EP3717407A1

EP3717407A1 - Highly dispersible precipitated silicas

Info

Publication number: EP3717407A1
Application number: EP18707891.0A
Authority: EP
Inventors: Torsten Gottschalk-Gaudig; Sebastian KRÖNER; Klaus Obermeier; Achim Schneider
Original assignee: Wacker Chemie AG
Current assignee: Wacker Chemie AG
Priority date: 2018-02-23
Filing date: 2018-02-23
Publication date: 2020-10-07
Also published as: JP2021514341A; US20210114888A1; CN111757850A; KR20200111748A; WO2019161912A1; BR112020017275A2

Abstract

The invention relates to highly dispersible precipitated silicas. The invention specifically relates to modified precipitated silica, characterized in that the particle size of at least 90% of its particles does not exceed 1 pm. The invention further relates to a process suitable for preparing said modified precipitated silicas and characterized by a combination of a homogeneous in-situ modification of the silica together with high-performance wet grinding. Further described is a process for reinforcing elastomers, wherein modified precipitated silica according to the invention is incorporated as a filler.

Description

Highly dispersible precipitated silicas

The invention relates to a modified precipitated silica, characterized in that the particle size of at least 90% of its particles is at most 1 mth and their re-dispersibility, i. the quotient from the passage 1 pm be true by laser diffraction after drying of the silica divi diert through the passage 1 mth determined by laser diffraction before drying the silica, at least 0.9, and a method which is suitable for the preparation of these modified precipitated kel silicas and characterized by a combination of a homogeneous in situ modification of the silica together with a high-performance liquid milling, and further the use of these modified precipitated silicas ren.

Precipitated silicas are oxides of the silicon which are produced industrially by precipitation processes and used in a wide range of applications. The products of precipitation processes usually do not have the desired particle size or must still be subjected to drying, the properties set by the production properties such as the specific surface should be changed as little as possible. Therefore, jet or impact mills and for drying spray dryers, floor dryers, rotary tube dryers or nozzle towers are common for crushing or milling of silicas. After carrying out these process steps, a typical property of precipitated silicas is their poor dispersibility, which is usually manifested by a coarse fraction in the particle size distribution.

There are increasing attempts by established manufacturers of precipitated silicas to develop highly dispersible silicic acids (see HDS types). Typical examples are Ultrasil 5000 GR or Ultrasil ^® ^® 7000 GR from Evonik. Field of application of this Silica is usually the use as a reinforcing filler for automobile tires,

In order to achieve the easy dispersibility of the silicas, the precipitation process is usually intervened as described e.g. in EP 0 901 986 A1 or EP 1 525 159 A1 of Evonik. The hallmark of these HDS grades is a reduced coarse fraction in the particle size measurement. However, products without any coarse fraction can not be produced this way.

As a measure of the dispersibility of a precipitated silica, for example, Evonik uses the wk coefficient, which is based on particle size distribution as measured by laser diffraction (see, for example, EP 0 901 986 A1). By analyzing the scattered light image of the precipitated silica, the particle size distribution can be determined over a wide measuring range of about 40 nm - 500 mth. The wk coefficient gives the ratio of the peak height of the uncut, very coarse silica particles whose maximum is in the range 1-100 m to the peak height of the crushed particles with particle sizes of 0-1 mth. The latter, very small particles are excellently dispersed in rubber mixtures. The wk coefficient is thus a measure of the dispersibility of the precipitated silica. A precipitated silica is more easily dispersible the smaller its wk coefficient is. Measurements of the particle size distribution of readily dispersible comparative silicas of the prior art have given values for the wk coefficient of from 3.4 to more than 10 (see, e.g., EP 0 901 986 A1).

In contrast, Evonik in EP 0 901 986 A1 and WO 2004/014797 A1 disclose easily dispersible precipitated silicas having a wk coefficient of <3.4. However, the measured peak of uncut, very coarse silica particles, as well as the representation in Figures 1-5 of EP 0 901 986 A1 and the mentioned value of the wk coefficient> 1, show that a significant proportion is also significant for the silicas mentioned therein on coarse particles with a maximum of their particle size in the range 1-100 pm is present. Therefore, there is a bimodal particle size distribution (see, for example, paragraph [0035] in EP 0 901 986).

EP 1 348 669 A1 also relates to finely dispersed silicic acids with narrow particle size distributions and processes for their preparation. Here, too, a wk coefficient of <3.4 is specified for the precipitated silicas disclosed (see paragraph [0040] b) and specifies that the diameter of 95% of the particles is less than 40 pm, but only 5% of the particles less than 10 pm (see paragraph [0027]). This means at the same time that 95% of the silica particles have a particle size of more than 10 pm.

EP 0 922 671 A1 of Degussa discloses precipitated silicas which have been ground by means of a classifier mill or fluidized bed counter-jet mill and a grain distribution index I <1 (measured with Malvern) on iron, where 1 = (d ₉₀ -di ₀ ) / 2 d ₅₀ . The measures d ₅ , dio, d ₅₀ , d ₉₀ or generally d _x indicate that x% of the totality of the particles have a particle size smaller than or equal to the corresponding value, ie d ₅₀ = l pm means that 50% of the particles have a particle size Particle size of less than or equal to 1 pm on wise. Despite being treated, the silicas described there do not meet the requirements of an easily dispersible silica, since, according to FIGS. 1 and 2, no significant proportion of the particles have a particle size <1 μm.

The object of the invention is ren modified precipitated silicic acid ren having a particle size distribution with the smallest possible to the extent of coarse fraction, wherein the coarse fraction is characterized by a particle size of about 1 pm, as well as to provide a method for their preparation.

This object is achieved by the invention, which has a modifi ed precipitated silica, characterized in that the particle size of at least 90% of their particles 0-1 pm and their Redispersibility is at least 0.9, as well as a procedural ren, which is suitable for the preparation of these silicas and is characterized by a combination of a homogeneous in situ modification of the silica together with a high performance liquid milling, provides. In this way, it has been possible to provide modified precipitated silicas having a particle size distribution which have less than 1% coarse fraction, ie less than 1% of particles with a size of more than 1 μm.

The invention relates to a modified precipitated silica, characterized in that the particle size of at least 90% of its particles is at most 1 pm and their re dispersibility, i. the quotient from the passage 1 pm be true by laser diffraction after drying of the silica divi diert through the passage 1 pm determined by laser diffraction before drying the silica, at least 0.9.

The large-scale production of synthetic silicic acids takes place mainly via precipitation processes. Silicas produced in this way are called precipitated silicas. Precipitated silicas are prepared by methods known to those skilled in the art, such as in US 2,657,149, US 2,940,830 and US 4,681,750, made of condensable tetra- or higher functional Sila NEN, alkoxysilanes, alkyl or alkali silicates (water glasses) or colloidal silica particles or solutions ,

A major advantage in providing precipitated silicas is that, in contrast to the significantly more expensive pyrogenic silicas, they are a cost-effective product.

Their modification, and in particular Oberflächenmodifi cation a better property profile is achieved, which is why the modification of silicas in many applications, the For example, require less water absorption or higher Reißfestig speed, is a prerequisite.

By determining the elemental constituents of the composition according to the invention by means of elemental analysis, the presence of the elements can be determined. The presence of the elements carbon, oxygen and silicon can be analyzed by elemental analysis, i. be detected and quantified in a combustion analysis in a corresponding analyzer. By means of elemental analysis or CHN analysis, the weight percentages of the chemical elements are determined in an appropriate analyzer and the ratio formula calculated therefrom.

