CA2291229A1 - Method for producing substantially globular lyogels and aerogels - Google Patents
Method for producing substantially globular lyogels and aerogels Download PDFInfo
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- CA2291229A1 CA2291229A1 CA002291229A CA2291229A CA2291229A1 CA 2291229 A1 CA2291229 A1 CA 2291229A1 CA 002291229 A CA002291229 A CA 002291229A CA 2291229 A CA2291229 A CA 2291229A CA 2291229 A1 CA2291229 A1 CA 2291229A1
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- lyosol
- gel
- air
- aerogels
- lyogels
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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
-
- 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
- B01J2/02—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops
- B01J2/04—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops in a gaseous medium
-
- 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
- C01B33/16—Preparation of silica xerogels
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Dispersion Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Silicon Compounds (AREA)
- Colloid Chemistry (AREA)
Abstract
The invention relates to a method for producing substantially globular lyogels, wherein the constituents which make up the gel are mixed, whereupon lyosol is introduced into an agitated medium which does not dissolve in said lyosol in a noticeable manner in order to form said gel. The present invention also relates to a method for producing substantially globular aerogels, wherein the lyogels produced according to said method are converted into an aerogel.
Description
04-Nov-99 16:04 From-GRAHAM WATT i Co ~ 01732450113 T-078 P.04/15 F-936 i fv The object of the irmeotion is a method of producing substtsntially globular lyogels and eerogels.
AerogeIs, particularly those with a porosity above 60% sad a deagily of less than 0.6 g/cu.at>, diap>Ay extremely, low thermal conductivity and are therefore used as a hear insulating material, as described for example in EP-A-0171 722. purtbe~nore, by virtue of their very low re&actian index faf solid substances, it is k»own to use them for Cerenkov detectors. Fl~r~ by reason of their particular acouspc impedance, the literature describes a possible use as an innpedance adaptatiop means, for example in the alpha sound range. It is also possible for them to be ua4d as carriers for e$ecTive substances in phanrracy or apiculture Aerogds in the broader sense, e.g. is the xnse of "gel with air as the dispersion agent"
are produced by the drying of a suitable gel. The tee, "a,~og~" ~ this sense embraces aerogels is the narrows xase, xerogels and cryogels. In this respect, a dried gel is tamed as aerogd in the narro~rer sense whrn the liquid of the gel is eliminated at above critical temperature and starring from pressures above critical pressure_ On the oti>er hand, ifthe dquad is eliminated from the gel under sub-ail coaditiot~ for exaxople with the formation of a liquid/favwr interphaac, then the rcavlting gel is frequently referred to also as s xaogel.
W6ea the team asrogals is used iu the presrnt invention, these are aerogels in the broader sense, e.g. in the sense of "gel with air as the dispersion medium. °
1'he teem does not include aerogels known from earlier literaaue and which are obtained for example by precipitation of silicic said (~e.g. DE 3025437, DD 296 898) or which occur as sdiCic and, e.g. A'r''s In these cases, during lure, no Ihree-dimerniional gel lattice develops which is homogeneous rnfet relatively great distances.
~~ ~ogels at'e coaee~ed, it is ppssible basically to diffcreptiate beiwoen inorganic and organic aeragels.
D4-Nov-99 16:04 From-GRAHAM WATT i Co D1732450113 T-078 P.05/15 F-936 Inorganic aetog~ds have already been laoowa since 1931 (S_ S. Kistler, Nature 7 93 i, 127, 741 ). Since rhea, aerogds have beau ~ortbcomrog from various materials. Iu this Tespect, for example SiO~, TiO~-, ZrOx , Sr~2., LiaO-, Ce0=., V=O~serogels and udxauea ofthese watt produced (H, D. Gesser, P. C. Goswatni, Cbem. Rev_ 1989, 89, 765 et seq.).
For wane yeaus, organic aerogels have also bees known which are derived from tt~e most widely diverse staring materials, e.~. melaatine foz>nsldelryde (tt W.
Pelcala, J. Mate, Sci. I9$9, 24, 3221 ).
Tnorganic aa-ogels tea thereby he produced i~a di$aent ways.
Oa the one hand, Si02 aerogels cao for exs~aplc be produced by acid hydrolysis ind condensation of teas-ethyl orthosiiicate is c~b~uwl. During this process, a gd is produced which can be dtiod by super-caitical drying whilo its suuc~ture is mamtaiaed.
Production methods based on this drying tochaique are k~wwn for example from EP-A-0 396 O~d, wo 92103378 or w~ 95/06517.
The high pressure techaiQue irrvolvad io the super-critical dryi»g of serogeis is however as expensive process and irivolyes a high security risk. In addition, however, supar-critica! drying of acrogels is a vrty cost-inte~ive production method.
