WO2020125956A1 - Procédé de préparation de particules de gel arrondies - Google Patents

Procédé de préparation de particules de gel arrondies Download PDF

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Publication number
WO2020125956A1
WO2020125956A1 PCT/EP2018/085603 EP2018085603W WO2020125956A1 WO 2020125956 A1 WO2020125956 A1 WO 2020125956A1 EP 2018085603 W EP2018085603 W EP 2018085603W WO 2020125956 A1 WO2020125956 A1 WO 2020125956A1
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Prior art keywords
sol
dispersion
gel
particles
hmdso
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PCT/EP2018/085603
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German (de)
English (en)
Inventor
Konrad HINDELANG
Dominik JANTKE
Richard Weidner
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Wacker Chemie Ag
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Priority to PCT/EP2018/085603 priority Critical patent/WO2020125956A1/fr
Publication of WO2020125956A1 publication Critical patent/WO2020125956A1/fr

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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
    • C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
    • C01B33/157—After-treatment of gels
    • C01B33/158—Purification; Drying; Dehydrating
    • C01B33/1585—Dehydration into aerogels
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • 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
    • C01P2006/11—Powder tap density
    • 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
    • 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
    • C01P2006/14—Pore volume
    • 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
    • C01P2006/40—Electric properties

Definitions

  • the invention relates to a method for producing an airgel, characterized in that in a first step (i) sol droplets are produced by distributing a silicate sol in a dispersion, the dispersion (1) hydrophobic silica and (2) contains an water-immiscible organic solvent, then in step ii a lyogel is formed from the sol in the presence of the dispersion, during gel formation at most 30% of the time in which the sol has already been added to the dispersion but is still liquid, is stirred, then in step iii the lyogel formed in step ii is surface-modified and finally in step iv the surface-modified lyogel is dried.
  • the sol-gel process is one of the most important processes for the production of nanostructured materials.
  • a range of silicate products e.g. silica aerogels, gels for applications in chromatography, etc.
  • sol-gel technology e.g. silica aerogels, gels for applications in chromatography, etc.
  • the control of this process is crucial in order to adjust the macroscopic and microscopic properties (particle size, particle shape, pore structure, density, etc.).
  • the wet chemical sol-gel process influences not only the quality of the wet gels, but also the properties of the derived products (e.g. aerogels).
  • the gels obtained in the sol-gel process can be converted into a wide variety of end products using a wide variety of processes (solvent exchange, modification, drying).
  • An important application of sol-gel processes is, for example, the production of aerogels.
  • Aerogels are highly porous solids that consist of pores up to more than 95% of the volume. While a lyogel one with Represents liquid-filled framework, the pores of the Ae rogel are filled with air. In the case of a hydrogel, which is a special case of the lyogel, the pore liquid consists of at least 50% water. Due to the porous structure, aerogels have a high specific surface area, small pore diameter and a particularly low density. There are different types of aerogels, the most common being those based on silicate.
  • Aerogels have a branching of particle chains with a large number of spaces in the form of open pores. These chains have contact points, so that ultimately a stable, sponge-like network is formed.
  • high-quality airgel granules are generally produced by crushing larger pieces of gel.
  • This process requires a comminution step, i.e. an additional process step (see e.g. EP 2 832 690 Al, examples).
  • this process provides angular fragments.
  • round particles have interesting properties due to their good flow properties, optimal particle size distribution and the formation of compact spherical packs (eg in fillings or in matrices), their production is particularly desirable.
  • the rounded shape of the particles can also reduce abrasion, for example during transport, further processing or end use.
  • spherical gel particles are produced, for example, using emulsion processes.
  • US 2013/0189521 A1 describes, for example, a process in which brine is emulsified in an immiscible solvent and gelled with constant stirring.
  • the dispersion does not contain any hydrophobic silica before the sol is added.
  • spherical particles in the size range of 1-20 pm can be produced, with an organic surfactant being added to the emulsion in all examples and stirring being carried out intensively during the entire sol-gel process.
  • EP 3 299 340 A1 also describes a process for producing spherical gel particles using an organic surfactant.
  • US 2013/0189521 A1 therefore requires a solvent exchange step (step iv) in claim 1, in which Ten side are removed at the same time. This not only requires increased amounts of the solvent, but each additional process step generally means additional time and costs.
  • WO 2016/173913 describes processes for the production of aero gel particles by gelling silicate sols in hexamethyldisiloxane (HMDSO) with stirring and then surface-modifying and drying the gel particles. In this method too, in all of the examples disclosed, there is intensive stirring throughout the entire sol-gel process.
