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WO2021093961A1 - Acide silicique précipité modifié à teneur en humidité réduite - Google Patents

Acide silicique précipité modifié à teneur en humidité réduite Download PDF

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Publication number
WO2021093961A1
WO2021093961A1 PCT/EP2019/081376 EP2019081376W WO2021093961A1 WO 2021093961 A1 WO2021093961 A1 WO 2021093961A1 EP 2019081376 W EP2019081376 W EP 2019081376W WO 2021093961 A1 WO2021093961 A1 WO 2021093961A1
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Prior art keywords
precipitated silica
weight
modified precipitated
drying
modified
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PCT/EP2019/081376
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German (de)
English (en)
Inventor
Torsten Gottschalk-Gaudig
Sebastian KRÖNER
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Wacker Chemie AG
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Wacker Chemie AG
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Priority to PCT/EP2019/081376 priority Critical patent/WO2021093961A1/fr
Publication of WO2021093961A1 publication Critical patent/WO2021093961A1/fr
Anticipated expiration legal-status Critical
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B33/00—Silicon; Compounds thereof
    • C01B33/113—Silicon oxides; Hydrates thereof
    • C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
    • C01B33/18—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof
    • C01B33/187—Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof by acidic treatment of silicates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area

Definitions

  • the invention relates to a modified one
  • Precipitated silicas are oxides of silicon (SiO 2 ) that are produced on an industrial scale using precipitation processes and are used in a wide range of applications. Due to their structural properties and the associated reinforcing effect, they represent an elementary component of both organic rubbers, e.g. for use in tires, and in silicone rubbers or other polymeric materials. Depending on the necessary crosslinking temperature, a distinction is made between cold and room temperature ( RTV) and hot or high temperature curing (HTV)
  • Free-flow additives or anti-blocking agents act as additives in powdery or granular materials to prevent the formation of lumps and thus enable easy packaging, transport and use.
  • WO 2018/019373 A1 discloses a method for producing a modified precipitated silica, which is characterized by an in-situ modification of the silica.
  • WO 2019/161912 A1 discloses a modified one
  • Precipitated silica with little to no coarse fraction and good redispersibility. This is achieved by combining a homogeneous in-situ modification of the silica together with high-performance liquid grinding.
  • WO 2019/129607 A1 discloses a precipitated silica modified by alkyl groups for use as a filler and a method for its production.
  • the precipitated silicas produced by known methods have a very high moisture content of 5 percent by weight (% by weight) or more.
  • Even commercial hydrophobic precipitated silicas such as SIPERNAT ® D17 (Evonik), still have a moisture content of 3 wt .-% or more.
  • a low moisture content is of particular importance for a large number of applications.
  • Precipitated silicas however, as a result of their production process, have a high proportion of moisture, especially in the form of adsorbed water. This water is problematic for many applications. During the extrusion of moldings, this water evaporates, for example, and leads to Bubbles in the extrudate. The quality of the corresponding moldings is impaired.
  • the precipitated silicas produced by known methods also have a high water absorption capacity on storage, in particular under the conditions of high atmospheric humidity.
  • a commercial hydrophilic precipitated silica SIPERNAT ® 288 (EVONIK) absorbs 9.6% by weight of water over 48 hours at 94% relative humidity, and even a commercial hydrophobic precipitated silica such as SIPERNAT ® D17 (Evonik) under the same conditions still 3 , 5% by weight of water.
  • This object is achieved by a modified precipitated silica which has a moisture content of 2.5% by weight or less, and a method that is achieved by a combination a homogeneous in-situ modification of the silica together with dynamic drying.
  • the invention relates to a modified precipitated silica, characterized in that it has a moisture content of 2.5% by weight or less, based on the total mass of the modified precipitated silica.
  • Another aspect of the invention relates to a process for the production of the modified precipitated silica mentioned above, wherein i) the modification in a reaction mixture comprising
  • one or more organosiliconates takes place as modifiers, the modification reaction taking place during or immediately after the preparation reaction of the precipitated silica, ii) the solid phase of the reaction mixture is then separated from the liquid phase, the solid phase being optionally washed, and iii) the solid phase is dynamically dried.
  • modified precipitated silica according to the invention is preferably produced by the process according to the invention, the following description is to be understood in such a way that features described in the context of the precipitated silica are disclosed equally for the process and vice versa Features described in the process are also disclosed for the precipitated silica.
  • the modified precipitated silica according to the invention is distinguished by a low moisture content.
  • the moisture content of the modified precipitated silica according to the invention is 2.5% by weight or less, based on the total mass of the modified precipitated silica.
  • the moisture content is particularly preferably 2.0% by weight or less, particularly preferably 1.8% by weight or less, very particularly preferably between 0.5 to 1.8% by weight.
  • the moisture content can be determined using a drying balance, with 1 g of the modified precipitated silica being dried to constant weight at 105 ° C.
  • the moisture content results as follows:
  • Moisture content 100% * (initial weight of the sample - final weight of the sample) / initial weight of the sample.
  • the modified precipitated silica according to the invention is preferably distinguished by low water absorption during storage.
  • the modified silica according to the invention preferably has a maximum water absorption in the range of less than or equal to 2.75% by weight, preferably from less than or equal to 2.5% by weight to greater than or equal to 0.5% by weight and particularly preferably of less than or equal to 2.25% by weight to greater than or equal to 0.5% by weight, in each case based on the total mass of the modified precipitated silica.
  • the maximum water absorption can be determined using an analytical balance with underfloor weighing and a hygrostat, whereby 500 mg of the modified precipitated silica is first pre-dried at 105 ° C for 2 h (pre-dried state) and then at a temperature of 22 ° C and a relative humidity of 94% is stored for 48 h.