Ia principle, an ahelaative to super-critical drying is afforded by a method for the suh-eritical dying of SiOZ ~ls. The costs invin Sub-critical drying are substantially less by ressorr of the simpler iecbnology, the lower energ~r costs and the lesser secmiiy risk_ The SQL gels can for example be obtaitKd by acid hydrolysis of teQa-alkoacy silaaes in a suitable organic solvent by mesins of waxcr. Once the solvent has been exc~hsngod for a ~~ . the gel obtained is in a further step reamed with a sdyla>ti~ agent.
The SiO~ gel rasulting from this can then, from an organic solwe~nt, be dried in air. Thus, aerogeis with densities of les$ than 0.4 g/cu.cau and porosities about 60~/e can be achieved.
04-Nov-99 16:04 From-GRAHAM WATT i Co ~ 01T32450113 T-018 P.06/15 F-936 The production method based oa this dryia,g technique is descn'b~d is detail in WO
94/25149.
Furthermore, the shouts-described gala can, prior to drying sad in the ~cohol-aqueous sohuio~ be mixed with te~a~.aikoxy silaae3 and aged, ~n order to irrc~ese the gal. lattice strength, as disclosed in WO 92/20b23 , 1"he recta-stllcoxy silwres used ac craning t»~erials in the about-deaaibad processes do, however, likewise represent an extretaely high cast factor A considerable cost reduadon eau be achievmd by using water-glass as s starting malaria!
for the produaiop of Si4i gds. To this end, it is possible for example to produce a silicic acid from an aqueous water-glass soluoon with the help of an ion atchauge resin, the siIicia acid that be3ag polycondensod by the addition of a base to produce an SiOz eel.
After exch8pge of the aqueous modiuta for a suitable orgatuc solvem, it is rhea possible in a step to react the resulting gel with $ silylati>ng agent containing chlorine. The SiOZ gel which is surface modified for example with methyl silyl groups cap they and likewise from an organic solvent, be dried in air. The pradueticm method beard ~t this teclu~ique is known from DE-A-43 42 548.
Ahet~ve methods with regard to the prodtu;aon of an Si0= aervgcl on a basis of water-glass with ~bsequent sub-critical drying are desrn'bcd in German Patent Application 195 ~i 1 715.1 arid 195 41 992. 8.
Disclosed in Crerman Pate~rJt Application No. 196 48 798.6 is a method of producing ae~e~ in which hydrogals are su~soe mn~d without prior solvsrt exeha~ i. e.
with essentially water in the pores, after which they are dried.
From DE-PS 896189, it is lcnuvrm that globular siliac acid hydrogels can be produced by produc~,ng iioru a rsw ttiaterial, e.g. water glass, which contains >iilicic acid, and by reaction with axe add, for exarr~ls sulphuric acid, a gel-forming silicic acid bydrosol which 04-Nov-90 16:05 From-GRAHAM WATT i Co ~ 01732450113 T-078 P.07/15 F-936 is then, in the form of individual drop, passed through a gaseous or liquid mediwu, erg.
a ttiinerai oil, which is not mi~,'ble with, water and the hpdrosol. The bydrosol drops thereby acquire a zswre or lees globular form and tamale in the oal layer cieotly long for the conversion from the sol to the solid hydmgel to take place. The hydrogd bast produced by the indicated method do however comma mineral oil coutarninatioas which c$:uiot be completely eliminated ever by very axpe~re washing processes.
to the case of this method, if the mixture is iajectod irno a gaseous tedium, then the praxd~,u~ adopted is one whereby srstly hydrosol droplets are produced by a mixing jet from water-glass, sulphuric acid and aluminium sulphate, these droplets then being irgecxed irao sa sir-filled vessel. Under the conditions applied, conversion of the hydrosol into a hydrogel occurs within about 1 second so that the tiny hydrogel droplets tea be trapped in s layer of water in the bottom of the vessel and further processed.
DE-C-21 03 243 describes a method ~ and au apparatus for producing substantially globular hydrogels which contain silicic acid, the s>7icic acid hydrosol being forazed irt a special mixes jet from a raw material comaira»g silicie acid and an sad sohrtioa. The hydrosol thus formed is, for the purpose of drop fonnauorr, sprayed into a gaseous medium which does not aotioeably dissolve in the hydrosol, far exaxaple air.
By reason of the necessary fall dare as a reaction time for gel formation, however, depcndrnt upon the particle size so the overall height for the apps into which the Izydrosol is injected is Vafottw~tely considerable As a resuh, this prior art method is very ~ ~~ once co~espp~Bly substantial n~at~al is required, the spay requir~rt is considerable and it takes longs to produce the apparatus. Furthermore, it1 the case of this known method, lyogel Particles of a aoa-homog~us size distnbutioa arise which pos$ibly then have to be sorted according to their size so that all in all this method becomes more time arid cost iutcnsjvc, ~om~ou to all the aforesaid methods is that in order to initiate g~ formation, two or ~ ts~ e.g. wares-glass solution and mistral acid, have to be brought 04-Nov-99 16:05 From-GRAHAM WATT i Co 01732450113 T-078 P.08/15 F-936 together. is this rrspcxx, iv is apparently favourable for the properties of the gel particles, particularly for their subsequcnt atabi>ityty, if ve form and size of the particles can be adjusted already poor to the gel formation process. it is in particular advanageous for the 9ubseguem stages of the process following gel iorlcnatioa and shaping, tech as for exaaap~ for washing, for possibly subsc-dueat reactions and for the later drying proocss, if the particles are p~~er~ in an easily-handled form, in other words for e~taa~ple as balls.
