FR2818631A1 - PROCESS FOR THE PREPARATION OF PRECIPITATED SILICA COMPRISING TWO FAMILIES OF AGGREGATES AND FOR DISPENSING SIZES OF MONOMODAL PORES - Google Patents

Abstract

The invention concerns a method for preparing a silica precipitate, for use as reinforcing filler in polymer compositions, comprising two families of aggregates of particles of different sizes, 4 to 15 mm for one and 16 to 35 mm for the other, and having a single-mode pore-size distribution, said method consisting in spray-drying a cake obtained by filtering a mixture of two different silica suspensions obtained each during the precipitating reaction of the two families of silica.

Description

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PROCESS FOR THE PREPARATION OF PRECIPITATED SILICA COMPRISING TWO FAMILIES OF AGGREGATES AND FOR DISPENSING SIZES OF MONOMODAL PORES
The present invention relates to a new process for the preparation of a precipitated silica, formed of two populations of aggregates while having a size distribution of the monomodal pores.

 It also relates to the precipitated silica capable of being obtained by this process, its use as a reinforcing filler in polymer compositions, as well as the finished articles based on these compositions.

tailles comprises entre 16 et 35 nm, de préférence entre 17 et 30 nm, notamment entre 20 et 25 nm, et, d'autre part, présente une distribution de tailles de pores monomodale (un seul pic est observé dans la représentation graphique de cette distribution). The main object of the invention is therefore a process for preparing a precipitated silica which, on the one hand, comprises two families of aggregates, the aggregates of the first family consisting of (individual) particles of silica of sizes between 4 and 15 nm, preferably between 10 and 15 nm, the aggregates of the second family consisting of (individual) particles of silica

sizes between 16 and 35 nm, preferably between 17 and 30 nm, in particular between 20 and 25 nm, and, on the other hand, have a distribution of monomodal pore sizes (a single peak is observed in the graphic representation of this distribution).

 The size of the particles can be measured in particular by Transmission Electron Microscopy; the pore size distribution is determined by mercury porosimetry (standard DIN 66133).

 According to the process of the invention: - two different suspensions (slurries) of silica are each obtained, before any filtration, during the precipitation reaction of silicas, - the mixture obtained is filtered so as to obtain a filtration cake, advantageously pumpable, - said cake is spray-dried, optionally after fluidization (disintegration).

 The precipitated silica obtained advantageously consists of an intimate mixture of two families (populations) of aggregates, the aggregates of the first family generally representing 15 to 85%, preferably 20 to 50%,

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 by weight of the silica, and the aggregates of the second family generally representing 15 to 85%, preferably 50 to 80%, by weight of the silica.

 Each (aqueous) silica suspension used in the process of the invention results from a precipitation reaction of a silica, before the filtration step, in particular by reaction between an alkali metal silicate (sodium silicate for example) and an acid (sulfuric acid for example).

 Silica suspensions can for example be used as obtained during the precipitation reactions described in applications EP 0520862, WO 95/09127, WO 95/09128 and WO 98/54090.

 The two silica suspensions used can be obtained from the precipitation reactions of silica having between them a difference in BET specific surface area values and / or a difference in CTAB specific surface area values of at least 30 m 2 / g, in particular of at least 40 m2 / g, for example at least 60 m2 / g.

 According to a variant of the invention, this difference is even at least 90 m2 / g, in particular at least 100 m2 / g, for example at least 120 m2 / g.

 The BET specific surface is determined according to the BRUNAUEREMMET-TELLER method described in "The Journal of the American Chemical Society", Vol. 60, page 309, February 1938 and corresponding to standard NF T 45007 (November 1987). The CTAB specific surface is the external surface determined according to standard NF T 45007 (November 1987) (5.12).

 The mass ratio between the two suspensions to be mixed is generally between 25: 75 and 75.25, in particular between 40: 60 and 60: 40. Most often, this ratio is approximately 50: 50.

 In the process according to the invention, the filtration of the mixture of the two suspensions (slurries) can be carried out by means of any suitable filter making it possible to advantageously obtain a pumpable filtration cake, in particular a press filter or a vacuum filter . Filtration can be accompanied by washing.