  • the modified precipitated silica according to the invention is preferably characterized in that its specific BET surface area is preferably 50 m 2 / g to 400 m 2 / g, particularly preferably 100 m 2 / g to 300 m 2 / g and particularly preferably 150 m 2 / g to 250 m 2 / g.
  • the specific surface can be determined by the BET method according to DIN 9277/66131 and 9277/66132.
  • the modified precipitated silica according to the invention is preferably characterized in that its carbon content is preferably 0.1% by weight or more, particularly preferably 0.5% by weight or more to 15% by weight or less, very particularly preferably 1, 0% by weight or more to 10% by weight or less, based in each case on the total mass of the modified precipitated silica.
  • the carbon content is essentially based on the modification of the precipitated silica with organic residues.
  • the carbon content can be determined by means of elemental analysis, ie in a combustion analysis in a suitable analyzer.
  • the modified precipitated silica according to the invention is preferably characterized in that the conductivity of its 5% methanolic-aqueous dispersion is preferably at most 500 S / cm, particularly preferably at most 100 S / cm and particularly preferably at most 25 S / cm.
  • the conductivity of a corresponding sample can be determined in a methanol / water mixture.
  • a small amount of sample (5 g of the precipitated silica modified according to the invention) is mixed with 10 g of methanol and only then is diluted with 85 g of deionized water.
  • the batch is alternately mixed well and left to stand for a long time.
  • the conductivity can be measured with any conductivity meter. It is determined for a reference temperature of 20 ° C. Determining the conductivity of a sample is also a very sensitive method for quantifying soluble impurities.
  • the modified precipitated silica is preferably distinguished by a homogeneous surface modification.
  • a homogeneous surface modification has proven to be particularly advantageous for achieving a low moisture content and a low water absorption capacity of the precipitated silica. Without being bound by theory, it is assumed that the high-energy surface areas present in the case of an inhomogeneous modification of the silica preferentially interact with and adsorb polar water molecules.
  • a wetting test in combination with a distribution test between an aqueous and an organic one has proven useful Phase proven.
  • the modified precipitated silica is hydrophilic. If this modified precipitated silica does not cloud the organic phase at the same time in a system consisting of a water and an organic phase, which can be butanol, for example, the modified precipitated silica, which is assessed as hydrophilic, is also lipophobic. In this case there is a homogeneous surface modification.
  • a homogeneous surface modification is also present if a modified precipitated silica is not wetted after intensive mixing with water, i.e. floats on the water phase and forms a separate phase, i.e. is hydrophobic, but at the same time the organic phase in a system consisting of a water and an organic phase Phase is cloudy, i.e. lipophilic.
  • a homogeneous surface modification is also present if a modified precipitated silica is not wetted after intensive mixing with water, i.e. floats on the water phase and forms a separate phase, i.e. is hydrophobic, but at the same time in a system of a water and an organic phase of both Phases is not wetted and forms a third phase rich in solids.
  • An inhomogeneous surface modification occurs when a modified precipitated silica is wetted with water after intensive mixing, that is, sinks into the water phase and makes it cloudy, that is, it is hydrophilic, but at the same time in a system from a water and an organic phase, the organic phase is cloudy, i.e. it is lipophilic.
  • a more precise assessment of the homogeneity of the boundary layer is possible with the help of inverse gas chromatography in finite dilution (IGC-FC).
  • IIC-FC inverse gas chromatography in finite dilution
  • This method allows the determination of the energetic homogeneity of a surface via the adsorption energy distribution function (AEDF).
  • AEDF adsorption energy distribution function
  • 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 approx. 28-32 kJ / mol of the AEDF of the modified precipitated silica determined by means of IGC-FC, is less than 0.2, in particular is preferably less than 0.15 and particularly preferably less than 0.1.
  • Precipitated silicas are produced by methods known to the person skilled in the art, as described, for example, in US Pat. No. 2,657,149, US Pat. No. 2,940,830 and US Pat. No. 4,681,750, from condensable tetra- or higher-functional silanes, alkoxysilanes, alkyl or alkali silicates (water glasses) or colloidal silica particles or solutions.
  • a great advantage of precipitated silicas is that, in contrast to the much more expensive pyrogenic silicas, they represent a cost-effective product.
  • the reaction mixture according to the invention comprises
  • Precipitated silicas and / or [SiO 4/2 ] starting materials are used in the reaction mixture, with alkoxysilanes and / or alkali metal silicates being used as [SiO 4/2] starting materials.
  • alkoxysilanes are used as [S1O4 / 2] starting materials.
  • alkali metal silicates are used as [SiO 4/2 ] starting materials.
  • the modification is preferably carried out comprehensively in a reaction mixture
  • [SiO 4/2 ] units denote compounds in which one silicon atom is bonded to four oxygen atoms, each of which in turn has a free electron for a further bond. Units with Si-O-Si bonds connected via the oxygen atom can be present. In the simplest case, the free oxygen atoms are bound to hydrogen or carbon or the compounds are present as salts, preferably alkali salts. According to the invention, alkoxysilanes or alkali silicates (water glasses) are used as starting material (precursor) for the formation of [SiO 4/2 ] units ([SiO 4/2] starting material). In the context of this invention, the [SiO 4/2 ] units denote the precipitated silica; Alkoxysilanes or alkali silicates serve as [S1O4 / 2] starting materials for their production.
  • the first reaction step involves the formation of soluble and low molecular weight silicas.
  • soluble and low molecular weight silicas For the sake of simplicity, only monomeric structures are described in the following reaction equations, although soluble oligomeric structures can also be involved.
  • alkoxysilanes are used as the starting material for the production of precipitated silicas, the hydrolysis in water can be catalyzed by acids or bases:
  • the hydrolysis is preferably carried out in aqueous solutions of mineral or organic acids, particularly preferably in aqueous sulfuric acid solution, hydrochloric acid solution or carbonic acid.