Globular particles are in tams of sabiliry, supeior to all outer shapea_ By virtue of tat regular geotrreuy and the tack of edges and corAers, it is poaslble substsniieily to avoid undesirable abrasiop during the foIlow~ng stages of the process_ Substantially globular lyog<ds have the advantage that the particla site diatribuiion of the end product produced from the Iyobel can be adjustcd pardculariy easily by the shaping pmceas.
~~~'S >~ preseui ittvcntioa is bascd ors the problem of providing a method of producing 3ubscautiaiiy globular lyogels in which the disadvantages of the prior art ~aethods are avoiaed.
This problem is resolved is that the gel forming components are mixcd together to form a lyosol and rhea tbc lrosol is introduced into a moving medium for forming the lyoget, the said nbring not noticxable is the iyosol.
In the preset Appiicatiori, the term lyosol or lyogel must be undett;tood to moan a sol or a gel in which the sol or ~l interstices ere filled with uuid. 1f the quid consists essentially of wafer, then ors speaks of a hydrosol or hydrogel, as the case gray bc.
Incorporation into s moving atmosphere greatly increascs the dwell tittle of the lyoaol particles iu the medium so that the overall height. of the appliance can be n~k~yy reduced. s ha-efare, the appliances or apparatus r~,quire considerably lets azaterial and space so that the co3rs of the method ecaording to the invention ere considera~uly reduced.
ideally, the modiu~u is art air atmosphere> whweby fiuther substances can be added to the lyosot before it is int~~uduced into tha sir atmosphere. The air ~n thereby also coruain 04-Nov-99 16.05 From-GRAHAM WATT i Co 01732450113 T-078 P.09/15 F-936 other g,~eout media. Aany apper~uSes known to s man Skilled in the art for this pwpose can be used for mixictg the gel forming component and for incorporating the lyosol.
Expediently, the lyosol is dripped or sprayed into the sir, pr~erably in the direction of gravity.
Acaordi~g to a preferred embodiment, the lyosol is added to au air scream which flows substantially against the direction of gravity. The air Bow can also contain otherwise directed velocity cotripoaerus. Thus, the dwell time of the particles in ttte air csa be incrcased under control, which resuhs in a furtl~r savir~ on the overall height of the apparaws into which the lyosol is introduced. The air flow which is opposite to the direction of gravity can more Ix used for any grading or classifying of the drops or particles duri4g gel formatioct. Iaarticle$ with a diatr~etet below the limit grain diameter which corresponds to tho flow vclocity are delivered upwardly whereas larger particles ara delivered downwardly. ConSequeatly, no additional step is needed for sorting the gel particles according to tbeir size so that the coats of the iuethod according to the iavemioa arc stiii further reduced.
A futtha development of this embodiment providcs for the Iyosol to be introduced imo an air flow, the velocity of which diminishes in the direction of flow_ A further preferred embodituettt of the method resides in that the lyosol droplets, after being converted to lyogel, are trapped in a layer of waver_ A 8ullar effect ofthe reduced falling rate of the balls is due to the air flowing against tla:
direction of fall; the elect is cue of so,>tiening the introduction of the lyogel balls in a I~yet of water for example.
Suitablo starting substances for the method according to the invernioa are basically say which are usable for the prior art ways of synthesising lyogela, for example as a preata$e for art aerogel (see for exaaipie 1. Brinkar, G. VIt. Schero, Sol-Gel Science;
Tbc Physic 04-Nov-9B 16:06 From-GRAHAM WATT i Co 01132450113 T-OT8 P.10/15 F-936 sad ~hemisuy of SoUGai Proc~sir~, Academic Press Ltd., Lorcdoa 1990;
pFrA-43 4Z 548; US-A-5 081 i 63; US-A-4 873 2I 8).
Pre~tred thereby are the pra-stages of SiOz bydrosols, e.g. silicic acid and rniaeral aoid.
Sodium waterglass solutions and hydrochloric acid are partiwlariy pr~acred.
A pcoblern oa which the present i>nvesuion is based resides in providi~ a method of producing substantially globular aerogels This problem is resolved by a method in uvhich a subs~tially globular lyogd, as can be produced in aecordaace with the present iavsutiorr, is convened to an aerogel.
The method of oonvertiug the lyogel to an aerogel is irc oa way limited. Any alternative mrt6ods .l~nown to a rnan skilled in the art can be applied;
In a prefetrod embodis;rent, the subsitaacially globular lyogel is reacted with a silylatiug agent. Any silylatiqg agenss such as for example trimethyl chlorosilane, which are known to a man sicihod is zhe art, may be uscd. Prior to silylatioa, the lyogels can be washed and/or the soivrant of the lyogel may be exchanged for another organic solvem.