  • HMDSO hexamethyldisiloxane
  • WO 2016/207096 also describes a method for producing airgel particles by emulsifying and gelling basic brine in HMDSO. The surface of the gel particles is then modified and dried. Again, in all of the examples disclosed, stirring is carried out intensively throughout the entire sol-gel process.
  • the gel formation time has a significant influence on the quality and structure of gels.
  • the prerequisite for a short gel formation time therefore significantly limits the product properties in terms of quality and structure.
  • this method must prevent the sol drops from touching while sinking, otherwise coalescence will occur.
  • the latter can be minimized by a high excess of organic phase, but this in turn leads to very high and cost-intensive total volumes and thus to a low space-time yield.
  • the gel formation time in this process should not be limited.
  • a method for producing an airgel characterized in that in a first step (i) sol droplets are produced by distributing a silicate sol in a dispersion, the dispersion (1) being hydrophobic silica and (2) contains a water-immiscible organic solvent, then in step ii a lyogel is formed from the sol in the presence of the dispersion, but during gel formation no more than 30% of the time in which the sol has already been added to the dispersion is still liquid, is stirred, then in step iii the lyogel surface modification formed in step ii is modified and finally in step iv the surface-modified lyogel is dried.
  • a lyogel is a disperse system consisting of at least two components, in which the solid component forms a sponge-like, three-dimensional network, the pores of which are filled with a liquid.
  • the lyogel or the lyogel particles are referred to as airgel or airgel particles.
  • airgel and “dried lyogel” are used synonymously.
  • a silicate sol contains at least one compound selected from the group consisting of [SXO4 / 2] units, [R x SiO ( 4-X) / 2] units, [SiC> 4/2 ] starting materials and [R x SiO ( 4- x) / 2] starting materials, where x can be the same or different and is 1, 2 or 3, and where R may be the same or different and is hydrogen or an organic, substituted or unsubstituted radical.
  • radicals R can be the same or different and, independently of one another, hydrogen, an organic, linear, branched, cyclic, saturated or unsaturated, aromatic or heteroaromatic radical, with or without substituents. This means that the radicals R can be substituted or unsubstituted.
  • Saturated or unsaturated residues with C 1 -C 4 -, particularly preferably C 1 -C 4 alkyl, vinyl, in particular methyl or ethyl, in particular methyl, are preferably used.
  • [S1O a 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 wells for an additional bond.
  • the free oxygen atoms are bound to hydrogen or carbon, or the compounds are preferably present as salts, alkali metal salts.
  • a starting material (precursor) for the formation of units can [Si0 4 2 /] (-Ausgangsstoff [S1O 4 2 /]) known in the art, kondensa ⁇ tion capable of tetra- or higher-functional silanes, alkoxysilanes, alkyl silicates, alkali metal silicates or colloidal silica particles or solutions are used.
  • the Si-R groups of the [R x SiO (4 -x) / 2] unit give the product (i.e. the gel) basic water repellency.
  • Methyltrialkoxysilanes, vinyltrialkoxysilanes, dimethyldialkoxysilanes, OH-, OR-, H- or CI-terminated polydimethylsiloxanes, alkali metal siliconates are particularly preferably used,
  • MTES methyltriethoxysilane
  • methyltrimethoxysilane potassium methyl siliconate or sodium methyl siliconate.
  • Methyltriethoxy silane (MTES) or potassium methyl siliconate is particularly preferably used.
  • Sol droplets also called brine drops, brine droplets
  • the liquid body of a sol drop preferably has a spherical shape in the idle state.
  • the mean diameter of the sol droplets according to the invention is preferably in the range from 0.01 mm to 10 mm, particularly preferably in the range from 0.1 mm to 5 mm and particularly preferably in the range from 0.3 mm to 3 mm.
  • the size of the lyogel particles or the airgel particle (d50) results directly from the size of the sol droplets.
  • the silicate sol is distributed in a dispersion in the process for the preparation of the airgel in step i, the dispersion containing (1) hydrophobic silica and (2) an immiscible organic solvent.
  • Silicic acid in the sense of the invention means oxygen acids of silicon (silicon oxides) and includes precipitated silicas and pyrogenic silicas, i.e. through a precipitation process or pyrogenic silicas.
  • the hydrophobic silica contained in the dispersion is preferably pyrogenic hydrophobic silica.
  • the specific surface area of the hydrophobic silica is preferably 30-500 m 2 / g and particularly preferably 150-350 m 2 / g, which can be determined by the BET method according to DIN 9277/66131 and
  • the silicas used according to the invention preferably have an average hydrodynamic equivalent diameter of the sinter aggregates greater than 1 nm, preferably from 10 to 5000 nm, particularly preferably from 10 to 1000 nm and in particular preferably from 100 to 600 nm, in each case preferably measured by means of dynamic light scattering
  • Sintering aggregates are secondary structures according to DIN 53206, which are permanent under shear conditions as they usually occur when dispersing fillers in liquid media such as solvent-based or solvent-free adhesives or coating materials, i.e. they cannot be broken down into their primary particles. This can be demonstrated, for example, by TEM images of hardened silica binder dispersions that only have aggregate structures but no isolated primary particles on iron.
