Precipitated silicas, process for their preparation and their use

Abstract

The invention relates to a precipitated silica, characterized in that it has the following physico-chemical parameters: The precipitated silica according to the invention is produced by the following method: a) initial charge of an aqueous solution of organic and / or inorganic salts and / or alkali and / or alkaline earth silicates and / or organic and / or inorganic bases with pH > 9, b) simultaneous metering of water glass and acidifying agent to this initial charge while stirring at 80 to 98°C for 60 to 120 minutes, c) then stopping the addition of water glass and metering the acid only in smaller amounts than before in order to bring the pH of the mixture (measured at 60°C) to 9.0 to 10.0, d) then stirring the mixture at high temperature > 85°C for 45 minutes to 200 minutes without further addition of reactants, e) acidification using sulfuric acid to a pH of about 3.5 to 4.5 (measured at 60°C) and f) filtration, drying to < 8% loss on drying and then granulation of the mixture. The silica according to the invention can be used for the production of rubber mixtures, in particular for the production of tyres, cable sheaths, hoses, drive belts, conveyor belts, roller coverings, shoe soles, gasket elements and damping elements.

Description

[0001] This invention relates to precipitated silica, its preparation method, and its uses.

[0002] WO2012059234 discloses an elastomer composition comprising at least one isoprene elastomer, silica as a reinforcing inorganic filler, and 3-acryloyloxypropyltriethoxysilane as an adhesion promoter, wherein the CTAB surface area of ​​the silica is 40 m². 2 / g and 525m 2 Between / g, the surface area of ​​BET is 45m² 2 / g and 550m 2 Between / g, after ultrasonic deagglomeration, the particle size was measured by XDC, with the range Ld((d84-d16) / d50) being at least 0.91 and the pore volume distribution range V(d5-d50) / V(d5-d100) being at least 0.66.

[0003] A method for producing silica is also known from EP2102104, wherein the CTAB surface area of ​​the silica is 40 m². 2 / g to 525m 2 / g, BET surface area is 45m² 2 / g to 550m 2 / g, the range of particle size Ld((d84-d16) / d50) measured by XDC particle size analysis after ultrasonic depolymerization is at least 0.91, and the pore volume distribution V(d5-d50) / V(d5-d100) is at least 0.66.

[0004] EP1831297 and WO2006072704 disclose the use of BET surfaces with a surface area of ​​at least 60 m² in thermoplastic polymer materials. 2 / g of silica is used as an inorganic filler to increase the hardness of the material while maintaining or improving its impact resistance.

[0005] From US2005032965 and WO2008077948, it is also known that the surface area of ​​CTAB is 40m². 2 / g to 525m 2 Between / g, BET surface area is 45m² 2 / g to 550m 2 Silica with a size distribution range of at least 0.91 and a pore volume distribution of at least 0.66 as measured by XDC particle size analysis after ultrasonic crushing, between / g.

[0006] One drawback of known silica within the required specific surface area range is its poor dispersibility in rubber compounds, resulting in poor wear performance of the rubber compounds, especially when used as tread compounds.

[0007] The object of this invention is to provide a silica with improved dispersibility in rubber mixtures compared to known silicas. Furthermore, if possible, the silica should be in pellet form to ensure excellent incorporability and easy workability within the rubber matrix.

[0008] This invention provides precipitated silica, characterized by having the following physicochemical parameters:

[0009] CTAB surface area ≤115m² 2 / g, preferably ≤105m 2 / g, more preferably ≤90m 2 / g、

[0010] Even better, 45m 2 / g-90m 2 / g, Specially Selected 65

[0011] m 2 / g-90m 2 / g and a very special preferred 70m 2 / g-90m 2 / g, DOA absorption ≥130ml / (100g), preferably ≥140ml / (100g), more preferably 145ml / (100g)-190ml / (100g),

[0012] Ro-Tap >300μm ≥86%, preferably 86%-98%, more preferably 86%-95%.

[0013] Especially 90%-95%,

[0014] V(d5-d50) / V(d5-d100)<0.66, preferably 0.30-0.65, especially 0.30-0.64.

[0015] The BET surface area of ​​the precipitated silica according to the present invention can be ≤125m². 2 / g, preferably ≤115m 2 / g, more preferably 70m 2 / g-105m 2 / g.

[0016] The Sears number of precipitated silica according to the present invention 原始The concentration of KOH (based on 1.5g of silica) can be 7.0-20.0 ml / (1.5g), preferably 9.0-15.0 ml / (1.5g), and more preferably 11.0-14.0 ml / (1.5g).

[0017] The silanol group density of the precipitated silica according to the present invention can be ≥5.4 OH / nm. 2 Preferably ≥5.5OH / nm 2 .

[0018] The drying loss of precipitated silica according to the present invention can be 2%-10%, preferably 4%-8%.

[0019] The pH of the precipitated silica according to the present invention can be 4.0-7.0, preferably 5.5-7.0.

[0020] The conductivity of the precipitated silica according to the present invention can be ≤1200μS / cm, preferably 200μS / cm-800μS / cm.

[0021] The calcination residue of precipitated silica according to the present invention can be 3%-5%, preferably 4%-5%.

[0022] The Ro-Tap < 75 μm value of the precipitated silica according to the present invention can be ≤ 10%, preferably ≤ 8%.

[0023] The bulk density of the precipitated silica according to the present invention can be at least 180 g / L, preferably 200 g / L to 350 g / L, more preferably 250 g / L to 330 g / L, and most preferably 250 g / L to 320 g / L.