By means of nuclear magnetic resonance spectroscopy, the presence of different [R _x SiO _(4-x) / ₂ ] units can be checked on the solid, and an estimate of the proportions can be made. Here, the substituent R can be identified by means of ¹³ C NMR spectroscopy and by means of ²⁹ Si NMR spectroscopy the number of substituents x in the [R _x SiO _(4-X) / ₂ ] units with x = 0 to x due to the different shift ranges = 4 be ^¬ votes.

According to the invention, the particle size of at least 90%, preferably at least 95%, particularly preferably at least 99% and especially preferably 100% of the particles of the modified precipitated silica is at most 1 mth. The particle size is defined as the size determined by a laser diffraction particle size analysis (laser granulometric measurement). This method is a measurement of the distribution of the size of solid or liquid particles in a liquid or gaseous medium by means of deflection (diffraction) of the light waves of a laser beam. To determine the particle size, measuring devices are available, such as laser diffraction measuring systems, laser diffraction sensors or laser diffraction particle size analyzers, in which a particle stream consists exclusively of the particles to be measured in a liquid or a gas is transported by the medium across the laser light or a glass cuvette is placed with the particles dispersed in a liquid medium in the laser beam. The intensity of the light scattered or diffracted by interaction with the particles is determined by means of detectors dependent on the angle. From the angle dependence of the scattered light signal, the particle size and particle size distribution can be determined with the help of suitable theories. Current commercial laser diffractometers usually use the so-called Mie theory to analyze the size range <1 pm, and the classical Fraunhofer theory for size classes> 1 pm, whereby different light sources can be used for the different size ranges.

Essential for the measurement result of the particle size determination is the dispersing method. The method used according to the invention is optimized for surface-modified silicas and ensures adequate wetting of the modified silicic acids and their dispersion.

Preferably, ultrasound is used for the dispersion. Ultrasonic baths are unsuitable for achieving adequate dispersing powers. Preference is therefore given to using ultrasonic tips or probes.

To evaluate the measurement result of the laser diffraction particle size analysis, the volume-weighted particle size distribution q ³ and the corresponding distribution sum curve Q ³ are used. The cumulative distribution curve is the cumulative representation of the particle size representation normalized to 100%.

The passage at 1 pm is the amount of distribution sum curve Q ³ at 1 p in percent. A value of 100% means that all particles have a particle size of less than or equal to 1 pm. The measures d _s , di ₀ , d ₅₀ , d ₉₀ or generally d _x indicate that x% of the particle population has a particle size less than or equal to the corresponding value, ie d _so = l pm says that 50% of the particles Particle size of less than or equal to 1 mhh have.

The determination of the wk coefficient analogous to WO 2004/014797 as the ratio of the peak height of the particles with a maximum in the range 1-100 pm to the peak height of the particles with a maximum in the range <1.0 pm always yields a value for the present invention of 0 / x = 0, where x is the peak height of the particles with a maximum in the range <1.0 pm.

Basically, the wk coefficient only seems to be a sure measure of the dispersibility of particles. The problem here is that only the ratio of mode B (= modal value of all particles with a size of 1 pm to 100 pm to mode A (= modal value of all particles with a size <1 pm) is reproduced, a wk value of 1 now states that the peak heights in the modes are identical, but this does not necessarily mean that a silica with a wk of eg 4 is more difficult to disperse than a silica with a wk of 1. Thus, it is quite possible that at a wk value of 1 there are more particles in the size range 1 to 100 pm than at a wk value of 4. This can be the case whenever there is a strongly distorted particle distribution curve with a pronounced positive (statistical) deviation ie a distribution with a pronounced tailing towards higher particle sizes, even a very broad symmetrical distribution around the B-mode value can produce a comparable effect.

Therefore, for the silicas of the invention, the passage at 1 pm is chosen here as a measure of the quality of the dispersibility, which clearly reflects the relative proportions of coarse and fines. The determination of the particle size distribution index I according to EP 0922671 Al with 1 = (dgo-dio) / 2 d ₅₀ is not an appropriate measure of the dis- pergierbärkeit of silicas, because the numerical value is analogous to wk-value is only a relative size and no Information about the location of the distribution provides.

The modified precipitated silica according to the invention, in contrast to the precipitated silicic acids available in the prior art, is characterized by a small particle size in the range of at most 1 mth, a very small to absent coarse part, i. Particles larger than 1 mtti in size, and therefore also characterized by a narrow particle size distribution.

This has the great advantage that silicone elastomers with better optical properties, in particular with better transparency are accessible. Due to the substantial absence of coarse particles, there are no large scattering centers at which the transmitted light is scattered and thus the component appears cloudy.

Furthermore, it has the advantage that elastomers and in particular silicone elastomers such as HTV, LSR or RTV rubbers with better mechanical properties, such as modulus, tensile strength or tear propagation resistance are accessible. The reason for this is the better and more homogeneous distribution of the silica particles in the polymer matrix, which results in a denser secondary particle network and thus more effective stress relaxation or greater overstraining.

In addition, the modified precipitated silica according to the invention has the advantage that the better dispersibility leads to a higher thickening effect when used as a rheological additive.

Another advantage is that when used as Antiblockaddi tive or as a flow aid, the distribution of the silica particles on the host particles better and thus the effectiveness of he inventive silica is increased. The silicic acid according to the invention with a homogeneous modification layer is characterized inter alia by having excellent redispersibility after drying. The redispersibility of the modified precipitation silica according to the invention is at least 0.9, preferably 0.95, more preferably 0.99 and particularly preferably 1, wherein the re dispersibility is defined as the quotient of the passage 1 pm determined by laser diffraction after drying the silica divided through the passage 1 pm determined by laser diffraction before drying the silica. A redispersibility of 1 means that the silica is completely redispersible after drying and all particles have a particle size of less than 1 μm.

The modified precipitated silica according to the invention is characterized in that its specific BET surface area is preferably 50 m ² / g to 400 m ² / g, more preferably 100 m ² / g to 300 m ² / g and particularly preferably 150 m ² / g to 250 m ² / g be wearing.

The specific surface area can be determined according to the BET method according to DIN 9277/66131 and 9277/66132.

The modified precipitated silica according to the invention is further characterized in that its carbon content is preferably at least 1.5% by weight, more preferably at least 2.0% by weight. The carbon content is essentially based on the modification of the precipitated silica with organic radicals.

The carbon content can be determined by means of elemental analysis, ie in a combustion analysis in a corresponding analyzer. The modified precipitated silica according to the invention is further characterized in that the conductivity of its 5% ethanolic-aqueous dispersion is preferably at most 500 S / cm, more preferably at most 100 S / cm and in particular before given at most 25 S / cm.

Since modified silicas are poorly or not at all wetted by water, the conductivity of a corresponding sample in a methanol / water mixture can be determined. For this purpose, a small amount of sample (5 g of the present invention modifi ed precipitated silica) mixed with 10 g of methanol and then diluted with 85 g of deionized water. To achieve a homogeneous mixture, the batch is mixed alternately well ge and allowed to stand for a long time. Before the conductivity is measured with a conductivity cell, the batch is shaken up again. The conductivity can be measured with any conductivity meter. It is determined for a reference temperature of 20 ° C. The determination of the conductivity of a sample is also a very sensitive method for the quantification of soluble impurities.

Essential for a small particle size and in particular for an excellent redispersibility of the silica after Trock tion is their homogeneous surface modification.

The modified precipitated silica is therefore preferably characterized by a homogeneous surface modification.

