), and T s is equal to the melting point of polyethylene glycol plus 30° C. In these embodiments, the weight of antioxidant based on the weight of polyethylene glycol is s The weight of the antioxidant based on the weight of polyethylene glycol and the solubility limit of the antioxidant in polyethylene glycol are advantageously less than the solubility limit of the antioxidant in polyethylene glycol measured at atmospheric pressure and at room temperature. The weight of the antioxidant based on the weight of polyethylene glycol and the solubility limit of the antioxidant in polyethylene glycol are expressed in the same units, for example, weight % (grams of antioxidant per 100 grams of polyethylene glycol). The solubility limit of the antioxidant can be determined by adding a certain amount of antioxidant to polyethylene glycol with stirring, waiting a sufficient time until a homogeneous solution is obtained, and repeating the same procedure until a homogeneous solution is no longer obtained at equilibrium (because the antioxidant can no longer dissolve in polyethylene glycol). The solubility limit can be determined visually and / or using a turbidity meter, ultraviolet-visible spectrophotometer, dynamic light scattering device, etc. The weight of the antioxidant based on the weight of polyethylene glycol is determined at a temperature T s It can also be at least 2 times, at least 5 times, at least 10 times, at least 20 times, at least 50 times, or at least 100 times lower than the solubility limit of the antioxidant in polyethylene glycol measured at atmospheric pressure.

[0025] In some further embodiments, the antioxidant is added at a temperature T s It is liquid at atmospheric pressure (1 atmosphere = 101.325 kPa), and T s is equal to the melting point of polyethylene glycol plus 30° C. In these embodiments, the weight of antioxidant and the weight of polyethylene glycol contained in the MPS are determined at a temperature T sand atmospheric pressure, the antioxidant and polyethylene glycol are such that when combined by weight to form a binary liquid mixture of the antioxidant and polyethylene glycol, the resulting binary liquid mixture is a homogeneous solution (in other words, a one-phase binary mixture in which the antioxidant and polyethylene glycol are miscible with each other). In these embodiments, the antioxidant preferably has a temperature T s and is completely miscible (i.e., in any proportion) with polyethylene glycol at atmospheric pressure, or it is s and is only partially miscible with polyethylene glycol at atmospheric pressure, but up to at least 2 times, preferably at least 5 times, at least 10 times, at least 20 times, at least 50 times, or even at least 100 times greater by weight of antioxidant, based on the weight of polyethylene glycol contained in the MPS. The miscibility of a liquid antioxidant in polyethylene glycol can similarly be evaluated by adding a quantity of antioxidant to polyethylene glycol with stirring, waiting a sufficient time for a homogeneous solution to be obtained, and repeating this until a homogeneous solution is no longer obtained at equilibrium (because the antioxidant and polyethylene glycol are a two-phase liquid binary mixture).

[0026] In a first embodiment, the antioxidant is a hydroxyfuranone derivative as detailed above.

[0027] The hydroxyfuranone derivative has the formula (IV): [ka] The hydrate of dehydroascorbic acid may be dehydroascorbic acid or a hydrate thereof represented by the formula (IVa) and (IVb): [ka] is a compound of

[0028] The hydroxyfuranone derivative may be of formula (I):

[0029] In formula (I), R 7 is preferably hydrogen or methyl, more preferably R 7 is hydrogen.

[0030] Furthermore, in formula (I), R 8 is preferably selected from the group consisting of hydroxy, C1-C4 alkoxy and C2-C4 alkenyloxy (e.g., allyloxy), more preferably R 8 is hydroxy or methoxy, more preferably R 8 is hydroxy.

[0031] Furthermore, in formula (I), R 9 is preferably C1-C4 alkyl, C1-C4 dihydroxyalkyl, [ka] and [ka] (In the formula, R c and R d are each independently selected from the group consisting of hydrogen and C1-C4 alkyl, preferably R c and R d At least one, more preferably both, of R is C1-C4 alkyl, particularly methyl, and even more preferably R 9 is -CHOH-CHOH) is selected from the group consisting of:

[0032] Non-limiting examples of hydroxyfuranone derivatives of formula (I) are: - Formula (Va) [ka] 5-ethyl 3-hydroxy 4-methyl 2(5H)-furanone, commonly known as maple furanone or ethyl fenugreek lactone, - Formula (Vb) [ka] L-ascorbic acid, also known as ascorbic acid (IUPAC name: L-threo-hex-2-enono-1,4-lactone or (R)-3,4-dihydroxy-5-((S)-1,2-dihydroxyethyl)furan-2(5H)-one, CAS Registry Number (registered trademark) 50-81-7), - Formula (Vc) [ka] D-ascorbic acid (IUPAC name: D-threo-hex-2-enono-1,4-lactone, CAS registration number (registered trademark) 10504-35-5), - Formula (Vd) [ka] L-isoascorbic acid (IUPAC name: L-erythro-hex-2-enono-1,4-lactone, CAS registration number (registered trademark) 26094-91-7), - Formula (Ve) [ka] D-erythorbic acid, also known as erythorbic acid or D-isoascorbic acid (IUPAC name: (5R)-5-[(1R)-1,2-dihydroxyethyl]-3,4-dihydroxyfuran-2(5H)-one or D-erythro-hex-2-enono-1,4-lactone, CAS Registry Number 89-65-6), and A mixture of these is.

[0033] Further examples of hydroxyfuranone derivatives of formula (I) are 5,6-O-isopropylidene-3-O-methyl-L-ascorbic acid, 5,6-O-isopropylidene-3-O-allyl-L-ascorbic acid, 3-O-methyl-L-ascorbic acid, 3-O-allyl-L-ascorbic acid, etc.

[0034] The hydroxyfuranone derivative may be of formula (II):

[0035] In formula (II), R 7 is preferably hydrogen or methyl, more preferably R 7 is hydrogen.

[0036] Furthermore, in formula (II), R 8 is preferably C1 to C4 alkyl or C2 to C4 alkenyl, more preferably C1 to C4 alkyl, and even more preferably methyl.

[0037] Furthermore, in formula (II), R 10 is hydrogen or methyl.

[0038] Non-limiting examples of hydroxyfuranone derivatives of formula (II) are 4-hydroxy-5-methyl-3-furanone and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (commonly known as strawberry furanone or furaneol).

[0039] Among all the hydroxyfuranone derivatives according to the invention, those according to formula (I) are generally preferred, with particularly good results being obtained when L-ascorbic acid and / or D-erythorbic acid are used as antioxidants, with D-erythorbic acid being more preferred.

[0040] In another first embodiment, the antioxidant is a phenol derivative of formula (III) as detailed above.

[0041] In formula (III), R 1 is preferably hydrogen or methyl, more preferably R 1 is hydrogen.