[0024] The TAR value (fraction of particles 3.14 mm to 5.00 mm) of the precipitated silica according to the present invention can be 15% to 60%, preferably 20% to 50%.

[0025] The PV value of precipitated silica according to the present invention, measured by the Hg porosity determination method at 0.0042 MPa-414 MPa and 140°, is 1.00-3.00 ml / g, preferably 1.35-2.40 ml / g, and more preferably 1.35-2.00 ml / g.

[0026] The maximum pore size (Hg, -dV / dlogD, contact angle 140°, surface tension 480mN / m) of the precipitated silica according to the present invention can be 35nm-100nm, preferably 45nm-80nm, and more preferably 50nm-70nm.

[0027] The precipitated silica according to the invention can be used in compacted form, more preferably in pellet form. At least 50% of the particles produced by the Ro-Tap >300 μm fraction have a longest dimension (defined as "particle length") of not less than 1.0 mm, preferably >1.5 mm, more preferably >2.5 mm, and particularly preferably >3.0 mm.

[0028] The present invention also provides a method for producing precipitated silica according to the present invention, characterized in that...

[0029] a) An aqueous solution of an organic salt and / or inorganic salt and / or alkali metal silicate or alkaline earth metal silicate and / or organic base and / or inorganic base with an initial charge pH ≥ 9.

[0030] b) Add water glass and acidifying agent to the initial charge simultaneously by metering, and stir at 80-98°C for 60-120 minutes, preferably at 85-98°C for 80-110 minutes.

[0031] c) Then stop adding water glass and add acid only in smaller amounts than before, so that the pH of the mixture (measured at 60°C) reaches 8.3–10.0.

[0032] d) The mixture is then further stirred at a high temperature of ≥85°C, preferably >90°C, for 45 to 200 minutes, preferably 60 to 150 minutes, without adding any other reactants.

[0033] e) Acidify with sulfuric acid until the pH is approximately 3.5-4.5 (measured at 60°C), and

[0034] f) Filter and dry the mixture until the drying loss is <8%, preferably by spray drying or rotary flash drying unit, and then granulate.

[0035] The method according to the invention can be carried out at a temperature ≥80°C throughout the precipitation process, and aging can be performed at ≥85°C. As a result, except for a specific surface area ≤115 m², 2 Within the range of / g, a very high level of internal structure was also generated within this surface area range, which is highly advantageous for bonding to a matrix (e.g., rubber). This is manifested in a high DOA value. Even after actual structural disruption during granulation, these structures remain largely unchanged because the resulting high density of silanol groups leads to a stable silica structure.

[0036] The initial charge can be 20% to 90% of the final volume of the precipitate, preferably 30% to 90%, more preferably 40% to 90%. An initial charge containing only a low level of electrolyte (salt) (if present) can be used, and the electrolyte can be added continuously or in batches (preferably at the start of precipitation).

[0037] Optionally, an organic or inorganic salt may be added during steps a), b), c), e), or f). This can be done in solution or solid form, and in each case, continuously or in batches. Alternatively, the salt can be dissolved in one or more components and then added simultaneously. The salt may contain the following anions and cations:

[0038] Li + Na + K + 、Rb + Be 2+ Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ H + F - Cl - ,Br - I - SO3 2- SO4 2- HSO4 - PO3 3- PO4 3- NO3 - NO2 - CO3 2- HCO3 - OH - TiO3 2- ZrO3 2- ZrO4 4- AlO2 - Al2O4 2- BO4 3- .

[0039] Suitable organic salts are salts of formic acid, acetic acid, and propionic acid. Cations include the alkali metal or alkaline earth metal ions mentioned above. The concentration of these salts in the initial charge can be from 0.01 to 5.00 mol / L. The inorganic salt used is preferably Na₂SO₄. The acidifying agent can be fed in the same or different manner in steps b), c), and e), i.e., at the same or different concentrations and / or feed rates. Similarly, water glass can be fed into the reaction in the same or different manner in steps a) and b).

[0040] Besides water glass (sodium silicate solution), other silicates, such as potassium silicate or calcium silicate, can also be used. The acidifying agent used, as well as sulfuric acid, can also be other acidifying agents, such as HCl, HNO3, H3PO4, or CO2. Filtration and drying of silica are well known to those skilled in the art, as described, for example, in EP1762544B1 and the patents cited therein. Silica is preferably dried in a flow dryer, spray dryer, staged dryer, belt dryer, rotary dryer, flash dryer, rotary flash dryer, or nozzle tower. These drying variations include operation using atomizers, single-phase or two-phase nozzles, or integrated fluidized beds. The precipitated silica after the drying step preferably has a particle shape with an average diameter greater than 15 μm, particularly greater than 80 μm, and more preferably greater than 200 μm. After drying, granulation can also be performed using a roller compactor with a downstream crusher, by which the final particle length is determined.

[0041] The present invention also provides a rubber compound comprising

[0042] (A) Rubber or a mixture of rubbers, and

[0043] (B) At least one precipitated silica according to the present invention.

[0044] The rubber used can be natural rubber and / or synthetic rubber. Preferred synthetic rubbers are described, for example, in W. Hofmann, Kautschuktechnologie [Rubber Technology], Genter Verlag, Stuttgart 1980. They may include:

[0045] - Polybutadiene (BR)

[0046] - Polyisoprene (IR),

[0047] - Styrene / butadiene copolymers, such as emulsion SBR (E-SBR) or solution SBR (S-SBR), preferably with a styrene content of 1% to 60% by weight, more preferably 5% to 50% by weight (SBR).

[0048] -Chloroprene (CR),

[0049] -Isobutylene / isoprene copolymer (IIR),

[0050] - Butadiene / acrylonitrile copolymer with an acrylonitrile content of 5% to 60%, preferably 10% to 50%, based on the weight of NBR.

