KR100244062B1 - Novel method for preparing precipitated silica, novel aluminium-containing precipitated silicas, and use thereeof for reinforcing elastomers - Google Patents

Abstract

A new process for producing precipitated silica with good dispersibility and very satisfactory reinforcement is disclosed. Also disclosed are novel precipitated silicas in the form of powders, substantially spherical beads or granules. The silica is from 140 to 200 m ² / g of the CTBA specific surface area, from 140 to 200 m ² / g BET specific surface area, 300 ml / less than 100 g of DOP oil absorbency, a median diameter, 10 after the ultrasonic disruption of less than 3 ㎛ It is characterized by having an ultrasonic disintegration index of more than ml and an aluminum content of at least 0.35% by weight. Moreover, the use of such silicas as fillers for elastomer reinforcement is disclosed.

Description

Manufacturing method of precipitated silica, precipitated silica containing aluminum and its use for reinforcing elastomers.NOVEL METHOD FOR PREPARING PRECIPITATED SILICA

The present invention relates to a new process for the preparation of precipitated silica, in particular its application as precipitated silica in the form of powders, substantially spherical beads or granules and fillers for elastomer reinforcement.

It is a known fact that precipitated silica has been used for a long time as a filler for white reinforcement in elastomers.

However, like other reinforcing fillers, this is easy to handle on the one hand, and above all, on the other hand, it must be suitable if it can be easily homogeneously mixed into the mixture.

In order to obtain the proper reinforcement imparted by the filler, it is generally known that the filler must be present in the elastomer matrix in the final form as finely ground as possible and as homogeneously distributed as possible. However, these conditions, on the one hand, are very good in terms of the ability of the filler to be homogeneously mixed into the matrix during mixing with the elastomer (homogeneous mixing properties of the filler) and can be collapsed or deagglomerated in the form of very fine powders. It should be very good in terms of performance (disintegrator of the filler), and on the other hand, the powder produced in the above-mentioned disintegration process can only be achieved if it is completely and uniformly dispersed (dispersibility of the powder) in the elastomer itself. have.

Moreover, due to mutual affinity, the silica particles have an undesirable tendency to aggregate with each other in the elastomer matrix. These silica / silica interactions have decisive consequences of limiting the reinforcement to substantially less than theoretically possible values, except where all silica / elastomer interactions are actually obtained, which can occur during the mixing process ( Theoretical figures of this silica / elastomer interaction, as is well known, are directly proportional to the outer surface of the silica used).

Moreover, in the raw state, such silica / silica interactions increase the stiffness and roughness of the mixture and thus tend to make their processing more difficult.

While relatively large in size, the problem arises of obtaining soluble fillers with very good dispersibility in the elastomer.

An object of the present invention is to overcome the disadvantages as described above and the problems as described above.

In more detail, the object of the present invention is particularly advantageously having very good dispersibility (and disintegrability) and very satisfactory reinforcement, especially when used as a reinforcing filler for elastomers. On the contrary, the present invention provides a new method for producing precipitated silica which gives excellent fluidity.

In addition, the present invention is relatively large in size, has excellent dispersibility (and disintegration), has a very satisfactory reinforcement, and is preferably settled in the form of powder, substantially spherical beads or optionally granules. Relates to silica.

Finally, the present invention relates to the use of the precipitated silica as a filler for reinforcement for elastomers.

In the specification below, the BET specific surface area is described in Journal of the American Chemical Society, Vol. Page 60, 309 (February 1938) and determined by the Brunauer-Emmet-Teller Act, which corresponds to NFT standard 45007 (November 1987).

CTAB specific surface area is the external surface area determined according to NFT standard 45007 (November 1987) (5.12).

DOP oil uptake is determined according to NFT Standard 30-022 (March 1953) using dioctyl phthalate.

Packing density (PD) is measured according to NFT standard 030100.

The pH is measured according to ISO standard 787/9 (the pH of the suspension at 5% concentration in water).

Finally, a given pore volume is measured by a mercury porosimetry and the pore diameter can be calculated from the Washburn relationship of 130 ° contact angle θ and surface tension γ of 484 dyne / cm (Micromeritics 9300 porosimeter).

Dispersibility and disintegration of the silica according to the present invention can be measured by a specific disintegration test.

The decay measurement is measured according to the following method:

Assessing the aggregation of aggregates by particle size measurement (using laser scattering method) in silica suspensions previously disintegrated by sonication; The disintegration of silica is measured (destroy the object from 0.1 to several tens of microns).

Disintegration in ultrasound is carried out using a Vibracell Bioblock (600 W) sonic transducer equipped with a 19 mm diameter probe. Particle size measurements are performed by laser scattering on a Sympatec particle size analyzer.

2 g of silica was weighed and placed in a sample tube (height: 6 cm, diameter: 4 cm), and desalted water was added to make 50 g or less; An aqueous suspension containing 4% silica is prepared, which is homogenized by magnetic stirring for 2 minutes. The disintegration by ultrasound is carried out as follows: With a probe soaked to a depth of 4 cm, the output is adjusted so that the needle deflection on the output dial is 20% (this is 120 W / cm ^2, which is dissipated by the tip of the probe). Corresponds to the energy of). The decay is performed for 420 seconds. Subsequently, a homogeneous suspension of known volume (in ml) is introduced into the cell of the particle size analyzer, followed by measurement of the particle size.

The obtained median diameter value Φ ₅₀ decreases proportionally as the disintegrability of silica increases. In addition, the ratio of the optical density (optical density is about 20) of the suspension detected by the volume of 10 x introduced dispersion (in ml) / particle size analyzer was determined. This ratio is an index indicating the proportion of fine particles, ie, a particle content of less than 0.1 μm, which is not detected by the particle size analyzer. This ratio, called the ultrasonic disintegration index (F _D ), increases proportionally as the degree of disintegration of silica increases.

Another object of the present invention is to prepare a precipitated silica of the type comprising reacting an acidifying agent with a silicate, thereby obtaining a suspension of precipitated silica, and then separating and drying the suspension, wherein the precipitation is carried out in the following steps. and:

(i) preparing an initial mother liquor comprising silicate and electrolyte, wherein the silicate concentration in initial mother liquor (denoted as SiO ₂ ) is less than 100 g / l and the concentration of electrolyte in initial mother liquor is less than 17 g / l,

(ii) adding an acidulant to the mother liquor until the pH value of the reaction mixture is at least about 7,

(iii) simultaneously adding an acidifying agent and a silicate to the reaction mixture,

A process for drying a suspension having a solids content of 24% by weight or less, comprising the following two processes (a) or (b):

(a) After step (iii), at least one aluminum compound A and then a basicizing agent is added to the reaction mixture, and the separating includes filtration and disrupting the cake resulting from the filtration. Silver is carried out in the presence of at least one aluminum compound B,

(b) After step (iii), a silicate and at least one aluminum compound A are simultaneously added to the reaction mixture, and when the separation process comprises filtration and disrupting the cake derived from this filtration process, a collapse process is preferred. Preferably in the presence of at least one aluminum compound B.