Washing of the ly~el or hydro~l and the solvent e~d~nge can also be carried out by say methods desctibed in thr state of the art.
Dtyi:ag can likewise be carried out by any methods Irnowa vo a man skilled in the arc. In tlris respect, super-cxitical as well as sub-critical drying processes known for aetogels are preferred, sub-critically drying being pstticularly pr~erred.
The mothod according to the invcniiort is described is greater detail hereinafter with rrFcreaoe to as example of emboditaeat.
A sodirttn watea:glasos solution is ptoduc~ by dilWioa of 53. 5 kg commercially available sodavm water-glaxs solution with 25_5°~o SiOZ arid 7.6°~ro NazO
with 31.7 kg of ddonised 04-Nov-99 16:06 From-GRAHAM WATT 4 Co 01732450113 T-078 P.11/15 F-936 water. A dilute hydroa6loric said is produced by diwiion of X9.3 kg cammer,;iaily available 25% hydrochloric acid with 65.8 kg deionssed watar_ 1n each cast 3o kg/hr of the dilute hydcoehloric acid and oC the dilute water-glass solution are fed to a tniacing and sprayi>Ag apparatus in precisely rneagured atnouats. The outlet of the mixing nozzle is situated xt the top end of a pipe through which heatai sir bows vertically upwards. The bocr~orn third of the pipe is find with water. Above the surf eve of the water, the pipe has sir inla aperaua. The flow of air is adjusted to an empty Pipe velocity of 4 ml3ec. Thr temperature inside the pipo is 100°c. 'ire lrydrogel spheres are capnucd in the water lays, settle t>uotigh the layer of water acrd are delivered from the spray tower is a. stream of water.
The small hydrogel bays are conisru~ously v~ashed with 0.1 atol hydrochloric acid and rhea with deiorvised water. Subsequently, the lyogei balls are washed with acetone in several stages uat~ the watr con»t in the gel is less than 1 %_ The a~ceione-moist gd is exposod to a rtruQUre w"acetotx: and 5% ttttnethyl chiarneilat~e for i0 bouts. 'fhea, again is scvet8l stages, ~e gel is washed with acetone. T'he acetono-uroist gel balls are dried iu a fluidised bed with nitrogen at 180°C for 5 mina. The aerogel bsDs obtained have a density of 7 30 kg/cu, m and their beat cor~ductiviry is 0. ~ 1 WimK.
AerogeIs, particularly those with a porosity above 60% sad a deagily of less than 0.6 g/cu.at>, diap>Ay extremely, low thermal conductivity and are therefore used as a hear insulating material, as described for example in EP-A-0171 722. purtbe~nore, by virtue of their very low re&actian index faf solid substances, it is k»own to use them for Cerenkov detectors. Fl~r~ by reason of their particular acouspc impedance, the literature describes a possible use as an innpedance adaptatiop means, for example in the alpha sound range. It is also possible for them to be ua4d as carriers for e$ecTive substances in phanrracy or apiculture Aerogds in the broader sense, e.g. is the xnse of "gel with air as the dispersion agent"
are produced by the drying of a suitable gel. The tee, "a,~og~" ~ this sense embraces aerogels is the narrows xase, xerogels and cryogels. In this respect, a dried gel is tamed as aerogd in the narro~rer sense whrn the liquid of the gel is eliminated at above critical temperature and starring from pressures above critical pressure_ On the oti>er hand, ifthe dquad is eliminated from the gel under sub-ail coaditiot~ for exaxople with the formation of a liquid/favwr interphaac, then the rcavlting gel is frequently referred to also as s xaogel.
W6ea the team asrogals is used iu the presrnt invention, these are aerogels in the broader sense, e.g. in the sense of "gel with air as the dispersion medium. °
1'he teem does not include aerogels known from earlier literaaue and which are obtained for example by precipitation of silicic said (~e.g. DE 3025437, DD 296 898) or which occur as sdiCic and, e.g. A'r''s In these cases, during lure, no Ihree-dimerniional gel lattice develops which is homogeneous rnfet relatively great distances.
~~ ~ogels at'e coaee~ed, it is ppssible basically to diffcreptiate beiwoen inorganic and organic aeragels.
D4-Nov-99 16:04 From-GRAHAM WATT i Co D1732450113 T-078 P.05/15 F-936 Inorganic aetog~ds have already been laoowa since 1931 (S_ S. Kistler, Nature 7 93 i, 127, 741 ). Since rhea, aerogds have beau ~ortbcomrog from various materials. Iu this Tespect, for example SiO~, TiO~-, ZrOx , Sr~2., LiaO-, Ce0=., V=O~serogels and udxauea ofthese watt produced (H, D. Gesser, P. C. Goswatni, Cbem. Rev_ 1989, 89, 765 et seq.).
For wane yeaus, organic aerogels have also bees known which are derived from tt~e most widely diverse staring materials, e.~. melaatine foz>nsldelryde (tt W.