To assess the homogeneity of the surface modification, a wetting test in combination with a distribution test between an aqueous and an organic phase has been granted. According to the invention, preference is given to using n-butanol as the organic phase. It is also preferred that water is used as the aqueous phase. When a modified precipitated silica is largely wetted by water after intensive mixing with water and sinks into the water phase and clouds it, the modified precipitated silica is hydrophilic. If this modified precipitate of silica now simultaneously in a system of a water and an organic phase, which may be eg butanol, the organic phase does not cloud, which is assessed as hydrophilic modified precipitated silica is also lipophobic. In this case, there is a homogeneous surface modification.

Homogeneous surface modification is also present when a modified precipitated silica is not wetted after intensive mixing with water, ie it floats on the water phase and forms a separate phase, ie is hydrophobic, but at the same time in a system of a water and an organic phase the organic phase is cloudy, that is lipophilic.

Homogeneous surface modification is also present when a modified precipitated silica is not wetted with water after thorough mixing, ie floats on the water phase and forms a separate phase, ie is hydrophobic, but at the same time in a system consisting of a water phase and an organic phase both phases is not wetted and forms a third solids-rich phase.

An inhomogeneous surface modification occurs when a modified precipitated silica is wetted with water after thorough mixing, ie it sinks into the water phase and clouds it, ie is hydrophilic, but at the same time clouds the organic phase in a system of a water and an organic phase is lipophilic.

A more accurate evaluation of the homogeneity of the boundary layer is possible with the aid of inverse gas chromatography in finite dilution (IGC-FC). This method allows the determination of the energetic homogeneity of a surface via the adsorptive Onenergieverteilungsfunktion (AEDF). The AEDF is a graphical representation of the energy distribution of a surface. For the silicas modified according to the invention, 3 peaks were found in the distribution function.

A homogeneous surface modification is preferably characterized in that the relative area fraction F (P3) of the peak P3, which is in the range of about 28-32 kJ / mol of the modified precipitated silica AEDF determined by means of IGC-FC, is smaller than 0.2 preferably less than 0.15 and particularly preferably less than 0.1. a The relative area fraction F (P3) is defined as F (P3) =

A (P3) / [A (P1) + A (P2) + A (P3)], where A (Px) with x = 1, 2 or 3 is the area of the peaks PI, P2 and P3. This means that the relative area fraction F (P3) of the high-energy peak P3 preferably has the lowest possible intensity.

Another object of the invention is a process for the preparation of these modified precipitated silicas, in which the modification reaction takes place during or immediately after the production reaction of the precipitated silica, characterized in that

i) to modify the precipitated silica more than 0.0075 mmol organosiliconate per m ² BET surface area (specific surface area) of the modified precipitated silica to be prepared measured by the BET method (according to DIN ISO 9277) is used,

ii) the organosiliconate at a pH of the reaction mixture

is added from 8-10 with a relative metering rate less than 5.0 mmol / (min * l) and

iii) grinding the modified precipitated silica in the liquid phase.

The inventive method is based on the so-called "one-pot process", in which the modification reaction during or immediately after the production reaction of the precipitated silica, as described in detail in WO 2018/019373. In addition to the characteristics of this "one-pot process" described in WO 2018/019373, this invention discloses a specific amount of added organosiliconate, a specific pH range of the reaction in which the organosiliconate is metered in at a specific relative metering rate and a milling step in liquid phase

The inventive method is preferably composed of the following method steps: i) the addition or formation of [S1O _{a _4/2]} units, especially be vorzugt formation of [Si0 _{_4/2]} units

ii) addition of organosiliconate, i. Surface modification (in the same approach)

iii) optionally completing the reaction by post-reaction iv) milling in the liquid phase

a) directly grinding the reaction mixture after step ii and optionally iii or

b) separating (i.e., separating the solid from the

liquid phase, for example by filtration or centrifugation, particularly preferably by Filtrati on), optionally washing, optionally drying, redispersing (be particularly preferably in water) and grinding the Dis persion

v) separation (i.e., separation of the solid from the liquid phase, for example by filtration or centrifugation, more preferably by filtration)

vi) optionally washing the solid

it is particularly preferred to wash step iv) when carrying out the process step

it is particularly preferred not to wash when carrying out the process step iv) b)

vii) drying the solid The above-mentioned individual steps are basic operations for the preparation of the silicic acid according to the invention. If necessary, individual steps can also be summarized. For example, step i) and step ii) can also take place in parallel. The individual process steps are preferably carried out successively and more preferably in the order indicated.

As starting material (precursor) for the formation of [Si0 _{_4/2]} units ([Si0 _{_4/2]} -Ausgangsstoff) are fiction, o- emäß alkoxysilanes of alkali silicates (water glass) is used. In the context of this invention, the [Si0 _{_4/2]} units denote the basic building blocks of the precipitated silica; Alkoxysilanes or alkali metal silicates as the NEN [Si0 _{_4/2]} -Ausgangsstoff their preparation.

Particularly preferred [Si0 _{_4/2]} -Ausgangsstoffe water glasses used. As a water glass from a melt he stared, glassy, so amorphous, water-soluble sodium, Ka lium and lithium silicates or their aqueous solutions designated net. Particularly preferred are aqueous solutions of sodium waterglass.

[Si0 _{_4/2]} units refer to compounds in which a Silici umatom is bonded to four oxygen atoms which in turn each comprise a free electron weils for an additional bond.

There may be oxygen-bonded units with Si-O-Si bonds. The free oxygen atoms are bound in the simplest case to hydrogen or carbon or the compounds are present as salts, preferably alkali metal salts.

In process step (i) for producing a modified precipitated silica, the reaction is carried out to produce a precipitated silica. Their modification (process step ii) takes place in the same batch, the modification reaction being carried out during or immediately after the production reaction of the precipitation can take place. This means that the modification takes place in the above-described reaction mixture which serves to prepare the precipitated silica. This process is referred to as "one-pot process" in the context of this invention just as in WO 2018/019373 The "one-pot process" is a clear difference from the state of the art, which generally works with multi-stage, separate processes.

Preferably, the reaction mixture in step i) contains water, alkali metal silicate and acid, more preferably water, alkali metal licat and sulfuric acid.

According to the invention, the reaction mixture for the production of the modified precipitated silica is added to a quantity of siliconate which is such that more than 0.0075 mmol, preferably 0.0075 mmol to 1.0 mmol and more preferably 0.01 mmol to 0.1 mmol Organosiliconate active ingredient per m ² BET surface area (specific surface area) of the modified precipitated silica produced by the BET method (corresponding to DIN ISO 9277) is used. This means and is a further particular advantage of the invention that the amount of organosiliconate agent can be selected according to the desired specific surface area of the product (BET).

The amount of substance organosiliconate active ingredient per m ² BET surface area (specific surface area) of the modified precipitated silica can be determined elementaryanalytically from the carbon content of the prepared modified precipitated silica, where, for the calculation of the bound Organosiliconat- Wirkstof fmenge starting from a Monomethylsiliconat the structural formula CH ₃ Si (0) _{_3/2} used for the bound Organosiliconat. Analogously, for the calculation of the bound organosiliconate active ingredient starting from a dimethylsiliconate, the structural formula (CH ₃ ) ₂ Si (O) 2/2 is used for the bound NEN organosiliconate active ingredient adopted. In general, for all organosiliconates of the general formula (I) (see below)

Calculation of the amount of active ingredient of each oxygen atom directly involved in the modification reaction takes into account only half and counterions such as cations not be taken into account.