Combined with low concentrations of silicate (denoted as SiO ₂ ), which follows a special method-the introduction of electrolytes in aluminum and the initial mother liquor and the appropriate solids content of the dried suspension give good properties to the obtained product, in particular marked dispersibility and very It has been found that an important condition is achieved to give satisfactory reinforcement.

In general, it should be noted that the relevant method is the method of synthesizing precipitated silica, ie the acidifying agent reacts with the silicate under very specific conditions.

The choice of acidifier and silicate is by known methods.

Generally used acidifying agents can be strong inorganic acids such as sulfuric acid, nitric acid or hydrochloric acid, or organic acids such as acetic acid, formic acid or carbonic acid.

The acidifying agent may be diluted or concentrated, and its normal concentration may be 0.4 to 36 N, such as 0.6 to 1.5 N.

In particular, when the acidifier is sulfuric acid, its concentration may be 40 to 180 g / l, such as 60 to 130 g / l.

Furthermore, as silicates it is possible to use any form of silicates, for example metasilicates, disilicates and advantageously alkali metal silicates, in particular sodium or potassium silicates.

The silicates may exhibit a concentration of 40 to 330 g / l, such as 60 to 300 g / l, in particular 60 to 250 g / l, based on silica.

It is common to use sulfuric acid as the acidifier and sodium silicate as the silicate.

When using sodium silicate, it is common for the SiO ₂ / Na ₂ O weight ratio to be 2-4, such as 3.0-3.7.

As far as the production process of the invention is concerned in particular, precipitation is carried out in a special way according to the following steps.

First of all, a mother liquor comprising a constant silicate and electrolyte is prepared (step (i)). The amount of silicate present in the initial mother liquor advantageously represents only a fraction of the total amount of silicate introduced into the reaction.

The term electrolyte is used in the conventional sense, and refers to any ionic or molecular material that, in solution, decomposes or separates to form ionic or charged particles. The electrolyte described above is a salt selected from the group consisting of alkali metal and alkaline earth metal salts, in particular sodium sulfate in the reaction of the metal salt of the starting silicate with an acidifying agent such as sulfuric acid and sodium silicate.

One feature of the production process according to the invention is that the concentration of the electrolyte in the initial mother liquor (more than 0 g / l) is less than 17 g / l, preferably less than 14 g / l.

Another feature of the production process according to the invention is that the silicate concentration in the initial mother liquor is less than 100 g of SiO ₂ (more than 0 g / l) per liter. This concentration is preferably less than 90 g / l, particularly preferably less than 85 g / l. In some cases, this may be less than 80 g / l.

The second step consists in adding an acidulant to the mother liquor of the composition described above (step (ii)).

Such additions are made which result in a lowering of the pH in the reaction mixture until the pH reaches approximately 7 or higher, generally 7-8.

Once the desired pH value is reached, the simultaneous addition of acidifying agent and silicate (step (iii)) is performed.

This simultaneous addition is preferably carried out so that the pH value is continuously the same (in the range of +/- 0.1) as reached in the last step of step (ii).

According to an essential feature of the production process of the invention, the latter comprises one of the two processes of (a) or (b) above:

(a) After step (iii), at least one aluminum compound A and then a basicizing agent is added to the reaction mixture, and the separation process used in the process includes filtration and disrupting the cake resulting from this filtration process. , The decay process is carried out in the presence of at least one aluminum compound B,

(b) after step (iii), when the silicate and at least one aluminum compound A are simultaneously added to the reaction mixture, and the separation process used in the process includes filtration and disrupting the cake derived from this filtration process, A process in which the decay process is preferably carried out in the presence of at least one aluminum compound B.

In the first method of the production process according to the invention (i.e. when the latter comprises process (a)), the following successive steps are precipitated according to steps (i), (ii) and (iii) as described above. It is advantageous to carry out after carrying out.

(iv) adding at least one aluminum compound A to the reaction mixture (ie, the obtained reaction suspension or slurry),

(v) preferably adding a basicizing agent to the reaction mixture until the pH of the reaction mixture is between 6.5 and 10, in particular between 7.2 and 8.6,

(vi) preferably adding an acidifying agent to the reaction mixture until the pH of the reaction mixture reaches between 3 and 5, in particular between 3.4 and 4.5.

After simultaneous addition in step (iii), it may be advantageous to age the reaction mixture, for example by sustaining the maturation for 1 to 60 minutes, in particular 3 to 30 minutes.

In the first method, it is preferred to add an additional amount of acidifying agent to the reaction mixture between step (iii) and step (iv), especially before any aging mentioned above. Such addition is usually carried out until the pH of the reaction mixture reaches 3 to 6.5, in particular 4 to 6.

The acidifiers used during this addition are generally the same as those used in the first methods (ii), (iii) and (vi) of the production process according to the invention.

Aging of the reaction mixture is usually carried out between steps (v) and (vi), for example between 2 and 60 minutes, in particular between 5 and 45 minutes.

Similarly, the maturing of the reaction mixture is in most cases carried out after step (vi), such as for 2 to 60 minutes, in particular for 5 to 30 minutes.

The basicizing agent used during step (iv) may be an aqueous ammonia solution, preferably a sodium hydroxide (or soda) solution.

In a second method of the production process according to the invention (i.e. comprising process (b)), step (iv) is carried out after steps (i), (ii) and (iii) as described above, This step consists in adding the silicate and at least one aluminum compound A simultaneously to the reaction mixture.

After the simultaneous addition of step (iv), it is common to carry out the aging of the reaction mixture, which is advantageously carried out, for example, for 2 to 60 minutes, in particular for 5 to 30 minutes.

In the second process, it is preferred to add an additional amount of acidifying agent to the reaction mixture after step (iv), especially after any aging. Such addition is usually carried out until the pH of the reaction mixture reaches 3 to 6.5, in particular 4 to 6.

The acidifiers used during this addition are generally the same as those used during steps (ii) and (iii) of the second method of the production process according to the invention.

After the addition of the acidifying agent, it is common to carry out the aging of the reaction mixture, for example for 1 to 60 minutes, in particular for 3 to 30 minutes.

The aluminum compound A used in the production process according to the invention is generally an organic or inorganic aluminum salt.

As examples of organic salts, mention may be made in particular of salts of carboxylic acids or polycarboxylic acids, such as salts of acetic acid, citric acid, tartaric acid or oxalic acid.

