Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/14—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic in rotating dishes or pans
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/16—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by suspending the powder material in a gas, e.g. in fluidised beds or as a falling curtain

Definitions

• the present invention relates to a method for granulating aerogels.
• Aerogels in particular those with porosities above 60% and densities below 0.6 g / cm 3 , have an extremely low thermal conductivity and are therefore used as heat insulation material, as described in EP-A-0 1 71 722, as catalysts or Catalyst carrier, as well as an adsorbent material.
• the use for Cerenkov detectors is known due to their very low refractive index for solids.
• the literature describes a possible use as an impedance matching, for example in the ultrasound range, due to its special acoustic impedance.
• Aerogels in the broader sense ie in the sense of "gel with air as the dispersion medium" are produced by drying a suitable gel.
• airgel in this sense includes aerogels in the narrower sense, xerogels and cryogels.
• a dried gel is referred to as an airgel in the narrower sense if the liquid of the gel is largely removed at temperatures above the critical temperature and starting from pressures above the critical pressure. If, on the other hand, the liquid of the gel becomes subcritical, for example with the formation of a liquid-vapor boundary phase removed, the resulting gel is often referred to as xerogel.
• aerogels in the broad sense, i.e. in the sense of "gel with air as a dispersion medium”.
• the term does not include xerogels known from the older literature, which e.g. obtained by precipitation of silica (e.g. DE 3025437, DD 296 898), or as pyrogenic silica, e.g. Aerosil TM. In these cases, a homogeneous three-dimensional gel network is not formed over large distances during production.
• Inorganic aerogels have been known since 1 931 (SS Kistler, Nature 1 931, 1 27.741). Since then, aerogels have been made from a wide variety of starting materials.
• z. B. SiO 2 -, AI 2 O 3 -, TiO 2 -, ZrO 2 -, SnO 2 -, Li 2 0, CeO 2 -, V 2 0 5 -Aerogels and mixtures of these can be prepared (H .D. Gesser, PCGoswami, Chem. Rev. 1 989, 89.765ff).
• organic aerogels made from a wide variety of starting materials, e.g. from melamine formaldehyde, known (R.W. Pekala, J. Mater. Sci. 1 989, 24, 3221).
• Inorganic aerogels can be produced in different ways.
• SiO 2 aerogels can be produced, for example, by acid hydrolysis and condensation of tetraethyl orthosilicate in ethanol. This creates a gel that is obtained by supercritical drying while maintaining the structure can be dried. Manufacturing processes based on this drying technique are known, for example, from EP-A-0 396 076, WO 92/03378 or WO 95/0661 7.
• An alternative to supercritical drying is a method for subcritical drying of SiO 2 gels.
• the SiO 2 gel can be obtained, for example, by acid hydrolysis of tetraalkoxysilanes in a suitable organic solvent using water. After replacing the solvent with a suitable organic solvent, the gel obtained is reacted with a silylating agent in a further step. The resulting SiO 2 gel can then be dried in air from an organic solvent. This enables aerogels with densities below 0.4 g / cm 3 and porosities above 60% to be achieved. The manufacturing process based on this drying technique is described in detail in WO 94/251 49.
• the gels described above can also be mixed with tetraalkoxysilanes and aged in the alcohol-aqueous solution before drying in order to increase the gel network strength, as disclosed in WO 92/20623.
• the tetraalkoxysilanes used as starting materials in the processes described above also represent an extremely high cost factor.
• a not inconsiderable cost reduction can be achieved by using water glass as the starting material for the production of the SiO 2 gels.
• a silica can be produced from an aqueous water glass solution with the aid of an ion exchange resin, and this polycondenses into an SiO 2 gel by adding a base. After replacing the aqueous medium with a suitable organic solvent, the gel obtained is then reacted with a chlorine-containing silylating agent in a further step. The resulting, on the surface z. B. modified with methylsilyl groups SiO 2 gel can also be dried in air from an organic solvent. The manufacturing method based on this technique is known from DE-A-43 42 548.
• DE-A-1 95 02 453 also describes the use of chlorine-free silylating agents in the production of subcritically dried aerogels.
• DE-A-1 95 34 1 98 also describes organofunctionalization using organofunctionalized silylating agents in the production of subcritically dried aerogels.
• airgel particles are, however, for the sake of Process engineering and the manufacturing costs on an industrial scale limited to particle sizes smaller than 5 mm, preferably smaller than 2 mm.
• the object of the present invention is therefore to provide a method by means of which small airgel particles below 2 mm can be formed into larger airgel particles.
• This object is achieved by a method in which the airgel particles are placed in a mixing device and mixed, and a binder is fed to the mixing device.
• the binder can be added to the mixing device before, during and / or after the addition of the airgel particles, the subsequent addition being preferred.
• the airgel particles are set in motion so that they have a relative movement with one another.
• the binder is used as an aqueous or non-aqueous solution or suspension or as a melt, e.g. by spraying.
• the binder leads to the agglomeration of the primary airgel particles into larger agglomerates.
• the binder leads through chemical reaction, solidification, crystallization due to evaporation or evaporation of the solvent, possibly also under the influence of elevated temperatures, to a connection of the mixture components.
• the binder is added as a solid.
• the binding then takes place by chemical reaction of the solid with one or more components of the mixture, or by softening a solid binder, e.g. through elevated temperatures, which makes it sticky and binds the particles of the mixture together.
• Another expedient embodiment provides that, in addition to the airgel particles, additives and / or fillers, which may be in the form of particles or fibers, are added to the mixing device.
• a preferred embodiment provides that the size of the agglomerates is separated. This is advantageously done by screening the target fraction from the resulting granules in accordance with the desired particle size range. Granules that are too large can optionally be comminuted, for example with a chopper or knife head, and sieved so that they are in the desired particle size range or are fed back to the agglomerating apparatus after comminution. Granules that are too small can possibly be returned to the agglomerating apparatus. which are fed.
• the agglomerates are dried before further processing.

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

Applications Claiming Priority (3)

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• 1997
  • 1997-05-02 DE DE19718740A patent/DE19718740A1/de not_active Ceased
• 1998
  • 1998-04-29 KR KR19997010098A patent/KR20010012153A/ko not_active Application Discontinuation
  • 1998-04-29 CN CN98805627A patent/CN1126592C/zh not_active Expired - Fee Related
  • 1998-04-29 WO PCT/EP1998/002519 patent/WO1998050144A1/de not_active Application Discontinuation
  • 1998-04-29 EP EP98925496A patent/EP0979141A1/de not_active Ceased
  • 1998-04-29 JP JP54769598A patent/JP2001523162A/ja not_active Ceased
  • 1998-04-29 CA CA002287849A patent/CA2287849A1/en not_active Abandoned
• 1999
  • 1999-11-01 US US09/433,931 patent/US6481649B1/en not_active Expired - Lifetime

Non-Patent Citations (1)

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