  • Hydrophobic means that at least 30%, preferably at least 50%, particularly preferably at least 60% and in particular preferably at least 70% of the surface silanol groups of the silicon oxide are modified, i.e. that an oxygen-bound hydrophobic group is bound to the silicon atom instead of the OH group.
  • the carbon content of the hydrophobic silica is preferably between 0.1 and 20% by weight, particularly preferably 1 and 10% by weight, particularly preferably 0.5 to 8% by weight and in particular preferably 3 to 5% by weight. -%.
  • the degree of free silanol groups or the coverage with e.g. carbon-containing end groups can be determined, for example, by elemental analysis, e.g. can be determined via the carbon content (description see analytical methods) or by determining the residual content of reactive surface silanol groups of the silicas (as described e.g. in WO 2015/078745.
  • hydrophobic silica 0.01-5% by weight, particularly preferably 0.1-1% by weight, particularly preferably 0.2-0.5% by weight of hydrophobic silica in the dispersion containing the silica and not with water are preferred miscible organic solvents used. It is preferred that the hydrophobic silica contain [O1 / 2S1 (CH 3 ) 3 ] units.
  • the [0i / 2 Si (CH 3 ) 3 ] units are oxygen-bonded trimethylsilyl groups (TMS, these groups are also referred to as triethylsiloxy groups). It is therefore preferred that the hydrophobic silica is composed of [Si0 2 ] and [O1 / 2S1 (CH 3 ) 3 ] units.
  • a trimethylsiloxy-functionalized, pyrogenic silica with a BET surface area of 200 to 350 m 2 / g and a C content in the range of 3 to 5% by weight is used.
  • a solvent is a substance that can dissolve or dilute gases, liquids or solids without causing chemical reactions between the dissolved substance and the dissolving substance.
  • the water-immiscible organic solvent forms an oil phase.
  • This can optionally consist of several components.
  • “Not miscible with water” means that the solubility of the components in water alone and / or as a mixture is less than 10 g / 100 g of water, preferably less than 1 g / 100 g of water, particularly preferably less than 0.1 g / 100 g of water is, measured at 20 ° C and the pressure of the surrounding atmosphere, that is at about 900 to 1100 hPa.
  • Examples of organic solvents which are not miscible with water and which form the oil phase of an emulsion according to the invention or can be contained in it aromatic or aliphatic hydrocarbons, silanes or organosiloxanes.
  • the hydrophobic silica is dispersed in the organic phase before the sol is added, i.e.
  • the hydrophobic silica is dispersed in the water-immiscible organic solvent and only then is the premixed sol distributed in the dispersion.
  • the sol is preferably distributed in the dispersion by stirring, shaking, dropping, spraying or by means of static mixing elements.
  • dropping or spraying must be carried out in such a way that separate droplets are formed.
  • static mixing element or static mixing devices refers to fixed internals, which are characterized by the fact that flow-influencing elements alternate the material flow divide and merge and thereby bring about the mixing.
  • a static mixer is installed, for example, in a pipe through which the liquids to be mixed are passed.
  • mixing elements also include dynamic mixing elements that are characterized by moving (e.g. rotating) internals.
  • phase A formed from the water-immiscible organic solvent, organic phase, continuous phase
  • phase B formed from the sol
  • hydrophobic silica arranged at the oil-water interface.
  • hydrophobic silica in the dispersion has the great advantage that no process residues such as, for example, organic surfactants are introduced into the product, as is the case in the prior art, which are also used to prevent sol droplets from melting.
  • this has the advantage that the hydrophobic silica can remain in the product without time-consuming, costly and energy-intensive washing steps, since it belongs to the same product group as the silicate sol.
  • the method according to the invention for producing the airgel is therefore technically simpler, more efficient and cheaper. Due to the missing washing steps, resources such as Chemicals are saved and the environment is also protected by the non-soiled washing solution.
  • Another advantage is that only very small amounts of the hydrophobic silica are required in the dispersion. These are below 0.5%, while EP 3 299 340 A1 discloses that less than 3% of surfactants no longer allow uniform droplet formation. This can save costs.
  • a gel is then formed in step ii from the sol in the presence of the dispersion from i in the process for producing the lyogel (gel formation).
  • Gel formation takes place according to methods known to the person skilled in the art, such as changing the pH value and / or increasing the temperature.