Examples of inorganic salts may in particular mention halides and oxyhalides (chlorides and oxychlorides), nitrates, phosphates, sulfates and oxysulfonates.

In practice, aluminum compound A can be used in the form of a solution, generally in the form of an aqueous solution.

Aluminum sulfate is preferably used as the aluminum compound A.

The temperature of the reaction mixture is generally from 70 to 98 ° C.

According to another form of the invention, the reaction is carried out at a constant temperature of 75 to 96 ℃.

According to another (preferred) form of the invention, the temperature at the end of the reaction is higher than the temperature at the beginning of the reaction; The initial temperature of the reaction is preferably maintained at 70 to 96 ℃; It is preferable to raise the temperature for several minutes, preferably 80 to 98 ° C. or lower, and to maintain this temperature until the end of the reaction; It is common to carry out process (a) or (b) in a constant temperature range.

In the final obtaining step of the step as described above, the silica slurry is obtained in a separated state (liquid-solid separation).

In a first method of the production process according to the invention (ie, in the case of comprising step (a)), the separation process comprises filtration (with washing, if necessary) and decay, wherein the decay is 1 In the presence of at least one species of aluminum compound B, it is preferably carried out in the presence of an acidifying agent as described above (in the latter case, aluminum compound B and the acidifying agent are advantageously added simultaneously).

For example, the disintegration process, which can be carried out through a filter cake in the form of a colloid or bead through a grinder, makes it possible in particular to lower the viscosity of the suspension which is subsequently dried.

In a second method of the production process according to the invention (ie, in the case of comprising step (b)), the separation process generally comprises filtration (if necessary, followed by washing) and decay. Is preferably carried out in the presence of at least one aluminum compound B, generally in the presence of an acidifying agent as described above (in the latter case, it is advantageous for the aluminum compound B and the acidifying agent to be added simultaneously).

The aluminum compound B is usually different from the aluminum compound A described above, and is generally composed of an alkali metal, in particular potassium, preferably sodium and aluminum salts.

The amount of aluminum compounds A and B used in the production process according to the invention is such that the precipitated silica produced contains at least 0.35% by weight, in particular at least 0.45% by weight, such as 0.50 to 1.50% by weight, in particular 0.75 to 1.40% by weight of aluminum. It is preferable.

The separation process used in the production process of the invention generally comprises a filtration process carried out using a suitable method, such as a belt filter, a rotary vacuum filter, or preferably a filtration rolling mill.

The suspension (filter cake) of the precipitated silica thus recovered is dried.

According to one feature of the production process according to the invention, such suspensions should exhibit a solids content just prior to drying of less than 24% by weight, preferably less than 22% by weight.

This drying process can be carried out according to the following known method.

Drying is preferably carried out by an injector.

Examples of suitable injectors that can be used for this purpose are in particular turbines, nozzles, hydraulic or two-fluid sprayers.

According to one embodiment of the invention, the solids content of the suspension to be dried may be greater than 15% by weight, preferably greater than 17% by weight, such as greater than 20% by weight. Drying is preferably carried out using a nozzle sprayer.

According to an embodiment of the present invention, the precipitated silica, preferably obtainable using a filtration rolling mill, is preferably in the form of substantially spherical beads, preferably having an average size of at least 80 μm.

Dry matter such as silica in ground form may also be added to the filter cake after filtration in a continuous process of the production process.

At the end of the drying step, the step of grinding is carried out on the recovered product, in particular on the product obtained by drying the suspension with a solids content of more than 15% by weight. Precipitated silicas thus obtained are generally in the form of powders having an average size of at least 15 μm, in particular 15 to 60 μm, such as 20 to 45 μm.

The milled product with the desired particle size can be separated from the non-qualified product, for example using a vibrating screen with the appropriate mesh size, and this recovered non-qualified product can be subjected to the grinding step again.

Similarly, according to another preferred embodiment of the invention, it is preferred that the solid component of the suspension to be dried is not more than 15% by weight. It is then common to carry out drying using a turbine injector. According to an embodiment of the present invention, the precipitated silica, which is preferably obtainable using a rotary vacuum filter, is generally in the form of a powder having an average size of at least 15 μm, in particular 30 to 150 μm, such as 45 to 120 μm.

Finally, the dried (particularly from suspensions with up to 15% by weight of solid components) or ground product can be subjected to a flocculation step according to another embodiment of the invention.

Here, agglomeration means any process that can be combined with each other to make finely separated products of greater size and mechanically stronger form.

These methods are in particular direct compression, wet granulation (ie with binders such as water, silica slurries), extrusion and preferably dry compression.

Using this technique, it has been found that it may be advantageous to degas the milled product prior to the compression process, to remove the air contained therein, and to ensure more uniform compression, prior to the compression process.

Precipitated silica obtainable according to an embodiment of the invention is advantageously in the form of granules having a size of at least 1 mm, in particular from 1 to 10 mm.

At the end of the flocculation step, the products are sorted by desired size, such as by screening, and packaged according to future use.

The powders as well as the beads of precipitated silica obtained by the process according to the invention are, among others, in a simple, efficient and economical manner as described above, in particular by granulation or compacting, for example by conventional molding methods. The use of conventional powders by processes such as these can provide granules without incurring collapse which can mask or extinguish the good intrinsic properties associated with these powders or beads as in conventional methods. There is an advantage.

Another object of the present invention is to provide excellent dispersibility (and disintegrability) and to provide very satisfactory reinforcement properties, especially when used as reinforcing fillers for elastomers, while providing good mechanical properties to the elastomers while providing excellent fluidity. It is in precipitated silica.

Thus, according to the present invention, there is provided a new precipitated silica having the following characteristics:

CTAB specific surface area of 140 to 200 m ² / g, preferably 145 to 180 m ² / g,

A BET specific surface area of 140 to 200 m ² / g, preferably 150 to 190 m ² / g,

A DOP oil absorption of less than 300 ml / 100 g, preferably 200 to 295 ml / 100 g,

Median diameter (φ ₅₀ ) after ultrasonic collapse of less than 3 μm, preferably less than 2.8 μm, such as less than 2.5 μm,

An ultrasonic disintegration index (F _D ) greater than 10 ml, preferably greater than 11 ml,

An aluminum content of at least 0.35% by weight, preferably at least 0.45% by weight.

The disintegration index of silica according to the invention is advantageously at least 15 ml, for example at least 21 ml.

The aluminum content of the silica according to the invention is preferably 0.50 to 1.50% by weight, in particular 0.75 to 1.40% by weight.