Pelcala, J. Mate, Sci. I9$9, 24, 3221 ).
Tnorganic aa-ogels tea thereby he produced i~a di$aent ways.
Oa the one hand, Si02 aerogels cao for exs~aplc be produced by acid hydrolysis ind condensation of teas-ethyl orthosiiicate is c~b~uwl. During this process, a gd is produced which can be dtiod by super-caitical drying whilo its suuc~ture is mamtaiaed.
Production methods based on this drying tochaique are k~wwn for example from EP-A-0 396 O~d, wo 92103378 or w~ 95/06517.
The high pressure techaiQue irrvolvad io the super-critical dryi»g of serogeis is however as expensive process and irivolyes a high security risk. In addition, however, supar-critica! drying of acrogels is a vrty cost-inte~ive production method.
Ia principle, an ahelaative to super-critical drying is afforded by a method for the suh-eritical dying of SiOZ ~ls. The costs invin Sub-critical drying are substantially less by ressorr of the simpler iecbnology, the lower energ~r costs and the lesser secmiiy risk_ The SQL gels can for example be obtaitKd by acid hydrolysis of teQa-alkoacy silaaes in a suitable organic solvent by mesins of waxcr. Once the solvent has been exc~hsngod for a ~~ . the gel obtained is in a further step reamed with a sdyla>ti~ agent.
The SiO~ gel rasulting from this can then, from an organic solwe~nt, be dried in air. Thus, aerogeis with densities of les$ than 0.4 g/cu.cau and porosities about 60~/e can be achieved.
04-Nov-99 16:04 From-GRAHAM WATT i Co ~ 01T32450113 T-018 P.06/15 F-936 The production method based oa this dryia,g technique is descn'b~d is detail in WO
94/25149.
Furthermore, the shouts-described gala can, prior to drying sad in the ~cohol-aqueous sohuio~ be mixed with te~a~.aikoxy silaae3 and aged, ~n order to irrc~ese the gal. lattice strength, as disclosed in WO 92/20b23 , 1"he recta-stllcoxy silwres used ac craning t»~erials in the about-deaaibad processes do, however, likewise represent an extretaely high cast factor A considerable cost reduadon eau be achievmd by using water-glass as s starting malaria!
for the produaiop of Si4i gds. To this end, it is possible for example to produce a silicic acid from an aqueous water-glass soluoon with the help of an ion atchauge resin, the siIicia acid that be3ag polycondensod by the addition of a base to produce an SiOz eel.
After exch8pge of the aqueous modiuta for a suitable orgatuc solvem, it is rhea possible in a step to react the resulting gel with $ silylati>ng agent containing chlorine. The SiOZ gel which is surface modified for example with methyl silyl groups cap they and likewise from an organic solvent, be dried in air. The pradueticm method beard ~t this teclu~ique is known from DE-A-43 42 548.
Ahet~ve methods with regard to the prodtu;aon of an Si0= aervgcl on a basis of water-glass with ~bsequent sub-critical drying are desrn'bcd in German Patent Application 195 ~i 1 715.1 arid 195 41 992. 8.
Disclosed in Crerman Pate~rJt Application No. 196 48 798.6 is a method of producing ae~e~ in which hydrogals are su~soe mn~d without prior solvsrt exeha~ i. e.
with essentially water in the pores, after which they are dried.
From DE-PS 896189, it is lcnuvrm that globular siliac acid hydrogels can be produced by produc~,ng iioru a rsw ttiaterial, e.g. water glass, which contains >iilicic acid, and by reaction with axe add, for exarr~ls sulphuric acid, a gel-forming silicic acid bydrosol which 04-Nov-90 16:05 From-GRAHAM WATT i Co ~ 01732450113 T-078 P.07/15 F-936 is then, in the form of individual drop, passed through a gaseous or liquid mediwu, erg.
a ttiinerai oil, which is not mi~,'ble with, water and the hpdrosol. The bydrosol drops thereby acquire a zswre or lees globular form and tamale in the oal layer cieotly long for the conversion from the sol to the solid hydmgel to take place. The hydrogd bast produced by the indicated method do however comma mineral oil coutarninatioas which c$:uiot be completely eliminated ever by very axpe~re washing processes.
to the case of this method, if the mixture is iajectod irno a gaseous tedium, then the praxd~,u~ adopted is one whereby srstly hydrosol droplets are produced by a mixing jet from water-glass, sulphuric acid and aluminium sulphate, these droplets then being irgecxed irao sa sir-filled vessel. Under the conditions applied, conversion of the hydrosol into a hydrogel occurs within about 1 second so that the tiny hydrogel droplets tea be trapped in s layer of water in the bottom of the vessel and further processed.
DE-C-21 03 243 describes a method ~ and au apparatus for producing substantially globular hydrogels which contain silicic acid, the s>7icic acid hydrosol being forazed irt a special mixes jet from a raw material comaira»g silicie acid and an sad sohrtioa. The hydrosol thus formed is, for the purpose of drop fonnauorr, sprayed into a gaseous medium which does not aotioeably dissolve in the hydrosol, far exaxaple air.
