Chemically assisted dry comminution of an inorganic powder

Chemicallyassisteddry comminutionof an inorganicpowder FUMIKAZU KUNIO KUNIO AKIKO IKAZAKI, KAMIYA, UCHIDA, KAWAI, SATOSHI YODA andAKIHIRO GOTOH 1-1 National Institute and Chemical Ibaraki Research, Tsukuba, 305, of Materials Higashi, Japan Received forAPT 21August 26October 1995 1995; accepted assisted ofaninorganic was conducted inorder to (CADC) Abstract-Chemically drycomminution powder obtain fine with surface area. Soda was comminuted with lithium nitrate under large powder specific glass powder lithium c onditions. The interaction of nitrate with soda the comminution assisted the dry glass during powder soda inbeing comminuted. Soda ofabout 180 was whereas glass powder glass powder m2/g prepared byCADC, inordinary thespecific surface area comminution ofsoda was 3.8 Zirconia (DC) dry glass powder only m2/g. inCADC inordinary content asacontaminant was lower than DC. The ofagglomeration ofthe prevention comminuted soda nitrate and the lithium sodium inthe between and ions soda bylithium glass ion-exchange glass were tohelp CADC thecomminution. powder during thought 1.INTRODUCTION Comminution ofa particle ismicroscopically thephenomena thatacrack isintroduced into aparticle formation ispropagated andthecrack mechanical forces (crack stage) bysome Thecomminution isdivided intotwodifferent (crack process stages: propagation stage). crack formation andpropagation. When cracks areintroduced inadvance topowders or comminution chemical treatment assisted crack bysome (chemically formation), during thecomminution ofthepowders willbecome more efficient. thecracks When introduced intotheparticle interaction witha grinding solvent propagate easily bychemical assisted crack theparticle willbebroken this From (chemically propagation), efficiently. consideration assisted which consists ofchemically assisted comminution, chemically crack formation andcrack wasdemonstrated [ 1 ]. propagation, Oneof the assisted comminution inwetconditions isthatmore problems of chemically from themillwall andgrinding balls arecontained inthepowder tobebroken. impurities Forexample, water isavery butcomminution inwater about solvent, good grinding brings serious contamination infine From thestandpoint of low problems [2],especially grinding. arewellknown tobebetter thanwetcomminutions. contamination, drycomminutions assisted ofinorganic wasconducted here Chemically drycomminution (CADC) powder inorder toobtain ultra-fine fewimpurities. Intheexperiment an powder containing wascomminuted with some other i.e.mixed inorganic powder inorganic powder, inorganic wascomminuted. powder There hadbeen several inthefield ofpharmacy onthecomminution ofmixed papers inordinary et [3]reported thatcrystalline powders dryconditions. [3-6].Nakai al. medicinals such asbenzoic acidandaspirin dissolved inanaqueous acid, salicylic quickly solution when comminuted with cellulose Itwas being together micro-crystalline powders. estimated thatthemedicinals withthecellulose were asamolecule oramicrodispersed ofthemolecules nopreferred orientation. usedorganic materials. assembly having They

112 Thecomminution ofmixed hadalsobeenreported Itwas inorganic powders [7-9]. withthatofthepowder tocompare therateofgrinding ofa powder under the intended theeffect existence ofanother Tanaka oftheothercomponent [7]classified powder. andpresented fivedifferent onthegrinding rateofacomponent powder powder, figures andgrinding time. Theaimof between surface areaofeachcomponent powder specific theresearch wastoexamine themechanism ofthecomminution rather thantoobtain fine bythecomminution. powders Inthispaper, CADC ofsoda wasconducted inorder toobtain ultra-fine glass powder withalarge surface area. InCADC, some soda and/or glass powder glass powder powder which could beeasily removed from thepowder tobeground after thecomminution was usedasasecond Lithium nitrate wasselected asthesecond powder. compocomponent found because molten lithium nitrate hadbeen toweaken soda inour nent, glass powder andlithium nitrate ofsodaglass wascomexperiment [1].Themixed powder powder after lithium nitrate followed fineglass minuted, byobtaining powder dissolving bywater etal.[ 10] andIkekawa Similar comminution methods were reported byHoberg cleaning. from ours. etal.used carbon andsodium etal.[11,12]byusing different Hoberg powders asthesecond chloride andIkekawa etal.phenylalanine component. 2.EXPERIMENTAL APPARATUS AND PROCEDURES 2.1.Basic ideaandprocedure inwhich Atobebroken isfirstmixed CADC ofmixed isacomminution powder powder withpowder Bandthemixed iscomminuted indryconditions, followed powder byeither orresolving thepowder Btoobtain finepowder A.Inthecomminution, dissolving powder Bassists Ainbeing comminuted and/or cracks. Soft powder byintroducing propagating B.Lithium andeasily deformed ispreferable aspowder nitrate was plastically powder B.Inourprevious wasfound selected aspowder tobemore [I],soda powder paper glass broken when thesodaglass wasimmersed inmolten lithium nitrate powder efficiently before comminuted. Itwasduetothecracks introduced tothesoda being glass powder by thedifference ofthesizebetween lithium andsodium ions.Theion-exchange between lithium ofthesoda andsodium ionsoccurred theimmersion inthe during glass powder molten lithium nitrate. InCADC, thelithium nitrate wasthought tointeract with powder thesoda thecomminution andtheinteraction wasexpected toassist glass powder during thesoda inbeing comminuted. glass powder easily 2.2.Sample powder Soda diameter = 3.4pmandspecific surface area= 11 was (median powder glass I M2/g) usedaspowder Aandlithium nitrate wasusedaspowder Binourexperiment. powder Lithium nitrate dissolves inwater. As-received lithium nitrate isa freeflowing powder whose diameter isaround a fewhundred microns. 2.3.Comminution condition = 80ml)wasused. Asmall vibration mill(inner volume Soda (3g)was glass powder mixed withlithium nitrate balls used asgrinding (0-3g).Zirconia (5mmdiameter) were media. Thepacking fraction balls intothemillwasabout ofthezirconia 0.6.Comminution wasconducted wasobtained andseparating upto24h.Soda glass powder bydissolving lithium inwater. nitrate