[0051] - Partially hydrogenated or fully hydrogenated NBR rubber (HNBR),

[0052] - Ethylene / propylene / diene copolymer (EPDM)

[0053] The aforementioned rubbers also possess functional groups, such as carboxyl, silanol, or epoxy groups, for example, epoxidized NR, carboxyl-functionalized NBR, or silanol (-SiOH)- or silanoxy (-Si-OR)-functionalized SBR.

[0054] And mixtures and masterbatches of these rubbers. Latex of the above-mentioned rubbers may also be used, especially in combination liquid-phase mixing or continuous liquid-phase mixing.

[0055] In a preferred embodiment, the rubber can be sulfur-vulcanizable. For the production of automotive tire treads, anionic polymeric S-SBR rubbers (solution SBRs) with glass transition temperatures above -50°C, and mixtures thereof with butadiene rubbers, are particularly preferred. S-SBR rubbers in which the vinyl content of the butadiene component exceeds 20% by weight are especially preferred. S-SBR rubbers in which the vinyl content of the butadiene component exceeds 50% by weight are very, particularly preferred.

[0056] Preferably, a mixture of the above-mentioned rubbers with an S-SBR content greater than 50% by weight, more preferably greater than 60% by weight, can be used.

[0057] More specifically, unfunctionalized and / or functionalized S-SBR / BR and S-SBR / BR / NR grade polymer blends can be used in tread compounds, often with the addition of resins. These resins can be of natural or synthetic origin and can be in chemically modified forms or blends of different resins.

[0058] The rubber compound according to the invention may contain additional fillers. The following fillers may be used as such fillers in the rubber compound according to the invention:

[0059] - Carbon black: Carbon black can be produced through lampblacking, furnace blacking, gas blacking, or thermal processes, with a surface area of ​​20m². 2 / g to 200m 2 / g. Carbon black may also optionally contain heteroatoms, such as Si.

[0060] - For example, amorphous silica prepared by precipitation from silicate solution or by flame hydrolysis of silicon halide, with a specific surface area of ​​5 to 1000 m². 2 / g, preferably 20 to 400m 2 / g (BET surface area), with a primary particle size of 10 to 400 nm. Silica may also optionally be in the form of a mixed oxide with other metal oxides, such as oxides of Al, Ga, B, Mg, Ca, Ba, Zn, and titanium. Silica may also be doped with one or more of these metal ions.

[0061] - Synthetic silicates such as aluminum silicate, and alkaline earth metal silicates such as magnesium silicate or calcium silicate, have a BET surface area of ​​20 to 400 m². 2 / g, with a primary particle size of 10 to 400 nm.

[0062] - Synthetic or natural aluminum oxides and synthetic or natural aluminum hydroxide.

[0063] - Natural silicates, such as kaolin and other naturally occurring silicas.

[0064] - Natural fibers, especially cellulose, microcellulose and / or nanocellulose and products made from them.

[0065] - Glass fiber and glass fiber products (pads, strands) or glass microspheres.

[0066] Amorphous silica prepared by precipitation from silicate solution is preferred, having a BET surface area of ​​20 to 400 m². 2 / g, more preferably 100m 2 / g to 250m 2 / g, in amounts ranging from 5 to 150 parts by weight, based on 100 parts of rubber in each case.

[0067] The filler can be used alone or in mixtures.

[0068] The rubber mixture may contain 5 to 150 parts by weight of precipitated silica according to the invention and 0.1 to 20 parts by weight, preferably 1 to 18 parts by weight, more preferably 5 to 15 parts by weight of organosilane, wherein the parts by weight are based on 100 parts by weight of rubber.

[0069] The rubber compound may additionally contain silicone oil and / or alkylsilanes.

[0070] The rubber mixtures according to the invention may contain other known rubber additives, such as crosslinking agents, vulcanization accelerators, reaction accelerators, reaction retarders, antioxidants, stabilizers (including aging stabilizers), processing aids, plasticizers, waxes or metal oxides, and optionally activators such as triethanolamine, polyethylene glycol or hexanetriol.

[0071] Rubber additives can be used in conventional amounts, depending on factors including the end use. Conventional amounts can be, for example, based on 0.1% to 50% by weight of the rubber.

[0072] The crosslinking agent used can be sulfur or an organic sulfur donor.

[0073] The rubber compound according to the invention may contain other vulcanization accelerators. Examples of suitable vulcanization accelerators that may be used include mercaptobenzothiazoles, sulfinamides, guanidines, dithiocarbamates, thioureas, thiocarbonates, and zinc salts of these, such as zinc dibutyldithiocarbamate.

[0074] The rubber compound according to the present invention may further comprise:

[0075] Thiuram sulfide accelerators and / or carbamate accelerators and / or corresponding zinc salts,

[0076] Nitrogen-containing co-activators,

[0077] Other optional rubber additives, and

[0078] Other optional promoters may be present.

[0079] The weight ratio of the accelerator to the nitrogen-containing co-activator can be equal to or greater than 1.

[0080] The rubber compound according to the invention may contain at least 0.25 parts by weight of tetrabenzylthiuram disulfide or tetramethylthiuram disulfide based on 100 parts by weight of rubber, at least 0.25 parts by weight of diphenylguanidine based on 100 parts by weight of rubber, and cyclohexylsulfinamide or dicyclohexylsulfinamide.

[0081] It is preferable to use sulfinamides with guanidines and thiurams together, and more preferably to use cyclohexylsulfinamide or dicyclohexylsulfinamide with diphenylguanidine and tetrabenzylthiuram disulfide or tetramethylthiuram disulfide together.

