Starch Xanthate-Polyethylenimine Reaction Mechanisms
Total Page:16
File Type:pdf, Size:1020Kb
3693 JOCR:-AL OF POLY:\IER SCIE:-CE, Polymer Chemistry Edition YOL. 13. 1-HI-1-156 iIQ75l Starch Xanthate-Polyethylenimine Reaction Mechanisms :'If. E. CARB, B. T. HOFRElTER, and C. H.. H.USSELL, Northern Re(liollal Research Laboratory, Auricultural Research Service, C.S. Department of Ayriculture. Peoria, Illinois 6'16'04- Synopsis Thl' C'hemiC'al nature of starch xanthate (SX)-polyethylenimine (PEl) reaction produC'ts ha.~ been studied berause of their effertiveness as wet-end additives for im prllving strength properties of paper. :\lodel rompounds, in ronjunction with ultra vitllct, infrared, and chemical analyses, served to elucidate SX-PEl reaction mecha nisms. Aqueous solutions of ~X (degree:s of :sub:;titution O.l-D.;,) were titrated with PEl at pI! :.-i (2,i-:lQoC) to form SX-PEl !locrulent precipitate:s that were determined til hl' polyelectrolyte complexes. However. when :solutions of SX-PEl were kept at pH Ill-I:!. produc·ts were formed that induded dithiocarbamic acid salts in major quantities, PEl thiourea.-, and minor quantities of O-:starch PEl thionrarbamate. Acid precipita tion of thesl' ~X-PEI polymeriC' reaction products from their alkaline solutions, which ('Ilntained residual xanthate and PEl. also yielded polyelectrolyte complexe:;. :\lodel ,.'·-tems suggest th:lt PEl thiurum disulfide and starch xanthide, pos:;ible products of air lOxidal iOII, ('ould he present in minor amount:; and would react rapidly with PEl to yield thi'l\lreas and thioncarbamates, respectively. Apparently, mixtures of xanthate and alnin!' gave (1) dithioearbamic aeid salts from both xanthate groups and CS, (decom positilln from xanthate), (2) thioureas from both dithioearbamic aeid salts and thiuram eli,ulfide, and (;l) thionearbamates, principally from xanthate a:s opposed to xanthide. INTRODUCTION Sodium :<tarch di thiocarbonat p (:<t arch xanthatp. SX), oxidatively cross linkpd in p:lJ){'rmakill~ fumi:<hl':<, improVC':< wpt and dr~' strpngth of paper. l III {'ontilluin~ ('ffort:< to improvp til!' l'ffl'ctivpnpss of SX as a wpt-end paper :-trl'll~thpnill~ additiVC', such rationir poJynH'r:< as E:ynwnp ;j;ji and poJy I'thyh'nimiIH' (PEl), whieh han :-itf'''; for ioni{' and covalPnt bonding of xanthatp [-OC(8)S- j, have' 1J('('n iIlVP:<ti~atpd as altprnativp crosslinking agpnt,.;,u Our lat(':<t \\'ork. whi('h inyolyp,; rpartions that occur in aqueous :-o!utions of SX with PEl. wa:< madp to facilitate application of SX-PEl products in pappr and studip,; of :<imilar p()!ydectroJ~,tic systpms. PEl. a po!yaminp which eOIltain:< primar~·. :-pcondary, and tertiary amine ~roup:< in thp ratio of I;:.?; i.4'prpviousJy has bpPIl reactpd with polymers of oppo,;itp chargp ~o forn~ polyplectrt'llyte complexes,:> For example, mercury ion in part:; ppr biliioIl.rol1,cpntration have bpPIl ,;ubstantially removed from wa:<t('watpr by sPqu('Ilti~1 n.qqitions of PEl and SX, forming watcr-insoluble po!yf'1pctro!ytp eomp]pxp,;.6 Ho\\,pver. thpsc complexes per se were not 1441 C' 19i;j hy John Wiley & :-;on~, Inc. 1-i1:2 CABB. 1I0FHEITEH. A:\D BeSSELL analyticall~' charactprizrd, InnonpolynlPric systpms. reactions of primar~' and "t'('ondar~' amilH'" \\'ith