The reaction mixture can be added in step i) other substances such as electrolytes and / or alcohols. The electrolyte may be a soluble inorganic or organic salt. Among the preferred alcohols include u.a. Methanol, ethanol or i-propanol. In a preferred embodiment, the reaction mixture as further substances in addition to water, alkali metal silicate and acid only Elekt rolytes and / or alcohols are added, more preferably only electrolytes and particularly preferably the reaction mixture are not added any further substances.

According to the invention, the modification reaction takes place during or immediately after the production reaction of the precipitated silica. According to the invention means "directly" in this context that the modification in the reaction mixture, the first acid and 2 the precipitated silica and / or [Si0 _{the _4/2]} -Ausgangsstoffe and 3 comprises a Organosiliconat as modifier, is carried out without prior the modification reaction, a procedural step for separating salts and / or other by-products is performed. The term "immediate" is not based on immediate time, stirring or standing between the reaction steps is not excluded. According to the invention, however, no ion exchange, filtration, washing, distillation or centrifugation step and no resuspension are performed prior to the modification reaction.

The absence of a prior process step for the separation of salts and / or other by-products has the great advantage that energy costs, time and resources such as As washing solution or wash water and solution or water can be saved for resuspension. This procedure makes the use of further aggregates superfluous. Economically, it is of particular interest, since the method according to the invention saves time and thus reduces the system document time. The other by-products include, but are not limited to, alcohols.

In the modification or modification reaction, which is also referred to in the context of this invention synonymous with hydrophobing or Hyd rophobierungsreaktion, the unmodi fied precipitated silica reacts with organosiliconate as modifying agent. Accordingly, the modifying agent in the context of this invention synonymous with modifying agent, slip medium, occupancy agents, water repellents or silylating agent referred to.

According to the invention, organosiliconates are compounds of the general formula (I)

RVsi (OR ² ) _{4 -n}

where R ¹ , R ² and n have the following meanings:

^R3 ^ are independently hydrogen, linear or verzweig tes, optionally functionalized Ci-C ₃₀ alkyl, linear or branched res, optionally functionalized C ₂ - C ₃₀ alkenyl, linear or branched, optionally radio tionalisiertes C ₂ -C ₃₀ alkynyl, , optionally functionalized C ₃ -C ₂ o-cycloalkyl, optionally functionalized C ₃ -C ₂ o-cycloalkenyl, optionally functionalized Ci- C ₂ o-heteroalkyl, optionally functionalized C ₅ -C ₂₂ - aryl, optionally functionalized C ₆ - C ₂₃ -alkylaryl, optionally functionalized C ₆ -C ₂₃ -arylalkyl, optionally functionalized C ₅ -C ₂₂ -heteroaryl,

R ² = independently of each other hydrogen, linear or verzweig tes, optionally functionalized Ci-C ₃₀ alkyl, linear or branched res, optionally functionalized C ₂ - C ₃₀ alkenyl, linear or branched, optionally functional functionalized C ₂ -C ₃₀ -alkynyl, optionally functional! - overbased C ₃ -C ₂₀ cycloalkyl, optionally functionalized C3-C ₂₀ cycloalkenyl, optionally functionalized C _x - C ₂₀ heteroalkyl, optionally functionalized C ₅ -C ₂₂ - aryl, optionally functionalized C ₆ - C ₂₃ alkylaryl, optionally functionalized C ₆ -C ₂₃ -arylalkyl, optionally functionalized C ₅ -C ₂₂ -eteroyl, NR ¹ ₄ ⁺ , where R ^{1 may} independently of one another have the abovementioned meanings, M ^{p +} _S , where M is a metal atom selected from the group consisting of metals of the main and subgroups of the Perio densystems of the elements, p oxidation number of the metal atom M, s = l / p,

and / or a group of the general formula (Ha)

-SiR ¹ _m (OR ²⁾ _3-ra

where R ¹ and R ² independently of one another have the abovementioned meanings and m independently of one another can denote 0, 1, 2 or 3,

n = 1, 2 or 3,

and at least one solvent, optionally at least one surface-active substance or a mixture thereof,

wherein in the compound of the general formula (I) or in the group of the general formula (Ha) at least one radical R ² NR ¹ ₄ ⁺ or with the meanings given above for R ¹ , p, s and M.

If R ² in the compound of the general formula (I) has the meaning of a group of the general formula (Ha) several times, for example more than once, corresponding compounds are present which carry two, three, four or more units with Si atoms , Therefore, in the case where R ^{2 is} a group of the general formula (Ha) several times, polysiloxanes or polysiloxanolates are present.

It is true that an organosiliconate has at least one Si-C bond, ie at least one remainder must be organic in nature. The particular advantage of using organosiliconates as modifiers is that they are highly water-soluble and therefore particularly suitable for a homogeneous reaction in an aqueous medium. The use of an aqueous solu tion of otherwise solid or waxy substances simplifies handling, as by means of pumps comparatively easy exact dosage can be achieved.

Typically used modifiers such as example organoalkoxysilanes or organochlorosilanes are poorly or not at all water-soluble. Partly they react spontaneously and with strong heat generation violently with water, whereby a safe, even and controlled reaction guidance is made considerably more difficult (this applies for example to the frequently used organochlorosilanes).

According to the invention, mixtures of different organosiliconates can also be used. Mixtures are preferably used when functional groups (eg, vinyl, allyl, or sulfur-containing groups such as C ₃ H _e SH) are to be introduced.

The organosiliconates used in the process according to the invention are preferably methylsiliconates, particularly preferably monomethyl siliconeates or dimethylsiliconates.

The use of methyl silicates is particularly advantageous beyond what has been stated above, since methylsiliconates can be obtained simply and in good yield from the readily available and inexpensive methylchlorosilanes, methylethoxysilanes or methylsilanes by reaction with alkaline substances, if appropriate in an aqueous medium.

In a particularly preferred embodiment, aqueous

Solutions of monomethylsiliconates of the general form

(CH ₃ ) Si (OH) _3-X OM _X and their oligomeric condensation products set, wherein the counterion M is preferably potassium or sodium and preferably x = 0.5-1, 5, more preferably 0.8-1.3. In a particularly preferred embodiment, x = 0.8-0, 9. x does not refer to 1 molecule, but to the totality of the molecules present in the mixture. Is preferred in particular as Organosiliconat SILRES ^® BS16 (aqueous potassium Methylsilikonatlösung, available from Wacker Chemie AG) whose Organosiliconat-active compound content approximately 34 wt .-%, calculated as CH ₃ Si (0) _{_3/2,} is.

In an alternatively preferred embodiment, aqueous solutions of dimethylsiliconates of the general form

(CH ₃ ) ₂ Si (OH) _2-x OM _x and their oligomeric condensation products, wherein the counterion M is preferably potassium or sodium, and preferably x = 0, 1-2,0. x does not refer to 1 molecule, but to the entirety of the molecules present in the mixture.

Particularly preferred are aqueous solutions containing belie bige mixtures of Dimethylsiliconaten the general form of (CH ₃₎ ₂ Si (OH) _2-x OM _x and their oligomeric condensation products and Monomethylsiliconaten the general form of (CH ₃₎ Si (OH) _3-X 0M _X and their oligomeric condensation products used, wherein M and x have the abovementioned meaning.