By reason of the necessary fall dare as a reaction time for gel formation, however, depcndrnt upon the particle size so the overall height for the apps into which the Izydrosol is injected is Vafottw~tely considerable As a resuh, this prior art method is very ~ ~~ once co~espp~Bly substantial n~at~al is required, the spay requir~rt is considerable and it takes longs to produce the apparatus. Furthermore, it1 the case of this known method, lyogel Particles of a aoa-homog~us size distnbutioa arise which pos$ibly then have to be sorted according to their size so that all in all this method becomes more time arid cost iutcnsjvc, ~om~ou to all the aforesaid methods is that in order to initiate g~ formation, two or ~ ts~ e.g. wares-glass solution and mistral acid, have to be brought 04-Nov-99 16:05 From-GRAHAM WATT i Co 01732450113 T-078 P.08/15 F-936 together. is this rrspcxx, iv is apparently favourable for the properties of the gel particles, particularly for their subsequcnt atabi>ityty, if ve form and size of the particles can be adjusted already poor to the gel formation process. it is in particular advanageous for the 9ubseguem stages of the process following gel iorlcnatioa and shaping, tech as for exaaap~ for washing, for possibly subsc-dueat reactions and for the later drying proocss, if the particles are p~~er~ in an easily-handled form, in other words for e~taa~ple as balls.
Globular particles are in tams of sabiliry, supeior to all outer shapea_ By virtue of tat regular geotrreuy and the tack of edges and corAers, it is poaslble substsniieily to avoid undesirable abrasiop during the foIlow~ng stages of the process_ Substantially globular lyog<ds have the advantage that the particla site diatribuiion of the end product produced from the Iyobel can be adjustcd pardculariy easily by the shaping pmceas.
~~~'S >~ preseui ittvcntioa is bascd ors the problem of providing a method of producing 3ubscautiaiiy globular lyogels in which the disadvantages of the prior art ~aethods are avoiaed.
This problem is resolved is that the gel forming components are mixcd together to form a lyosol and rhea tbc lrosol is introduced into a moving medium for forming the lyoget, the said nbring not noticxable is the iyosol.
In the preset Appiicatiori, the term lyosol or lyogel must be undett;tood to moan a sol or a gel in which the sol or ~l interstices ere filled with uuid. 1f the quid consists essentially of wafer, then ors speaks of a hydrosol or hydrogel, as the case gray bc.
Incorporation into s moving atmosphere greatly increascs the dwell tittle of the lyoaol particles iu the medium so that the overall height. of the appliance can be n~k~yy reduced. s ha-efare, the appliances or apparatus r~,quire considerably lets azaterial and space so that the co3rs of the method ecaording to the invention ere considera~uly reduced.
ideally, the modiu~u is art air atmosphere> whweby fiuther substances can be added to the lyosot before it is int~~uduced into tha sir atmosphere. The air ~n thereby also coruain 04-Nov-99 16.05 From-GRAHAM WATT i Co 01732450113 T-078 P.09/15 F-936 other g,~eout media. Aany apper~uSes known to s man Skilled in the art for this pwpose can be used for mixictg the gel forming component and for incorporating the lyosol.
Expediently, the lyosol is dripped or sprayed into the sir, pr~erably in the direction of gravity.
Acaordi~g to a preferred embodiment, the lyosol is added to au air scream which flows substantially against the direction of gravity. The air Bow can also contain otherwise directed velocity cotripoaerus. Thus, the dwell time of the particles in ttte air csa be incrcased under control, which resuhs in a furtl~r savir~ on the overall height of the apparaws into which the lyosol is introduced. The air flow which is opposite to the direction of gravity can more Ix used for any grading or classifying of the drops or particles duri4g gel formatioct. Iaarticle$ with a diatr~etet below the limit grain diameter which corresponds to tho flow vclocity are delivered upwardly whereas larger particles ara delivered downwardly. ConSequeatly, no additional step is needed for sorting the gel particles according to tbeir size so that the coats of the iuethod according to the iavemioa arc stiii further reduced.
A futtha development of this embodiment providcs for the Iyosol to be introduced imo an air flow, the velocity of which diminishes in the direction of flow_ A further preferred embodituettt of the method resides in that the lyosol droplets, after being converted to lyogel, are trapped in a layer of waver_ A 8ullar effect ofthe reduced falling rate of the balls is due to the air flowing against tla:
direction of fall; the elect is cue of so,>tiening the introduction of the lyogel balls in a I~yet of water for example.
Suitablo starting substances for the method according to the invernioa are basically say which are usable for the prior art ways of synthesising lyogela, for example as a preata$e for art aerogel (see for exaaipie 1. Brinkar, G. VIt. Schero, Sol-Gel Science;
Tbc Physic 04-Nov-9B 16:06 From-GRAHAM WATT i Co 01132450113 T-OT8 P.10/15 F-936 sad ~hemisuy of SoUGai Proc~sir~, Academic Press Ltd., Lorcdoa 1990;
pFrA-43 4Z 548; US-A-5 081 i 63; US-A-4 873 2I 8).