 Likewise, the drying can be carried out using a turbine atomizer; the precipitated silica obtained is then generally in the form of a powder, preferably of average size of at least 15 μm, in particular between 30

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et 120 um. Il peut être effectué à l'aide d'un atomiseur à buses, à pression liquide ou à deux fluides ; la silice précipitée obtenue se présente alors plutôt sous forme de billes sensiblement sphériques, de préférence de taille moyenne d'au moins 80 um, par exemple d'au moins 150 um et généralement d'au plus 300 um (norme NF X 11507).

and 120 µm. It can be carried out using a nozzle atomizer, at liquid pressure or with two fluids; the precipitated silica obtained is then more in the form of substantially spherical beads, preferably of average size of at least 80 μm, for example of at least 150 μm and generally of at most 300 μm (standard NF X 11507).

 The drying can be preceded by a fluidification operation (disintegration) of the cake, by a mechanical action, for example by passing the cake through a grinder of the colloidal or ball type; this mechanical action can be carried out in the presence of an aluminum compound, in particular sodium aluminate and, preferably, in the presence of an acidifying agent. The fluidification operation notably makes it possible to lower, if necessary, the viscosity of the cake to be dried.

 After drying, a grinding step can optionally be carried out on the silica obtained; this grinding generally leads to a powder.

 The dried (in particular by a turbine atomizer) or ground product can be subjected to an agglomeration operation (in particular direct compression, wet granulation, extrusion, and preferably dry compaction); the precipitated silica obtained is then usually in the form of granules, preferably of size at least 1 mm, in particular between 1 and 10 mm.

 The precipitated silica capable of being obtained by the process according to the invention generally has a DOP oil intake of between 180 and 400 ml / 100g, preferably between 200 and 370 ml / 100g (the DOP oil intake is determined according to standard NFT 30-022 (March 1953) using dioctylphthalate.

 It usually has: - a BET specific surface area between 110 and 260 m2 / g, in particular between 140 and 230 m2 / g, - a CTAB specific surface area between 100 and 250 m2 / g, for example between 140 and 230 m2 / g .

 It generally has a BET surface / CTAB surface ratio varying between 1.0 and 1.2, that is to say a low microporosity.

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 Its pH is, for example, between 6.0 and 7.5, in particular between 6.4 and 7.0.

 A subject of the present invention is also the silica capable of being obtained by the process according to the invention.

présentent, de manière préférée, une bonne aptitude à la dispersion/désagglomération ; cette aptitude peut être quantifiée au moyen du test décrit dans la demande WO 98/54090 ; ainsi, elles peuvent présenter un diamètre médian (05o), après désagglomération aux ultra-sons, inférieur à 5 um, elles peuvent aussi présenter un facteur de désagglomération aux ultra-sons (Fo) d'au moins 5,5 ml. The silicas (capable of being) obtained by the process according to the invention

preferably have good dispersibility / disaggregation properties; this ability can be quantified by means of the test described in application WO 98/54090; thus, they can have a median diameter (05o), after deagglomeration with ultrasound, less than 5 μm, they can also have a deagglomeration factor with ultrasound (Fo) of at least 5.5 ml.

 They find a particularly advantageous application as a reinforcing filler in polymer compositions. It gives the latter a very satisfactory compromise in mechanical, rheological and dynamic properties and, preferably, these properties are rather improved compared to those obtained by using as a filler a direct mixture of the two silicas (in solid form) than one would obtain from the two suspensions used in the process described above.

 These polymer compositions are generally based on one or more polymers or copolymers, in particular on one or more elastomers (in particular hermoplastic elastomers), preferably having a glass transition temperature of between −150 and +300. C, for example between-150 and + 20 C.

 Mention may in particular be made, as possible polymers, of diene polymers, in particular diene elastomers.

 For example, mention may be made of natural rubber, polymers or copolymers derived from aliphatic or aromatic monomers, comprising at least one unsaturation (such as, in particular, ethylene, propylene, butadiene, isoprene, styrene), polybutylacrylate or their combinations, mention may also be made of silicone elastomers and halogenated polymers.

 Said polymer compositions can be vulcanized with sulfur.

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 In general, they further comprise at least one coupling agent and / or at least one recovery agent; they can also comprise, inter alia, an oxidizing agent.

 The proportion by weight of silica in the polymer composition can vary within a fairly wide range. In general, it represents 20 to 70%, for example 25 to 60%, of the amount of the polymer (s).

 The present invention also relates to the finished articles based on the polymer compositions described above. Mention may be made, as finished articles, of floor coverings, shoe soles, parts of vehicle tracks, tire casings (in particular the sidewalls and tire tread), cable car rollers, seals for household appliances, sheaths, cables, transmission belts.