[0082] Depending on the rubber used, the amount of vulcanization accelerator and sulfur can be from 0.1% to 10% by weight, preferably from 0.1% to 5.0% by weight. Sulfur and sulfinamides are particularly preferred, in amounts from 1.0% to 4.0% by weight, thiurams in amounts from 0.2% to 1.0% by weight, and guanidines in amounts from 0.0% to 3.0% by weight.

[0083] The present invention also provides a method for preparing a rubber mixture according to the invention, characterized in that rubber or a mixture of rubbers, precipitated silica according to the invention, and other optional rubber additives are mixed in a mixing unit.

[0084] Blending of rubber with fillers and any rubber additives can be carried out in commonly used mixing units, such as roll mills, internal mixers, and mixing extruders. This type of rubber blend can typically be prepared in an internal mixer by first mixing the rubber, filler, precipitated silica according to the invention, and rubber additives at 100°C to 170°C in one or more consecutive thermomechanical mixing stages. The order and timing of the addition of the individual components can have a critical impact on the final properties of the blend. Typically, the resulting rubber blend can be mixed with crosslinking chemicals in an internal mixer or roll mill at 40°C to 110°C, and the blend can be treated to obtain a so-called crude blend for subsequent steps of the process, such as molding and vulcanization.

[0085] The rubber compound according to the invention can be vulcanized at a temperature of 80°C to 200°C, preferably 130°C to 180°C, and optionally at a pressure of 10 bar to 200 bar.

[0086] The rubber compound according to the invention can be used to produce molded articles by vulcanization.

[0087] The rubber compound according to the invention can be used to produce molded articles, such as tires, especially tire treads, in tire carcasses or tire sidewalls, cable sheaths, hoses, drive belts, conveyor belts, roll coverings, shoe soles, padding elements, such as padding rings, and damping elements.

[0088] The advantage of the precipitated silica according to the present invention is that the corresponding rubber compound has improved silica dispersibility. Furthermore, the rubber compound according to the present invention has improved reinforcement and better tear propagation characteristics. In addition, the increased dynamic stiffness measured at 60°C should result in higher driving stability, i.e., improved handling characteristics on dry roads.

[0089] Test method:

[0090] Determination of alkalinity

[0091] The base value (AN) refers to the amount of hydrochloric acid consumed, expressed in ml, in a direct potentiometric titration of an alkaline solution or suspension with a maximum pH of 8.30 (for a sample volume of 50 ml, 50 ml of distilled water, using 0.5 mol / L hydrochloric acid). This determines the free base content of the solution or suspension.

[0092] The pH meter (Knick, model: 766 pH meter, Calicut, with temperature sensor) and pH electrode (Schott combined electrode; model: N7680) were calibrated at room temperature with the aid of two buffer solutions (pH = 7.00 and pH = 10.00). The combined electrode was immersed in a standard solution or suspension equilibrated to 40°C, consisting of 50.0 ml of precipitate suspension and 50.0 ml of deionized water. Subsequently, a 0.5 mol / L hydrochloric acid solution was added dropwise until a constant pH of 8.30 was established. Since the equilibrium between silica and free base content is established slowly, a 15-minute waiting period is required before finally reading the acid consumption. Given the selected molar amount and concentration, the hydrochloric acid consumption, read in ml, directly corresponds to the base value and is reported dimensionlessly.

[0093] pH - pH of silica (warm) according to DIN EN ISO 787-9

[0094] pH measurements during the silica production process are performed on “warm” silica, at 60°C.

[0095] The procedure is based on DIN EN ISO 787-9 and is specified as follows:

[0096] Prepare a 5% (m / m) aqueous suspension of the sample to be analyzed. Softened (DM) water is used for this purpose.

[0097] Before measuring pH, stir the sample suspension on a stirrer for at least 5 minutes.

[0098] pH was measured on a previously calibrated pH meter from Metrohm, model 780, with pH electrode 6.0228.000 (from Metrohm).

[0099] CTAB surface area - determined according to ISO 5794-1G

[0100] This method is based on the adsorption of buffered CTAB (N-hexadecyl-N,N,N-trimethylammonium bromide) in aqueous solution onto an "outer" surface of silica, also known as a "rubber-active surface." The unadsorbed CTAB is back-titrated using NDSS (sodium dioctyl sulfosuccinate solution). The titration endpoint is the point of maximum increase in solution opacity.

[0101] This procedure conforms to ISO 5794-1G, and its descriptions, additions, and deviations are as follows:

[0102] During sample preparation, it is preferable to use a suitable grinder to ultrafine grind coarse-grained silica and silicate samples, or to pulverize them using a mortar and pestle and then sieve them through a 90 μm sieve, rather than pulverizing them using a mortar and pestle and then grading them using a 150 μm sieve as described in the standard.

[0103] The sample and the expected CTAB surface area are less than 200 m². 2 A suspension consisting of / g CTAB solution was stirred for 10 minutes. As described in the standard, the sample and the expected CTAB surface area were not less than 200m². 2 A suspension consisting of / g CTAB solution was stirred for 35 minutes.

[0104] After adsorption, the silica is filtered through a 0.2μm polyamide filter.

[0105] The filtrate was titrated using a Metrohm titration processor equipped with an autosampler and a Tirando 809. The photometric electrode used was a Spectrosense 523nm from Metrohm.