Pre~tred thereby are the pra-stages of SiOz bydrosols, e.g. silicic acid and rniaeral aoid.
Sodium waterglass solutions and hydrochloric acid are partiwlariy pr~acred.
A pcoblern oa which the present i>nvesuion is based resides in providi~ a method of producing substantially globular aerogels This problem is resolved by a method in uvhich a subs~tially globular lyogd, as can be produced in aecordaace with the present iavsutiorr, is convened to an aerogel.
The method of oonvertiug the lyogel to an aerogel is irc oa way limited. Any alternative mrt6ods .l~nown to a rnan skilled in the art can be applied;
In a prefetrod embodis;rent, the subsitaacially globular lyogel is reacted with a silylatiug agent. Any silylatiqg agenss such as for example trimethyl chlorosilane, which are known to a man sicihod is zhe art, may be uscd. Prior to silylatioa, the lyogels can be washed and/or the soivrant of the lyogel may be exchanged for another organic solvem.
Washing of the ly~el or hydro~l and the solvent e~d~nge can also be carried out by say methods desctibed in thr state of the art.
Dtyi:ag can likewise be carried out by any methods Irnowa vo a man skilled in the arc. In tlris respect, super-cxitical as well as sub-critical drying processes known for aetogels are preferred, sub-critically drying being pstticularly pr~erred.
The mothod according to the invcniiort is described is greater detail hereinafter with rrFcreaoe to as example of emboditaeat.
A sodirttn watea:glasos solution is ptoduc~ by dilWioa of 53. 5 kg commercially available sodavm water-glaxs solution with 25_5°~o SiOZ arid 7.6°~ro NazO
with 31.7 kg of ddonised 04-Nov-99 16:06 From-GRAHAM WATT 4 Co 01732450113 T-078 P.11/15 F-936 water. A dilute hydroa6loric said is produced by diwiion of X9.3 kg cammer,;iaily available 25% hydrochloric acid with 65.8 kg deionssed watar_ 1n each cast 3o kg/hr of the dilute hydcoehloric acid and oC the dilute water-glass solution are fed to a tniacing and sprayi>Ag apparatus in precisely rneagured atnouats. The outlet of the mixing nozzle is situated xt the top end of a pipe through which heatai sir bows vertically upwards. The bocr~orn third of the pipe is find with water. Above the surf eve of the water, the pipe has sir inla aperaua. The flow of air is adjusted to an empty Pipe velocity of 4 ml3ec. Thr temperature inside the pipo is 100°c. 'ire lrydrogel spheres are capnucd in the water lays, settle t>uotigh the layer of water acrd are delivered from the spray tower is a. stream of water.
The small hydrogel bays are conisru~ously v~ashed with 0.1 atol hydrochloric acid and rhea with deiorvised water. Subsequently, the lyogei balls are washed with acetone in several stages uat~ the watr con»t in the gel is less than 1 %_ The a~ceione-moist gd is exposod to a rtruQUre w"acetotx: and 5% ttttnethyl chiarneilat~e for i0 bouts. 'fhea, again is scvet8l stages, ~e gel is washed with acetone. T'he acetono-uroist gel balls are dried iu a fluidised bed with nitrogen at 180°C for 5 mina. The aerogel bsDs obtained have a density of 7 30 kg/cu, m and their beat cor~ductiviry is 0. ~ 1 WimK.
Claims (12)
1. A method of producing substantially globular lyogels in which tire gel forming components are mixed to produce a lyosol, after which the lyosol, in order to form a lyogel, is introduced into a moving medium which flows substantially against the direction of the force of gravity and which does not perceptibly dissolve in the lyosol.
2. A method according to claim 1, characterised in that the medium is air.
3. A method according to claim 2, characterised is that the air contains at least one further gaseous medium.
4. A method according to claim 2 or 3, characterised in that the lyosol is introduced dropwise into the moving air.
5. A method according to claim 2 or 3, characterised in that the lyosol is sprayed into the moving air.
6. A method according to at least one of claims 2 to 5, characterised in that the lyosol particles are screened according to size by the air stream which is directed is opposition to the force of gravity.
7. A method according to at lease one of claims 2 to 5, characterised in that the velocity of the air stream diminishes in the direction of flow.
8. A method according to at least one of the preceding claims, characterised is that the lyosol particles are trapped in a layer of water.
9. A method according to at least one of the preceding claims, characterised in that the lyosol is formed from silicic acid and mineral acid.
10. A method according to at least one of claims 1 to 8, characterised in that the lyosol is from a sodium water-glass solution and hydrochloric acid.
11. Use of substantially globular lyogels, produced according to at least one of the preceding claims, for the production of aerogels.