 The following examples illustrate the invention without, however, limiting its scope.

pondérât SiOz sur Na20 égat à 3, 5 Le mélange obtenu a une concentration en Si02 égale à 74 gll. Maintenu sous agitation il est porté à 90 C par chauffage double enveloppe. Quand cette température est atteinte on introduit à un débit de 4,91 1/h de l'acide sulfurique dilué de densité à 20 C égale à 1050 kg/m3 jusqu'à l'obtention dans le milieu réactionnel d'une valeur de pH égale à 8 (après 60 minutes d'introduction d'acide). La température est égale à 90 C pendant les 40 premières minutes de Example 1
1. 1- Preparation of the reaction mixture (suspension) N 1
In a stainless steel reactor equipped with a temperature and pH regulation system and a propeller stirring system, 66 g of water, 8585 g of a sodium sulfate solution concentrated at 47 gll 8550 g of sodium silicate with density at 20'C equal to 1133 kg / m3 and ratio

weight SiOz over Na20 equal to 3.5 The mixture obtained has a concentration of SiO2 equal to 74 gll. Maintained with stirring, it is brought to 90 ° C. by double jacket heating. When this temperature is reached, a diluted sulfuric acid with a density at 20 C equal to 1050 kg / m3 is introduced at a flow rate of 4.91 l / h until a pH value is obtained in the reaction medium. equal to 8 (after 60 minutes of introduction of acid). The temperature is 90 C during the first 40 minutes of

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la réaction, elle est ensuite portée de 90 C à 95 C en 5 minutes environ par chauffage par double enveloppe, puis maintenue à 95 C jusqu'à la fin de la réaction.

the reaction, it is then brought from 90 ° C. to 95 ° C. in about 5 minutes by heating with a double jacket, then maintained at 95 ° C. until the end of the reaction.

 Once the pH value equal to 8 has been reached (after 60 minutes of introduction of acid), aqueous sodium silicate of the type described above is introduced jointly into the reaction medium at a flow rate of 2.38 ich and sulfuric acid, also of the type described above at a controlled rate so as to maintain the pH value of the reaction medium equal to 8 +/- 0.1. After 30 minutes of simultaneous addition, the introduction of the silicate and one then continues to introduce dilute acid so that the pH value of the reaction medium reaches 5.2 in about 7 minutes. The reaction suspension is then kept at this pH for 5 minutes.

1. 2- Preparation of the reaction mixture (suspension)? 2
In a stainless steel reactor equipped with a temperature and pH regulation system and a propeller stirring system, 5544 g of water, 2839 g of a sodium sulfate solution concentrated at 46.8 gll, 4370 g of sodium silicate with a density at 20 "C equal to 1230 kg / m3 and a Si02 to Na20 weight ratio equal to 3.5
The mixture obtained has an SiO2 concentration equal to 75 gll. Maintained with stirring, it is brought to 73 ° C. by double jacket heating. When this temperature is reached, a dilute sulfuric acid with a density of 20 C equal to 1050 kg / m3 is introduced at a flow rate of 5.2 l / h until a pH value is obtained in the reaction medium. equal to 8. The temperature is equal to 73 ° C. during the first 25 minutes of the reaction, it is then brought from 73 ° C. to 95 ° C. in about 20 minutes by heating with a double jacket, then maintained at 92 ° C. until end of reaction.

 Once the pH value equal to 8 has been reached (after 50 minutes of introduction of acid), aqueous sodium silicate of the type described above is introduced jointly into the reaction medium at a flow rate of 1.76 l / h and sulfuric acid, also of the type described above at a rate regulated so as to

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 maintain the pH value of the reaction medium equal to 8 +/- 0.1. After 15 minutes of simultaneous addition, the introduction of the silicate is stopped and the diluted acid is then continued to introduce so that the value the pH of the reaction medium reaches 5.2 in about 7 minutes. The reaction suspension is then kept at this pH for 5 minutes.

 1. 3- Then mix the 2 reaction slurries? 1 and 2 up to 50/50 by mass of slurry, the resulting mixture being filtered under vacuum and washed using a flat filter.

 The cake obtained is then fluidized by mechanical action. After this disintegration operation, a pumpable cake is obtained having a dry matter content of 15%; this cake is dried by means of a turbine atomizer.