  • the alkoxysilanes used are preferably tetramethoxysilane and particularly preferably tetraethylorthosilicate (TEOS).
  • TEOS tetraethylorthosilicate
  • Water glasses are particularly preferably used as the [SiO 4/2 ] starting materials.
  • Water glass is the term used to denote solidified, glass-like, i.e. amorphous, water-soluble sodium, potassium and lithium silicates or their aqueous solutions.
  • acid particularly preferably in aqueous sulfuric acid solution, hydrochloric acid solution or carbonic acid, low molecular weight soluble silicas are also formed here:
  • the orthosilicic acid Si (OH) 4 or oligomeric compounds formed in this way react under suitable reaction conditions with condensation and form particulate solids which are essentially composed of SiO 4/2 units: z Si (OH) 4 ⁇ SiO 4z / 2 + 2n H 2 0 where z is any positive number.
  • the condensation is favored in an acidic or especially in an alkaline environment.
  • Mineral acids, organic acids and / or carbon dioxide can be used as the acid.
  • electrolytes and / or alcohols can be added to the reaction mixture.
  • the electrolyte can be a soluble inorganic or organic salt.
  • Preferred alcohols include including methanol, ethanol or i-propanol.
  • only electrolytes and / or alcohols are added to the reaction mixture as further substances in addition to water, alkali silicate, acid and organosiliconate, particularly preferably only electrolytes and particularly preferably no further substances are added to the reaction mixture.
  • the reaction mixture preferably contains water, alkali silicate, acid and organosiliconate, particularly preferably water, alkali silicate, acid and methylsiliconate, particularly preferably water, sodium silicate (sodium water glass), sulfuric acid and sodium monomethylsiliconate.
  • This composition has the advantage that, in addition to the product, only the salt sodium sulfate is obtained as a by-product. This readily water-soluble salt can be separated from the product relatively easily, using separation methods such as filtration, sedimentation and / or centrifugation.
  • the temperature of the reaction mixture is preferably between 50.degree. C. and 105.degree. C., particularly preferably between 75.degree. C. and 95.degree. C. and particularly preferably between 85.degree. C. and 95.degree. In a particularly preferred embodiment, the reaction temperature is kept constant in the further process.
  • the pH is kept constant during the further process.
  • further acid particularly preferably sulfuric acid or hydrochloric acid and particularly preferably concentrated sulfuric acid, is preferably added to the reaction mixture in order to counteract the alkalinity of the waterglass that may have been added.
  • the starting materials such as acid, [SiO 4/2 ] starting materials, modifiers and any other substances are preferably metered in at a constant metering rate.
  • Constant dosing speed means that it changes in the course of the dosing time preferably by a maximum of 15%, particularly preferably by a maximum of 5% and particularly preferably by a maximum of 1% based on the average speed, which is calculated as the quotient of the total dosing amount and time.
  • the metering takes place preferably over a period of 30 minutes to 120 minutes, particularly preferably over a period of 45 minutes to 90 minutes and particularly preferably over a period of 60 minutes to 70 minutes.
  • the total amount of [SiO 4/2 ] starting materials metered in is preferably chosen so that the solids content, calculated as the mass of [SiO 4/2 ] units, is 20% by weight, particularly preferably 10% by weight, based on the total mass of the starting materials does not exceed. Most preferably, the solid content is calculated as mass [Si0 4/2] units between 4 wt .-% and 8 wt. ⁇ %, Based on the total mass of the reaction mixture. The mass of the starting materials is determined gravimetrically.
  • the reactants are mixed by simply stirring. Easily dispersible silica fillers with particularly uniform particle size, specific surface area and "structure" can also be produced by reacting alkali silicate solutions with acids and / or acidic substances, optionally in the presence of neutral salts produce that the precipitation of the silica by rapid and intensive mixing of the reaction components under the action of high shear forces that of a steep
  • the high speed gradient is preferably generated by means of continuously operating dispersers, such as a colloid mill.
  • the reaction for producing a precipitated silica and its modification takes place in the same batch, the modification reaction taking place during or immediately after the reaction for producing the precipitated silica.
  • the modification takes place in the reaction mixture described above, which is used to produce the precipitated silica.
  • this process is also referred to as a one-pot process.
  • the one-pot process is a clear difference to the state of the art, which generally works with multi-stage, separate processes.
  • the modification reaction takes place during or immediately after the reaction for preparing the precipitated silica.
  • "directly” in this context means that the modification in the reaction mixture, which comprises 1. the acid and 2. the precipitated silica and / or [SiO 4/2 ] starting materials and 3. an organosiliconate as a modifier, takes place without prior notice the modification reaction, a process step for separating salts and / or other by-products is carried out.
  • the term “immediately” does not refer to immediate temporal, stirring or allowing to stand between the reaction steps is not excluded. According to the invention before the
  • Dispensing with a previous process step for separating salts and / or other by-products has the great advantage that energy costs, time and resources such as washing solution or washing water and solution or water for resuspension are saved. This procedure makes the use of further units superfluous. It is of particular economic interest since the method according to the invention saves time and thus reduces the system occupancy time.
  • the other by-products include alcohols, among others.
  • the unmodified precipitated silica reacts with a modifier.
  • the modifying agent is also referred to synonymously in the context of this invention with modifying agent, covering agent, covering agent, water repellent or silylating agent.
  • the modified precipitated silica of the present invention is also referred to synonymously with hydrophobized precipitated silica.
  • the degree of modification can be determined by the carbon content according to DIN ISO 10694. This is preferably 0.1% by weight to 15% by weight based on the total mass of the modified precipitated silica. Depending on the desired use of the modified precipitated silica, certain degrees of modification can be particularly preferred.