According to a preferred embodiment of the invention, another property of silica is in the distribution, or dispersion, of the pore volume, in particular in the distribution of pore volumes formed by pores having a diameter of up to 400 mm 3. This pore volume corresponds to the useful pore volume of the filler used to strengthen the elastomer. Silica according to a particular method of the present invention has a pore distribution in which the pore volume consisting of pores having a diameter of 175 to 275 mm 3 exhibits at least 50% of the pore volume consisting of pores having a diameter of 400 mm 3 or less, such as at least 60%. Porosity analysis can be seen.

According to yet another highly preferred form of the invention, the ratio of BET specific surface area / CTAB specific surface area of silica exhibits 1.0 to 1.2, ie preferably very low microporosity.

The pH of the silica according to the invention is generally between 6.5 and 7.5, such as between 6.7 and 7.3.

The silica according to the invention may be in the form of powder, substantially spherical beads or any granules, in particular being relatively large in size while having excellent dispersibility and disintegration and very satisfactory reinforcement Is characterized by. Thus, they show that they are the same or close in terms of specific surface area and size as conventional silica, but are better in dispersibility and disintegration.

The silica powder according to the invention preferably has an average size of at least 15 μm, such as 15 to 60 μm (particularly 20 to 45 μm) or 30 to 150 μm (particularly 45 to 120 μm).

They preferably have a DOP oil absorbency of 240 to 290 ml / 100 g.

The packing density (PD) of the powder is generally at least 0.17, such as 0.2 to 0.3.

The powders generally have a total pore volume of at least 2.5 cm ³ / g, preferably 3 to 5 cm ³ / g.

They can in particular achieve a very good balance between workability and mechanical properties in the vulcanized state.

These also form a preferable precursor of the synthesis of the granules described later.

The substantially spherical beads according to the invention preferably have an average size of at least 80 μm.

According to another form of the invention, this average bead size is at least 100 μm, such as at least 150 μm, which is generally at most 300 μm, preferably 100 to 270 μm. This average size is determined according to NF standard X 11507 (December 1970) by dry screening and determination of diameter corresponding to cumulative transient size of at least 50%.

They preferably have a DOP oil absorbency of 240 to 290 ml / 100 g.

The packing density (PD) of the beads (or pearls) is generally at least 0.17, such as 0.2 to 0.34.

They generally have a total pore volume of at least 2.5 cm ³ / g, in particular from 3 to 5 cm ³ / g.

As mentioned above, silica in the form of a substantially spherical bead which is advantageously solid, homogeneous, low in impurities and good in fluidity has excellent disintegration and dispersibility. This also shows good reinforcement. Such silicas also constitute a preferred precursor for the synthesis of powders or granules according to the invention.

Such silica in substantially spherical bead form constitutes another very advantageous form of the present invention.

The dimensions of the granules according to the invention are preferably at least 1 mm, in particular 1 to 10 mm, along the axis of their longest dimension (length).

They preferably have a DOP oil absorption of 200 to 260 ml / 100 g.

Such granules can have a wide variety of shapes. Shapes that may be mentioned in particular may be, for example, spheres, cylinders, cubes, tablets, flakes, pellets and spherical or multilobed extrudates.

The packing density (PD) of the granules is generally 0.27 or more, and may be 0.37 or less.

They generally have a total pore volume of at least 1 cm ³ / g, in particular 1.5 to 2 cm ³ / g.

The silica according to the invention, in particular in the form of powders or substantially spherical beads or granules, is preferably prepared according to one of the other suitable forms of the production process according to the invention described above.

Silicas according to the invention or silicas produced by the process according to the invention may be particularly advantageously applied for the reinforcement of natural or synthetic elastomers. They provide good mechanical properties, generally good wear resistance, while giving the elastomer excellent fluidity. In addition, it is preferable that these elastomers are not easy to be heated.

The following examples are intended to illustrate the invention, but do not limit the scope of the invention.

Example 1 (Comparative Example)

The following components are introduced into a stainless steel reactor equipped with a stirring system using a propeller and a heating system using a jacket:

350 liters of water

7.5 kg of Na ₂ SO ₄

A solution of 580 L of sodium silicate having a weight ratio of SiO ₂ / Na ₂ O of 3.45 and a relative density of 1.133 at 20 ° C.

The silicate concentration, expressed as SiO ₂ in the initial mother liquor, is 84 g / l. Next, the mixture is heated to a temperature of 82 ° C. while maintaining the agitation. 395 L of dilute sulfuric acid with a relative density of 1.050 at 20 ° C is introduced until the pH value (measured at the same temperature) in the reaction mixture reaches 7.5. The reaction temperature is 82 ° C. for the first 25 minutes; The temperature is raised from 82 to 94 ° C. for about 15 minutes and maintained at 94 ° C. until the reaction is complete.

Next, an aqueous solution of 75L sodium silicate in the form described above and 121L sulfuric acid in the form also described above are introduced into the reaction mixture, so that the introduction of acid and silicate takes place simultaneously so that the pH of the reaction mixture continues during the introduction period. To 7.5 ± 0.1. The silicate is finally introduced, followed by the introduction of dilute sulfuric acid for 8 minutes to bring the pH of the reaction mixture to a value of 5.2. After the acid was introduced, the reaction slurry obtained was stirred for 5 minutes.

Total reaction time is 117 minutes.

A precipitated silicate slurry or suspension (called reaction suspension S) is obtained by filtration and washing with a filter rolling mill.

The cake obtained is then fluidized by mechanical and chemical action (simultaneous addition of sulfuric acid and sodium aluminate corresponding to 0.28% by weight of Al / SiO ₂ ). After this decay operation, the resulting slurry with a pH of 6.5 and a ignition loss of 79.0% (and therefore a solids content of 21.0% by weight) is sprayed by a nozzle injector.

The characteristics of silica Al obtained in the form of substantially spherical beads are as follows:

-CTAB specific surface area 155 m ² / g

-BET specific surface area 170 m ² / g

-DOP oil absorption 270 ml / 100 g

-Aluminum content 0.25%

by pores of d ≤ 400 Å

Pore volume expressed as V1 0.99 cm 3 / g

By pores of 175 Å ≤ d ≤ 275 Å

Pore volume expressed as V2 0.61 cm 3 / g

62% V2 / V1 ratio

pH 7.2

-Average particle size 250 μm

Silica Al is subjected to a collapse test as described above in the specification.

After disintegration with ultrasonic waves, silica Al has a median diameter of 40 μm (φ ₅₀ ) and an ultrasonic disintegration index (F _D ) of 8 ml.

Example 2 (Comparative Example)

1600 L of reaction suspension S as prepared in Example 1 is introduced into a stainless steel reactor equipped with a stirring system using a propeller and a heating system using a jacket.