- pH 6. 8 - Na2S04 0, 7 % Elle présente un diamètre médian (0so), après désagglomération aux ultrasons, de 3, 5 um. The characteristics of the silica obtained (in powder form) are as follows: - BET specific surface area 155 m2 / g - CTAB specific surface area 155 m2 / g - DOP oil intake 306 m! / 100g

- pH 6. 8 - Na2SO4 0.7% It has a median diameter (0so), after deagglomeration with ultrasound, of 3.5 μm.

 Examination by transmission electron microscopy shows that the silica is made up of an intimate mixture of two populations of aggregates.

The pore size distribution of this silica is monomodal
Example 2
2. 1- Preparation of the reaction slurry (suspension) N 1
In a stainless steel reactor equipped with a temperature and pH regulation system and a propeller stirring system, the following are introduced:

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5100 g d'eau, 2920 g d'une solution de sulfate de sodium concentrée à 46. 8 gll 4530 g de silicate de soude de densité à 20 C égale à 1230 kg/m3 et de rapport pondéral Si02 sur Na20 égal à 3,5.

5100 g of water, 2920 g of a sodium sulphate solution concentrated at 46. 8 gll 4530 g of sodium silicate with a density at 20 C equal to 1230 kg / m3 and a Si02 to Na20 weight ratio equal to 3, 5.

 The mixture obtained has an SiO2 concentration equal to 75 gll. Maintained with stirring, it is brought to 91 ° C. by double jacket heating. When this temperature is reached, a dilute sulfuric acid with a density at 20 C equal to 1050 kg / m3 is introduced at a flow rate of 5 ich until a pH value equal to 8 is obtained in the reaction medium. The temperature is equal to 91 ° C. during the first 25 minutes of the reaction, it is then brought from 91 ° C. to 95 ° C. in about 5 minutes by heating with a double jacket, then maintained at 95 ° C. until the end of the reaction. .

 Once the pH value equal to 8 has been reached (after 50 minutes of introduction of acid), aqueous sodium silicate of the type described above is introduced jointly at a flow rate of 2.59 l / h and sulfuric acid, also of the type described above at a controlled rate so as to maintain the pH value of the reaction medium equal to 8 +/- 0.1. After 20 minutes of simultaneous addition, the introduction of the silicate is stopped and then continues to introduce dilute acid so that the pH value of the reaction medium reaches 5.2 in about 8 minutes. The reaction suspension is then kept at this pH for 5 minutes.

2. 2- Preparation of the reaction mixture (suspension)? 2
In a stainless steel reactor equipped with a temperature and pH regulation system and a propeller stirring system, there are introduced: 5912 g of water, 4910 g of a sodium sulfate solution concentrated at 46.8 gll 4430 g of sodium silicate with a density at 20 C equal to 1230 kg / m3 and a Si02 to Na20 weight ratio equal to 3.5

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Le mélange obtenu a une concentration en Si02 égale à 60 gll. Maintenu sous agitation il est porté à 74 C par chauffage double enveloppe. Quand cette température est atteinte on introduit à un débit de 5,94 I/h de l'acide sulfurique dilué de densité à 20"C égale à 1050 kg/m3 jusqu'à l'obtention dans le milieu réactionnel d'une valeur de pH égale à 8. La température est égale à 91 C pendant les 25 premières minutes de la réaction, elle est ensuite portée de 74 C

à 94 C en 20 minutes environ par chauffage par double enveloppe, puis maintenue à 94 C jusqu'à la fin de la réaction. On introduit conjointement dans le milieu réactionnel du silicate de sodium aqueux du type décrit ci-avant à un débit de 2 I/h et de l'acide sulfurique, également du type décrit ci-avant à un débit régulé de façon à maintenir la valeur du pH du milieu réactionnel égale à 8 +/-0, 1. Après 40 minutes d'addition simultanée on arrête l'introduction du silicate et on continue ensuite à introduire de l'acide dilué de façon à ce que la valeur du pH du milieu réactionnel atteigne 5.2 en 9 minutes environ. On maintient alors la suspension réactionnelle à ce pH pendant 5 minutes.