  • step ii at most 30% of the time, preferably at most 10% of the time and particularly preferably at most 5% of the time in which the sol has already been added to the dispersion but is still liquid,
  • stirring means that the sol droplets lying on the bottom are caused by mechanical components, e.g. using paddle stirrers, stirring fish, coils etc. the stirrer geometries known to the person skilled in the art are brought into motion in the dispersion.
  • the advantage of stirring only a little or not at all in the preferred case is that hardly any shear forces act on the brine drops. As described at the beginning, shear forces affect the structuring and stabilization of the silicate network. This procedure has the advantage that there is little or no The particles are sheared in the sol (in the form of stirring) and mechanically stable particles are formed. Even larger gel particles (> 500 mki) do not shatter during subsequent drying.
  • the sol droplets After the sol has been completely added to the dispersion, about 5 ml of the sol droplets are removed with a pipette and dropped onto a filter paper. If more than 75% of the sol droplets are sucked up by the filter paper, the sol is still liquid. If, on the other hand, gelation has already started, a gel-like solid remains on the filter paper.
  • the stirring can be stopped while the sol is still liquid, e.g. after the sol has been mixed (phase B) into the water-immiscible organic phase (phase A) the mixing process can be stopped.
  • a gas or liquid e.g. on a sieve or perforated base, as shown for example in game 13, take place.
  • reaction vessel itself can be moved during the gel formation, for example by swiveling or shaking.
  • Gel formation can take place in a laminar flow, for example in a
  • the brine drops can gel in the continuous phase without permanent stirring.
  • Gel formation time and temperature of the process can be chosen arbitrarily, so that the gel particles can be optimally equipped with the properties necessary for the end use or further processing. In contrast to the prior art, a short gelation time is not required.
  • the minimum amount of continuous phase i.e. organic solvent which is not miscible with water can be significantly reduced in comparison with the emulsion processes and the drop column from the prior art.
  • the decisive factor for the optimization of space-time yield in emulsion processes is the ratio between the two immiscible phases (sol and organic solvent).
  • the water-immiscible organic solvent containing the hydrophobic silica after removal of the lyogel i.e. after step ii or after step iii can be used again for step i.
  • the lyogel is surface-modified in step iii.
  • the free and accessible silanol groups of the silicate lyogel react with the Silylating agents.
  • Si-OH groups form Si-0-SiR 3 groups, where the given definition applies to R.
  • the lyogel is particularly preferably hydrophobicized by the process of surface modification.
  • the water-immiscible organic solvent is a silylating agent.
  • the silylating agent is preferably an organosiloxane or a solution of organosiloxanes in a non-reactive, non-polar solvent.
  • the non-reactive, non-polar solvents are preferably hydrocarbons such as pentane, hexane, heptane and toluene.
  • the silylating agent is particularly preferably used undiluted, ie without the addition of non-reactive, non-polar solvents.
  • organosiloxanes are linear, cyclic or branched compounds of the type
  • a linear organosiloxane has, for example, the general formula R 3 Si [0-SiR 2 ] n -0-SiR 3 . It applies that an organosiloxane has at least one Si-C bond, ie at least one residue must be organic in nature.
  • mixtures of various organosiloxanes can also be used.
  • a disiloxane is preferably used as the organosiloxane.
  • Disiloxanes are chemical compounds with the formula R 3 Si-0-S1R3 or [R 1 R 2 R 3 SiOi / 2 ] 2, where again the definition given above applies to R or R 1 , R 2 and R 3 and at least the disiloxane has a Si-C bond.
  • a disiloxane of the formula R3Si-0-SiR3 is preferably used as the organosiloxane, where R can be identical or different and is hydrogen or an organic, substituted or unsubstituted radical.
  • the organosiloxane is particularly preferably hexamethyldisiloxane (HMDSO).
  • initiators, organosilanes or initiators and organosilanes can optionally be added in step iii).
  • an initiator accelerates the surface modification and is preferably an acid or a chlorosilane or mixtures thereof. If an acid is used as the initiator, it is preferably a mineral acid and particularly preferably hydrochloric acid. If a chlorosilane is used as the initiator, it is preferably trimethylchlorosilane.
  • the proportion of organosiloxane, preferably disiloxane, in the silylating agent is, according to the invention, at least 20% by weight, preferably at least 50% by weight, particularly preferably at least 90% by weight and particularly preferably at least 95% by weight.
  • the proportion of organosiloxane in the mixture is at least 98% by weight, i.e. commercially available concentrated organosiloxane is used.
  • the surface modification can be checked and, if necessary, accelerated using all methods known to the person skilled in the art (temperature, pressure, amount of silylating agent, removal of by-products). It is preferred that the surface modification is carried out without separation of the gel after step ii in the dispersion described in step i.