  • the carbon content is particularly preferably 0.5% by weight to 4% by weight and particularly preferably 1% by weight to 2% by weight, based on the total mass of the modified Precipitated silica.
  • it is particularly preferably 4% by weight to 10% by weight and particularly preferably 5% by weight to 7% by weight, based on the total mass of the modified precipitated silica.
  • the temperature of the reaction mixture during the modification is preferably furthermore between 50.degree. C. and 105.degree. C., particularly preferably between 75.degree. C. and 95.degree. C. and particularly preferably between 85.degree. C. and 95.degree.
  • the reaction temperature is particularly preferably kept constant during process step i, i.e. it fluctuates by a maximum of ⁇ 5 ° C, particularly preferably by a maximum of ⁇ 2 ° C.
  • the pH value is particularly preferably kept constant during process step i, i.e. it fluctuates by a maximum of 0.5 units, particularly preferably by a maximum of 0.2 units.
  • further acid particularly preferably sulfuric acid or hydrochloric acid and particularly preferably concentrated sulfuric acid, is preferably added to the reaction mixture in order to counteract the alkalinity of any siliconate added.
  • This process step preferably takes place with stirring.
  • This process step preferably takes place under the action of high shear forces, which originate from a steep gradient in speed.
  • the high speed gradient is preferably generated by means of continuously operating dispersants such as a colloid mill. This has the advantage that finely divided silica with good dispersing properties is obtained.
  • the modifying agent in preparation of the reaction mixture is preferably added in parallel with the [SiO 4/2] -Ausgangsstoffen and the acid to the reaction mixture. In this case, it is particularly preferred that the end point of dosing [4/2 SiO] -Ausgangsstoffe of the modifying agent is carried out together with the end point of the dosage of the. In another preferred embodiment, the end point of the metering of the modifying agent goes beyond the end point of the metering of the [SiO 4/2 ] starting materials.
  • the dosage of the [SiO 4/2 ] starting materials is gradually reduced, whereas that of the modifier is gradually increased during the overlap period, ie the joint dosage of [SiO 4/2] starting materials and modifying agents.
  • This procedure has the advantage that the modification reaction can be controlled by the controlled addition of the modifying agent. Following a theoretical model of thought on particle structure, the degree of modification in the core of the particles is lower and then increases.
  • the use of the compared to the modifier which is more costly to use with the [S1O4 / 2] starting materials, is particularly efficient in this case.
  • the modifying agent is added to the reaction mixture at different times. This means that acid and [SiO 4/2 ] starting materials are metered in in a targeted manner at a defined temperature and a defined pH value (preferred conditions see above) and the modifying agent is only then metered in sequentially, i.e. staggered in time. This means that the modifying agent is added to the reaction mixture only after the acid and [SiO 4/2] starting materials have been metered in completely.
  • the reaction to produce the precipitated silica and its modification take place in the same approach (one-pot process), but it is a two-step process.
  • the metering takes place preferably over a period of 5-120 min, preferably 5-90 min and particularly preferably 10-30 min.
  • the modifying agent can be added to the reaction mixture in one step or in several small portions, it being possible to add it in each case at a constant metering rate or at a metering rate which is gradually increased.
  • staggered in time refers to the response.
  • the modification reaction starts at a different time.
  • spatially offset in relation to the system design (see below).
  • the infeed in order to achieve a staggered addition, the infeed must be spatially offset. This procedure has the advantage that the addition of the modifier, and thus the modification reaction, takes place in a controlled manner.
  • the core of the produced particles can be formed from the cheaper alkali silicate by this procedure, while the outer part of the particles (shell) may be increasingly modified, that is, a chemically bound, by the Has modifying agent-transferring group.
  • the advantage of this process is that it is predominantly the particle surface that has a major impact on subsequent use reacts with the more cost-intensive modifier.
  • the modifying agents can be added to the reaction mixture in liquid form or as a dry powder.
  • the modifying agents can be added in pure form or as solutions in water or known technically used solvents, for example alcohols such as methanol, ethanol or i-propanol, ethers such as diethyl ether, tetrahydrofuran or dioxane, or hydrocarbons such as hexanes or toluene.
  • alcohols such as methanol, ethanol or i-propanol
  • ethers such as diethyl ether, tetrahydrofuran or dioxane
  • hydrocarbons such as hexanes or toluene.
  • a modifying agent is understood to mean organosiliconates and their solutions.
  • organosiliconates denote compounds of the general formula (I)
  • M is a metal atom selected from the group consisting of metals from the main and subgroups of the Periodic Table of the Elements, X is an anion, p is the oxidation number of the metal atom M, n is a integer from 1, 2 or 3 and y denotes an integer from 0, 1 or 2, and / or
  • R 2 in the compound of the general formula (I) has the meaning of a group of the general formula (H a) several times, for example more than once, then there are corresponding compounds which have two, three, four or more units with Si atoms wear. Therefore, in the event that R 2 more than once denotes a group of the general formula (H a), there are polysiloxanes.
  • organosiliconate has at least one Si-C bond, i.e. at least one residue must be organic in nature.
  • organosiliconates as modifiers are highly water-soluble and therefore particularly suitable for a homogeneous reaction in an aqueous medium.
  • Modifying agents typically used are poorly or not at all water-soluble. Some of them react violently with water and generate a lot of heat, which makes it much more difficult to conduct the reaction safely, uniformly and in a controlled manner (this applies, for example, to the chlorosilanes that are often used).
  • Organosiliconates can also be used according to the invention. Mixtures are preferably used when functional groups (for example vinyl, allyl, or sulfur-containing groups such as, for example, C 3 H 6 SH) are to be introduced.