113 2.4.Characterization sizedistribution andspecific surface areaofthecomminuted Theparticle glass powder thesedimentation method were measured byusing photoextinction (Shimadzu SA-CP3) method Flowsorb Zirconia was andtheBETone-point (Micromeritics 2200). impurity fluorescence identified (Seiko 2010). byX-ray AND 3.RESULTS DISCUSSIONS 3.1.Time variation of properties of comminuted powder inthesample shown inthissection was0.5,i.e.soda Theweight fraction of lithium nitrate withlithium nitrate of3g.Figure 1shows thetimeof3gwascomminuted glass powder comminuted. DCandCADC inthefigure variation ofmedian diameter ofthepowder andchemically assisted indicate, (DC) drycommirespectively, ordinary drycomminution diameters ofthesoda in nution withlithium nitrate. Themedian powder (CADC) glass withtheincrease ofgrinding timeupto methods decreased bothcomminution gradually inordinary 12h.However, for24hcomminution themedian diameter drycomminution themedian diameter inCADC than thatof the initial whereas became larger glass powder, wasmeasured withdispersing thecomdecreased. Particle sizedistribution continuously wt.% sodium minuted indistilled water 0.05 hexametaphosphate. containing glass powder oftheglass became Atthecondition theabsolute value ofthezetapotential powder larger than60mV(Fig. 2). surface areaofthecomminuted soda 3shows thetimevariation ofthespecific Figure inthecaseofthemedian a larger Incomparison oftheresults obtained diameter, glass. methods. Thesurface areaofthe difference wasfound between thetwodifferent milling smaller thanthatofthe sodaglass comminuted byDCwaswithout powder exception

1.Time variation ofmedian diameter ofsoda glass powder. Figure

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and concentration ofsodium zeta (Na-HMP). between 2.Relation hexa-metaphosphate potential Figure

area ofsoda surface 3.Time variation ofspecific powder. glass Figure

115 initial sodaglass InCADC, thesurface areaincreased withthegrinding powder. time, there wassome scatter ofthedata. although electron ofthesoda were shown inFig.4.Initial Scanning micrographs glass powders have andthere were InDC,there glass particles sharp edges onlyafewsmaller particles.

4.SEM of(a)initial Figure and photographs (b)comminuted powder byCADC (c)comminuted =24h. powder, time powder byDC. Grinding

116 andthesmall became coarse were small andafewlarge particles many particles particles, were found butsome ofthem looked like InCADC, small agglomerates. many particles agglomerated particles. inthepowder from i.e.contaminants, comminuted 5shows thezirconia content, Figure thegrinding media. Thezirconia content inCADC wasabout ahalfofthatinordinary DC. Thegrinding media andthesoda Lithium nitrate isavery deformable salt. easily plastically were coated withthelithium nitrate CADC andthegrinding media glass during powder Thecoating wasprobably thereason didnotdirectly contact withthesoda glass powder. thanin comminuted hada lower zirconia content whythesoda glass powder byCADC DC. 3.2.Effect nitrate inmixed ofweight fraction oflithium powder Thegrinding timeofthesodaglass inthissection was24h.Theeffect ofthe powder inmixed onthespecific surface areaofpowder fraction oflithium nitrate powder weight comminuted for24hinCADC isshown inFig.6.Thedatum intheweight fraction of DC. Theweight fraction of lithium lithium nitrate of0 wt.% tothatinordinary corresponds nitrate influenced thespecific surface areaofthecomminuted The powder. significantly Atthe tobeabout 15wt.%. concentration ofthelithium nitrate wasfound optimum lithium nitrate thecomminuted soda hadaspecific surface areaof content, glass optimum microisabout 14nm.Ascanning electron about 180M2/g, theBET diameter ofwhich area ofabout isshown inFig.7ofthesoda thespecific surface graph glass powder having from thatshown ofFig.7wasnotsodifferent 180m2/g. Thescanning electron micrograph inFig.7.Themedian inFig.4,although there seemed tobeslightly more small fragments the ofthecomminuted butwasstillover1um.InCADC diameter decreased, powder

incomminuted contained 5.Time variation ofzirconia content asacontaminant powder. Figure

