Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
  • C01B33/126—Preparation of silica of undetermined type
  • C01B33/128—Preparation of silica of undetermined type by acidic treatment of aqueous silicate solutions
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/113—Silicon oxides; Hydrates thereof
  • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
  • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
  • C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
  • C01B33/193—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates of aqueous solutions of silicates

Definitions

• precipitated silicas as reinforcing filler in silicone matrices (for example for coating electrical cables) or in compositions based on polymer (s), natural or synthetic, in particular elastomer (s), especially diene, for example for shoe soles, floor coverings, gas barriers, fire-retardant materials and also technical parts such as ropeway rollers, appliance seals, liquid or gas line joints, brake system seals, ducts, cables and transmission belts.
• the acid used in steps (ii), (iii) and (iv) can then be, for example, a dilute acid, advantageously dilute sulfuric acid, that is to say having a concentration much lower than 80% by weight, in this case a concentration of less than 20% by weight (and in general of at least 4% by weight), in particular less than 14% by weight, especially not more than 10% by weight, for example between 5 and 10% by weight.
• the invention is a new process for the preparation of precipitated silica comprising the reaction of a silicate with at least one acid, whereby a suspension of silica is obtained. , then separating and drying this suspension, in which the reaction of the silicate with the acid is carried out according to the following successive steps:
• step (v) the reaction medium obtained at the end of step (iv) is brought into contact (mixture) (thus having a pH of between 2.5 and 5.3, preferably between 2.8 and 5.2 ) with acid and silicate, so that the pH of the reaction medium is maintained between 2.5 and 5.3, preferably between 2.8 and 5.2, in which process in at least a portion of step (iii) (i.e., in at least a portion or all of step (iii)), the acid used is a concentrated acid, preferably selected from the group consisting of sulfuric acid having a concentration of at least 80% by weight, in particular at least 90% by weight, the acetic acid or formic acid having a concentration of at least 90% by weight, nitric acid having a concentration of at least 60% by weight, the phosphoric acid having a concentration of at least 75% by weight, the hydrochloric acid having a concentration of at least 30% by weight.
• the acid used is a concentrated acid, preferably selected from the group consisting of sulfuric acid having
• silicate any common form of silicates such as metasilicates, disilicates and advantageously an alkali metal silicate M in which M is sodium or potassium.
• the silicate may have a concentration (expressed as SiO 2) of between 2 and 330 g / l, for example between 3 and 300 g / l, in particular between 4 and 260 g / l.
• the second step (step (ii)) is to add acid in the initial stock.
• step (v) the acid and the silicate (for example the alkali metal silicate M) are added simultaneously to said reaction medium; preferably, this simultaneous addition is carried out with regulation of the pH of the reaction medium obtained during this addition to a value (substantially) constant within the aforementioned ranges.
• the silicate for example the alkali metal silicate M
• step (v) it may be advantageous to proceed at the end of step (v) or of the optional step (vi) to a maturation of the reaction medium obtained, in particular at the pH obtained at the end of this step (v) ( or step (vi)), and in general with stirring.
• This curing can for example last from 2 to 30 minutes, in particular from 3 to 20 minutes and can be carried out between 75 and 97 ° C., preferably between 80 and 96 ° C., in particular at the temperature at which the reaction was carried out.
• step (v) (or step (vi) It preferably does not include any addition of acid or addition of silicate.
• an asymmetrical T-shaped or Y-shaped mixer or tube
• a symmetrical T-shaped or Y-shaped mixer or tube
• one of the fluids is injected into the central tube by means of a smaller diameter side tube.
• the latter forms with the central tube an angle of 90 ° in general (T-tube); this angle may be different from 90 ° (Y-tube), giving co-current systems (for example 45 ° angle) or counter-current (for example 135 ° angle) relative to the other current.
• a fast mixer As a fast mixer, a tangential jet mixer, a Hartridge-Roughton mixer or a vortex mixer (or precipitator) are preferably used, which are derived from symmetrical T-shaped devices.
• step (v) it is possible to use a tangential jet fast mixer, Hartridge-Roughton or vortex, comprising a chamber having (a) at least two tangential admissions through which enter separately (but at the same time ) on the one hand, the silicate, and on the other hand, the medium resulting from the addition of acid to the reaction medium resulting from step (iv), namely, on the one hand, silicate and the acid, and on the other hand, the reaction medium resulting from step (iv), and (b) an axial outlet through which the reaction medium obtained in this step (v) leaves, preferably to a reactor (tank) arranged in series after said mixer.