[0042] Furthermore, in formula (III), R 2 is preferably hydroxy, C1-C4 alkyl, C1-C4 alkoxy, —C(═O)H, —COOH and —R f -COOH (where R fis C1-C4 alkanediyl or C2-C4 alkenediyl), more preferably R 2 is selected from the group consisting of hydroxy, C1-C4 alkyl, methoxy, -COOH and -CH=CH-COOH, more preferably R 2 is selected from the group consisting of hydroxy, methoxy and tertbutyl, most preferably R 2 is hydroxy.

[0043] Furthermore, in formula (III), R 3 is preferably hydrogen or methyl, more preferably R 3 is hydrogen.

[0044] Furthermore, in formula (III), R 4 is preferably hydrogen, hydroxy, C1-C4 alkyl, C1-C4 alkoxy, C1-C4 hydroxyalkyl, C2-C4 alkenyl, —C(═O)H, —COOH, —R f -COOH (where R f is selected from the group consisting of C1-C4 alkanediyl or C2-C4 alkenediyl) and —SO3Me (wherein Me is an alkali metal), more preferably R 4 is selected from the group consisting of hydrogen, hydroxy, methyl, methoxy, —CHOH, —C(═O)H, —COOH, —CH—COOH, and —SONa, more preferably, R 4 is selected from the group consisting of hydrogen, hydroxy, methoxy and -COOH, most preferably R 4 is -COOH.

[0045] Furthermore, in formula (III), R 5 is preferably hydrogen or methyl, more preferably R 5 is hydrogen.

[0046] Furthermore, in formula (III), R 6is preferably selected from the group consisting of hydrogen, hydroxy, C1-C4 alkoxy and -SO3Me (wherein Me is an alkali metal), more preferably R 6 is selected from the group consisting of hydrogen, hydroxy, methoxy and -SO3Na, more preferably R 6 is hydroxy.

[0047] Non-limiting examples of phenol derivatives of formula (III) include 2-tert-butyl-4-hydroxyanisole, 3-tert-butyl-4-hydroxyanisole, protocatechuyl alcohol, hydroxytyrosol, dihydrocaffeoyl alcohol, caffeoyl alcohol, vanillyl alcohol, homovanillyl alcohol, dihydroconiferyl alcohol, coniferyl alcohol, veratryl alcohol, homoveratryl alcohol, 3-(3,4-dimethoxyphenyl)-1-propanol, catechol, galloyl alcohol, 5-methoxy-protocatechuyl alcohol, syringyl alcohol, p-coumaric acid, ferulic acid, sinapic acid, caffeic acid, o-coumaric acid, pyrogallol, veratrol, guaiacol, 4-methylcatechol, salicylic acid, gallic acid, tiron, protocatechuic acid, protocatechualdehyde, hydroxychavicol, eugenol, chabibetol, catechol, 4-tert-butylcatechol, 4-allylcatechol, 3-allylcatechol, and mixtures thereof.

[0048] Suitable mixtures of phenol derivatives of formula (III) are commonly referred to as butylated hydroxyanisole, which are mixtures consisting essentially of or consisting of 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole, and usually contain more than 50% by weight, most often at least 80% by weight, and often at least 90% by weight, of 3-tert-butyl-4-hydroxyanisole, based on the total weight of butylated hydroxyanisole.

[0049] R 1 is hydrogen and R 2is C1-C4 alkyl (especially tert-butyl) or hydroxy, and R 3 is hydrogen and R 4 is hydrogen or C1-C4 alkoxy (especially methoxy), and R 5 is hydrogen and R 6 Good results have been obtained with phenol derivatives according to formula (III) where is hydrogen. Excellent results have been obtained with 3-tert-butyl-4-hydroxyanisole (which may be found in butylated hydroxyanisole) and gallic acid, of which gallic acid is more preferred.

[0050] The MPS may further comprise additional components.

[0051] The MPS may further comprise water (moisture). As known to those skilled in the art, water (moisture) is a normal component of any unmodified precipitated silica. Water (moisture) is typically present in the MPS in the same or substantially the same amount as that found in unmodified precipitated silica containing the same or substantially the same precipitated silica particles.

[0052] Water (moisture content) is typically contained in the MPS in an amount of 1.0 wt % to 20 wt %, in most cases 3.0 wt % to 15 wt %, often 5.0 wt % to 10.0 wt %, and particularly 7.0 wt % to 8.0 wt %, based on the total weight of the MPS.

[0053] MPS may further contain an alkali metal salt. As mentioned above, precipitated silica particles are usually obtained by a process of reacting a silicate with an acid. The silicate is usually an alkali metal silicate, often sodium silicate, while the acid is often sulfuric acid. Therefore, alkali metal salts, often sodium salts, especially sodium sulfate, are inevitably produced together with the precipitated silica particles, and residual amounts thereof are found in MPS.

[0054] The alkali metal salt is usually contained in the MPS in an amount of 0.10 to 5.0% by weight, in most cases 0.30 to 3.0% by weight, often 0.50 to 2.0% by weight, and particularly 1.0 to 1.5 or 1.0 to 2.0% by weight.

[0055] Other components are believed to be largely absent in MPS, but may be present as trace impurities. In other words, MPS can consist essentially of or can further consist of precipitated silica particles, polyethylene glycol, antioxidants, water (moisture), and alkali metal salts.

[0056] Alternatively, the MPS may further comprise additional components such as, for example, polypropylene glycol, monocarboxylic acids such as stearic acid, or dicarboxylic acids such as 2-methylglutaric acid. These additional components, when present, are typically contained in the MPS in a total amount of up to 10% by weight, preferably up to 5.0% by weight, and sometimes up to 2.0% by weight or up to 1.0% by weight, based on the total weight of the MPS. Furthermore, these additional components, when present, are typically contained in the MPS in an amount less by weight than polyethylene glycol, typically at least two times less by weight than polyethylene glycol.

[0057] The present invention relates to a method for preparing the above-mentioned modified precipitated silica (MPS), comprising the steps of: - reacting at least one silicate with at least one acid in an aqueous medium to provide a first precipitated silica suspension; - subjecting said first precipitated silica suspension to a liquid / solid separation step to obtain a cake; - subjecting said cake to a liquefaction step to obtain a second precipitated silica suspension; - subjecting said second precipitated silica suspension to a drying step to recover precipitated silica particles. wherein the polyethylene glycol and the antioxidant are added, independently of one another, simultaneously or sequentially to at least one of (i) the cake before and / or during the liquefaction step, and (ii) the second precipitated silica suspension after the liquefaction step but before the drying step; and / or The method also relates to a process wherein after the drying step, the precipitated silica particles are simultaneously or sequentially impregnated with polyethylene glycol and an antioxidant.

[0058] The silicate is typically an alkali metal silicate, preferably sodium and / or potassium silicate, more preferably sodium silicate. The silicate may be in any known form, such as metasilicate and / or disilicate. When sodium silicate is used, the latter typically has a SiO / NaO weight ratio of 2.0 to 4.0, particularly 2.4 to 3.9, for example 3.1 to 3.8.