[0106] BET surface area (N2, multi-point) - determined according to DIN ISO 9277

[0107] This method is used to determine the specific N2 surface area of ​​silica by the BET method according to DIN ISO 9277. In this method, the measurement is determined by adsorbing nitrogen at a specified partial pressure at low temperature. The analysis was performed as a multi-point determination, showing almost linear behavior in the partial pressure range (p / po) of 0.05–0.20 with a total of 5 measurement points.

[0108] The procedure is based on DIN ISO 9277 and is specified as follows:

[0109] Before weighing, carefully crush the granulated sample with a spatula, then use MICROMERITICS VacPrep. TM The 061 vacuum degassing thermostat was degassed under reduced pressure for 60 minutes at (160±2)℃.

[0110] To determine the BET surface area, the following five relative pressure points (p / po) were recorded during the adsorption phase: 0.0500; 0.0875; 0.1250; 0.1625 and 0.2000.

[0111] For measurements, the TriStar 3000 series (3000 / 3020 / 3030) from MICROMERITICS was used, employing the static capacity test method and a Dewar container.

[0112] Ro-Tap > 300 μm; Ro-Tap < 75 μm - sieve analysis according to Annex F of ISO 5794-1

[0113] Sieve analysis was performed using a rotary sieve separator (Tyler Ro-Tap RX-29 analytical sieve separator with timer switch). The method was performed according to Annex F of ISO 5794-1. For sieve analysis, test sieves with different aperture sizes were stacked one on top of another (analytical sieves with metal mesh, ISO 3310-1, nominal aperture size 75 μm, sieve diameter 200 mm; analytical sieves with metal mesh, ISO 3310-1, nominal aperture size 150 μm, sieve diameter 200 mm; analytical sieves with metal mesh, ISO 3310-1, nominal aperture size 300 μm, sieve diameter 200 mm). The sieve column was inserted into the analytical sieve separator in the prescribed order. The residue was determined as follows: Before determination, the sample was gently homogenized. 100 g of sample, accurate to 0.01 g, was weighed on a precision balance and placed in a beaker. The sample was then quantitatively transferred to the uppermost sieve (300 μm). Ro-Tap sieving was performed for 5 minutes using a tapper. After sieving, the sieving tower was removed, and the fractions on the sieve trays and on the 75μm, 150μm, and 300μm sieves were weighed.

[0114] Calculation of sieve residue

[0115] Ro-Tap<75μm,%=AS·100% / E

[0116] and

[0117] Ro-Tap>300μm,%=A300·100% / E

[0118] and

[0119] Ro-Tap>150μm,%=A150·100% / E

[0120] in

[0121] A300 = Residue (g) on ​​a 300μm sieve.

[0122] AS = Residue in the sieve (g)

[0123] E = Starting weight (g)

[0124] pH - determined on silica according to DIN EN ISO 787-9

[0125] The procedure is based on DIN EN ISO 787-9 and is specified as follows:

[0126] The sample material was pulverized and granulated using a mortar and pestle before weighing.

[0127] Prepare a 5% (m / m) aqueous suspension of the sample to be analyzed. Softened (DM) water is used for this purpose.

[0128] Before measuring pH, stir the sample suspension on a stirrer for at least 5 minutes.

[0129] pH was measured at 23°C ± 2°C on a previously calibrated pH meter from Metrohm, model 780, with pH electrode 6.0228.000 (from Metrohm).

[0130] Loss on drying – determined according to DIN EN ISO 787-2

[0131] The weight loss of a sample heated in a drying oven at 105°C for 2 hours was measured.

[0132] The procedure is based on DIN EN ISO 787-2 and is specified as follows:

[0133] Remove the cap from the weighing bottle (with a flanged cap; approximately 80 mm in diameter and 30 mm in height) and heat at 105°C for approximately 1 hour. After cooling in a desiccator, reinsert the cap. Accurately weigh to 0.01 g using a precision balance. Accurately weigh 5 g–10 g of the sample (weight depends on bulk density) and spread it evenly in a layer at the bottom of the weighing bottle. Carefully open the weighing bottle and heat in a desiccator at (105±2)°C for 2 hours (the cap is also heated, but the weighing bottle is not yet sealed with it).

[0134] Afterward, carefully seal the weighing bottle with the cap, place it in a desiccator to cool, and reweigh it to an accuracy of 0.01g.

[0135] calculate

[0136]

[0137] E = starting weight, in grams.

[0138] A = Final weight, in grams

[0139] Sears number 原始 (SN) – Determined on hydrophilic silica

[0140] The Sears number can be determined by titrating silica with a standard 0.1 mol / L potassium hydroxide solution within a pH range of 4 to 9. 原始 As a measure of the number of free silanol groups.

[0141] The determination method is based on the following chemical reaction, where ≡SiOH is considered to represent the silanol group of silicon dioxide:

[0142]

[0143]

[0144] program:

[0145] Approximately 10.0 g of powdered, spherical, or granular silica was uniformly pulverized at 10,000 rpm for 60 seconds using a Fritsch mill (Pulverisette 14 with an 80 μm sieve). Approximately 1.50 g of this treated silica, accurate to 0.1 mg, was weighed and placed in a 250 ml beaker, and mixed with 150 ml of NaCl solution (β(NaCl) = 200 g / L, adjusted to pH 3 with hydrochloric acid c(HCl) = 1 mol / L). After the sample was completely wetted, the suspension was dispersed at 20,000 rpm for 30 seconds using an Ultra Turrax PT1300D (from Polytron).