  • a methyl siliconate, particularly preferably a monomethyl siliconate, is preferably used as the organosiliconate in the process according to the invention.
  • monomethylsiliconates are particularly advantageous beyond what has been said above, because monomethylsiliconates are simple and in good yield from the easily available and inexpensive substances methyltrichlorosilane,
  • Methyltrimethoxysilane or methylsilanetriol can be obtained by reaction with alkaline substances, if necessary in an aqueous medium.
  • the organosiliconate solution used preferably has a density of 1.2-1.4 g / cm 3.
  • the density can be determined in accordance with DIN 12791, for example.
  • the impurities in the organosiliconate solution in alcohols (eg ethanol or methanol) contained in the production process are preferably ⁇ 1% by weight, particularly preferably ⁇ 100 ppm, based on the total mass of the organosiliconate solution.
  • the alcoholic impurities can be determined by quantitative gas chromatography (for example with the 6890 gas chromatograph from Agilent equipped with an FID detector and OV-1 separation column).
  • the solids content of the aqueous organosiliconate solutions is preferably 20% by weight to 70% by weight, particularly preferably 30% by weight to 60% by weight, based on the total mass of the organosiliconate solution.
  • the solids content can be determined with an IR moisture analyzer (for example with the IR moisture analyzer MA 30 from Sartorius) at a measuring temperature of 105 ° C.
  • the active ingredient content calculated as (CH 3 ) SiO 3/2 in the reaction mixture is preferably 15% by weight to 40% by weight, particularly preferably 30% by weight to 35% by weight, based on the total mass of the reaction mixture.
  • the alkali metal content of the organosiliconate solution is preferably 5% by weight to 20% by weight, particularly preferably 9% by weight to 18% by weight, based on the total mass of the organosiliconate solution.
  • the alkali content can be determined, for example, by titration with 0.1 molar hydrochloric acid against the indicator phenolphthalein.
  • the number of groups with a basic reaction corresponds to the number of alkali metal ions.
  • the silicas according to the invention can be modified with only one organosiliconate, but a mixture of two or more compounds from the group of organosiliconates can also be used.
  • the total amount of modifier metered is preferably chosen so that the solids content calculated as [SiO 4/2 ] g [(CH 3 ) SiO 3/2 ] j (with g and j independently of one another as any positive number), ie the solids content of modified [SiO 4/2 ] units in the modified precipitated silica produced does not exceed 25% by weight, particularly preferably 15% by weight, based on the total mass of the reaction mixture.
  • the solids content, calculated as [SiO 4/2 ] m [(CH 3) SiO 3/2 ] n is between 5% by weight and 10% by weight based on the total mass of the reaction mixture.
  • the concentration of modified groups in the primary particles increases from the inside out.
  • reaction mixture is preferably cooled to a temperature of less than 55 ° C and particularly preferably to room temperature, preferably continuing to stir during cooling.
  • the solid phase of the reaction mixture is separated from the liquid phase, the solid phase being optionally washed.
  • This process step serves, among other things, to separate salts that would interfere with the later use of the modified precipitated silica.
  • the solid phase is preferably separated off from the liquid phase by filtering, sedimenting, pressing or centrifuging, particularly preferably by filtering.
  • Water, polar organic solvents or mixtures thereof can be used for washing; washing is preferably carried out with water, particularly preferably with fully demineralized, deionized (VE) water, which is characterized by that it has a conductivity of ⁇ 5 ⁇ S / cm, preferably of ⁇ 3 ⁇ S / cm and particularly preferably of ⁇ 0.1 ⁇ S / cm.
  • VE deionized
  • Washing can be done in several ways.
  • the solid separated by filtration is rinsed with fresh water until a sufficiently low (preferably constant) conductivity value of the wash water of ⁇ 500 ⁇ S / cm, preferably ⁇ 100 ⁇ S / cm, particularly preferably ⁇ 10 ⁇ S / cm is reached.
  • the flow through can take place continuously or in portions.
  • a particularly efficient form of washing is the redispersion of the filter cake in clean water followed by further filtration.
  • the conductivity of water can be measured with a commercially available conductivity meter.
  • An example of a conductivity meter that can be used is given in the analysis methods.
  • the separated solid phase ie for example the filter cake of the reaction mixture
  • the separated solid phase has a solids content of 50% by weight or less, based on the total mass of the separated solid phase, preferably 10% by weight or more to 35% by weight or less, based on the total mass of the separated solid phase, and particularly preferably 20% by weight or more to 30% by weight or less, based on the total mass of the separated solid phase.
  • the separated solid phase of the reaction mixture ie for example the filter cake, is dynamically dried in a further process step (iii).
  • Drying processes are generally differentiated according to the type of energy supply: contact dryers, in which the heat is introduced into the goods to be dried via a heated wall, and convection dryers, in which the heat is introduced into the goods to be dried via a warm to hot gas flow.
  • a convection dryer is preferably used in the method according to the invention.
  • Dynamic drying is understood to mean drying processes with movement of the items to be dried. Due to the high exposed mass transfer surface and the resulting more intensive heat transfer, these generally lead to significantly higher drying speeds than with static drying processes in which the material to be dried is dried without active movement (e.g. drying cabinet, tray dryer, belt dryer, drum dryer).
  • Typical dynamic drying devices are paddle dryers, flow dryers or fluidized bed dryers.
  • the drying can also take place continuously or in portions (batch drying).
  • the drying is preferably carried out continuously.
  • a further acceleration of the drying speed and the avoidance of lump formation in the items to be dried can be achieved by using increased mechanical loads on the items to be dried.
  • a dryer is preferably used which has elements for the mechanical loading of the material to be dried.