[0059] The silicate is typically supplied as a solution having a concentration of 3.9% to 25% by weight, for example 5.6% to 23% by weight, especially 5.6% to 20.7% by weight. Throughout this specification, silicate concentrations in solution are expressed in terms of the weight of SiO.

[0060] Any acid can be used in this method. Inorganic acids such as sulfuric acid, nitric acid, or hydrochloric acid can be used. Organic acids such as acetic acid, formic acid, or carbonic acid can also be used. Sulfuric acid is preferred.

[0061] The acid may be metered into the reaction medium in diluted or concentrated form. Different concentrations of the same acid may be used in different stages of the process.

[0062] In a preferred embodiment of the method, sulfuric acid and sodium silicate are used.

[0063] For the precipitation of silica, several methods can be adopted: in particular, the acid can be added to a solution of silicate, and / or the acid and silicate can be added simultaneously to water or a silicate solution already present in a container.

[0064] At the end of the precipitation reaction, a suspension is obtained comprising precipitated silica particles suspended in an aqueous medium (herein "first precipitated silica suspension").

[0065] The precipitated silica particles are then separated from the aqueous medium (liquid / solid separation step). Advantageously, the separation step is carried out by filtering the first precipitated silica suspension on a filter, optionally followed by washing the precipitated silica particles retained on the filter. Filtration can be carried out by any suitable device, such as a belt filter, a rotary filter (e.g., a vacuum filter), or preferably a filter press. The solid mass recovered after the liquid / solid separation step is generally called a "cake," and in particular, when the liquid / solid separation step is carried out by filtering the first precipitated silica suspension through a filter, the solid mass retained on the filter after the aqueous medium containing it has passed through is called a "filter cake."

[0066] The cake, particularly the filter cake, is then subjected to a liquefaction step. The term "liquefaction" is intended herein to refer to the overall operation or process of converting a solid, i.e., cake, into a fluid-like mass. After the liquefaction step, the cake is in a flowable, fluid-like form and constitutes another new suspension (herein "second precipitated silica suspension") comprising precipitated silica particles suspended in an aqueous medium.

[0067] The liquefaction step advantageously includes a mechanical treatment that narrows the particle size distribution of the precipitated silica particles in the suspension. In other words, the precipitated silica particles contained in the second precipitated silica suspension after the liquefaction step advantageously have an average particle size significantly smaller than the number average particle size of the precipitated silica particles contained in the first precipitated silica suspension. The mechanical treatment can be carried out by passing the cake, especially the filter cake, through a high-shear mixer, colloid mill, or ball mill. Alternatively or complementary, the liquefaction step can be carried out by subjecting the cake, especially the filter cake, to chemical action, for example by adding water and / or an acid, such as sulfuric acid.

[0068] The second precipitated silica suspension is then dried to recover the precipitated silica particles contained therein. Drying can be carried out by any means known in the art. Preferably, drying is carried out by atomizing (spray drying) the second precipitated silica suspension. For this purpose, any type of suitable atomizer can be used, in particular a turbine, nozzle, liquid pressure or two-fluid spray dryer.

[0069] When the drying operation is carried out using a nozzle spray dryer, the precipitated silica particles recovered from the second precipitated silica suspension are typically in the form of substantially spherical beads (commonly called "micropearls").

[0070] After drying, the recovered precipitated silica particles may be subjected to an additional step of grinding or micronization, and the precipitated silica particles resulting from this optional additional step are then typically in the form of a powder.

[0071] Finally, the dried and optionally ground or micronized precipitated silica particles may be further subjected to an agglomeration step, which may consist of direct compression, wet granulation (i.e., using a binder such as water, a silica suspension, etc.), extrusion or, preferably, a dry compaction operation. The precipitated silica particles obtained from this optional additional agglomeration step are usually in the form of granules.

[0072] Notable non-limiting examples of suitable methods for preparing precipitated silica particles are disclosed, for example, in EP 396450A, EP 520862A, EP 647591A, EP 670813A, EP 670814A, EP 901986A, EP 762992A, EP 762993A, EP 917519A, EP 983966A, EP 1355856A, WO 03 / 016215, WO 2009 / 112458, WO 2011 / 117400.

[0073] Compared to these methods of the prior art, the method of the present invention is characterized by the following: - polyethylene glycol and antioxidant are added independently of each other simultaneously or successively to at least one of (i) the cake before and / or during the liquefaction step, and (ii) the second precipitated silica suspension after the liquefaction step but before the drying step, and / or After the drying step, the precipitated silica particles are simultaneously or successively impregnated with polyethylene glycol and an antioxidant.

[0074] If the antioxidant is a solid, a suitable vehicle can be used to facilitate incorporation of the antioxidant into the cake, the second precipitated silica suspension and / or the dried precipitated silica particles, as the case may be. For example, an organic solvent such as an alcohol or a ketone can function as the vehicle.

[0075] Preferably, the polyethylene glycol and antioxidant are simultaneously added to or simultaneously impregnated into the cake, the second precipitated silica suspension and / or the dried precipitated silica particles, as the case may be.

[0076] More preferably, the polyethylene glycol and antioxidant are simultaneously added to or simultaneously impregnated into the cake, the second precipitated silica suspension and / or the dried precipitated silica particles, as the case may be, in the form of a single solution (preferably a single homogeneous solution) comprising the polyethylene glycol and the antioxidant, which solution may optionally contain water and / or an organic solvent, such as an alcohol.

[0077] More preferably, the polyethylene glycol and antioxidant are simultaneously added to or simultaneously impregnated into the cake, the second precipitated silica suspension, and / or the dried precipitated silica particles, as the case may be, in the form of a single solution (preferably a single homogeneous solution) consisting essentially of (or further consisting of) polyethylene glycol, the antioxidant, and optionally water. The homogeneous solution may consist essentially of polyethylene glycol and the antioxidant, or may further consist of polyethylene glycol and the antioxidant. However, preferably, the solution (preferably a homogeneous solution) contains some water, preferably in an amount of at least 5% by weight, more preferably at least 8% by weight, and even more preferably at least 11% by weight, based on the total weight of water and polyethylene glycol. Furthermore, for economic reasons, it is advantageous to include water in the solution in an amount of up to 25% by weight, preferably up to 20% by weight, and even more preferably up to 15% by weight, based on the total weight of water and polyethylene glycol. When water is included in the solution, it is advantageous to prepare this solution by first forming a liquid mixture consisting essentially of polyethylene glycol and water, and then adding the antioxidant to the liquid mixture.