An aluminum sulfate solution with a relative density of 1.2 at 20 ° C. is then introduced at a rate of 4.8 L / min for 6 minutes. At the end of the addition, 18% strong concentrated soda is introduced into the reaction mixture at a rate of 3.8 L / min until the pH value of the reaction mixture is 8.0.

The introduction of soda is then stopped and the reaction mixture is aged at 94 ° C. for 20 minutes.

Sulfuric acid of the form described above in Example 1 is introduced into the reaction mixture at a rate of 4.0 l / min until the pH value of the reaction mixture reaches 4.5.

The introduction of the acid is then stopped and the reaction mixture is aged at 94 ° C. for 10 minutes.

The reaction time (starting with the introduction of aluminum sulfate) is 48 minutes.

The slurry of precipitated silica is obtained by filtration and washed by filtration rolling mill.

The cake obtained is then fluidized by simple mechanical action. After the decay operation, the resulting slurry with a pH of 6.6 and a loss of ignition of 80.0% (and therefore a solids content of 20.0% by weight) is sprayed by a nozzle injector.

The characteristics of silica Al obtained in the form of substantially spherical beads are as follows:

-CTAB specific surface area 151 m ² / g

-BET specific surface area 161 m ² / g

-DOP oil absorption 254 ml / 100 g

Aluminum weight content 1.04%

by pores of d ≤ 400 Å

Pore volume expressed as V1 1.01 cm 3 / g

By pores of 175 Å ≤ d ≤ 275 Å

Pore volume expressed as V2 0.58 cm 3 / g

57% V2 / V1 ratio

pH 6.7

Average particle size 270 μm

Silica A2 is subjected to a disintegration test as described above in the specification.

After disintegration by ultrasonication, Silica A2 has a median diameter of 5.3 μm (φ ₅₀ ) and an ultrasonic disintegration index (F _D ) of 5.3 ml.

Example 3

1800 L of the reaction suspension S as prepared in Example 1 is introduced into a stainless steel reactor equipped with a stirring system using a propeller and a heating system using a jacket.

An aluminum sulfate solution with a relative density of 1.2 at 20 ° C. is then introduced at a rate of 4.8 L / min for 3 minutes 20 seconds. At the end of the addition, 18% strong concentrated soda is introduced into the reaction mixture at a rate of 3.8 L / min until the pH value of the reaction mixture reaches 7.7.

The introduction of soda is then stopped and the reaction mixture is aged at 94 ° C. for 10 minutes.

Sulfuric acid of the form described above in Example 1 is introduced into the reaction mixture at a rate of 4.7 L / min until the pH value of the reaction mixture is 4.1.

The introduction of acid is then stopped and the reaction mixture is aged at 94 ° C. for 5 minutes.

The reaction time (starting with the introduction of aluminum sulfate) is 34 minutes.

The slurry of precipitated silica is obtained by filtration and washed by filtration rolling mill.

The cake obtained is then fluidized by mechanical and chemical action (simultaneous addition of sulfuric acid and sodium aluminate equivalent to 0.30% of Al / SiO ₂ ). After the decay operation, the resulting slurry with a pH of 6.6 and a ignition loss of 78.0% (hence 22.0% by weight of solids) is sprayed by a nozzle injector.

The characteristics of the silica Pl (according to the invention) obtained in the form of substantially spherical beads are as follows:

-CTAB specific surface area 161 m ² / g

-BET specific surface area 178 m ² / g

-DOP oil absorption 266 ml / 100 g

Aluminum weight content 0.75%

by pores of d ≤ 400 Å

Pore volume 1.08 cm 3 / g expressed as V1

By pores of 175 Å ≤ d ≤ 275 Å

Pore volume expressed as V2 0.66 cm 3 / g

61% V2 / V1 ratio

pH 7.2

-Average particle size 260 μm

Silica P1 is subjected to the collapse test as described above in the specification.

After disintegration with ultrasonic waves, silica P1 has a median diameter of 2.5 μm (φ ₅₀ ) and an ultrasonic disintegration index (F _D ) of 21 ml.

Example 4

1670 L of reaction suspension S as prepared in Example 1 is introduced into a stainless steel reactor equipped with a stirring system using a propeller and a heating system using a jacket.

An aluminum sulfate solution with a relative density of 1.2 at 20 ° C. is then introduced at a rate of 4.8 L / min for 5 minutes. At the end of the addition, 18% strong concentrated soda is introduced into the reaction mixture at a rate of 3.8 L / min until the pH value of the reaction mixture reaches 7.8.

The introduction of soda is then stopped and the reaction mixture is aged at 94 ° C. for 10 minutes.

Sulfuric acid in the form described above in Example 1 is introduced into the reaction mixture at a rate of 4.7 L / min until the pH value of the reaction mixture is 4.0.

The introduction of acid is then stopped and the reaction mixture is aged at 94 ° C. for 5 minutes.

The reaction time (starting with the introduction of aluminum sulfate) is 40 minutes.

The slurry of precipitated silica is obtained by filtration and washed by filtration rolling mill.

The cake obtained is then fluidized by mechanical and chemical action (simultaneous addition of sulfuric acid and sodium aluminate corresponding to 0.25% Al / SiO ₂ ). After the decay operation, the resulting slurry with a pH of 6.6 and a ignition loss of 79.0% (thus a solids content of 21.0% by weight) is sprayed by a nozzle injector.

The characteristics of silica P2 (according to the invention) obtained in the form of substantially spherical beads are as follows:

-CTAB specific surface area 156 m ² / g

-BET specific surface area 160 m ² / g

-DOP oil absorption 274 ml / 100 g

Aluminum weight content 1.06%

by pores of d ≤ 400 Å

Pore volume 1.04 cm 3 / g expressed as V1

By pores of 175 Å ≤ d ≤ 275 Å

Pore volume expressed as V2 0.69 cm 3 / g

66% V2 / V1 ratio

pH 7.0

-Average particle size 250 μm

Silica P2 is subjected to the collapse test as described above in the specification.

After disintegration with ultrasonic waves, silica P2 has a median diameter (φ ₅₀ ) of 2.4 μm and an ultrasonic disintegration index (F _D ) of 17 ml.

Example 5

The following components are introduced into a stainless steel reactor equipped with a stirring system using a propeller and a heating system using a jacket:

350 liters of water

7.5 kg of Na ₂ SO ₄

A solution of 580 L of sodium silicate having a weight ratio of SiO ₂ / Na ₂ O of 3.45 and a relative density of 1.133 at 20 ° C.

The silicate concentration, expressed as SiO ₂ in the initial mother liquor, is 84 g / l.

Next, the mixture is heated to a temperature of 82 ° C. while maintaining the agitation. 390 L of dilute sulfuric acid with a relative density of 1.050 at 20 ° C. is introduced in the reaction mixture until the pH value is 7.5 (measured at the same temperature). The reaction temperature is 82 ° C. for the first 25 minutes; The temperature is raised from 82 to 94 ° C. for about 15 minutes and maintained at 94 ° C. until the reaction is complete.