12. A method of producing substantially globular aerogels is which a substantially globular lyogel, produced according to at least one of claims 1 to 10, is converted to an aerogel.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19722738A DE19722738A1 (en) | 1997-05-30 | 1997-05-30 | Process for the production of essentially spherical lyogels and aerogels |
| DE19722738.4 | 1997-05-30 | ||
| PCT/EP1998/003161 WO1998053905A1 (en) | 1997-05-30 | 1998-05-28 | Method for producing substantially globular lyogels and aerogels |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2291229A1 true CA2291229A1 (en) | 1998-12-03 |
Family
ID=7830964
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002291229A Abandoned CA2291229A1 (en) | 1997-05-30 | 1998-05-28 | Method for producing substantially globular lyogels and aerogels |
Country Status (8)
| Country | Link |
|---|---|
| EP (1) | EP0984829B1 (en) |
| JP (1) | JP4241938B2 (en) |
| KR (1) | KR100534194B1 (en) |
| CN (1) | CN1103243C (en) |
| CA (1) | CA2291229A1 (en) |
| DE (2) | DE19722738A1 (en) |
| ES (1) | ES2189210T3 (en) |
| WO (1) | WO1998053905A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9199853B2 (en) | 2011-04-28 | 2015-12-01 | Tokuyama Corporation | Metal oxide powder and method for manufacture thereof |
| US9216909B2 (en) | 2010-10-25 | 2015-12-22 | Tokuyama Corporation | Aerogel and method for manufacture thereof |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111302348B (en) * | 2020-04-08 | 2022-01-18 | 天津纳科世纪新材料有限公司 | Normal pressure preparation method of silicon dioxide aerogel spherical particles |
| CN114149010B (en) * | 2021-12-15 | 2023-04-28 | 河北三棵树涂料有限公司 | Silica aerogel ball and preparation method thereof |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB607234A (en) * | 1946-01-15 | 1948-08-27 | Standard Oil Dev Co | Improved process for the preparation of gel particles |
| DE1667078B2 (en) * | 1967-10-31 | 1979-07-19 | W.R. Grace & Co., New York, N.Y. (V.St.A.) | Process for the preparation of spherical silica hydrogels |
| SE319161B (en) * | 1968-01-30 | 1970-01-12 | Fosfatbolaget Ab | |
| DE2103243C3 (en) * | 1971-01-25 | 1979-01-11 | Basf Ag, 6700 Ludwigshafen | Process and device for the production of largely spherical, silica-containing hydrogels |
| DE3329016A1 (en) * | 1983-08-11 | 1985-02-28 | Basf Ag, 6700 Ludwigshafen | METHOD FOR PRODUCING POLYMERISATES OF ETHYLENE BY MEANS OF A SILICONE XEROGEL / CHROMTRIOXIDE CATALYST |
| US4649037A (en) * | 1985-03-29 | 1987-03-10 | Allied Corporation | Spray-dried inorganic oxides from non-aqueous gels or solutions |
| DE4231749A1 (en) * | 1992-09-23 | 1994-03-24 | Basf Ag | Process for the preparation of a supported catalyst for the polymerization of alpha-olefins |
-
1997
- 1997-05-30 DE DE19722738A patent/DE19722738A1/en not_active Withdrawn
-
1998
- 1998-05-28 EP EP98936291A patent/EP0984829B1/en not_active Expired - Lifetime
- 1998-05-28 DE DE59806633T patent/DE59806633D1/en not_active Expired - Lifetime
- 1998-05-28 KR KR10-1999-7011133A patent/KR100534194B1/en not_active IP Right Cessation
- 1998-05-28 WO PCT/EP1998/003161 patent/WO1998053905A1/en active IP Right Grant
- 1998-05-28 JP JP50024699A patent/JP4241938B2/en not_active Expired - Fee Related
- 1998-05-28 ES ES98936291T patent/ES2189210T3/en not_active Expired - Lifetime
- 1998-05-28 CN CN98805665A patent/CN1103243C/en not_active Expired - Fee Related
- 1998-05-28 CA CA002291229A patent/CA2291229A1/en not_active Abandoned
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9216909B2 (en) | 2010-10-25 | 2015-12-22 | Tokuyama Corporation | Aerogel and method for manufacture thereof |
| US9199853B2 (en) | 2011-04-28 | 2015-12-01 | Tokuyama Corporation | Metal oxide powder and method for manufacture thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1103243C (en) | 2003-03-19 |
| WO1998053905A1 (en) | 1998-12-03 |
| EP0984829B1 (en) | 2002-12-11 |
| ES2189210T3 (en) | 2003-07-01 |
| EP0984829A1 (en) | 2000-03-15 |
| JP4241938B2 (en) | 2009-03-18 |
| KR100534194B1 (en) | 2005-12-08 |
| CN1258228A (en) | 2000-06-28 |
| DE19722738A1 (en) | 1998-12-03 |
| KR20010013150A (en) | 2001-02-26 |
| DE59806633D1 (en) | 2003-01-23 |
| JP2002500557A (en) | 2002-01-08 |
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