[0078] To implement the above-mentioned preferred embodiment in which the antioxidant and the polyethylene glycol are contained in a single homogeneous solution, said single homogeneous solution is usually prepared at a pressure that is atmospheric pressure and at a temperature that is advantageously at least 10° C., preferably at least 20° C., more preferably at least 25° C. higher than the melting point of the polyethylene glycol on the one hand, and advantageously at least 20° C., preferably at least 30° C., more preferably at least 40° C. higher on the other hand. Furthermore, the preparation temperature is usually not higher than 90° C., and preferably at most 70° C.

[0079] In some preferred embodiments, the polyethylene glycol and antioxidant (optionally in the form of a single homogeneous solution consisting essentially of polyethylene glycol, antioxidant, and optionally water) are added to the cake just prior to or during the liquefaction step. More preferably, the polyethylene glycol and antioxidant are added completely to the cake before the liquefaction step or during the first half of the entire liquefaction step. Even more preferably, the polyethylene glycol and antioxidant are added completely to the cake before the liquefaction step begins.

[0080] The addition of polyethylene glycol and antioxidant (optionally in the form of a single homogeneous solution consisting essentially of polyethylene glycol, antioxidant, and optionally additionally water) is usually carried out at atmospheric pressure. Furthermore, said addition is carried out at a temperature which is advantageously at least 10°C, preferably at least 20°C, more preferably at least 25°C above the melting point of polyethylene glycol on the one hand, and advantageously at least 20°C, preferably at least 30°C, more preferably at least 40°C on the other hand. Furthermore, the addition temperature is usually not more than 90°C, preferably at most 70°C.

[0081] As is clear from the above, in order to optimize the introduction of polyethylene glycol and antioxidant, it is preferable to adjust several parameters such as flow rate, temperature, form (i.e., physical state) of polyethylene glycol and antioxidant, and mechanical stirring conditions. For example, polyethylene glycol can be introduced as a pure solid or liquid, or as a dispersion or solution in a solvent, and the same applies to antioxidants. The addition flow rates of polyethylene glycol and antioxidant are preferably adjusted according to their form (solid or liquid). For solid polyethylene glycol and antioxidant, it is practically convenient to add them all at once, but for polyethylene glycol and antioxidant in the form of a liquid solution or dispersion, stepwise addition or all at once can be carried out.

[0082] Finally, the polyethylene glycol and antioxidant are preferably added with stirring to promote uniform redistribution of the polyethylene glycol and antioxidant in the cake or second precipitated silica suspension, particularly when the polyethylene glycol and antioxidant are added to the cake, preferably with vigorous stirring at a speed of at least 300 rpm and preferably through a shear blade to thoroughly break down the cake.

[0083] The use of low molecular weight polyethylene glycol makes it possible to obtain a low viscosity second precipitated silica suspension, even when the polyethylene glycol is used without water or in aqueous solutions or dispersions where the polyethylene glycol concentration is greater than 85% by weight. Obtaining a low viscosity slurry makes it "pumpable", which is very useful for the drying process, which is often spray drying.

[0084] The Applicant has also found that the presence of polyethylene glycol during liquefaction increases the size of the precipitated silica particles (i.e., agglomerates of silica particles), which in turn increases the cohesion of the micropearls or granules obtained from these agglomerates, thereby reducing the production of fines, without altering the dispersibility (i.e., dispersibility) of the MPS in polymer compositions, particularly elastomeric compositions.

[0085] The MPS according to the invention can be used in many applications, especially as a filler in polymer compositions, especially polymer compositions comprising at least one elastomer and the MPS according to the invention.

[0086] The elastomer preferably exhibits at least one glass transition temperature between -150°C and +30°C, for example between -150°C and +20°C.

[0087] Possible elastomers include diene elastomers. Among diene elastomers, mention may be made, for example, of polybutadiene (BR or butadiene rubber), polyisoprene (IR or isoprene rubber), butadiene copolymers, isoprene copolymers or mixtures thereof, in particular styrene / butadiene copolymers (SBR, in particular ESBR (emulsion) or SSBR (solution)), isoprene / butadiene copolymers (BIR), isoprene / styrene copolymers (SIR), isoprene / butadiene / styrene copolymers (SBIR) and ethylene / propylene / diene terpolymers (EPDM). Natural rubber (NR) and epoxidized natural rubber (ENR) may also be mentioned. Good results have been obtained with SBR, possibly in combination with BR and / or NR.

[0088] The polymer compositions may be sulfur vulcanized or crosslinked, among others, with peroxides or other crosslinking systems (eg, diamines or phenolic resins).

[0089] Usually, the polymer composition additionally comprises at least one (silica / elastomer) coupling agent and / or at least one coating agent.

[0090] Non-limiting examples of suitable coupling agents include, for example, "symmetric" or "asymmetric" 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, e.g., triethoxysilylpropyl tetrasulfide. Monoethoxydimethylsilylpropyl tetrasulfide may also be mentioned. Silanes containing masked or free thiol functional groups may also be mentioned.

[0091] The coupling agent can be pre-grafted to the elastomer. It can be used in free form or can also be grafted to the surface of the silica. The same applies to the optional coating agent.

[0092] Precipitated silica may advantageously be the only reinforcing filler of the polymer composition. Alternatively, the MPS of the present invention may be combined with at least one other reinforcing filler, such as another modified precipitated silica (e.g., precipitated silica "doped" with cations such as aluminum) and / or a reinforcing filler other than MPS, such as unmodified precipitated silica, alumina, or carbon black.

[0093] The weight proportion of MPS in the composition can vary over a fairly wide range. It usually represents 10% to 200% by weight based on the weight of the elastomer (i.e., 10 to 200 phr (or parts per hundred parts of "rubber"), where rubber as used herein has the same meaning as "elastomer"). In particular, amounts of 20 to 150 phr are used when MPS is used as the primary filler, and 10 to 50 phr are used when MPS is used in combination with other fillers, usually carbon black, in which case the other fillers are present in the polymer composition in an amount greater than the weight of MPS.

[0094] These polymer compositions can be used to manufacture many articles. Non-limiting examples of semi-finished or finished products comprising the above-mentioned polymer compositions are, for example, shoe soles, flooring, gas barriers, flame retardant materials, and also engineering parts, such as rollers for aerial cables, seals for household appliances, seals for liquid or gas piping, brake system seals, pipes (flexible), sheaths (especially cable sheaths), cables, engine supports, battery separators, conveyor belts, transmission belts, and preferably tires and tire components, in particular tire treads, tire subtreads, and tire belt components (especially for light or heavy vehicles, such as trucks).