[0146] Prior to titration, the pH meter (LL Unitrode pH electrode, model: PT1000 from Metrohm) was calibrated at room temperature using buffer solutions (pH 4.00, pH 7.00, and pH 9.00). The initial pH of the suspension was first measured using the pH meter, and then adjusted to 4.00 using either potassium hydroxide solution (0.1 mol / L) or hydrochloric acid solution (0.1 mmol / L). Subsequently, titration to pH 9.00 was performed using 0.1 mol / L standard KOH solution. The volume (ml) of KOH solution consumed from pH 4.00 to pH 9.00 corresponds to V. pH4-9 Similarly, a blank titration is performed (without adding silica). The blank value of the solution describes the volume V of potassium hydroxide solution required to titrate a silica-free NaCl solution from pH 4 to pH 9. BL .

[0147] Sears number based on the original material 原始 (Unit: ml / (1.5g)) is calculated using the following formula:

[0148] Sears number 原始 =(V pH4-9 -V BL )*T*(1.5g) / E

[0149] Where T = titer of the standard KOH solution used.

[0150] E = Initial mass of the sample, in grams.

[0151] Silanol group density (SD) – calculated using AN based on CTAB surface area

[0152] AN gives the consumption of 0.1n KOH (ml / (1.5g)):

[0153]

[0154] Applying CTAB surface area and Avogadro's constant (N) A The conclusion is:

[0155]

[0156] This yielded OH / nm 2 The density of silanol groups (SD) is expressed as follows:

[0157]

[0158]

[0159] In the formula for SD, the surface areas of AN and CTAB are used in dimensionless form because they have already been taken into account in the calculation.

[0160] Residue on ignition – determined according to ISO 3262-1 or ASTM D 6740

[0161] The total water content (physically and chemically combined water) is determined by calcining precipitated silica at 1000°C for 2 hours in an incineration furnace, thereby determining the content of all volatile components (loss on ignition), and the ignition residue can also be calculated.

[0162] program:

[0163] Using an analytical balance with an accuracy of ±0.1 mg, approximately 500 mg of silica was weighed in each case into two porcelain crucibles or melting crucibles with the aid of a spatula. Subsequently, the crucibles and silica were ignited together in an ignition furnace at (1000±50) °C for (120±5) min.

[0164] After ignition, place the crucible in a desiccator with a suitable desiccant to cool for about 1.5-2 hours, and then weigh it again using an analytical balance. Perform the determination in duplicate.

[0165] Assessment: First, calculate the loss on ignition based on the dry matter content:

[0166]

[0167] IL (DM) Loss on ignition (%) based on the substance dried at 105°C for 2 hours.

[0168] m E Mass of silicon dioxide weighed (g)

[0169] m A Mass (g) of silicon dioxide after ignition

[0170] DL: Drying loss (%) at 105℃ for 2 hours

[0171] The calculation based on the ignition residue of the original material is as follows:

[0172] IL (primitive) = IL (DM) *(100-DL) / 100, therefore

[0173] IR (raw) = 100% - DL - IL (raw)

[0174] Therefore, the drying loss was determined by the method of "Determination of drying loss according to DIN EN ISO 787-2" (see above).

[0175] TAR - Wear of granulated material through brittleness testing

[0176] For wear testing via brittleness testing of granulated materials, fine and coarse fractions of silica were removed using a 3.15 mm–5.00 mm fraction. The granulated material fractions were subjected to repeated mechanical stress for 30 minutes in a rotating brittleness chamber (e.g., ERWEKA TAR 220, with brittleness drums on both the left and right sides). Subsequently, the resulting fine fractions were removed using a 500 μm sieve. The mass difference (%) corresponds to the wear of the granulated material.

[0177] Wear test results are in duplicate.

[0178] Take a representative sample of silica to be analyzed, weigh 50 g. Sift the 3.15 mm–5.00 mm fraction using a careful manual sieve (analytical sieve with metal mesh, ISO 3310-1, 200 mm diameter – nominal aperture sizes 500 μm, 3.15 mm, and 5 mm, and sieve disc). This excludes fine and very coarse particles. Accurately weigh (5.00 ± 0.1) g of the 3.15 mm–5 mm fraction on an analytical or precision balance. Measurements cannot be performed if the sieved amount is insufficient. A representative sample fraction must be collected. Introduce the sample into a brittle drum mounted on an abrasion tester. Run the instrument at 65 rpm for 30 minutes. Subsequently, quantitatively apply the material onto a 500 μm sieve and remove any adhering fine fractions by moderate stirring / movement. Then reweigh the granulated material particles to an accuracy of 0.01 g on a precision or analytical balance.

[0179] evaluate:

[0180]

[0181] Wear: Wear (%) in brittleness test of granulated materials

[0182] E: Starting weight (g) of the 3.15-5mm fraction sieved out.

[0183] A: Stress and residue (g) after fine particle removal

[0184] The measurement result is the average of two separate measurements, expressed as a percentage to one decimal place.

[0185] DOA absorption – determined according to ISO 19246

[0186] To perform this procedure, 12.50 ± 0.02 g of sample was introduced into the kneading chamber of a Brabender Absorptometer E equipped with an extended function / evaluation unit. Then, dioctyl adipic acid (e.g., 2-ethylhexyl adipate) was metered at a rate of 4 ml / min while continuously kneading. DOA). The kneader speed was 125 rpm. The program used the raw data curve to calculate a polynomial. The 70% value of the maximum torque of this polynomial was used to determine the DOA absorption based on the raw material, in ml / (100g). The determination was performed according to ISO 19246.

[0187] For granulated silica, a particle size of 1.0-3.15 mm is used for determination, which must be sieved beforehand with an appropriate sieve.