The siliconates are preferably used without prior isolation or separation of by-products or splitting-off products. This means that, for example, dimethyldimethoxysilane is reacted directly with the required amount of aqueous potassium hydroxide solution or sodium hydroxide solution and the resulting aqueous solution of Dimethylsiliconates directly without further Aufreini supply, eg by separation of the resulting methanol, is set is. Surprisingly, the process products have a homogeneous surface modification, the determination of the homogeneity as described above.

The reaction mixture can be added in step ii other substances such as electrolytes and / or alcohols. The electrolyte may be a soluble inorganic or organic salt. Among the preferred alcohols include u.a. Methanol, ethanol or i-propanol.

The reaction components are preferably mixed in step ii by simple stirring.

The temperature of the reaction mixture in step ii) is preferably 70-95 ° C., more preferably 90 ° C.

The metered addition of the Organosiliconates preferred Methylsilico- NATs, may be parallel to addition of the [Si0 _{_4/2]} -Ausgangsstoffs as particularly preferred water glass or after completion of the dosage to the [Si0 _{_4/2]} -Ausgangsstoffs as particularly preferably water glass. The metered addition of the ganosiliconates Or, preferably Methylsiliconats is preferably carried out after completion of the addition of the [Si0 _{_4/2]} -Ausgangsstoffs as particularly preferably water glass.

Surprisingly, it was found that the metering rate of the organosiliconate is essential for the homogeneity of the surface modification. According to the invention, therefore, the organosiliconate is at a pH of the reaction mixture of 8-10 with a re dative dosing rate less than 5.0 mmol / (min * l), preferably 5.0 mmol / (min * l) to 0.5 mmol / (min * l) and more preferably 4.0 mmol / (min * l) to 1.0 mmol / (min * 1) are added. The relative dosing rate is defined as the dosing rate of the organosiliconate active ingredient in mmol per minute based on 1 1 reaction volume, the reaction volume being composed of the volume of the used deionized water and the volume of the solution used the [Si0 _{_4/2]} -Ausgangsstoffs, preferably What serglas.

According to the invention, the organosiliconate is metered in at a pH of the reaction mixture of 8-10, preferably 8.0-10.0 and particularly preferably 8.5 to 9.0. For this purpose, it is preferred to add to the reaction mixture acid, particularly preferably sulfuric acid or hydrochloric acid, and in particular preferably concentrated sulfuric acid, in order to counteract the alkalinity of the siliconate.

The preferred reaction mixture of water, [Si0 _{_4/2]} - starting material, such as more preferably water glass, acid such as be Sonders preferably sulfuric acid and Organosiliconat as particularly preferred methylsiliconate, and optionally th electrolyzer and / or alcohols is then preferably from 30 min to 120 min, particularly preferably after-reacted for 60 minutes, ie the reaction completes.

In this post-reaction time, the pH is preferably kept constant. This can be achieved by adding further acid to the mixture in the process.

In this post-reaction time, the temperature is preferably kept constant.

To terminate the reaction without or after a possibly. This reaction is preferably stopped by lowering the pH to about 3.5 and / or the temperature to 50 ° C.

Subsequently, the reaction mixture is preferably filtered and more preferably also washed. For washing, water, polar organic solvents or mixtures thereof may be used, preferably washing with water, especially preferably with demineralized, deionized (VE) water, which is characterized in that it has a conductivity of <5 pS / cm, preferably of <3 pS / cm and particularly preferably of <0.1 pS / cm.

Washing can be done in several ways. For example, the solid separated by filtration is flushed with fresh water until a sufficiently low (before preferably constant) conductivity value of the wash water of <500 pS / cm, preferably <100 pS / cm, particularly preferably <10 pS / cm is achieved. The flow can be continuous or in portions. A particularly efficient form of washing is the redispersion of the filter cake in clean water followed by further filtration.

If necessary, a centrifugation can be used to separate off the silica instead of a filtration.

According to the invention, the modified precipitated silica is ground in a further process step in the liquid phase. This process step can take place before or after washing.

The liquid phase is preferably an aqueous phase, particularly preferably water, particularly preferably demineralized water.

In the case of the liquid phase milling according to the invention before washing, the preferred reaction mixture is water,

[Si0 _{_4/2]} -Ausgangsstoff as more preferably water glass, acid, such as particularly preferably sulfuric acid, and Organosiliconat as particularly preferably mono- or Dimethylsiliconat, as well as, where appropriate electrolyte and / or alcohols action after completion of the Re and optionally further reaction and / or lowering the pH and / or the temperature ground directly. Subsequently The silica may then be washed as described above, separated from the liquid phase and dried.

In the case of grinding according to the invention in the liquid phase after washing, the wet filter cake or Zentrifu gationsrückstand is redispersed in demineralized water and then this dispersion on milled in the liquid phase.

The pH of the dispersion may preferably be adjusted to a pH of from 3 to 10, more preferably from 5 to 8, before milling.

For the preparation of the dispersion for liquid phase milling according to the invention, i. for mixing and dispersion of the modified precipitated silica, conventional mixers or stirrers such as beam mixers or anchor stirrers or fast-running dispersing machines such as rotor-stator machines, dissolvers, colloid mills or ultrasonic dispersers or Hochdruckhomo genisatoren be used.

The solids content of the dispersion containing the modified precipitated silica before grinding is preferably 1 to 50% by weight, more preferably 2 to 20% by weight and most preferably 5 to 15% by weight. Following the grinding according to the invention in the liquid phase, the dispersion can be dried directly ge or filtered off or centrifuged off, in which case optionally one or more times can be washed, followed by the drying step. Preference is given to closing filtration, without further washing step, and then the final drying.

For grinding according to the invention in the liquid phase, all mills can be used in which the millbase is present in a liquid phase FLÜS. Typical examples are horizontal or vertical ball mills and bead mills, in which grinding media are used for comminuting the material to be ground. In addition to the In order to reduce the impact between particles and grinding media, a multiplicity of grinding media grinding bodies as well as grinding media apparatus wall impacts occur in these mill types, which may possibly cause undesired abrasion and wear and the associated product contamination.

Further typical examples are dispersing aggregates, such as, for example, rotor-stator apparatuses (colloid mill, ring gear disperser), whose comminuting action is essentially due to shear forces due to the surrounding fluid, and high-pressure homogenizers whose dispersing action affects both expansion flow, shear flow, turbulence and, if appropriate, Also cavitation is due. Roller mills, such as roller mills or muller mills, are particularly suitable for reducing the viscosity of viscous dispersions.

Preference is given to impact or autogenous liquid mills (liquid jet dispersers) in which dispersion jets containing the predispersible material are directed against one another with high kinetic energy or directed against baffles. The comminution is based on particle-particle collisions, particle-wall collisions and turbulence and possibly cavitation of the surrounding fluid.

Preference is given to grinding a liquid

Beam disperser used. In these, the dispersion to be treated by means of high-pressure pumps such as piston pumps to high pressures of up to several thousand bar tensioned. The dis persion is then relaxed by a pinhole of different geometries or columns. The liquid jet is greatly accelerated under pressure drop. The liquid jet thus generated can be passed in a baffle chamber against a baffle body or directed to a second, oppositely directed liquid jet. The directional kinetic energy of the beam or the radiation is reduced during impact by particle collisions, particle-fluid interaction and energy dissipation in the fluid. A crushing of Particles occur both in the passage through the diaphragm, as well as the impact of the dispersion on the baffle or the oppositely directed liquid jet instead. Especially before geous is the generation of the opposite liquid radiate from the same Ausgangsdispersion on a gemeinsa mes high-pressure pumping system and a flow divider, which separates the total flow of the dispersion to be treated into two partial streams. In this embodiment, the expenditure on equipment is the ge ringsten and the wear and corresponding Produktkontamina functions due to the autogenous comminution process also minimal.