  • This procedure has the advantage that no washing and / or purification steps are required. As already described above, this not only makes the process more efficient but also simpler.
  • step iv the surface-modified lyogel is dried. Drying can be carried out using all methods known to the person skilled in the art, for example using hot air, in a vacuum or drying cabinet.
  • the method according to the invention can be used to produce aerogels which are largely spherical.
  • the shape of the aerogels can be assessed microscopically. A largely spherical shape is shown in FIGS. 1, 2 and 3b, whereas FIG. 4b shows a sample from the prior art with an increased number of corners and edges.
  • the aerogels that can be produced are stable.
  • Stable in the sense of the invention means that the gel particles survive the manufacturing process and do not, for example, crack during drying.
  • the stability of the aerogels can in turn be determined microscopically by comparing the shape of the aerogels before drying with that after drying.
  • the aerogels that can be produced by the method according to the invention are free-flowing.
  • Aerogels have an extremely low thermal conductivity and are therefore used as a heat insulation material, e.g. in EP 0 171 722.
  • the use of the aerogels which can be produced according to the invention in thermal insulation has the advantage that they contain no process residues, such as organic surfactants, which, if at all, could only be removed with great effort.
  • the aerogels according to the invention achieved values for the heat conductivity of the bed of on average 17.27 mW / m * K (milli-watts per meter and Kelvin). These values, which have been confirmed several times, show the good insulating effect of the aerogels produced by the process according to the invention.
  • the thermal conductivity for aerogels from the prior art was at least 20 mW / m * K.
  • the bulk density was determined in accordance with DIN 53468, in which the powder was poured into a cylindrical vessel of known volume (50 cm 3 ) without further compaction and the weight was then determined by weighing. The bulk density is given in grams per liter (g / 1).
  • the specific surface area of the aerogels was determined according to the BET method in accordance with DIN 9277/66131 and 9277/66132).
  • the pore analysis was carried out according to the method of Barett Joyner and Halenda (BJH, 1951) according to DIN 66134. The data from the desorption isotherm were used for the evaluation.
  • the thermal conductivity of the granules was determined at room temperature in the form of a loose bed with a THB Transient Hot Bridge Analyzer (THB-100) from Linseis using an HTP sensor (measuring time 120 seconds, measuring current: 17.50 mA, current for temperature measurement 5 , 00 mA).
  • the sensor was calibrated on a reference with a thermal conductivity of 0.025 W / (K * m).
  • the sensor was placed in a bed of the material to be examined (approx. 100 ml bed volume). The bulk was slightly compacted by shaking the vessel or tapping lightly on the vessel wall. Care was taken to ensure that the sensor is covered with the material from both sides. The average of three measurements is given. Determination of the pH
  • the pH was measured using a Mettler Toledo Seven Multi pH meter; Electrode: determined in Lab Science.
  • the carbon content (C content) of the samples was determined on a Leco CS 230 analyzer. The analysis was carried out by high-frequency combustion of the sample in an oxygen stream. Detections were made using non-dispersive infrared detectors.
  • SLS Static light scattering
  • the particle distribution was measured by static laser scattering (SLS) using the Mie model with a Horiba LA 950 in a highly diluted suspension in ethanol.
  • the specified average particle diameters (d50) are volume-weighted.
  • HDK ® H30 hydrophobic, pyrogenic silica (surface modification: trimethylsiloxy) from Wacker Chemie AG with a BET surface area of 270-320 m 2 / g and a C content of 1.4 - 2.6
  • HDK ® SKS 300 were dispersed in 385 g of HMDSO in a 2 1 round-bottom flask equipped with a KPG stirrer.
  • the stirrer was then stopped.
  • the sol which was still liquid, was in the form of droplets, with hardly any coalescence (flowing together or melting of the droplets) being observed.
  • About 5 ml of the brine droplets were removed with a pipette and dropped onto a filter paper. The brine droplets were sucked up by the filter paper, which shows that they were still liquid after stopping the stirrer.
  • the mixture was heated at 60 ° C for 2 hours to form a gel without stirring.
  • the gel particles obtained were separated by filtration.
  • the d50 value was 420 pm (static light scattering).
  • the gel particles were prepared as described in Example 1, the gel particles not being separated by filtration but the mixture containing the gel particles after gel formation, 25 g of concentrated hydrochloric acid (37%) was added. The mixture was surface modified with gentle stirring (100 rpm) for 4 h at 70 ° C. The gel particles were then separated off by filtration, washed with 100 g of fresh HMDSO and then dried in a vacuum drying cabinet (120 ° C., 30 mbar). As the light micrograph (Fig. 1) shows, largely spherical particles were obtained, for which the following parameters were determined:
  • HDK ® SKS 300 were dispersed in 385 g of HMDSO in a 2 1 screw-top bottle.