55 L aqueous solution of sodium silicate of the above-mentioned type and 89 L sulfuric acid of the above-mentioned type are also introduced jointly into the reaction mixture in turn, so that the introduction of acid and silicate takes place simultaneously so that the pH of the reaction mixture Continue to 7.5 ± 0.1. The introduction of acid is then stopped and a 86 L aqueous solution of sodium silicate of the type described above and a solution of 33 L aluminum sulfate having a relative density of 1.2 at 20 ° C. are introduced jointly into the reaction mixture for 24 minutes.

This co-introduction is stopped and the reaction mixture is aged at 94 ° C. for 10 minutes.

Sulfuric acid in the above-described form is then introduced into the reaction mixture for 7 minutes to bring the pH of the reaction mixture to 5.0. After the acid was introduced, the reaction slurry obtained was stirred for 5 minutes.

Total reaction time is 109 minutes.

The precipitated silicate slurry is obtained by filtration and washed by filtration rolling mill.

The cake obtained is then fluidized by simple mechanical action. After the decay operation, the resulting slurry with a pH of 6.5 and a ignition loss of 78.3% (hence 21.7% by weight of solids) is sprayed by a nozzle injector.

The characteristics of silica P3 obtained in the form of beads which are substantially spherical (according to the invention) are as follows:

-CTAB specific surface area 149 m ² / g

-BET specific surface area 178 m ² / g

-DOP oil absorption 260 ml / 100 g

Aluminum weight content 0.96%

by pores of d ≤ 400 ms

Pore volume expressed as V1 1.01 cm 3 / g

By pores of 175 Å ≤ d ≤ 275 Å

Pore volume expressed as V2 0.54 cm 3 / g

-V2 / V1 ratio 53%

pH 7.1

-Average particle size 260 μm

Silica P3 is subjected to the collapse test as described above in the specification.

After disintegration with ultrasonic waves, silica P3 has a median diameter of 2.7 μm (φ ₅₀ ) and an ultrasonic disintegration index (F _D ) of 17 ml.

Example 6

The following components are introduced into a stainless steel reactor equipped with a stirring system using a propeller and a heating system using a jacket:

350 liters of water

7.5 kg of Na ₂ SO ₄

A solution of 580 L of sodium silicate having a weight ratio of SiO ₂ / Na ₂ O of 3.45 and a relative density of 1.133 at 20 ° C.

The silicate concentration, expressed as SiO ₂ in the initial mother liquor, is 84 g / l.

Next, the mixture is heated to a temperature of 82 ° C. while maintaining the agitation. 390 L of dilute sulfuric acid with a relative density of 1.050 at 20 ° C. is introduced in the reaction mixture until the pH value is 7.5 (measured at the same temperature). The reaction temperature is 82 ° C. for the first 25 minutes; The temperature is raised from 82 to 94 ° C. for about 15 minutes and maintained at 94 ° C. until the reaction is complete.

55 L aqueous solution of sodium silicate of the above-mentioned type and 89 L sulfuric acid of the above-mentioned type are also introduced jointly into the reaction mixture in turn, so that the introduction of acid and silicate takes place simultaneously so that the pH of the reaction mixture Continue to 7.5 ± 0.1. The introduction of the acid is then stopped and a 50 L aqueous solution of sodium silicate of the type described above and a solution of 28.5 L of aluminum sulfate having a relative density of 1.2 at 20 ° C. are introduced jointly into the reaction mixture for 21 minutes.

This co-introduction is stopped and the reaction mixture is aged at 94 ° C. for 10 minutes.

Sulfuric acid in the above-described form is then introduced into the reaction mixture for 7 minutes to bring the pH of the reaction mixture to 5.0. After the acid was introduced, the reaction slurry obtained was stirred for 5 minutes.

Total reaction time is 109 minutes.

The precipitated silicate slurry is obtained by filtration and washed by filtration rolling mill.

The cake obtained is then fluidized by mechanical and chemical action (simultaneous addition of sulfuric acid and sodium aluminate equivalent to 0.40% of Al / SiO ₂ ). After the decay operation, the resulting slurry with a pH of 6.5 and a ignition loss of 78.3% (hence 21.7% by weight of solids) is sprayed by a nozzle injector.

The characteristics of silica P4 obtained in the form of substantially spherical beads (according to the invention) are as follows:

-CTAB specific surface area 158 m ² / g

-BET specific surface area 185 m ² / g

-DOP oil absorption 258 ml / 100 g

Aluminum weight content 1.15%

by pores of d ≤ 400 Å

Pore volume 1.05 cm 3 / g expressed as V1

By pores of 175 Å ≤ d ≤ 275 Å

Pore volume expressed as V2 0.59 cm 3 / g

56% V2 / V1 ratio

pH 7.1

-Average particle size 260 μm

Silica P4 is subjected to the collapse test as described above in the specification.

After disintegration with ultrasonic waves, silica P4 has a median diameter of 2.7 μm (φ ₅₀ ) and an ultrasonic disintegration index (F _D ) of 16 ml.

Example 7

The following components are introduced into a stainless steel reactor equipped with a stirring system using a propeller and a heating system using a jacket:

350 liters of water

7.5 kg of Na ₂ SO ₄

A solution of 580 L of sodium silicate having a weight ratio of SiO ₂ / Na ₂ O of 3.45 and a relative density of 1.133 at 20 ° C.

The silicate concentration, expressed as SiO ₂ in the initial mother liquor, is 84 g / l. Next, the mixture is heated at a temperature of 82 ° C. while maintaining agitation. At 20 ° C., 390 L of dilute sulfuric acid with a relative density of 1.050 is introduced in the reaction mixture until the pH value (measured at the same temperature) reaches 7.5. The reaction temperature is 82 ° C. for the first 25 minutes; The temperature is raised from 82 to 94 ° C. for about 15 minutes and maintained at 94 ° C. until the reaction is complete.

Next, 55 L aqueous sodium silicate solution of the above-described type and 89 L sulfuric acid of the above-described type are also introduced into the reaction mixture so that the introduction of acid and silicate takes place simultaneously so that the pH of the reaction mixture continues during the introduction period. To 7.5 ± 0.1.

The introduction of the acid is then stopped and a 54 L aqueous solution of sodium silicate of the form described above and a solution of 20.5 L aluminum sulfate having a relative density of 1.2 at 20 ° C. are introduced jointly into the reaction mixture for 15 minutes.

This co-introduction is stopped and the reaction mixture is aged at 94 ° C. for 10 minutes.