The mixture obtained has an SiO2 concentration equal to 60 gll. Maintained with stirring, it is brought to 74 ° C. by double jacket heating. When this temperature is reached, a diluted sulfuric acid with a density of 20 "C equal to 1050 kg / m3 is introduced at a flow rate of 5.94 I / h until a value of pH equal to 8. The temperature is equal to 91 C during the first 25 minutes of the reaction, it is then brought to 74 C

at 94 ° C. in approximately 20 minutes by heating with a double jacket, then maintained at 94 ° C. until the end of the reaction. Is introduced jointly into the reaction medium of aqueous sodium silicate of the type described above at a flow rate of 2 l / h and sulfuric acid, also of the type described above at a flow rate regulated so as to maintain the value the pH of the reaction medium equal to 8 +/- 0.1. After 40 minutes of simultaneous addition, the introduction of the silicate is stopped and the diluted acid is then continued to introduce so that the pH value of the reaction medium reaches 5.2 in about 9 minutes. The reaction suspension is then kept at this pH for 5 minutes.

 2. 3- Then mix the 2 reaction slurries? 1 and 2 up to 50/50 by mass of slurry, the resulting mixture being filtered under vacuum and washed using a flat filter.

 The cake obtained is then fluidized by mechanical and chemical action.

(addition of sulfuric acid and addition of a sodium aluminate solution corresponding to the AI / SIO2 ratio = 0.3%) After this disintegration operation, a pumpable cake is obtained having a dry matter content of 16%; this cake is dried by means of a turbine atomizer.

- pH 6. 7 - Na2S04 0, 7 % Silica is obtained in the powder state, the values of which are as follows: - aluminum content 0.3% - BET specific surface area 186 m2 / g - CTAB specific surface area 182 m2 / g - DOP oil intake 344 ml / 100g

- pH 6. 7 - Na2S04 0.7%

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Elle présente un diamètre médian (ovo), après désagglomération aux ultrasons, de 3, 0 um.

It has a median diameter (ovo), after deagglomeration with ultrasound, of 3.0 μm.

 Examination by transmission electron microscopy shows that the silica is made up of an intimate mixture of two populations of aggregates.

 The pore size distribution of this silica is monomodal.

92C à 95 C en 3 minutes environ par introduction de vapeur vive, puis maintenue à 95 C jusqu'à la fin de la réaction. Example 3
3. 1- Preparation of the reaction slurry (suspension) N 1
In a stainless steel reactor equipped with a propeller stirring system and a heating by introduction of live steam, are introduced: - 280 l of silicate with a density at 20 ° C equal to 1230 kg / m3 and ratio by weight Si02 on Dna20 equal to 3.5 - 618 1 of aqueous solution containing 19 kg of Na2SO4
The mixture obtained has an SiOz concentration equal to 73 g / l. Maintained with stirring, it is brought to 92 ° C. by double jacket heating. When this temperature is reached, a diluted sulfuric acid with a density of 20 C equal to 1050 kg / m3 is introduced at a flow rate of 360 ich until a pH value equal to 8 is obtained in the reaction medium. The temperature is 92 C during the first 30 minutes of the reaction, it is then brought to

92C at 95 C in about 3 minutes by introduction of live steam, then maintained at 95 C until the end of the reaction.

 Once the pH value equal to 8 has been reached (after 60 minutes of introduction of acid), aqueous sodium silicate of the type described above is introduced jointly into the reaction medium at a flow rate of 153 l / h and sulfuric acid, also of the type described above at a controlled rate so as to maintain the pH value of the reaction medium equal to 8 +/- 0.1. After 30 minutes of simultaneous addition, the introduction of the silicate is stopped and then the introduction of dilute acid is continued so that the pH value of the medium

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 reaction time reaches 5.2 in about 7 minutes. The reaction suspension is then kept at this pH for 5 minutes.

3. 2- Preparation of the reaction mixture (suspension) N 2
In a stainless steel reactor equipped with a propeller stirring system and a heating by introduction of live steam, are introduced: - 342 I of silicate with a density at 20 C equal to 1230 kg / m3 and a weight ratio SiOz on Na20 equal to 3.5 - 720 1 of aqueous solution containing 12.7 kg of Nu2804
The mixture obtained has a concentration of SiO 2 equal to 76 gll. Maintained with stirring, it is brought to 66 C by double jacket heating. When this temperature is reached, a diluted sulfuric acid with a density at 20 C equal to 1050 kg / m3 is introduced at a flow rate of 520 l / h until a pH value equal to 10 is obtained in the reaction medium. 8. The temperature is equal to 66 C during the first 30 minutes of the reaction, it is then brought from 66 C to 95 C in about 11 minutes by introduction of live steam, then maintained at 95 C until the end of the reaction.