  • the mixture was then placed in a warming cabinet at 60 ° C. for 2 hours without shaking, whereby the gelation started and was completed.
  • the mixture was poured onto a stainless steel sieve with a mesh size of 0.1 mm, as a result of which the aqueous phase resulting from the surface modification and the HMDSO were separated from the gel particles using the dispersed HDK ® SKS 300.
  • the gel particles were washed with 200 ml of fresh HMDSO in order to wash off any HDK ® SKS 300 adhering to the gel particles.
  • the collected liquid phases were transferred to a separatory funnel.
  • the aqueous phase was drained, the organic phase (HMDSO with HDK ® SKS 300) washed twice with 100 ml of water and the dispersion of HDK ® SKS 300 in HMDSO used in Example 4 for a further run).
  • the surface-modified gel particles were dried in a vacuum drying cabinet (120 ° C., 30 mbar). As the light micrograph (Fig. 2) shows, largely round airgel particles with good flowability were obtained, for which the following parameters were determined:
  • Example 3 In a 2 1 erflasche the used in Example 3, and separated by screening and washed organic phase was containing HDK ® SKS 300 and HMDSO (s. Example 3) were introduced. 200 g of Sol A were adjusted in a beaker with a 0.25 molar ammonia solution to a pH of 5.9.
  • template b screw-top bottle
  • 500 g of an aqueous ammonia solution (0.017 M) were prepared and also cooled to 15 ° C.
  • a template c was also prepared for the activation of the sol.
  • a beaker equipped with a magnetic stirrer, was made available in a water bath for cooling to 15 ° C.
  • the sol was conveyed into template c using a peristaltic pump at a rate of 5 ml / min.
  • the ammonia solution was conveyed from template b at a rate of 5 ml / min into template c.
  • the solutions from template a and b were mixed and cooled to about 15 ° C. It posed a pH of 6.
  • the delivery rate of the pumps was adjusted slightly if necessary.
  • the sol was sucked out of template c with a third hose pump at a rate of about 10 ml / min and dropped into the reactor with the continuous phase heated to 50.degree.
  • the reactor contents were poured out through a sieve (mesh width 0.1 mm), whereby the gel particles were separated from the continuous phase.
  • the separated continuous phase consisting of HDK ® SKS 300 and HMDSO could be used in a repeat experiment according to Example 5, with no significant differences in terms of. the stabilization of the sol drops during the sol-gel process could be observed.
  • HDK ® SKS 300 was dispersed in 285 g of HMDSO in a 2 1 screw-top bottle.
  • the mixture was then placed in a warming cabinet at 60 ° C. for 2 hours without shaking, whereby the gelation started and was completed.
  • 25 g of concentrated hydrochloric acid (37% strength) were then added to start the surface modification, and the mixture was stored at 70 ° C. for 4 h.
  • the mixture was shaken about every 30 minutes for about 30 seconds.
  • the mixture was poured onto a stainless steel sieve with a mesh size of 0.1 mm, so that the aqueous phase resulting from the surface modification and the HMDSO with the dispersed HDK ® SKS 300 from the gel particles were separated.
  • the gel particles were washed with 200 ml of fresh HMDSO.
  • the surface-modified gel particles were dried in a vacuum drying cabinet (120 ° C., 30 mbar). To a large extent, round airgel particles with good flowability were obtained, for which the following parameters were determined:
  • HDK ® SKS 300 were dispersed in 385 g of HMDSO in a 2 1 screw-top bottle.
  • the mixture was then placed in a warming cabinet at 60 ° C. for 2 hours without shaking, whereby the gelation started and was completed. Then 25 g of concentrated hydrochloric acid (37%) and 100 g of ethanol were added to start the surface modification and the mixture for 4 h stored at 70 ° C. The mixture was shaken about every 30 minutes for about 30 seconds. After cooling, the mixture was poured onto a stainless steel sieve with a mesh size of 0.1 mm, as a result of which the aqueous phase resulting from the surface modification and the HMDSO were separated from the gel particles using the dispersed HDK ® SKS 300. The gel particles were washed with 200 ml of fresh HMDSO in order to wash off any HDK ® SKS 300 adhering to the gel particles.
  • the surface-modified gel particles were dried in a vacuum drying cabinet (120 ° C., 30 mbar). Round airgel particles with good free-flowing properties were largely obtained, for which the following parameters were determined:
  • the mixture was then placed in a warming cabinet at 60 ° C. for 2 hours without shaking, whereby the gel formation started and was completed.