Sulfuric acid in the above-described form is then introduced into the reaction mixture for 7 minutes to bring the pH of the reaction mixture to 5.0. After the acid was introduced, the reaction slurry obtained was stirred for 5 minutes.

Total reaction time is 104 minutes.

The precipitated silicate slurry or suspension is obtained by filtration and washing with a filter rolling mill.

The cake obtained is then fluidized by mechanical and chemical action (simultaneous addition of sulfuric acid and sodium aluminate equivalent to 0.35% of Al / SiO ₂ ). After the decay operation, the resulting slurry with a pH of 6.5 and a ignition loss of 78.3% (hence 21.7% by weight of solids) is sprayed by a nozzle injector.

The characteristics of silica P5 obtained in the form of beads which are substantially spherical (according to the invention) are as follows:

CTAB specific surface area 166 m ² / g

-BET specific surface area 178 m ² / g

-DOP oil absorption 260 ml / 100 g

Aluminum weight content 0.93%

by pores of d ≤ 400 Å

Pore volume expressed as V1 1.02 cm 3 / g

By pores of 175Å≤ d ≤275Å

Pore volume expressed as V2 0.61 cm 3 / g

-V2 / V1 ratio 60%

pH 6.9

-Average particle size 260 μm

Silica P5 is subjected to the collapse test as described above in the specification.

After disintegration with ultrasonic waves, silica P5 has a median diameter of 2.7 μm (φ ₅₀ ) and an ultrasonic disintegration index (F _D ) of 15 ml.

The properties of the silicas prepared in Examples 1 to 7 and the commercially available silica in powder form of Degussa, in this case the properties of the trademarked Ultrasil VN3 powder (product number A3) are compared in Table 1 below.

A1 A2 A3 P1 P2 P3 P4 P5 S _CTAB (m ² / g) 155 151 155 161 156 149 158 166 S _BET (m ² / g) 170 161 170 178 160 178 185 178 DOP (ml / 100 g) 270 254 260 266 274 260 258 260 Al (%) 0.25 1.04 0.05 0.75 1.06 0.96 1.15 0.93 V1 (cm ³ / g) 0.99 1.01 0.93 1.08 1.04 1.01 1.05 1.02 V2 (cm ³ / g) 0.61 0.58 0.43 0.66 0.69 0.54 0.59 0.61 V2 / V1 (%) 62 57 46 61 66 53 56 60 pH 7.2 6.7 6.5 7.2 7.0 7.1 7.1 6.9 Average size (μm) 250 270 17 260 250 260 260 260 φ ₅₀ (μm) 4.0 5.3 9.9 2.5 2.4 2.7 2.7 2.7 F _D (ml) 8 5.3 2.3 21 17 17 16 15

Example 8

This example illustrates the use and function of silica according to the invention and silica not according to the invention in a combination of industrial rubber.

The following combinations are used (parts expressed by weight):

-Tufdene 2330 rubber ⁽¹⁾ 50

-BR 1220 Rubber ⁽²⁾ 25

Natural rubber 25

Silica 51

Active ZnO ⁽³⁾ 1.81

-Stearic acid 0.35

-6DPD ⁽⁴⁾ 1.45

-CBS ⁽⁵⁾ 1.1

DPG ⁽⁶⁾ 1.45

Sulfur ⁽⁷⁾ 0.9

Silane X50S ⁽⁸⁾ 8.13

(1) Styrene Butadiene Copolymer Type Tufdene 2330

(2) butadiene polymer type 1220

(3) rubber grade zinc oxide

(4) N- (1,3-dimethylbutyl) -N'-phenyl-p-phenylenediamine

(5) N-cyclohexyl-2-benzothiazylsulfenamide

(6) diphenylguanidine

(7) vulcanizing agent

(8) Silica / Rubber Coupling Agent (commercially available from Degussa)

The formulation is prepared in the following way:

In a sealed mixer [type Banbury], the following components are introduced in that order and at the time and temperature indicated in parentheses:

-Tufdene 2330, BR 1220 and natural rubber (t ₀ ) (60 ° C)

-2/3 of X50S and silica (t ₀ + 1 min) (80 ° C)

ZnO, stearic acid, 6PPD and 1/3 of silica (t ₀ + 2 min) (100 ° C.)

Release from the mixer (mixing droplets) occurs when the chamber temperature reaches 165 ° C. (ie at approximately t ₀ + 5 minutes 15 seconds). This blend is introduced into a roll mill and the roll is kept at 30 ° C. and rolled thereon. This mill introduces CBS, DPG and sulfur.

After homogenization and three good passes of the test, the final mixture is rolled in the form of sheets of thickness 2.5 mm to 3 mm.

The results of the test were as follows:

1- liquidity

Measurements are taken on unprocessed blends.

The results are reported in Table 2 below. The apparatus used to perform the measurements is shown.

A1 A3 P1 P2 P3 P4 P5 Mooney illuminance ⁽¹⁾ 163 177 142 133 127 143 138 Torque (ln lb) ⁽²⁾ 37.3 42.5 34.6 32.7 30.8 34.1 33.8

(1) Mooney MV 2000E Viscometer (Money Broad (1 + 4) measurement at 100 ° C)

(2) Monsanto 100 S rheometer

The blend obtained from the silica according to the invention gives the lowest value results.

This shows a greater processability of the formulations prepared from the silica according to the invention, especially for extrusion and rolling operations which are often carried out during the preparation of the elastomeric composition (a reduction in the energy consumption for processing the formulations, of injection during formulation). Increased ease, reduced shrinkage during rolling, etc.).

2- mechanical properties

Measurements are made on vulcanized formulations.

Vulcanization is performed by heating the blend to 150 ° C. for 40 minutes.

The following criteria were used:

(i) Tensile test (modulus, tensile strength, elongation at break):

NFT 46-002 or ISO 37-1977

(ii) wear resistance test

DIN 53-516

The results are listed in Table 3 below.

A1 A3 P1 P2 P3 P4 P5 10% Modulus / 100% Modulus 0.33 0.32 0.30 0.28 0.27 0.29 0.30 Tensile strength (MPa) 20.6 17.7 20.8 20.6 20.2 20.6 21.1 Elongation at Break (%) 470 430 510 510 485 495 495 Abrasion Resistance (mm ³ ) ⁽¹⁾ 55 58 48 48 52 47 42

(1) The measured value is the decrease in wear: the lower it is, the better the wear resistance.

These last results demonstrate the good reinforcing effect that the silica according to the invention provides.

Thus, while clearly bringing better flowability, the silica according to the present invention provides at least equally or even better mechanical properties that can be perceived at least as much as the mechanical properties obtained from prior art silicas.