The liquid jet dispersion can be characterized by the following essential parameters:

- Specific energy E:

E is the energy applied to the system via pressure build-up per dispersion mass, which can be used to generate the orifice flow and the jet formation in the impact chamber. The calculation is carried out approximately according to the law of Bernoulli, ignoring specific positional energy and specific kinetic energy, since these are the amount of the specific pressure energy in the Hochdruckbe rich liquid jet dispersion negligible. _Hence E = p / p _diSp , where p is the static pressure in [Pa (abs.)] And p _{disp is} the dispersion _density in [kg / m ³ ]. The specific energy is preferably greater than lxlO ⁴ m ² / s ^2, special DERS preferably, the specific energy in a range of 5xl0 ^{4 2} / s ² to lxlO ⁶ m ² / s ² and in a specific embodiment, the specific energy in a Range from lxlO ⁵ m ² / s ² to 5x10 ^s m ² / s ² .

- mean jet velocity u in the aperture cross-section:

The mean flow velocity in the aperture cross-section can be determined from the quotient of the volume flow through the aperture Q [m ³ / s] and the aperture cross-sectional area A _Biende [m ² ]. _{We have} u = Q / A _end The average jet velocity in the aperture cross section is preferably greater than 10 m / s, more preferably the average jet velocity in the aperture cross section is in a range of 10 m / s to 2000 m / s, in a special embodiment, the average jet velocity in the aperture cross section in one Range from 100 m / s to 1000 m / s.

To improve the grinding quality, the millbase can preferably be conveyed more than once through the liquid jet disperser. The millbase is particularly preferably conveyed through the liquid jet disperser 1 to 20 times, in a special embodiment the millbase is conveyed 5 to 10 times through the liquid jet disperser.

It is preferred that the ground and optionally warmed mixture, i. the modified precipitated silica is dried in the next process step. The drying temperature is preferably more than 100 ° C. The drying process is completed when the powder reaches constant weight, i. that the weight of the powder does not change during further drying. The drying can by means of conventional tech nical methods such as static drying in Tro ckenschränken on tray plates or dynamic drying un ter promotion of the dry matter through a zone of increased temperature Tempe z. As in drum dryers, conical dryers or fluidized bed or fluidized bed dryers. Preference is given to drying under dynamic conditions.

Drying is preferably carried out by atomizing a possibly diluted dispersion into a stream of hot air, i. by

Spray drying.

The BET surface area (specific surface area) is preferably measured from the dried modified precipitated silica by the BET method (in accordance with DIN ISO 9277). The particle size of preferably at least 90% of the particles of the produced modified precipitated silica is preferably at most 1 pm. There is preferably a narrow particle size distribution. The coarse fraction with particle sizes of 1-10 mt ^h is preferably at most 10%, particularly preferably at most 5% and particularly preferably 0%.

Dried modified precipitated silicas such as Sipernat D10 or Sipernat D17 from Evonik can no longer be post-ground in the liquid phase, since they are not wettable with water. A dried hydrophilic precipitate of silica such as Sipernat D288, in contrast, is wettable with water. Nevertheless, the redispersibility of the particles is low after post-milling in the liquid phase (see Comparative Example 4).

The modified precipitated silica according to the invention can be prepared by the process according to the invention; the modified precipitated silica according to the invention is particularly preferably produced by the process according to the invention.

The process according to the invention preferably serves for the preparation of the modified precipitated silicas according to the invention.

Another object of the invention is process for Ver strengthening of elastomers, in which one of the above-described modified precipitated silicas according to the invention is eingear processed.

The silicas according to the invention are particularly suitable as reinforcing fillers in elastomers, in particular as reinforcing fillers in silicone elastomers such as silicone solid rubbers, so-called HTV or HCR rubbers, and silicone liquid rubbers, so-called LSR rubbers. The invention will be described in more detail below with reference to Ausführungsbeispie len, without being limited thereby.

Analysis methods:

Determination of the BET surface area

The specific surface area was determined by the BET method according to DIN 9277/66131 and 9277/66132 using an SA ™ 3100 analyzer from Beckmann-Coulter.

Determination of carbon content (% C)

The elemental analysis on carbon was carried out according to DIN ISO 10694 using a CS-530 elemental analyzer from Eitra GmbH (D-41469 Neuss).

Determination of particle size, particle size distribution and redispersibility by means of laser diffraction

Sample preparation: a) solids:

9.5 g of isopropanol were initially introduced into a 30 ml snap-cap glass and then 0.5 g of the silicic acid to be measured was added. Any existing coarse particles were crushed before using a spatula. The dispersion was thoroughly mixed for about 20 minutes with the aid of a magnetic stirrer.

4 g of the sample mixture were then added to a solution of 0.3 g of BYK192 in 15.7 g of demineralized water with a pH of 10 (pH was adjusted with 1 M aqueous NaOH solution), shaken vigorously several times and then mixed for a further 20 min on a magnetic stirrer.

The mixture was then dispersed with gentle stirring with a magnetic stirrer for 15 minutes with ultrasound: Ultra sounder Dr. Hilscher UP 400s with sonotrode 3 at 50% power, with the sonotrode at a distance of about 2 cm from the magnetic stir bar. This resulted in a dispersion having a solids content of about 0.8%. b) Aqueous dispersions:

By means of a commercial IR solids balance, the solids content of the dispersion was determined by drying to a mass consistency.

According to the previously determined solid content of the dispersion, the sample was diluted with deionized water having a pH of 10 (pH was adjusted with 1 M aqueous NaOH solution) to a solids content of about 0.8%, several times inten shaken vigorously and then mixed on a magnetic stirrer for 20 min.

The mixture was then dispersed with gentle stirring with a magnetic stirrer for 15 minutes with ultrasound: Ultra sounder Dr. Hilscher UP 400s with sonotrode 3 at 50% power, with the sonotrode at a distance of about 2 cm from the magnetic stir bar.

Measurement :

The measurement was carried out with a Mastersizer 3000 laser diffraction apparatus from Malvern with wet cell Hydro MV.

The measuring cell was filled with demineralized water at pH 10 (pH was adjusted with 1 M aqueous NaOH solution) and the background measured with a measuring time of 20 s. Subsequently, the sample dispersion described above was added dropwise until the Laserabschattung had reached a value of about 2 - 2.5. The measuring temperature was 25 ° C. Before the actual measurement, the measurement dispersion was stirred for 5 min in the measuring cell at 1800 rpm in order to ensure uniform mixing. To determine the particle size, three individual measurements were carried out. Between the measurements, the dispersion was stirred for 5 min at 1800 rpm. The measurement was started immediately after the end of the stirring time. The following parameters were specified:

- Refractive index of the particles: 1,400

- Particle absorption value: 0.010 Refractive index of the dispersion medium: 1.330

- Particle type: non-spherical

Measuring time: 20 s

The analysis was carried out according to the Mie theory with the aid of the universal analysis model implemented in the software.

The data presented in Table 1 are values of the second individual measurement, whereby it was to be ensured that the deviation of the d ₅₀ value in the individual measurements was <5%. Table 1 lists the passage at 1 pm and the redispersibility.

To evaluate the measurement result of the laser diffraction particle size analysis, the volume-weighted particle size distribution q ³ and the corresponding distribution sum curve Q ^{3 were} used. The cumulative distribution curve is the cumulative representation of the particle size representation normalized to 100%.