  • the gel particles in a screw-top bottle were mixed with 285 g HMDSO and 25 g concentrated hydrochloric acid (37%) and the mixture was stored for 4 h at 70 ° C (surface modification). The mixture was about every 30 minutes for about
  • the surface-modified gel particles were dried in a vacuum drying cabinet (120 ° C., 30 mbar). Round airgel particles with good free-flowing properties were largely obtained, for which the following parameters were determined:
  • HDK ® SKS 300 were dispersed in 2.0 kg of HMDSO.
  • the activated sol from template A was pumped into a third vessel simultaneously with the dispersion from template B via a static mixer (also called a static mixer).
  • a spiral mixer was used as the static mixer (10 mm in diameter and 20 cm in length).
  • the activated sol from template i was pumped into the static mixer at a delivery rate of 2.0 1 / min and the dispersion from template i at a delivery rate of 4.0 1 / min.
  • the sol was distributed in the form of droplets in the dispersion of silica and HMDSO by mixing in the static mixer.
  • the mixture was heated at 60 ° C for 2 hours to form a gel without stirring.
  • the gel particles obtained were separated by filtration.
  • the d50 value was 450 pm (static light scattering).
  • HDK ® SKS 300 was dispersed in 385 g of HMDSO in a 2 1 screw bottle.
  • the mixture was placed in a reactor, the structure of which is described below.
  • the reactor has a volume of 2 1 and is equipped with a Bodenven valve. An intermediate floor with holes is installed about 2 cm above the bottom valve (hole diameter 1 mm).
  • the reactor was filled with a dispersion consisting of 2.0 g HDK ® SKS 300 in 800 g HMDSO. Liquid can be pumped out of the upper part of the reactor by means of a peristaltic pump and returned to the reactor via the bottom valve.
  • the mixture with the brine droplets was transferred into the reactor with the dispersion and the peristaltic pump was switched on.
  • the delivery rate of the peristaltic pump and the suction height of the hose were adjusted so that the brine droplets accumulated in the lower part of the reactor and not from the
  • Peristaltic pump were sucked in. Approx. 1 minute after the pump was switched on, about 5 ml of the brine droplets were removed with a pipette and dropped onto a filter paper. The brine droplets were sucked up by the filter paper, which shows that they were still liquid at this time.
  • the contents of the reactor were heated to 50 ° C. for 3 hours using a heating jacket, with the pump still running, whereby the gel formation started and was completed.
  • a reflux condenser was then fitted, the temperature in the reactor increased to 70 ° C. and 100 g of concentrated hydrochloric acid (37%) were added to start the surface modification.
  • the pump running the mixture was surface-modified at 70 ° C. for 4 h.
  • the gel particles were then separated off by filtration, washed with 100 g of fresh HMDSO and then dried in a vacuum drying cabinet (120 ° C., 30 mbar). Largely spherical particles were obtained for which the following parameters were determined:
  • SLS Average particle diameter
  • the stirrer was then stopped.
  • the still liquid sol immediately sank downward and formed a separate phase below half of the organic phase. Stable droplets could not form due to the lack of stabilization with the surface-active particles.
  • the mixture was heated at 60 ° C for 2 hours without stirring, whereby gelation was carried out.
  • a continuous gel phase was obtained at the bottom of the round bottom flask. After a rough crushing with a The spatula could be mixed up again by stirring.
  • the gel pieces obtained were not rounded or droplet-shaped, but existed as undefined fragments with edges.
  • the mean particle diameter (d50 value) was not determined due to the strong fragmentation during drying.
  • Light microscopy Surface-modified gel particles were sprinkled on a slide (Fig. 4a) and dried on this (Fig. 4b). A picture was taken before and after drying, with a significant breakage of the gel particles being observed.
  • the comparative experiment was carried out in accordance with Example 5, with the difference that 420 g of pure HMDSO were placed in the reactor (double-walled cylinder with heating) and the addition of surface-active particles was dispensed with.
  • the surfactant (type and amount see table) was added to 100 ml HMDSO and shaken for 1 minute to distribute the surfactant.
  • the shaking was then stopped. Already within the first 10 minutes after the end of the pouring phase, it could be observed that the sol phase (aqueous phase) coalesces or grows together. Approx. 5 ml of the sol phase was removed with a pipette and dropped onto a filter paper. The sol phase was absorbed by the filter paper, which proves that it is still liquid after the chute has stopped were. The mixture was then placed in a warming cabinet at 60 ° C. for 2 hours without shaking, whereby the gelation started and was completed.
  • the liquid was then poured off and the appearance of the gel was assessed.
  • the gel was not in the form of separate, largely spherical particles but in the form of a connected piece of gel.