[0095] The MPS of the present invention has the advantages of superior processability and improved performance compared to unmodified precipitated silica. The MPS of the present invention fulfills the need for a modified precipitated silica having significantly higher thermal stability than "plain" polyethylene glycol-modified silicas, such as those of Canadian Patent No. 2,255,456, and advantageously provides a level of thermal stability approaching that of unmodified precipitated silica while maintaining excellent dispersibility in an elastomeric matrix, and still permits the preparation of elastomeric compositions having a good balance of mechanical properties similar to, or in some cases even better than, those achieved with prior art polyethylene glycol-modified silicas. In particular, when included in a tire rubber composition, the MPS of the present invention provides the tire rubber composition with a better balance between abrasion resistance and rolling resistance than that obtained with unmodified precipitated silica, while maintaining significantly higher thermal stability than that obtained with conventional precipitated silicas modified with polyethylene glycol in the absence of an antioxidant having the specific properties required by the present invention.

[0096] To the extent that the disclosure of any patents, patent applications, and publications incorporated herein by reference conflicts with the statements of this application to the extent that a term may be unclear, the statements of this application shall control. [Example]

[0097] Example 1. Preparation of modified silica S1 (invention) The starting material for the preparation of modified silica was ZEOSIL® 1165MP silica powder (commercially available from Solvay, sometimes referred to as ZEOSIL® 160 silica, hereafter referred to as CS1). PEG 600 polyethylene glycol (CAS No. 25322-68-3, commercially available from Sigma-Aldrich, product number 8.07486, batch number S8111586121) was heated in an oven at 50°C for 12 hours. Then, 870.03 g of the heated PEG 600 was mixed with 130.3 g of distilled water to obtain an 87 wt% PEG solution. While stirring, 3.47 g of 2(3)-t-butyl-4-hydroxyanisole (BHA, CAS No. 25013-16-5, commercially available from Sigma-Aldrich, product number B1253, batch number 59995) was added to 400 g of the PEG solution. The weight concentration of BHA in the PEG-BHA solution was 0.86%, and the solution contained 1.00 pbw of BHA per 100 parts of PEG.

[0098] 1008 g of ZEOSIL® 1165MP silica powder was placed in a 6-liter WAM blade mixer. The PEG-BHA solution (403.47 g) was injected through a nozzle into the mixer, which was operating at 160 rpm, 33.7°C, and a relative pressure of 1 bar (1 bar g). This injection operation lasted 6.31 minutes, which corresponded to 92.60 g of PEG-BHA solution being injected into the mixer, including 80.64 g of PEG and BHA (i.e., a total of 8.00 parts by weight (pbw) of PEG and BHA per 100 parts of ZEOSIL® 1165MP silica already contained therein), and 11.96 g of water. The injection operation was then stopped. The contents of the mixer, i.e., ZEOSIL® 1165MP silica simultaneously impregnated with 7.921 pbw PEG and 0.079 pbw BHA per 100 parts silica, were allowed to settle for several minutes before being recovered from the mixer and reported as modified silica S1. Modified silica S1 had a moisture content, as determined by a thermobalance, of 7.22 wt. % based on the total weight of S1. The thermobalance was a Mettler Toledo HC103 moisture meter. A 3000 mg sample was dried at 105°C, and measurements were stopped when the measured weight loss was less than 1 mg per 50 seconds. The same equipment and method were used for all subsequent moisture content measurements.

[0099] Example 2. Preparation of modified silica S2 (invention) ZEOSIL® 1165MP silica powder (commercially available from Solvay, hereafter referred to as CS1) was used as the starting material for the preparation of modified silica. PEG 600 polyethylene glycol (CAS No. 25322-68-3, commercially available from Sigma-Aldrich, product number 8.07486, batch number S8111586121) was heated in an oven at 50°C for 12 hours. 174 g of the heated PEG 600 was then mixed with 26 g of distilled water to obtain 200 g of an 87 wt% PEG solution. 1.74 g of gallic acid (CAS No. 149-91-7, commercially available from Sigma-Aldrich, product number G7384) was added to the resulting PEG solution with stirring. The weight concentration of gallic acid in the PEG-gallic acid solution was 0.86%, and the solution contained 1.00 pbw of gallic acid per 100 parts PEG.

[0100] 1008 g of ZEOSIL® 1165MP silica powder was placed in a 6-liter WAM blade mixer. The PEG-gallic acid solution (201.74 g) was injected through a nozzle into the mixer, which was operating at 1 bar (1 bar g), 50°C, and 160 rpm. This injection operation lasted 7.48 minutes, which corresponded to 97.05 g of the PEG-gallic acid solution being injected into the mixer, of which 84.54 g of PEG and gallic acid (i.e., a total of 8.39 parts by weight (pbw) of PEG and gallic acid per 100 parts of ZEOSIL® 1165MP silica already contained therein). The injection operation was then stopped. The contents of the mixer, i.e., ZEOSIL® 1165MP silica co-impregnated with 8.304 pbw PEG and 0.083 pbw gallic acid per 100 parts silica, were allowed to settle for several minutes and then recovered from the mixer and reported as Modified Silica S2, which had a water content of 7.60 wt. % based on the total weight of S2.

[0101] Example 3. Preparation of modified silica S3 (invention) ZEOSIL® 1165MP silica powder (commercially available from Solvay, hereafter referred to as CS1) was used as the starting material for the preparation of modified silica. PEG 600 polyethylene glycol (CAS No. 25322-68-3, commercially available from Sigma-Aldrich, product number 8.07486, batch number S8111586121) was heated in an oven at 50°C for 12 hours. Then, 174 g of the heated PEG 600 was mixed with 26 g of distilled water to obtain 200 g of an 87 wt% PEG solution. While stirring, 1.74 g of D-erythorbic acid (commercially available from Sigma-Aldrich, product number 856061) was added to the PEG solution. The weight concentration of D-erythorbic acid in the PEG / D-erythorbic acid solution was 0.86%, and the solution contained 1.00 pbw of D-erythorbic acid per 100 parts of PEG.

[0102] 1008 g of ZEOSIL® 1165MP silica powder was placed in a 6-liter WAM blade mixer. The PEG / D-erythorbic acid solution (201.74 g) was injected through a nozzle into the mixer, which was operating at 1 bar (1 bar g), 50°C, and 160 rpm. This injection operation lasted 7.08 minutes, which corresponded to 97.05 g of the PEG / D-erythorbic acid solution being injected into the mixer, of which 84.54 g of PEG and D-erythorbic acid (i.e., a total of 8.39 parts by weight (pbw) of PEG and D-erythorbic acid per 100 parts of ZEOSIL® 1165MP silica already contained therein). The injection operation was then stopped. The contents of the mixer, i.e., ZEOSIL® 1165MP silica co-impregnated with 8.304 pbw PEG and 0.083 pbw D-erythorbic acid per 100 parts silica, were allowed to settle for several minutes and then recovered from the mixer and reported as Modified Silica S3, which had a water content of 7.76 wt. % based on the total weight of S3.

[0103] Example 4. Preparation of modified silica S4 (invention) - Preparation of silica cake An aqueous suspension of precipitated silica (hereinafter "silica suspension") was prepared on a pilot scale substantially according to the formulation described in Example 3 of US Pat. No. 9,938,154.