  • classifying elements with the return of relatively heavy (moist or agglomerated) particles can be integrated into the drying room.
  • classifying elements are air separators, ascending pipe separators, cyclones, swirl separators or also deflector wheel separators.
  • a dryer is preferably used which has classifying elements.
  • a dryer which contains elements for the mechanical loading of the material to be dried and classifying elements.
  • a convection dryer which contains elements for the mechanical loading of the material to be dried and classifying elements.
  • a flow pipe with a downstream cyclone dryer or a dryer with a spin flash dryer with a deflector wheel sifter is used in the method according to the invention.
  • the material to be dried is exposed to temperatures above the boiling point of the liquid to be removed, so that it can evaporate once the boiling point has been reached (depending on the process pressure). If dry drying gas is used convectively, drying below the boiling point of the liquid is also possible in principle, since the substance of the liquid is also transferred into the gas phase by evaporation.
  • the free liquid between the particles and on the particle surface of the material to be dried is drawn off.
  • the drying speed is mostly only influenced to a small extent by the particulate material to be dried and shows its maximum value in this phase.
  • the evaporation / evaporation is similar to that of the pure liquid.
  • the drying level in the pores drops and there are transport resistances for diffusive removal of the water vapor from the pores as well as conductive heat conduction relevant from the particle surface to the interior of the solid.
  • the drying speed decreases steadily with increasing dryness.
  • the last remaining quantities of the liquid e.g. water of crystallization
  • the last remaining quantities of the liquid can usually only be removed with very small amounts in the last drying step
  • Drying speeds are deducted, since both transport resistances increase and mass transfer forces are reduced.
  • a common measure for characterizing a drying process is the surface-specific drying speed, which is maximum in the second drying section described above and which decreases with increasing dryness of the items to be dried.
  • the surface-specific drying speed in batch drying processes is determined by: m Fl mass of evaporated liquid [kg]
  • a Surface of the dry material [m 2 ] A BET specific BET surface of the dry material [m 2 / kg] X o Moisture content at the beginning of drying [-] X t Moisture content at the end of drying [-]
  • V surface-specific drying speed [kg / (m 2 * s) j or [g / (m 2 * h)]
  • the masses are given by corresponding mass flows ([kg / h]) and the Replace the drying time with the mean residence time of the product in the drying area ([s]).
  • the surface-specific drying speed over the entire drying process is preferably
  • the drying temperature is preferably 70 ° C. or more to 200 ° C. or less, particularly preferably 90 ° C. or more to 170 ° C. or less, very particularly preferably 100 ° C. or more to 150 ° C. or less.
  • the drying temperature is understood to mean the hot gas temperature (supply air temperature to the dryer) and, in the case of contact drying, the temperature of the heating elements (for example, heating jacket, pipe coils, heating strips or similar).
  • the mean residence time (in the case of continuous drying) or drying time (in the case of batch drying) is preferably 5 s or more to 3,600 s or less, particularly preferably 10 s or more to 1,800 s or less.
  • the mean residence time is preferably 5 s or more to 600 s or less, particularly preferably 10 s or more to 300 s or less.
  • the mean residence time of the material to be dried in the continuous drying is calculated from the quotient of the dry matter mass hold-up in the dryer and the mass flow of dry product through the dryer.
  • the dry material can be ground after cleaning.
  • units such as pin mills, classifier mills, hammer mills, countercurrent mills, impact mills or devices for grinding classification can be used.
  • the silica is ground in the liquid phase before dynamic drying.
  • All mills in which the ground material is in a liquid phase can be used for this purpose.
  • Typical examples are horizontal or vertical ball mills and bead mills, in which grinding media are used to comminute the material to be ground.
  • these types of mills also have a large number of grinding media-grinding media and grinding media-apparatus wall impacts that can cause undesirable abrasion and wear and the associated product contamination.
  • dispersing units such as rotor-stator apparatus (colloid mill, toothed ring disperser), the crushing effect of which is essentially due to shear forces from the surrounding fluid, as well as high-pressure homogenizers, the dispersing effect of which can be attributed to stretching flow, shear flow, turbulence and possibly also cavitation is.
  • Roller mills such as roller mills or pan mills are particularly suitable for comminuting more viscous dispersions.
  • Impact or autogenous liquid mills liquid jet dispersers
  • dispersion jets containing the predispersed ground material are directed towards one another with high kinetic energy or are directed towards impact surfaces.
  • the comminution is based on particle-particle impacts, particle-wall impacts as well as turbulence and possibly cavitation of the surrounding fluid.
  • the individual process steps can be carried out as a discontinuous (batch process) or continuous process. For technical reasons, preference is given to carrying out the reaction batchwise. This procedure has the advantage that the systems are very simple and less prone to failure. Standard agitators can be used. From the nucleation of the particles to the finished product, there is a very well-defined, narrow distribution of the "growth time", an important prerequisite for the manufacture of homogeneous products.
  • the batch process water is provided and heated. Then the starting materials such as acid, [SiO 4/2 ] starting materials and, if necessary, other substances are metered in.
  • the modifying agent is metered in in parallel or at different times. After process step i) has taken place, the entire reaction mixture is removed, the solid phase is separated from the liquid phase, the solid phase optionally being washed, (ii), the solid phase being dynamically dried (iii) and optionally grinding.
  • the method steps take place in a continuous process.
  • the continuous process includes:
  • organosiliconates as modifiers in parallel with the starting materials from (a) or spatially offset with respect to the system (in order to achieve a time-delayed addition with respect to the reaction mixture) into the reaction zone;
  • a reactor for carrying out continuous chemical processes is a tube or tank reactor.
  • WO 2011/106289 describes, for example, the continuous production of silica in a loop reactor, which can also be used in this process.