  • the gel was not further converted to the aero gel, since the gel piece was not in the form of separate, largely spherical particles.
  • the surfactants are not suitable for carrying out the process according to the invention.
  • the comparative experiment was carried out analogously to Example 13 with the difference that no HDK ® SKS 300, in which the sol beads herstel in the flow reactor development was added to this comparative test without the use of HDK ® SKS 300 during the production of the brine droplets and in the reactor through which flow occurred, showed that with otherwise the same settings and reaction conditions, the brine droplets grew together by coalescence and a coherent gel body was formed on the reactor bottom. The connected gel body was no longer converted to the airgel.

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

Abstract

L'objet de l'invention est un procédé de préparation d'un aérogel, caractérisé par la préparation de gouttelettes de sol au cours d'une première étape (i), par répartition d'un sol silicaté dans une dispersion, la dispersion contenant (1) un acide silique hydrophobe et (2) un solvant organique non hydromiscible, puis, au cours d'une étape (ii), la formation d'un lyogel à partir du sol en présence de la dispersion, pendant la formation de gel, une agitation étant effectuée au plus 30 % du temps, le sol ayant déjà été ajouté à la dispersion mais étant toujours liquide, ensuite, au cours d'une étape (iii), la modification en surface du lyogel formé à l'étape (ii), et enfin, au cours d'une étape (iv), le séchage du lyogel modifié en surface. Les aérogels pouvant être préparés sont de préférence utilisés dans l'isolation thermique.
PCT/EP2018/085603 2018-12-18 2018-12-18 Procédé de préparation de particules de gel arrondies WO2020125956A1 (fr)

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EP0171722A2 (fr) 1984-08-11 1986-02-19 BASF Aktiengesellschaft Procédé pour l'obtention d'aergels
DE19801004A1 (de) * 1998-01-14 1999-07-15 Cabot Corp Verfahren zur Herstellung von im wesentlichen kugelförmigen Lyogelen in wasserunlöslichen Silylierungsmitteln
US20130189521A1 (en) 2010-10-25 2013-07-25 Tokuyama Corporation Aeogel and method for manufacture thereof
EP2832690A1 (fr) 2013-08-02 2015-02-04 EMPA Eidgenössische Materialprüfungs- und Forschungsanstalt Procédé de fabrication d'un matériau aérogel
WO2015078745A1 (fr) 2013-11-27 2015-06-04 Wacker Chemie Ag Oxydes métalliques particulaires modifiés en surface
WO2016173913A1 (fr) 2015-04-29 2016-11-03 Wacker Chemie Ag Procédé de fabrication d'aérogels modifiés par des groupes organiques
WO2016207096A1 (fr) 2015-06-25 2016-12-29 Wacker Chemie Ag Procédé économique pour produire des lyogels ou des aérogels organiquement modifiés
EP3299340A1 (fr) 2016-03-28 2018-03-28 LG Chem, Ltd. Procédé de préparation d'un granule d'aérogel de silice sphérique, et granule d'aérogel de silice sphérique préparé par ce procédé

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EP0171722A2 (fr) 1984-08-11 1986-02-19 BASF Aktiengesellschaft Procédé pour l'obtention d'aergels
DE19801004A1 (de) * 1998-01-14 1999-07-15 Cabot Corp Verfahren zur Herstellung von im wesentlichen kugelförmigen Lyogelen in wasserunlöslichen Silylierungsmitteln
EP1047633A2 (fr) 1998-01-14 2000-11-02 Cabot Corporation Procede de production de lyogels sensiblement spheriques dans des agents de silylation hydrosolubles
EP1047633B1 (fr) 1998-01-14 2002-11-27 Cabot Corporation Procede de production de lyogels sensiblement spheriques dans des agents de silylation hydrosolubles
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EP2832690A1 (fr) 2013-08-02 2015-02-04 EMPA Eidgenössische Materialprüfungs- und Forschungsanstalt Procédé de fabrication d'un matériau aérogel
WO2015078745A1 (fr) 2013-11-27 2015-06-04 Wacker Chemie Ag Oxydes métalliques particulaires modifiés en surface
WO2016173913A1 (fr) 2015-04-29 2016-11-03 Wacker Chemie Ag Procédé de fabrication d'aérogels modifiés par des groupes organiques
WO2016207096A1 (fr) 2015-06-25 2016-12-29 Wacker Chemie Ag Procédé économique pour produire des lyogels ou des aérogels organiquement modifiés
EP3299340A1 (fr) 2016-03-28 2018-03-28 LG Chem, Ltd. Procédé de préparation d'un granule d'aérogel de silice sphérique, et granule d'aérogel de silice sphérique préparé par ce procédé

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