[0104] The silica suspension was filtered and washed using a filter press to obtain a silica cake having a silica content of 19.73 wt % based on the total weight of the silica cake.

[0105] The silica cake so prepared was similar to the cake obtained before disintegration ("liquefaction") and drying when producing ZEOSIL® 1165MP silica on an industrial scale.

[0106] - Preparation of modified silica from silica cake PEG 600 polyethylene glycol (CAS No. 25322-68-3, commercially available from Sigma-Aldrich, product number 8.07486, batch number S8111586121) was heated in a 50°C oven for 12 hours. Then, 870.03 g of the heated PEG 600 was mixed with 130.3 g of distilled water to obtain an 87 wt% PEG solution. While stirring, 3.47 g of 2(3)-t-butyl-4-hydroxyanisole (BHA, CAS No. 25013-16-5, commercially available from Sigma-Aldrich, product number B1253, batch number 59995) was added to 400 g of the PEG solution. The weight concentration of BHA in the PEG-BHA solution was 0.86%, and the solution contained 1.00 pbw BHA per 100 parts PEG.

[0107] 2000 g of silica cake with a silica concentration of 19.73 wt. % was mechanically and chemically disintegrated by adding 7.7 wt. % sulfuric acid solution. A sulfuric acid solution flow rate of 0.76 g / min was used to reach a pH of 3.0. Next, 34.31 g of PEG-BHA solution was added to the disintegrated silica cake at a constant flow rate (3.43 g / min) over 10 minutes while stirring. At the end of this process, the thus-modified disintegrated filter cake contained PEG and BHA in total at 7.57 parts by weight (pbw) per 100 parts of silica, i.e., 7.497 pbw of PEG and 0.074 pbw of BHA. The thus-modified disintegrated filter cake was then spray-dried using a nozzle atomizer. The atomizer was placed under an inert atmosphere. The PEG- and BHA-modified silica powder was recovered and reported as modified silica S4.

[0108] Example 5. Preparation of modified silica CS2 (for comparison purposes) ZEOSIL® 1165MP silica powder (available from Solvay, hereafter referred to as CS1) was used as the starting material for the preparation of modified silica. PEG600 polyethylene glycol (CAS No. 25322-68-3, available from Sigma-Aldrich, product number 8.07486, batch number S8111586121) was heated in an oven at 50°C for 12 hours. 870.03 g of the PEG600 thus heated was then mixed with 130.3 g of distilled water to obtain an 87 wt% PEG solution.

[0109] 1008 g of ZEOSIL® 1165MP silica powder was placed in a 6-liter WAM blade mixer. 400 g of PEG solution was injected through a nozzle into the mixer, which was operating at 160 rpm, 33.7°C, and a relative pressure of 1 bar (1 bar g). This injection operation lasted 6.32 minutes, which corresponded to the injection of 92.70 g of PEG solution into the mixer, including 80.62 g of PEG (i.e., a total of 8.00 parts by weight (pbw) of PEG per 100 parts of ZEOSIL® 1165MP silica already contained therein) and 12.08 g of water. The injection operation was then stopped. The contents of the mixer, i.e., ZEOSIL® 1165MP silica simultaneously impregnated with 8.00 pbw of PEG per 100 parts of silica, were allowed to settle for several minutes before being recovered from the mixer and reported as modified silica CS2. The modified silica CS2 had a water content of 7.30 wt % based on the total weight of CS2.

[0110] Example 6. Preparation of modified silica S5 (invention) ZEOSIL® 1165MP silica powder (available from Solvay, hereafter referred to as CS1) was used as the starting material for the preparation of modified silica. PEG 600 polyethylene glycol (CAS No. 25322-68-3, available from Sigma-Aldrich, product number 8.07486, batch number S8111586121) was heated in an oven at 50°C for 12 hours. 522 g of the heated PEG 600 was then mixed with 78 g of distilled water to obtain 600 g of an 87 wt% PEG solution. 3.91 g of gallic acid (CAS No. 149-91-7, available from Sigma-Aldrich, product number G7384) was added to the PEG solution while stirring. The weight concentration of gallic acid in the PEG-gallic acid solution was 0.65%, and the solution contained 0.75 parts by weight of gallic acid per 100 parts of PEG.

[0111] 1008 g of ZEOSIL® 1165MP silica powder was placed in a 6-liter WAM blade mixer. The PEG-gallic acid solution (605.22 g) was injected through a nozzle into the mixer, which was operating at 1 bar (1 bar g), 50°C, and 160 rpm, to impregnate the silica powder. This injection operation lasted 7.48 minutes, which corresponded to 97.05 g of the PEG-gallic acid solution being injected into the mixer, of which 83.46 g of PEG and gallic acid (i.e., a total of 8.28 parts by weight (pbw) of PEG and gallic acid per 100 parts of ZEOSIL® 1165MP silica already contained therein). The injection operation was then stopped. The contents of the mixer, i.e., ZEOSIL® 1165MP silica co-impregnated with 8.304 pbw PEG and 0.083 pbw gallic acid per 100 parts silica, were allowed to settle for several minutes before being recovered from the mixer and reported as Modified Silica S5, which had a water content of 6.80 wt. % based on the total weight of S5.

[0112] Example 7. Preparation of modified silica CS3 (for comparison purposes) - Preparation of silica cake An aqueous suspension of precipitated silica (hereinafter "silica suspension") was prepared on a pilot scale substantially according to the formulation described in Example 3 of US Pat. No. 9,938,154.

[0113] The silica suspension was filtered and washed using a filter press to obtain a silica cake having a silica content of 19.73 wt % based on the total weight of the silica cake.

[0114] The silica cake so prepared was similar to the cake obtained before disintegration ("liquefaction") and drying when producing ZEOSIL® 1165MP silica on an industrial scale.

[0115] - Preparation of modified silica from silica cake PEG600 polyethylene glycol (CAS number 25322-68-3, commercially available from Sigma-Aldrich, product number 8.07486, batch number S8111586121) was heated in an oven at 50° C. for 12 hours. Then, 870.03 g of the thus-heated PEG600 was mixed with 130.3 g of distilled water to obtain an 87 wt % PEG solution.

[0116] 2000 g of silica cake with a silica concentration of 19.73 wt. % was mechanically and chemically disintegrated by adding 7.7 wt. % sulfuric acid solution. A sulfuric acid solution flow rate of 0.76 g / min was used to reach a pH of 3.0. Next, 34.31 g of PEG solution was added to the disintegrated silica cake at a constant flow rate (3.43 g / min) over 10 minutes while stirring. At the end of this process, the thus-modified disintegrated filter cake contained a total of 7.57 parts by weight (pbw) of PEG per 100 parts of silica. The thus-modified disintegrated filter cake was then spray-dried using a nozzle atomizer. The atomizer was placed under an inert atmosphere. The PEG-modified silica powder was recovered and reported as modified silica CS3.