  • a Taylor-Couette reactor as described, for example, in DE 10151777, is particularly preferably used. This usually consists of two coaxial concentrically arranged cylinders, the outer hollow cylinder resting and the inner solid cylinder rotating. The volume that is formed by the gap between the cylinders serves as the reaction space.
  • the Taylor number is 50-50,000, preferably 500-20,000, particularly preferably 3,000-10,000, and the Reynolds number (axial) 0.0724 to 7.24, preferably 0.1348-2.69, particularly preferably 0.4042-1.35.
  • the mean residence time in the Taylor reactor can be between 5 and 500 minutes.
  • the reactor is preferably operated in a vertical position with a flow from bottom to top or top to bottom.
  • the advantage of the process according to the invention in which the production and modification of the precipitated silica are carried out in one pot, is that the process is particularly inexpensive, quick and easy to use, as well as works in a way that conserves resources.
  • a particular advantage of the method is that compositions can be produced which have a high chemical purity.
  • non-volatile water-soluble impurities such as sodium, potassium and sulfur can easily be removed in process step (ii). It is particularly advantageous that a good separation of ionic impurities can be achieved even under normal washing conditions, ie with small amounts of the washing medium or in a few washing steps, which is expressed, for example, in a constant low conductivity of the washing medium.
  • Sulfuric acid was obtained in a concentration of 50% in technical purity from Brenntag.
  • the aqueous sodium silicate solution used was commercial water glass 38/40 from Wöllner with a density at 20 ° C according to the manufacturer's instructions of approx. 1.37 g / cm 3 .
  • the potassium methyl siliconate solution was aqueous
  • the fully demineralized (deionized) water (deionized water) used had a conductivity of ⁇ 0.1 ⁇ S / cm. Unless otherwise mentioned, the process steps up to the filtration and washing step are carried out with stirring. Analysis methods:
  • the specific surface was determined by the BET method according to DIN 9277/66131 and 9277/66132 using an SA TM 3100 analyzer from Beckmann-Coulter.
  • the elemental analysis for carbon was carried out in accordance with DIN ISO 10694 using a CS-530 elemental analyzer from Eitra GmbH (D-41469 Neuss).
  • IIC-FC finite dilution
  • the gas chromatograph was a common commercial device with an FID detector.
  • 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.
  • 1.5 to 3.0 ml isopropanol purity at least GC quality
  • the amount of sample injected had to be determined iteratively.
  • the aim was to have a maximum peak height at a relative pressure of 0.1 to 0.25. This could only be determined from the overall chromatogram.
  • methane was injected together with isopropanol.
  • the isotherm for determining the BET constant C BET was calculated according to Conder ("Physicochemical measurement by gas chromatography”. JR Conder and CL Young. Wiley (Chichester), 1979).
  • the adsorption energy distribution functions (AEDF) were determined 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).
  • Software from Adscientis, "In-Pulse” ® and “FDRJ07.5.F” ® was used to calculate the isotherm and the physical parameters derived from it or the AEDF.
  • the distribution function was broken down into the individual peaks by means of peak deconvolution.
  • the raw data from the AEDF was read into the ORIGIN program and a deconvolution was carried out assuming a Gaussian distribution of the individual peaks.
  • the best fit was obtained assuming 3 peaks with peak positions of PI approx. 17-19 kJ / mol, P2 approx. 21-25 kJ / mol and P3 approx. 28-32 kJ / mol.
  • a (P3) / [A (P1) + A (P2) + A (P3)] in the range 28 - 32 kJ / mol, where A (Px) with x 1, 2 or 3 is the area of the peaks P1, P2 and P3 is.
  • the initial weight corresponds to the initial weight and the final weight corresponds to the weight of the sample after it has been dried to constant weight.
  • the water absorption during storage was determined using an analytical balance with underfloor weighing (Mettler Toledo LW1956).
  • the scale is set up on a scale table with an integrated draft shield above a hygrostat (desiccator).
  • the sample carrier is hung through the lock inside the hygrostat.
  • a saturated KNO 3 solution sets a constant relative humidity depending on the ambient temperature.
  • the hygrostat can be lowered on a lifting table and the lock with the sample carrier is released.
  • the construction of the suspension and the lock allows the hygrostat to be lowered for several hours and the balance to be kept engaged.
  • the balance is read out by a computer via the interface built into the balance. The measured values are saved and their progress is shown in an Excel spreadsheet.
  • a temperature and humidity sensor in the hygrostat record the temperature and humidity curve during the measurement and output them in the Excel spreadsheet.
  • the measuring device is set up in a climatic room with a constant temperature of 22 ° C (+/- 0.5 ° C).
  • the cleaned sample dish with holder is dried for 30 minutes at 105 ° C. and then cooled in a desiccator with a drying agent for 30 minutes.
  • the sample pan with holder is then placed in the hygrostat, the sample holder is attached and weighing is started. After reaching constant weight, the scale is set to tare.
  • the silica sample to be determined is then weighed into the sample dish (approx. 500 mg), dried at 105 ° C in a drying cabinet with nitrogen flushing (300 l / h) for 2 h, cooled in a desiccator for 30 min for 30 min, placed in the measuring device and the measurement started.
  • the filter cake with 75% moisture content was brought to dryness by means of a flow tube and a downstream cyclone dryer at a temperature of 105 ° C., a gas flow rate of 15,000 m 3 / h and an average residence time of the dry material of 25 s.
  • the circulating air flow implemented in the cyclone dryer by the built-in components ensures that heavy or residual moist particles are retained for further drying, so that only Silica particles with a moisture content of ⁇ 2% by weight could leave the dryer. (:; Classifier 20,000 min- 1: 16,000 min- 1 mill)
  • the product was ground to a ZPS50 separator mill from Hosokawa-Alpine. The solid was then analyzed as described in the analysis methods. The results are shown in Table 1.