The passage at 1 pm is the absolute value of the cumulative distribution curve Q ³ at 1 pm in percent. A value of 100% means that all particles have a particle size of less than or equal to 1 pm.

To determine the redispersibility, both the silica dispersion after liquid milling without prior separation or drying was measured as well as the dried powder after liquid milling.

The redispersibility is the quotient of 1 pm after drying of the silica divided by the passage 1 pm before the silicic acid is dried. A redispersibility of 1 means that the silica is completely redispersible after drying and all particles have a particle size of less than 1 μm.

Determination of the homogeneity of the surface modification

Trial 1: In a 50 ml snap-cap glass 25 ml of deionized water were pre-lays. Then 100 mg of the pebble acid powder to be examined were added, the glass was closed and shaken vigorously for 30 s.

Rating :

Hydrophilic: The silica was mostly wetted and dropped into the water phase.

Hydrophobic: The silica was mostly not wetted and did not sink. She swam on the water phase and formed a separate phase.

Trial 2;

In a 50 ml snap-cap glass 15 ml of deionized water and 15 ml of butanol were submitted. Subsequently, 100 mg of the silica powder to be examined were added, the glass was sealed and shaken vigorously for 30 seconds. After separation of the phases, the distribution of the particles was optically evaluated in both phases. Rating :

Lipophil: The upper butanol phase was very cloudy, the lower one

Water phase largely clear.

Lipophobic: The upper butanol phase was largely clear, the lower water phase very cloudy.

Determination of homogeneity:

*) In this case, a third solids-rich forms

Phase between the aqueous phase and the butanol phase. Determination of the BET constant C _BE T and the adsorption energy

Distribution functions.

The determination was carried out by means of inverse gas chromatography in finite dilution (IGC-FC). For this purpose, a non-rusting chromatography column having an inner diameter of 2 mm and a length of 15 cm was filled with the silica to be investigated. The sample amount was about 190 mg. The two ends of the column were sealed with silanized glass wool. The packed column was connected to the gas chromatograph using 1/8 'Swagelok ports. The gas chromatograph was a common commercial instrument with FID detector. Helium was used as the carrier gas. Before the measurement, the sample was degassed for 16 h at 110 ° C and a gas flow rate of 12 ml / min. The subsequent measurement was carried out at 50 ° C and a gas flow rate of 20 ml / min. For this purpose, 1.5 to 3.0 mΐ of isopropanol (purity of at least GC quality) were usually injected with a 10 mI injection molding. The injected sample quantity had to be determined iteratively. The aim was to achieve a maximum peak height at a relative pressure of 0.1 to 0.25. This could only be determined from the total chromatogram.

To determine the dead volume, methane was injected together with isopropanol.

The calculation of the isotherms for determining the BET constant C _B E _{T was} carried out according to Conder ("Physicochemical Measurement by Gas Chromatography", JR Conder and CL Young, Wiley (Chichester), 1979). The determination of the adsorption energy distribution functions (AEDF) was carried out according to Balard (H. Balard, "Estimation of the Surface Energetic Heterogeneity of a Solid by Inverse Gas Chromatography", Langmuir, 13 (5), pp 1260-1269, 1997). To calculate the isotherm and the derived physical parameters or the AEDF software was the Fa.

Adscrentis, "In-Pulse" and "FDRJ07.5.F" used. To determine the area fraction of the high-energy peak of the AEDF, the distribution function was decomposed into the individual peaks by means of peak deconvolution. For this purpose, the raw data of the AEDF were read into the ORIGIN program and a deconvolution was carried out assuming a Gaussian distribution of the individual peaks. In all of the examples given here, the best fit was obtained assuming 3 peaks with peak levels of PI of approximately 17-19 kJ / mol, P2 approximately 21-25 kJ / mol and P3 approximately 28-32 kJ / mol. In Table 1, the area ratio of the high-energy peak is F (P3) =

A (P3) / [A (PI) + A (P2) + A (P3)] in the range 28-32 kJ / mol, where A (Px) with x = 1, 2 or 3 represents the area of the peaks PI .

P2 and P3 is.

Used raw materials:

Aqueous sodium silicate solution: Commercial water glass 38/40 from Wöllner with a density at 20 ° C. according to the manufacturer stated to be about 1.37 g / cm ³ .

Potassium methylsiliconate: Aqueous potassium methylsiliconate Silres ^® BS16 fanteil with an active compound, calculated as CH ₃ Si (0) _{_3/2,} of about 34 wt .-% according to manufacturer's instructions.

Example 1 :

In a 40 1 -Universal-Stirrer (steel / enamel) equipped with a propeller paddle stirrer 18 kg of demineralized water were heated to 90 ° C. With stirring (250 min ¹ ) at this tempera ture 5.04 kg of water glass dosing rate within 60 min with constant Do. At the same time, 1.22 kg of 50% sulfuric acid were metered in parallel, as a result of which the pH was kept substantially constant (pH = approx. 8.5). The mixture was stirred for a further 5 minutes at 90 ° C. and then with stirring at 90 ° C. within 60 minutes 0.59 kg of an aqueous potassium methylsiliconate solution having a relative metering rate of 2.3 mmol / (min * l) and 0, 29 kg 50% sulfuric acid dosed (pH = approx. 8.5). The mixture was stirred for 1 h at 90 ° C and pH = 8.5 and then acidified by addition of 50% sulfuric acid with stirring to pH = 3.5. After cooling to 50 ° C was filtered through a chamber filter press un ter using K100 filter plates and washed pH neutral. The moist filter cake was redispersed in 20 kg of demineralized water with a paddle stirrer and the resulting dispersion was ground with a solids content of about 7.6% by weight of egg ner Starburst 10 autogenous liquid mill with propellant water from Sugino. The millbase was at a speci fic energy input of 224565 m ² / s ² (p _disp = 1091 kg / m ³ ) per pass with a pressure in front of the orifice of 2450 bar and a mean suspension velocity in the aperture cross section of 490 m / s at a throughput from 40 1 / h four times through the mill promoted.

The silica was filtered off via a chamber filter press using K100 filter plates and blown dry with nitrogen. The filter cake was dried on trays in a dry cabinet at 150 ⁰ C to constant weight. Subsequently, the solid was analyzed as described in the analysis methods. The results are listed in Tab. 1.

At game 2:

In a 40 1 universal stirrer (steel / enamel) equipped with a propeller paddle stirrer, 18 kg DI water were heated to 90 ° C. With stirring (250 min ¹ ) at this tempera ture 5.04 kg of water glass dosing rate within 60 min with constant Do. At the same time, 1.22 kg of 50% sulfuric acid were metered in parallel, as a result of which the pH was kept substantially constant (pH = approx. 8.5). The mixture was stirred for a further 5 minutes at 90 ° C. and then with stirring at 90 ° C. within 110 minutes 1.54 kg of an aqueous potassium methylsiliconate solution having a relative metering rate of 2.4 mmol / (min * l) and 0, 77 kg 50% sulfuric acid dosed (pH = approx. 8.5). The mixture was stirred for 1 h at 90 ° C and pH = 8.5 and then acidified by addition of 50% sulfuric acid with stirring to pH = 3.5. After cooling to 50 ° C., filtration was carried out using a chamber filter press using K100 filter plates and washed neutral. The moist filter cake was redispersed in 20 kg of demineralized water with a paddle stirrer and the resulting dispersion was ground with a solids content of about 7.6% by weight of egg ner Starburst 10 autogenous liquid mill with propellant water from Sugino. The regrind was at a speci fic energy input of 224565 m ² / s ² (pai _sp = 1091 kg / m ³ ) per pass with a pressure in front of the orifice of 2450 bar and a mean suspension velocity in the aperture cross section of 490 m / s at a throughput from 40 1 / h eight times through the mill promoted. The silica was filtered through a chamber filter press using K100 filter plates and blown dry with nitrogen. The filter cake was dried to sheets in a drying oven at 150 ° C to constant weight. Subsequently, the solid was analyzed as described in the analysis methods. The results are listed in Tab. 1.