[0117] Example 8. Thermal stability test The thermal stability of the precipitated silica samples was evaluated by thermogravimetric analysis (TGA). Samples were analyzed using a Mettler LF1100 thermobalance according to the following protocol: - Heat from 25°C to 800°C at 10°C / min in air. - The thermal stability of the samples was above 130°C, i.e. after removal of water from the samples. - The temperature at which the mass of the sample (after water removal) begins to decrease (again) was determined. This temperature was designated T 分解開始点 It is called.

[0118] The thermal stability results are shown in Table 1.

[0119] [Table 1]

[0120] The modified precipitated silicas S1, S2, S3 and S5 containing PEG and specific antioxidants according to the present invention exhibited much higher thermal stability than the PEG-modified precipitated silica CS3, which did not contain antioxidants. 分解開始点 increased by at least 27°C, and by up to 70°C for silica S1.

[0121] Example 9. Use of precipitated silica for the preparation of an elastomeric composition - Material The precipitated silica was evaluated in an SBR / BR matrix suitable for the manufacture of tire treads. The nature and amounts of the components of the elastomer composition are set forth in Table 2 below. The amounts of each are expressed as phr, i.e., parts by weight per 100 parts of elastomer contained in the elastomer composition.

[0122] [Table 2]

[0123] Method for preparing an elastomeric composition The preparation of the elastomer composition was carried out in three successive preparation stages: two stages of high-temperature thermomechanical processing followed by a third stage of mechanical processing at a temperature below 110° C. to introduce the vulcanization system. The first of the two stages was carried out using a mixing device of the Brabender brand internal mixer type (380 mL capacity).

[0124] In the first pass of the first stage, the elastomer and precipitated silica (introduced in portions) were mixed with the coupling agent, plasticizer, stearic acid and carbon black, the duration was 4 minutes and the drop temperature was about 150°C.

[0125] In the second stage, 6-PPD and ZnO were added to the composition and milled for 3 minutes and 30 seconds. The dropping temperature was about 150°C.

[0126] After the mixture had cooled (to a temperature below 100°C), the vulcanization system was added during the third stage, which was carried out on an open mill preheated to 50°C. The duration of this stage was 2 to 6 minutes. Each final mixture was then calendered into plaques 2 to 3 mm thick.

[0127] - Properties of vulcanizates The measurements were carried out after vulcanization at 160°C.

[0128] The hardness of the samples was measured using a Shore A Hildebrand HD3000 durometer according to the standard procedure of ISO 7619-1. Each measurement was performed six times for all samples.

[0129] The values ​​of the loss factor (tanδ) and the amplitude of the elastic modulus in dynamic shear (ΔG') were measured using vulcanized specimens (parallel hexahedral specimens: cross-sectional area 8 mm 2 The measurements were recorded at a frequency of 10 Hz and a double alternating sinusoidal shear strain (height 7 mm). The samples were subjected to a double alternating sinusoidal shear strain at a temperature of 40°C. The strain amplitude sweep process was carried out according to a forward-reverse cycle, proceeding outward from 0.1% to 50% and then returning from 50% to 0.1%. The values ​​reported in Table 3 below were obtained from the return strain amplitude sweep and represent the maximum value of the loss factor (tanδ max) and the amplitude of the elastic modulus (ΔG') between values ​​of 0.1% and 50% of strain (Payne effect). The measurements were carried out on a Metravib DMA+1000 according to standard ASTM D5992.

[0130] Uniaxial tensile tests were carried out in an Instron 5564 instrument at a speed of 500 mm / min using H2 type specimens according to the standard NF ISO 37 instructions. The x% modulus, which corresponds to the stress measured at x% tensile strain, is expressed in MPa. The tensile strength is expressed in MPa and the elongation at break is expressed in MPa. For all samples, each measurement was carried out 10 times.

[0131] The results are shown in Table 3 below.

[0132] [Table 3]

[0133] The lower the Mooney viscosity, the better the processability. Thus, the processability of the compositions containing PEG-modified precipitated silica, i.e. compositions CS2, S3 and S5, was significantly improved by reducing the Mooney viscosity. The lowest Mooney viscosities were measured for the inventive silicas S3 and S5, which contain the inventive PEG / antioxidant (of a specific nature) combination.

[0134] The use of PEG or a combination of PEG / antioxidants (of a specific nature) as modifiers for precipitated silica also resulted in a better balance of hardness / hysteresis compared to the unmodified precipitated silica CS1. Both PEG and the combination of PEG / antioxidants (of a specific nature) increased hardness while decreasing the dissipation factor (tanδ max) at 40°C. Furthermore, the ultimate properties (tensile strength at break, elongation at break) known to those skilled in the art to affect the abrasion resistance of the composition were unaffected or only slightly affected.

[0135] It can thus be seen that the precipitated silicas S3 and S5 according to the invention, which have been modified with a combination of PEG and an antioxidant of the specific properties required by the invention, exhibit a better wear resistance / rolling resistance balance than the unmodified precipitated silica CS1, said balance being at least as good as that obtained with the precipitated silica CS2, which has been modified with PEG but does not contain antioxidant.

[0136] Overall, taking the results of the thermal stability tests in Table 2 and the results of the mechanical property tests in Table 3 together, the MPS of the present invention, when included in a tire rubber composition, was able to provide said tire rubber composition with a better balance of abrasion resistance and rolling resistance than that obtained with unmodified precipitated silica, while retaining thermal stability significantly higher than that obtained with prior art precipitated silicas modified with polyethylene glycol without the antioxidant of the specific properties required by the present invention.