• the two tangential admissions are of preferably located symmetrically and oppositely to the central axis of said chamber.
• Each tangential inlet tube may have an internal diameter d of 0.5 to 80 mm.
• This internal diameter d may be between 0.5 and 10 mm, in particular between 1 and 9 mm, for example between 2 and 7 mm. However, especially on an industrial scale, it is preferably between 10 and 80 mm, in particular between 20 and 60 mm, for example between 30 and 50 mm.
• the flow rates of the silicate and the acid are for example determined so that at the confluence point the two reactant streams come into contact with each other in a sufficiently turbulent flow zone.
• the separation used in the preparation process according to the invention usually comprises a filtration, followed by washing if necessary.
• the filtration is carried out by any suitable method, for example by means of a filter press, a belt filter, a vacuum filter.
• the drying is done by atomization.
• any suitable type of atomizer may be used, such as a turbine, nozzle, liquid pressure or two-fluid atomizer.
• a turbine nozzle
• liquid pressure two-fluid atomizer.
• the silica that can then be obtained is usually in the form of substantially spherical balls.
• the silica that is then likely to be obtained is generally in the form of a powder.
• the silica that may then be obtained may be in the form of a powder.
• the silica that can then be obtained by this agglomeration step is generally in the form of granules.
• the powders, as well as the silica beads, obtained by the process according to the invention thus offer the advantage, among others, of having a simple, effective and economical way of accessing granules, in particular by conventional setting operations. shaped, such as for example granulation or compaction.
• the precipitated silicas prepared by the process according to the invention are generally in at least one of the following forms: substantially spherical beads, powder, granules.
• the process according to the invention makes it possible to obtain silicas formed from aggregates of large primary particles of silica, on the surface of which there are small primary particles of silica.
• the implementation of the preparation method according to the invention makes it possible in particular to obtain during said process (at the end of step (v) or of the optional step (vi)) a more concentrated suspension of precipitated silica than that obtained by an identical process using only dilute acid, and therefore a productivity gain in precipitated silica (which can reach for example at least 10 to 40 %), in particular to the precipitation reaction (that is to say at the end of step (v) or of the possible step (vi)), while surprisingly accompanying the obtaining precipitated silicas having, preferably, a particular morphology, particle size and porosity.
• the precipitated silicas obtained by the process according to the invention preferably have good dispersibility in the polymers and give them a compromise of satisfactory properties, for example in terms of their mechanical, dynamic and rheological, comparable to those precipitated silicas obtained by an identical process using only diluted acid.
• the polymer compositions in which the precipitated silicas prepared by the process according to the invention can be used, in particular as reinforcing filler, are generally based on one or more polymers or copolymers, in particular a or more elastomers, especially thermoplastic elastomers, preferably having at least a glass transition temperature of between -150 and +300 ° C, for example between -150 and +20 ° C.
• finished articles based on the polymer compositions described above, such as shoe soles, tires, floor coverings, gas barriers, fireproofing materials and the like. also technical parts such as ropeway rollers, appliance joints, liquid or gas line joints, brake system joints, hoses, ducts (especially cable ducts) , cables, motor mounts, conveyor belts and transmission belts.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Inorganic Chemistry (AREA)
• Silicon Compounds (AREA)

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Publications (1)

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Cited By (5)

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Citations (3)

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• 2012
  • 2012-01-25 FR FR1200213A patent/FR2985992B1/fr not_active Expired - Fee Related
• 2013
  • 2013-01-23 WO PCT/EP2013/051237 patent/WO2013110658A1/fr not_active Ceased
  • 2013-01-23 BR BR112014018051A patent/BR112014018051A8/pt not_active Application Discontinuation
  • 2013-01-23 KR KR1020147023222A patent/KR20140116213A/ko not_active Abandoned
  • 2013-01-23 US US14/373,799 patent/US10011494B2/en active Active
  • 2013-01-23 MX MX2014009002A patent/MX2014009002A/es unknown
  • 2013-01-23 EP EP13701979.0A patent/EP2807117B1/fr active Active
  • 2013-01-23 CN CN201380006533.4A patent/CN104080736A/zh active Pending
  • 2013-01-23 CA CA2862475A patent/CA2862475A1/fr not_active Abandoned

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