[0188] The following settings should be made in the measuring instrument software:

[0189] Test conditions

[0190] Dosage rate (burette): 4.0 ml / min

[0191] Kneader speed: 125 min -1

[0192] Temperature: 23.0℃

[0193] evaluate

[0194] Torque threshold: 100mNm

[0195] End: 60 seconds after reaching maximum torque

[0196] Torque limit: 10,000 mNm

[0197] polynomial

[0198] Starting: 50% of maximum torque

[0199] End: 20 seconds after reaching the maximum value

[0200] By using suitable reference materials with different DOA absorptions, one can... The software performs individual standardization on the kneader. Based on a defined standardization function (linear equation Y = a*x + b), the DOA absorption (standardized) based on the original material is obtained from the measurement report, in ml / (100g), and expressed as 70% of the maximum torque.

[0201] Electrical conductivity – determined according to DIN EN ISO 787-14

[0202] The electrical conductivity of silica was determined according to DIN EN ISO 787-14. The procedure has been modified as follows compared to the requirements of this standard:

[0203] A 4% aqueous suspension (4.00 g silica / 100 ml deionized water) was prepared and analyzed.

[0204] The measurement is performed directly on the suspension, rather than on the filtrate.

[0205] The measurements were taken at 20.0℃ ± 0.5℃, and the conductivity at the reference temperature of 20℃ was reported.

[0206] According to DIN 66133, pore radius and pore volume are determined based on mercury intrusion.

[0207] The pore radius, corresponding pore volume, and pore distribution of the silica samples were determined within a pressure range of 0.003 to 420 MPa. Measurements were performed using a Micromeritics AutoPore IV 9520 according to DIN 66133.

[0208] The sample was dried in a drying cabinet at 105±2℃ for 2 hours.

[0209] For measurement, the prepared sample was weighed into a Micromeritics Model 16 penetrometer. Approximately 330 mg was weighed, accurate to 0.001 g. The penetrometer was then gradually evacuated to 50 μm Hg through the low-pressure port of the instrument and maintained at this pressure for 5 minutes. Subsequently, mercury was filled into the penetrometer first through the low-pressure port and then through the high-pressure port until the pressure reached 420 MPa, and the measurement curve (pressure / volume curve) was recorded. The Autopore instrument was operated according to the Micromeritics instructions and was software-controlled. Each measurement was calibrated using blank measurements of the penetrometer. The total measurement range was 0.003–420 MPa.

[0210] The measurement results are calculated based on the measurement curve as follows:

[0211] Maximum porosity:

[0212] Hg, -dV / dlogD; contact angle 140°, surface tension 480mN / m (unit: nm)

[0213] PV:

[0214] Mercury, 0.0042-414 MPa; contact angle 140°, surface tension 480 mN / m (ml / g)

[0215] V(d5-d50) / V(d5-d100):

[0216] The porosity was determined by the Hg porosity determination method according to WO2008077948.

[0217] Bulk density – determined according to ASTM D 1513

[0218] Weigh a 1000ml graduated cylinder (20ml graduations) with a powder funnel (at least 1L capacity) on a precision balance (accuracy 0.1g). Carefully rotate the sample container to thoroughly mix the sample to be analyzed. For granulated materials, special care should be taken to ensure that no additional fine particles are generated. After mixing, carefully transfer 500 to 700ml of silica to a 1L beaker (with coarse divisions) using a spoon. Pour the silica sample into the graduated cylinder along with the beaker through the funnel. After settling (without mechanical densification), read the volume of the bulk material to an accuracy of 5ml. It should be ensured that the filling volume is between 500ml and 700ml. Meanwhile, to calculate the bulk density, the sample weight should be determined to an accuracy of ±0.1g.

[0219] Bulk density calculation:

[0220]

[0221] In this formula:

[0222] Bulk density (D) (g / L)

[0223] V. Volume of the sample after stirring (ml)

[0224] m Sample mass (g)

[0225] The measurement should be performed in duplicate. If the two results differ by more than 3%, a third value should be used to form the average. The reported results should not have any decimal places. Example

[0226] Example 1

[0227] First, 1140 L of water and 150 kg of water glass were added to a reactor equipped with a propeller agitator system, and the mixture was heated to 88.8 °C. Over 100 minutes, 727.9 kg of water glass (density 1.345 kg / L, 27% SiO2, 8% Na2O) and 77.6 kg of sulfuric acid (density 1.84 kg / L, 96% H2SO4) were simultaneously added to bring the AN value of the reaction mixture to 24-27.

[0228] Subsequently, sulfuric acid (density 1.84 kg / l, 96% H2SO4) was added to bring the pH of the reaction mixture to 8.6 (measured at 60°C).

[0229] The temperature in the sedimentation container is raised to 94°C within 5 minutes, and the suspension is aged for 55 minutes while being stirred at 94°C.

[0230] Subsequently, sulfuric acid (density 1.84 kg / l, 96% H2SO4) was added at a metering rate of 0.70 kg / min until a pH of 7 was reached (measured at 60 °C). Then, sulfuric acid was added at a metering rate of 0.35 kg / min until the pH reached 4.0 (measured at 60 °C).

[0231] The resulting suspension was filtered and washed with water as usual, and then subjected to rotary flash drying. The resulting powder was granulated, i.e., compacted in a roller compactor and then crushed by a crusher.

[0232] Example 2

[0233] First, add 1164 L of water and 150 kg of water glass (AN 25-26) to a reactor equipped with a propeller agitator system, and heat to 89.0 °C. Simultaneously add the following substances over 100 minutes: water glass (density 1.345 kg / L, 27% SiO2, 8% Na2O) at an average metered addition rate of 7.3 kg / min, and sulfuric acid (density 1.84 kg / L, 96% H2SO4) at an average metered addition rate of 0.82 kg / min.