Claims

1. Modified precipitated silica (MPS), - at least 70% by weight of precipitated silica particles, based on the total weight of said MPS; - at least 1.0% by weight, based on the total weight of said MPS, of at least one polyethylene glycol; - at least 0.0010% by weight, based on the total weight of said MPS, of at least one antioxidant; wherein the antioxidant comprises (i) Dehydroascorbic acid and its hydrate, hydroxyfuranone derivatives of formula (I) and hydroxyfuranone derivatives of formula (II) 【Chemistry 1】 (In the formula, -R ７ is hydrogen or C １ ~C ４ is alkyl, -R ８ is hydroxy, C １ ~C ４ Alkyl, C １ ~C ４ Alkoxy, C ２ ~C ４ Alkenyl and C ２ ~C ４ alkenyloxy; -R ９ is hydrogen, C １ ~C ４ Alkyl, C １ ~C ４ Hydroxyalkyl, C １ ~C ４ dihydroxyalkyl, 【Chemistry 2】 and 【Transformation 3】 and R ｃ and R ｄ are each independently hydrogen and C １ ~C ４ is selected from the group consisting of alkyl, -R １０ is hydrogen or C １ ~C ４ alkyl) and / or at least one hydroxyfuranone derivative selected from the group consisting of (ii) Formula (III) 【Chemistry 4】 (In the formula, -R １ , R ３ and R ５ are each independently hydrogen or C １ ~C ４ is alkyl, -R ２ is hydroxy, C １ ~C ４ Alkyl, C １ ~C ４ Alkoxy, C １ ~C ４ Hydroxyalkyl, C ２ ~C ４ Alkenyl, C ２ ~C ４ Alkenyloxy, C ２ ~C ４ Hydroxyalkenyl, —C(═O)H, —COOH, —COOMe (wherein Me is an alkali metal), —COOR ｆ (where R ｆ is C １ ~C ４ Alkanediyl or C ２ ~C ４ alkenediyl), -R ｆ -COOH (where R ｆ is C １ ~C ４ Alkanediyl or C ２ ~C ４ alkenediyl) and -R ｆ -COOMe (where R ｆ is C １ ~C ４ Alkanediyl or C ２ ~C ４ alkenediyl, and Me is an alkali metal; -R ４ is hydrogen, hydroxy, C １ ~C ４ Alkyl, C １ ~C ４ Alkoxy, C １ ~C ４ Hydroxyalkyl, C ２ ~C ４ Alkenyl, C ２ ~C ４ Alkenyloxy, C ２ ~C ４ Hydroxyalkenyl, —C(═O)H, —COOH, —COOMe (wherein Me is an alkali metal), —COOR ｆ (where R ｆ is C １ ~C ４ Alkanediyl or C ２ ~C ４ alkenediyl), -R ｆ -COOH (where R ｆ is C １ ~C ４ Alkanediyl or C ２ ~C ４ alkenediyl), -R ｆ -COOMe (where R ｆ is C １ ~C ４ Alkanediyl or C ２ ~C ４ alkenediyl, and Me is an alkali metal) and —SO ３ Me, where Me is an alkali metal; -R ６ is hydrogen, hydroxy, C １ ~C ４ Alkyl, C １ ~C ４ Alkoxy, C １ ~C ４ Hydroxyalkyl, C ２ ~C ４ Alkenyl and —SO ３ Me (where Me is an alkali metal) Phenol derivatives of Modified precipitated silica (MPS).

2. 2. The MPS of claim 1, wherein the antioxidant is a hydroxyfuranone derivative of formula (I).

3. R ７ is hydrogen.

4. R ８ The MPS of claim 2 or 3, wherein is hydroxy.

5. R ９ is -CHOH-CH ２ 5. The MPS according to claim 2, wherein the MPS is OH.

6. 3. The MPS of claim 2, wherein the hydroxyfuranone derivative is selected from the group consisting of maple furanone, L-ascorbic acid, D-ascorbic acid, L-isoascorbic acid, D-erythorbic acid, and mixtures thereof, preferably D-erythorbic acid.

7. 2. The MPS of claim 1, wherein the antioxidant is a phenol derivative of formula (III):

8. R １ is hydrogen.

9. R ２ The MPS of claim 7 or 8, wherein is hydroxy.

10. R ４ The MPS according to any one of claims 7 to 9, wherein is -COOH.

11. R ６ The MPS according to any one of claims 7 to 10, wherein is hydroxy.

12. R ３ and R ５ The MPS according to any one of claims 7 to 11, wherein is hydrogen.

13. The phenol derivatives include 2-tert-butyl-4-hydroxyanisole, 3-tert-butyl-4-hydroxyanisole, protocatechuyl alcohol, hydroxytyrosol, dihydrocaffeoyl alcohol, caffeoyl alcohol, vanillyl alcohol, homovanillyl alcohol, dihydroconiferyl alcohol, coniferyl alcohol, veratryl alcohol, homoveratryl alcohol, 3-(3,4-dimethoxyphenyl)-1-propanol, galloyl alcohol, 5-methoxy-proto 8. The MPS of claim 7, wherein the MPS is selected from the group consisting of catechuyl alcohol, syringyl alcohol, p-coumaric acid, ferulic acid, sinapic acid, caffeic acid, o-coumaric acid, pyrogallol, veratrol, guaiacol, 4-methylcatechol, salicylic acid, gallic acid, tiron, protocatechuic acid, protocatechualdehyde, hydroxychavicol, eugenol, chabibetol, catechol, 4-tert-butylcatechol, 4-allylcatechol, 3-allylcatechol, and mixtures thereof, preferably gallic acid.

14. The antioxidant is heated to a temperature T ｓ and is solid at atmospheric pressure, T ｓ is equal to the melting point of the polyethylene glycol plus 30°C, and the weight of the antioxidant based on the weight of the polyethylene glycol is equal to the temperature T ｓ and less than the solubility limit of the antioxidant in the polyethylene glycol, measured at atmospheric pressure, and the weight of the antioxidant based on the weight of the polyethylene glycol and the solubility limit of the antioxidant in the polyethylene glycol are expressed in the same units, e.g., grams of antioxidant per 100 grams of polyethylene glycol; or The antioxidant is heated to a temperature T ｓ and is liquid at atmospheric pressure, and the weight of the antioxidant and the polyethylene glycol contained in the MPS is ｓ and such that when the antioxidant and the polyethylene glycol are combined at atmospheric pressure in amounts by weight to form a binary liquid mixture consisting of the antioxidant and the polyethylene glycol, the binary liquid mixture resulting from said combination is a homogeneous solution.

15. A method for preparing modified precipitated silica (MPS) according to any one of claims 1 to 14, comprising the steps of: - reacting at least one silicate with at least one acid in an aqueous medium to provide a first precipitated silica suspension; - subjecting said first precipitated silica suspension to a liquid / solid separation step to obtain a filter cake; - subjecting said filter cake to a liquefaction step to obtain a second precipitated silica suspension; - subjecting said second precipitated silica suspension to a drying step to recover the precipitated silica particles. Including, the polyethylene glycol and the antioxidant are added, independently of one another, simultaneously or sequentially to at least one of (i) the filter cake before and / or during the liquefaction step, and (ii) the second precipitated silica suspension after the liquefaction step but before the drying step; and / or A method wherein after said drying step, said precipitated silica particles are simultaneously or sequentially impregnated with said polyethylene glycol and said antioxidant.

16. 16. The method of claim 15, wherein the polyethylene glycol and the antioxidant are simultaneously added to or simultaneously impregnated into the cake, the second precipitated silica suspension and / or the dried precipitated silica particles, as the case may be, in the form of a homogeneous solution of a single solution consisting essentially of the polyethylene glycol, the antioxidant, and optionally in addition, water.

17. A composition or a semi-finished or finished product, in particular a tire component, comprising at least one elastomer and a modified precipitated silica (MPS) according to any one of claims 1 to 14.

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