Comparative Example 3 (not according to the invention) s

In a 40 l universal stirrer (steel / enamel) equipped with a propeller blade stirrer, 17 kg of deionized water were heated to 90 ° C. With stirring (250 min ¹ ) 5.21 kg of water glass were metered sierrate within 60 min with constant Do at this tempera ture. At the same time, 1.21 kg of 50% sulfuric acid were metered in parallel, as a result of which the pH was kept substantially constant (pH = approx. 9.0). The mixture was stirred for a further 5 minutes at 90 ° C. and then, with stirring at 90 ° C., within 13 minutes, 0.659 kg of an aqueous potassium methylsiliconate solution having a relative metering rate of 12.3 mmol / (min * 1) and 0.30 kg 50% sulfuric acid is metered (pH = approx. 8.5). The mixture was stirred for 1 h at 90 ° C and pH = 9.0 and then acidified by adding to 50% sulfuric acid with stirring to pH = 3.5. After cooling to 50 ° C was filtered through a chamber filter press using K100 filter plates, washed pH neutral and blown dry with nitrogen. The filter cake was dried on sheets in a drying oven at 150 ° C. to constant weight and after cooling to room temperature. mill on a ZPS50 classifier mill from Hosokawa-Alpine (mill: 20,000 min ¹ , classifier: 16,000 min ¹ ).

A portion of the dry-milled silica was redispersed in demineralized water with a paddle stirrer to give a 7.5% dispersion, and 250 ml of the dispersion were ground on a Starburst Mini laboratory autogenous liquid mill with water propellant from Sugino. The millbase was at a specific energy input of 183486 m ² / s ² (pai _sp = 1090 kg / m ³ ) per pass with a pressure in front of the orifice of 2000 bar and a mean suspension velocity in the aperture cross section of 120 m / s at a throughput of 5 1 / h seven times through the mill promoted. It was then dried in a drying oven at 150 ° C for Ge weight constancy. Subsequently, the solid was analyzed as described in the analysis methods. The results are listed in Tab. 1.

Comparative Example 4 (not according to the invention):

75 g of a hydrophilic precipitated silica (available from Evonik as Sipernat 288) were dispersed in 0.925 kg of demineralized water with a paddle stirrer and 250 ml of the dispersion were milled on a Starburst Mini laboratory autogenous liquid mill with propellant water from Sugino. The millbase was at a specific energy input of 183486 m ² / s ² (p _diSp = 1090 kg / m ³ ) per pass with a pressure in front of the shutter of 2000 bar and a mean suspension speed in the aperture cross-section of 120 m / s at a throughput of 5 1 / h five times through the mill promoted. It was then dried in a drying oven at 150 ° C to constant weight. The solid as described in the analytical analy ^¬ Siert. The results are listed in Tab. 1.

Example 5:

In a 40 1 universal stirrer (steel / enamel) equipped with a propeller paddle stirrer, 18 kg of deionized water were added to 90 ° C heated. With stirring (250 min ¹ ) at this tempera ture 5.04 kg of water glass dosing rate within 60 min with constant Do. At the same time, 1.22 kg of 50% sulfuric acid were metered in parallel, as a result of which the pH was kept substantially constant (pH = approx. 8.5). The mixture was stirred for a further 5 minutes at 90 ° C. and then with stirring at 90 ° C. within 60 minutes 0.59 kg of an aqueous potassium methylsiliconate solution having a relative metering rate of 2.3 mmol / (min * 1) and 0, 29 kg 50% sulfuric acid dosed (pH = approx. 8.5). The mixture was stirred for 1 h at 90 ° C and pH = 8.5 and then acidified by addition of 50% sulfuric acid with stirring to pH = 3.5. After cooling to 50 ° C was filtered through a chamber filter press using K100 filter plates, washed pH neutral and blown dry with nitrogen. The filter cake was on trays in a drying oven at 150 ° C for weight - dried to constant and after cooling to room temperature egg ner ZPS50- classifier mill from Hosokawa Alpine-milled (mill: 20.000 min ^1; classifier: 16.000 min ^1).

A portion of the milled silica was redispersed in demineralized water with a paddle stirrer to give a 7.5% dispersion and 250 ml of the dispersion were ground on a Starburst mini laboratory autogenous liquid mill with propellant water from Sugino. The millbase was at a specific energy input of 183,486 m ² / s ² (p _disp = 1090 kg / m ³ ) per pass with a pressure in front of the shutter of 2000 bar and a medium suspension speed in the diaphragm cross-section of 120 m / s at a

Throughput of 5 1 / h seven times through the mill promoted. At closing was introduced in a drying oven at 150 ° C to dry ge. Subsequently, the solid was analyzed as described in the analysis methods. The results are listed in Tab. 1. Table 1: O

O

n H o o

Claims

claims

1. Modified precipitated silica, characterized in that

i) the particle size of at least 90% of its particles

not more than 1 pm and

ii) their redispersibility, i. the quotient from the

Run 1 pm determined by laser diffraction after drying of the silica divided by the passage 1 pm determined by laser diffraction before drying the silica, at least 0.9.

2. Modified precipitated silica according to claim 1, characterized in that its specific BET surface area is 50 m ² / g to 400 m ² / g.

3. Modified precipitated silica according to one or more of claims 1 or 2, characterized in that its content of carbon is at least 1.5% by weight.

4. Modified precipitated silica according to one or more of claims 1 to 3, characterized in that the conductivity of its 5% strength methanolic-aqueous dispersion is preferably not more than 500 S / cm.

5. Modified precipitated silica according to one or more of claims 1 to 4, characterized in that it is characterized by a homogeneous surface modification auszeich net.

6. Modified precipitated silica according to one or more of claims 1 to 5, characterized in that the re lative surface portion F (P3) of the peak P3, which is in the range of about 28 - 32 kJ / mol of IGC-FC determined AEDF of modified precipitated silica is less than 0.2.

7. A process for the preparation of modified precipitated silicas according to one of claims 1 to 6, in which the modification reaction takes place during or immediately after the production reaction of the precipitated silica, characterized in that:

i) to modify the precipitated silica more than 0.0075 mmol organosiliconate active ingredient per m ² BET surface area (specific surface area) of the produced modified precipitated silica is measured according to the BET method (according to DIN ISO 9277) is used,

ii) the organosiliconate at a pH of the reaction mixture of 8-10 with a relative metering rate less than 5.0 mmol / (min * l) is added and iii) the modified precipitated silica in liquid

Phase is ground.

8. The method according to claim 7, characterized in that is used as the organosiliconate potassium methylsiliconate.

9. The method according to one or more of claims 7 or 8, characterized in that the solids content of the dis persion containing the modified precipitated silica prior to grinding is 1 to 50 wt .-%.

10. The method according to one or more of claims 7 to 9, characterized in that for grinding a liquid jet disperser is used.

11. A process for reinforcing elastomers, in which he inventive modified precipitated silica according to one or more of claims 1 to 6 eingear ^¬ as filler.