On the other hand, the silica according to the present invention yields a lower 10% modulus / 100% modulus ratio than that obtained with silica of the prior art, which proves that the silica is better dispersed in the rubber matrix.

On the other hand, the high reinforcement of the silica according to the invention is supported by the high values obtained for tensile strength and elongation at break.

Finally, with regard to the wear resistance, it can be seen that the amount of reduction due to abrasion is substantially reduced (5% to 20%) compared to the comparative silica.

3- kinematic properties

Measurements are made on vulcanized formulations.

Vulcanization is obtained by heating the blend to 150 ° C. for 40 minutes. The results (showing a rise in temperature) are reported in Table 4 below (the lower the value, the lower the rise in temperature). The apparatus used to perform the measurements is shown.

A1 A3 P1 P2 P3 P4 P5 Internal heating (℃) ⁽¹⁾ 102 101 95 101 95 98 90 Tangent Delta 70 ° C ⁽²⁾ 0.139 0.130 0.128 0.138 0.127 0.130 0.124

(1) Goodrich Flexural Testing Machine

(2) Instron viscoelastic system

The temperature rising tendency obtained in the silica according to the invention is quite low.

Claims (25)

A process for preparing precipitated silica of the type comprising reacting an acidifying agent with a silicate, thereby obtaining a suspension of precipitated silica, and then separating and drying the suspension, wherein precipitation is carried out in the following steps: (i) preparing an initial mother liquor comprising silicate and electrolyte, wherein the silicate concentration in initial mother liquor (denoted as SiO ₂ ) is less than 100 g / l and the concentration of electrolyte in initial mother liquor is less than 17 g / l, (ii) adding an acidulant to the mother liquor until the pH value of the reaction mixture is at least 7, (iii) simultaneously adding an acidifying agent and a silicate to the reaction mixture, A process for drying a suspension having a solids content of 24% by weight or less, comprising the following two steps (a) or (b): (a) After step (iii), at least one aluminum compound A and then a basicizing agent is added to the reaction mixture, and the separating includes filtration and disrupting the cake resulting from the filtration. Silver is carried out in the presence of at least one aluminum compound B, (b) After step (iii), a silicate and at least one aluminum compound A are simultaneously added to the reaction mixture, and when the separation process comprises filtration and disrupting the cake derived from this filtration process, a collapse process is preferred. Preferably a process which may be carried out in the presence of at least one aluminum compound B. The process for producing precipitated silica according to claim 1, comprising reacting the acidifying agent with the silicate, thereby obtaining a suspension of precipitated silica, and then separating and drying the suspension. Settling is carried out in the following steps: (i) preparing an initial mother liquor comprising silicate and electrolyte, wherein the silicate concentration in initial mother liquor (denoted as SiO ₂ ) is less than 100 g / l and the concentration of electrolyte in initial mother liquor is less than 17 g / l, (ii) adding an acidulant to the mother liquor until the pH value of the reaction mixture is at least 7, (iii) simultaneously adding an acidifying agent and a silicate to the reaction mixture, The following successive steps are then carried out: (iv) adding at least one aluminum compound A to the reaction mixture, (v) adding a basicizing agent to the reaction mixture, (vi) adding an acidifying agent to the reaction mixture, The separation process comprises filtration and the disruption of the cake derived from the filtration process, the disintegration process being carried out in the presence of at least one aluminum compound B, A process for the preparation of precipitated silica characterized by drying a suspension having a solids content of up to 24% by weight. A process according to claim 2, characterized in that between step (iii) and step (iv), an acidifying agent is added to the reaction mixture. The process for preparing precipitated silica according to claim 1, comprising reacting the acidifying agent with the silicate, thereby obtaining a suspension of precipitated silica, and then separating and drying the suspension, wherein precipitation is carried out in the following steps: (i) preparing an initial mother liquor comprising silicate and electrolyte, wherein the silicate concentration in initial mother liquor (denoted as SiO ₂ ) is less than 100 g / l and the concentration of electrolyte in initial mother liquor is less than 17 g / l, (ii) adding an acidulant to the mother liquor until the pH value of the reaction mixture is at least 7, (iii) simultaneously adding an acidifying agent and a silicate to the reaction mixture, (iv) simultaneously adding the silicate and at least one aluminum compound A to the reaction mixture, A process for producing precipitated silica, characterized by drying a suspension having a solids content of up to 24% by weight. 5. The process of claim 4, wherein after step (iv), an acidifying agent is added to the reaction mixture. A process according to claim 4 or 5, wherein the separating process comprises filtration and disrupting the cake derived from the filtration process, wherein the disintegrating process is performed in the presence of at least one aluminum compound B. The method according to any one of claims 1 to 5, wherein the amount of aluminum compounds A and B used is such that the precipitated silica produced contains 0.35% by weight or more of aluminum. The method according to any one of claims 1 to 5, wherein the aluminum compound A is an organic or inorganic aluminum salt. The method according to any one of claims 1 to 5, wherein the aluminum compound A is aluminum sulfate. The process according to any one of claims 1 to 5, wherein compound B is an alkali metal aluminate. The process according to any one of claims 1 to 5, wherein the separating process comprises a filtration process performed using a filtration rolling mill. The method according to any one of claims 1 to 5, wherein the drying process is carried out by spraying. 13. Process according to claim 12, characterized in that the suspension is dried with a solids content of more than 15% by weight. 12. The method of claim 11, wherein the drying process is performed using a nozzle dryer. 12. The method of claim 11, wherein the dried product is subsequently milled. 16. The method of claim 15, wherein the milled product is subsequently coagulated. 13. Process according to claim 12, characterized in that the suspension is dried with a solids content of up to 15% by weight. 18. The method of claim 17, wherein the dried product is subsequently coagulated. Precipitated silica with the following characteristics: A CTAB specific surface area of 140 to 200 m ² / g, A BET specific surface area of 140 to 200 m ² / g, DOP oil absorption of less than 300 ml / 100 g, Median diameter (φ ₅₀ ) after ultrasonic collapse of less than 3 μm, An ultrasonic disintegration index (F _D ) of more than 10 ml, Aluminum content of 0.35% by weight or more. 20. The silica of claim 19, having an aluminum content of at least 0.45% by weight. The silica according to claim 19 or 20, wherein the pore volume consisting of pores having a diameter of 175 to 275 mm 3 has a pore distribution indicating at least 50% of the pore volume made of pores having a diameter of 400 mm 3 or less. The silica according to claim 19 or 20, characterized in that it is in the form of a substantially spherical bead having an average size of at least 80 μm. A silica according to claim 19 or 20, characterized in that it is in the form of a powder having an average size of at least 15 μm. The silica according to claim 19 or 20, characterized in that it is in the form of granules having a size of at least 1 mm. Silica according to claim 19 used as an elastomeric filler.