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6.Effect ofweight fraction oflithium nitrate onspecific surface area ofcomminuted powder. Figure were coated withlithium nitrate. Themelting media andthesoda glass powder grinding of lithium nitrate is537K.Itwasprobable inDCthatthetemperature ofthecontact point media andthepowder tobeground became over537K.The between thegrinding point molten lithium nitrate adhered tothenascent surface ofthesodaglasspowder easily inCADC, which andprevented thesodaglass comminuted lowered thesurface energy from lithium nitrate wasnotgood asa However, powders strong agglomeration. enough

7.SEM ofsericite aspecific surface area of180 Figure having photograph M2/g.

118 todisperse thecomminuted sodaglass asinwater dispersing agent powder separately, some surfactant. Thiswasthereason comcontaining good whythesodaglass powder minuted inCADC thatinDC,butthemedian hadamuch surface areathan larger specific diameter wasnotsomuch different from thatinDC. 8shows thezirconia inthecomminuted Theimpurity level Figure impurities powder. Aslow decreased inthecaseofCADC. decrease oftheimpurity level with theincrease oftheweight fraction oflithium nitrate isevidence thatthecoating oflithium nitrate onto thesoda decreased theimpurity level. glass powder 9istheconcentration ofsodium inthecomminuted soda Figure glass powder analyzed There islittle leftinthecomminuted soda fluorescence. sodium byX-ray glass powder by thecomminution ofmixed butsodium remained inordinary DCofthe powder, unchanged sodaglass Itwasprobable inCADC thatthetemperature ofthecontact powder. point between media andthepowder tobeground became over537K.Atthistemgrinding lithium nitrate wasmelted andthesodium ionwasestimated tobereplaced perature, by lithium ionduring thecomminution. Lithium could notbedetected fluorescence. byX-ray Lithium ionswere detected inthesoda byatomic absorption spectrometry glass powder comminuted Lithium content inthesoda comminuted for24hby byCADC. glass powder CADC 57wt.p.p.m., i.e.about twoorders lower thantheamount ofthe was,however, decrease ofsodium content. Lithium ionsexchanged forsodium ionsinthefinely ground afterthecomminution. The wereconsidered toberemoved powder bywater cleaning ionsizeoflithium strain intheglass smaller would about tensile surface, bring powder which made theglass more iswhat wecallchemically assisted comminution. This fragile. inCADC Thision-exchange wasanother reason thesoda comminuted why glass powder hada larger surface areathaninDC. specific

8.Effect fraction oflithium nitrate onzirconia content asa contaminant contained in ofweight Figure comminuted powder.

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9.Effect ofweight fraction oflithium nitrate onsodium content incomminuted Figure powder. 4.CONCLUSION CADC ofsoda wasconducted inorder toobtain finepowder witha larger glass powder InCADC, surface area. lithium nitrate wasmixed with soda andthe specific glass powder mixed wascomminuted under Thefollowing results were obtained powder dryconditions. intheexperiment. surface areaofthesoda comminuted inCADC wasmuch (1)Thespecific powder glass thaninordinary DC.Soda ofabout 180m'/gwasobtained when larger glass powder theweight fraction oflithium nitrate was15wt.%. inthecomminuted content wasabout 50% of (2)Thecontamination powder byCADC thatofordinary DC. ionsinthesoda comminuted were notdetected (3)Sodium glass powder byCADC byXItwasestimated thatthesodium ionwasion-exchanged with rayfluorescence analysis. lithium nitrate ionsinlithium CADC. during ofagglomeration andtheion-exchange thecomminution were (4)Theprevention during thereasons comminuted hada much whythesodaglass powder byCADC larger surface area. specific REFERENCES 1.F.Ikazaki, K.Kamiya, A.Gotoh and M.Kawamura, Siberian J.Chem. K.Uchida, 5,11,1991. 2.Y.Kuwahara, Funsai 1992. 36,159, KY . amamoto, II.Fukuoka, 3.Y.Nakai, S.Nakajima and Chem. Pharm. Bull. 1977. 25,3340, 4.K.Yamamoto, M.Nakano, T.Arita, Y.Takayama and Y.Nakai, J.Pharm. Sci. 1976. 65,1484, 5.K.Yamamoto, Adv. Pharm. Sci. 1989. 5,124, 6.T.Oguchi, M.Okada, E.Yonemochi, K.Yamamoto and Y.Nakai, Int. J.Pharm. 1990. 61,27, 1962. 7.T.Tanaka and S.Kawai, J.Chem. 26,792, Japan Eng., K.Tsunematsu, 8.H.Tatiyama, T.Jin-nai, K.Kimura and J.Soc. Powder 1981. Technol., 18, 498, Japan

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