[0234] Subsequently, sulfuric acid (density 1.84 kg / l, 96% H2SO4) was added to bring the pH of the reaction medium to 8.5 (measured at 60°C).

[0235] The temperature in the sedimentation container is raised to 94°C within 5 minutes, and the suspension is aged for 55 minutes while being stirred at 94°C.

[0236] Subsequently, sulfuric acid (density 1.84 kg / l, 96% H2SO4) was added at a metering rate of 0.70 kg / min to first lower the pH to 7 (measured at 60 °C), and then acidification was continued at a metering rate of 0.35 kg / min until the pH dropped to 4.0 (measured at 60 °C).

[0237] The resulting suspension was filtered and washed with water as usual, and then subjected to rotary flash drying. The resulting powder was granulated, i.e., compacted in a roller compactor and then crushed by a crusher.

[0238] Silica has the analytical parameters reported in Table 1.

[0239] Table 1

[0240]

[0241] Reference silica 1 is from Solvay SA. 1085GR.

[0242] Example 3

[0243] Rubber property testing

[0244] The formulations for the rubber compounds (green tyre compound) are given in Table 2 below. In this table, the unit phr refers to the number of parts by weight of 100 parts of crude rubber used.

[0245] Table 2: Formula of Raw Fetal Mixture

[0246]

[0247] VSL 4526-2HM is a solution of styrene-butadiene rubber supplemented with 37.5 phr TDAE oil; Mooney (1+4@100℃): 62ME; Vinyl: 44.5%; Styrene: 26%.

[0248] As shown in Table 3 below, the rubber compound is produced in three stages in the internal mixer:

[0249] Table 3: Methods for preparing mixtures

[0250]

[0251] The general methods for producing rubber blends and their vulcanizates are described in the following book: "Rubber Technology Handbook", W. Hofmann, Hanser-Verlag 1994.

[0252] The vulcanization time for each specimen was 15 minutes at 165°C. Rubber tests were conducted according to the test methods specified in Table 4.

[0253] Table 4: Procedures for Physical Performance Testing

[0254]

[0255]

[0256]

[0257] Table 5: Performance data of the examples

[0258]

[0259] Table 5 shows the rubber data of the rubber compounds according to the invention, demonstrating the superior dispersion / dispersion of the silica according to the invention compared to prior art rubber compound 1 (comparison). Rubber compounds 2 and 3 of the invention, when measured directly through defects across the vulcanized rubber cross-section, exhibit significantly lower levels of undispersed silica through tactile morphology measurements and visual observation using a dispersion tester. Combined with this, all measurements related to reinforcement show significant improvement: in tensile tests, stress values ​​are significantly increased for the same elongation at break. This also aligns with improved Die C and Graves tear results under various measurement conditions. DIN wear of the rubber compounds according to the invention is also improved compared to the control compound. These advantages indicate that tires with treads comprising and reinforced with silica according to the invention will exhibit significantly improved wear characteristics. Furthermore, ball rebound and tanδ indices at 23°C and 0°C also show significantly improved wet grip properties for such treads. Compared to existing technologies, the high stiffness (E*, 60°C and modulus (max) in RPA) at high temperatures under these measurement conditions also demonstrates improved handling characteristics on dry roads. In summary, these rubber compounds and silica according to the invention are therefore particularly capable of optimizing and improving the overall performance of, for example, winter tires or even more specifically, Nordic winter tires to a very high degree.

Claims

1. Precipitated silica, characterized in that... It has the following physicochemical parameters: CTAB surface area ≤115 m² 2 / g, DOA ≥130 ml / 100g, RoTap >300µm ≥86%, V(d5-d50) / V(d5-d100) 0.30-0.

64.

2. The precipitated silica according to claim 1, characterized in that, CTAB surface area ≤90m² 2 / g.

3. The precipitated silica according to claim 1, characterized in that, At 0.0042 MPa-414 MPa and 140°C, the PV value is in the range of 1.00-3.00 ml / g.

4. The precipitated silica according to claim 1, characterized in that, Silanol group density ≥ 5.4 OH / nm 2 .

5. The precipitated silica according to claim 1, characterized in that, The bulk density is at least 180 g / l.

6. The precipitated silica according to claim 1, characterized in that, Particle length ≥ 1 mm.

7. The method for preparing precipitated silica according to claim 1, characterized in that... a) An aqueous solution of organic salts and / or inorganic salts and / or alkali metal silicates or alkaline earth metal silicates and / or organic bases and / or inorganic bases with an initial charge pH ≥ 9. b) Simultaneously meter water glass and acidifying agent into the initial charge, while stirring at 80-98°C for 60-120 minutes. c) Then stop adding water glass and add acid only in smaller amounts than before, so that the pH of the mixture, measured at 60°C, reaches 8.3–10.

0. d) The mixture is then stirred at a high temperature of >85°C for 45 to 200 minutes without adding any other reactants. e) Acidify with sulfuric acid until the pH reaches 3.5-4.5 as measured at 60°C, and f) Filter and dry the mixture until the drying loss is <8%, and then granulate it.

8. A rubber compound containing (A) Rubber or a mixture of rubbers, and (B) At least one precipitated silica according to claim 1.

9. A method for preparing the rubber mixture according to claim 8, characterized in that, The rubber or mixture of rubbers, the precipitated silica according to claim 1, and other optional rubber additives are mixed in a mixing unit.

10. Use of the rubber compound according to claim 8 in the production of tires, cable sheaths, hoses, drive belts, conveyor belts, roller covers, shoe soles, padding elements, and damping elements.

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