  • the mixture was filtered through a chamber filter press using K100 filter plates, washed pH-neutral and blown dry with nitrogen. The filter cake was statically dried to constant weight on metal sheets in a drying cabinet at 150 ° C.
  • Example 3 (:; Classifier 20,000 min- 1: 16.000 min 1 mill) After cooling to room temperature, the product was ground to a ZPS50 separator mill from Hosokawa-Alpine. The solid was then analyzed as described in the analysis methods. The results are shown in Table 1.
  • Example 3 Example 3:
  • the filter cake with a moisture content of 75% by weight was brought to dryness by means of a flow tube and a downstream cyclone dryer at a temperature of 105 ° C., a gas flow rate of 15,000 m 3 / h and an average residence time of the dry material of 25 s.
  • the circulating air flow created in the cyclone dryer by the internals ensures that heavy or residual moisture particles are retained for further drying, so that only silica particles with a moisture content of ⁇ 2% by weight could leave the dryer.
  • the product was ground in a ZPS50 classifier mill from Hosokawa-Alpine (mill: 20,000 min -1 ; classifier: 16,000 min -1 ). The solid was then analyzed as described in the analysis methods. The results are shown in Table 1.
  • the mixture was filtered through a chamber filter press using K100 filter plates, washed pH-neutral and blown dry with nitrogen. The filter cake was statically dried to constant weight on metal sheets in a drying cabinet at 150 ° C.

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

Abstract

L'invention concerne un acide silicique précipité modifié dont la teneur en humidité est inférieure ou égale à 2,5 % en poids, par rapport à la masse totale de l'acide silicique précipité modifié, et un procédé approprié pour produire les acides siliciques précipités modifiés et caractérisé par une combinaison d'une modification in situ homogène de l'acide silicique conjointement avec un séchage dynamique.
PCT/EP2019/081376 2019-11-14 2019-11-14 Acide silicique précipité modifié à teneur en humidité réduite Ceased WO2021093961A1 (fr)

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Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2657149A (en) 1952-10-21 1953-10-27 Du Pont Method of esterifying the surface of a silica substrate having a reactive silanol surface and product thereof
US2940830A (en) 1955-08-23 1960-06-14 Columbia Southern Chem Corp Method of preparing silica pigments
GB2001303A (en) * 1977-06-29 1979-01-31 Degussa Hydrophobised Precipitated silica
DE3309272A1 (de) * 1983-03-15 1984-09-20 Consortium für elektrochemische Industrie GmbH, 8000 München Verfahren zur herstellung von faellungskieselsaeure
US4681750A (en) 1985-07-29 1987-07-21 Ppg Industries, Inc. Preparation of amorphous, precipitated silica and siliceous filler-reinforced microporous polymeric separator
EP1048696A2 (fr) * 1999-04-28 2000-11-02 Dow Corning Corporation Procédé de préparation de silice de précipitation hydrophobe
DE10151777A1 (de) 2001-10-19 2003-08-07 Degussa Fällung von Kieselsäure in einem Taylor-Reaktor
WO2011106289A2 (fr) 2010-02-24 2011-09-01 J.M. Huber Corporation Procédé continu de production de silice et produit de silice préparé par ce procédé
WO2018019373A1 (fr) 2016-07-27 2018-02-01 Wacker Chemie Ag Procédé de production d'un acide silicique précipité modifié et composition contenant ledit acide
WO2019129607A1 (fr) 2017-12-27 2019-07-04 Rhodia Operations Silice précipitée et procédé pour sa fabrication
WO2019161912A1 (fr) 2018-02-23 2019-08-29 Wacker Chemie Ag Acides siliciques précipités hautement dispersables

Patent Citations (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2657149A (en) 1952-10-21 1953-10-27 Du Pont Method of esterifying the surface of a silica substrate having a reactive silanol surface and product thereof
US2940830A (en) 1955-08-23 1960-06-14 Columbia Southern Chem Corp Method of preparing silica pigments
GB2001303A (en) * 1977-06-29 1979-01-31 Degussa Hydrophobised Precipitated silica
DE3309272A1 (de) * 1983-03-15 1984-09-20 Consortium für elektrochemische Industrie GmbH, 8000 München Verfahren zur herstellung von faellungskieselsaeure
US4681750A (en) 1985-07-29 1987-07-21 Ppg Industries, Inc. Preparation of amorphous, precipitated silica and siliceous filler-reinforced microporous polymeric separator
EP1048696A2 (fr) * 1999-04-28 2000-11-02 Dow Corning Corporation Procédé de préparation de silice de précipitation hydrophobe
DE10151777A1 (de) 2001-10-19 2003-08-07 Degussa Fällung von Kieselsäure in einem Taylor-Reaktor
WO2011106289A2 (fr) 2010-02-24 2011-09-01 J.M. Huber Corporation Procédé continu de production de silice et produit de silice préparé par ce procédé
WO2018019373A1 (fr) 2016-07-27 2018-02-01 Wacker Chemie Ag Procédé de production d'un acide silicique précipité modifié et composition contenant ledit acide
WO2019129607A1 (fr) 2017-12-27 2019-07-04 Rhodia Operations Silice précipitée et procédé pour sa fabrication
WO2019161912A1 (fr) 2018-02-23 2019-08-29 Wacker Chemie Ag Acides siliciques précipités hautement dispersables

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
"Estimation of the Surface Energetic Heterogeneity of a Solid by Inverse Gas Chromatography", LANGMUIR, vol. 13, no. 5, 1997, pages 1260 - 1269
J. R. CONDERC. L. YOUNG: "Physicochemical measurement by gas chromatography", 1979, WILEY

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