 Once the pH value equal to 8 has been reached (after 50 minutes of introduction of acid), aqueous sodium silicate of the type described above is introduced jointly into the reaction medium at a flow rate of 167 l / h and sulfuric acid, also of the type described above at a controlled rate so as to maintain the pH value of the reaction medium equal to 8 +/- 0.1. After 15 minutes of simultaneous addition, the introduction of the silicate and then the introduction of dilute acid is continued so that the pH value of the reaction medium reaches 5.2 in about 10 minutes. The reaction suspension is then kept at this pH for 5 minutes.

 3. 3- Then mix the 2 reaction slurries? 1 and 2 up to 50/50 by mass of slurry, the resulting mixture being filtered and washed using a vertical filter press, the filter trays being fitted with a membrane

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 deformable allowing the cake to be compressed by introducing pressurized air.

 The cake formed is then washed with water; after washing, the cake is compacted by the introduction of air. The silica cake recovered after deburring the filter has a dry matter content of 22%.

 This cake is then fluidized by mechanical and chemical action (addition of sulfuric acid and addition of a solution of sodium aluminate corresponding to the ratio A! / Si02 = 0.3%). After this disintegration operation, a pumpable cake is obtained; this cake is dried by means of a nozzle atomizer.

- pH 6. 7 - Na2S04 0, 6 % Elle présente un diamètre médian (0so), après désagglomération aux ultrasons, de 4, 6 um
L'examen par microscopie électronique à transmission montre que la silice est constituée d'un mélange intime de deux populations d'agrégats. A silica is obtained in the form of substantially spherical beads (average size: 250 μm), the characteristics of which are as follows: - aluminum content 0.3% - BET specific surface area 162 m2 / g - CTAB specific surface area 157 m2 / g - DOP oil intake 222 ml / 100g

- pH 6. 7 - Na2SO4 0.6% It has a median diameter (0so), after deagglomeration with ultrasound, of 4.6 um
Examination by transmission electron microscopy shows that the silica is made up of an intimate mixture of two populations of aggregates.

 The pore size distribution of this silica is monomodal.

Claims (14)

 1. Method for preparing a precipitated silica comprising two families of aggregates, the aggregates of the first family consisting of silica particles of sizes between 4 and 15 nm, the aggregates of the second family consisting of silica particles of sizes between 16 and 35 nm, the pore size distribution of the silica being single-mode, process in which: - two different silica suspensions are obtained, each obtained, before filtration, during the silica precipitation reaction, - filters the mixture obtained so as to obtain a filtration cake, - said cake is spray-dried, optionally after fluidization.  2. Method according to claim 1, characterized in that the aggregates of the first family consists of silica particles of sizes between 10 and 15 nm.  3. Method according to one of claims 1 and 2, characterized in that the aggregates of the second family consists of silica particles of sizes between 17 and 30 nm.  4. Method according to one of claims 1 to 3, characterized in that the aggregates of the first family represent 15 to 85%, preferably 20 to 50%, by weight of the silica.  5. Method according to one of claims 1 to 4, characterized in that the aggregates of the second family represent 15 to 85%, preferably 50 to 80%, by weight of the silica. 6. Method according to one of claims 1 to 5, characterized in that the two suspensions used result from the precipitation reactions of two <Desc / Clms Page number 14>  silicas exhibiting between them a BET specific surface difference and / or a CTAB specific surface difference of at least 30 m2 / g.

 7. Method according to one of claims 1 to 5, characterized in that the two suspensions used result from the precipitation reactions of two silicas having between them a difference in specific BET surface area and / or a difference in specific CTAB area at least 90 m2 / g.  8 Method according to one of claims 1 to 7, characterized in that the filtration of the mixture of the two suspensions is carried out by means of a press filter or a vacuum filter.  9. Method according to one of claims 1 to 8, characterized in that the drying is carried out by means of a nozzle or turbine atomizer. 10. Precipitated silica capable of being obtained by the process according to one of claims 1 to 9. 11. Use of a silica according to claim 10 as a reinforcing filler in a polymer composition. 12. A polymer composition based on at least one polymer, comprising a reinforcing filler, characterized in that said reinforcing filler consists of silica according to claim 10. 13. Composition according to claim 12, characterized in that it further comprises at least one coupling and / or covering agent. 14. Finished article based on at least one composition as defined in one of claims 12 and 13.