xanthut{' "alts in aqueous alkaliIlP "olution" can yidcl thioncarbamat{',.;! H{'portpdly, aqueous solutions of SX and PEl a~('cl at pH 1O-1:.! and room t{'mpprature have yielded thionearbamatp [-0('(:-;):\<, 1intPrpolyn1l'r::,,3 Howen:r, others have stated that aqueous alkalilll' mixturp;; of edlulo,.;(' xanthatp and PElon aging yielded dithio carbamic' acid salb [):\C(S)S-l and thioureas [)XC(S):,\(1of PEl but no thilllll'arhamat{' producl.' Thc' PEl dithiocarbamic groups were beIipvcd to form from CS~ of dc'composed xanthate, Reportedly, air oxidation of nOllp,,],I'IlH'ri~ dithiorarbamic aci(-alts can yield:thiuram disulfides [):\C (~)~~(:-;)(':\(l aIllI thiourc'a;;,9 TllP thiourpas may bp fornlPd readiI~' by rc'a('lion of primary and ,,('condar~' aminp;; with thiuram disulfides. Anal og'l\l" I 0 air oxidution of dithiocarhamic group;;, air oxidation of xanthatps can .\'it,ld xanthidp,.; [-OC(S)S~(S)CO-l which readily react \\'ith primary alld ,,('c'ondar~' amiIH's to yidd thioncarbamates. ~('\'('ral reaction products inrluding polyelectrolytf' complexes \\wp fornH'd in aqueous solution;; of SX \\'ith PEl at pH ranging from 5 to 12. \\'ith tIll' aid of modd system;;, tl1("se products wpre charactprized by ultra \"ioll'l. infrarc'd. and c1l<'mical analy;;ps. All reactions \\"ere at :25-:30°C. RESULTS AND DISCUSSION SX-PEI Polyelectrolyte Complex \\'llI'n a 1Sc aqu('ou" "olution of PEl GOO was slowly admixpd with a O,:!r; aqu('ou;; ;;oIution of SX havinf!; a dpgT('{' of substitution (DS) of 0.15, alld \dll'1I pH \\'a" maintailwd at 7,0, a flocculent precipitate \\'as formrd aI a dr.\'-\\'(,ight ratio of 0.1-1;) part PEI/1.0 part SX. Alternatively, wlwn "oIUlioll" of tIl<' alkalinl' rC'actant;; WPr{' combill<'d at the sanw concentra til In" and ratio". but pH wa" ;;lowly 100\'('rc,d, precipitation occurred at pH i. TIll' frc':-:h pn'C'ipitate;;. obtailwd in U;-)% yields (SX-PEI addition basis), had ;;ullllr (·L-IS;) and nitrog('n (:3.HSc) content;; that \\we about theory for a produC't c(,ntaining 0.1-1'-) part PEl 1.0 part of DS O.L':> SX (theory; 4.8% S. -!.1C;( :\). WI1('n tIll' fn'"h undri{'d prpcipitate:-; were treated with acid (pH Li) t.o deccJlnpo;;(' xantllatl' group". CS~ \\'as recovered 10 in amounts corn'"pondiug to origiual xauthat(· cout('ut;;. PEl dithiocarbamic acid salt,.;, !l0;;;;iblc' compon('ut,.; iu tIl<' SX-PEI precipitates, abo would release C~: at pH L'). Ho\\'('v('r at pH 11. thC' fn'sh undried precipitates readily "ululJiliz('d and contailll'd U:3-!l7SO of the theoretical amounts of xanthate, a;; d('(prmiIH'd by ultra\'iol('( analysis (t-~~~ = 30;'), E 17,500). These data :::ho\\'ed that tIll' [n'sh undried precipitates were SX-PEI polyclectro Iyt(, complex('s. TIl<' ('ff('cts of pH, xanthate DS, and concentration on the amount of PEl requin'd to form these complexes, and analytical data are ginn iu Table 1. STAHCII XA \TfIATE-/,OI.YETIIYLE\I\J/\E IH:l TABLE I I'rrp:lr:ltilln :lnd Analy~p." of :-'tan·h X:lnt hate (~,x )-!'olyet liyll'niminr (PEl) l'ol\'p]petrlllyte Complexe~" Amoullt of PEl rl'ljuired to pre('ipitate Analy~es of ;-;'x-PEl l'OInplpx. preeipitated eomplexh ])pgn'(' .,f Coneell part~!] 00 part~ s,x ~ul"t it ut illll tration, Yield, :-'ulfur, Xitrogell, 1):-' ,.. e c-' c-' ,I pH .i pI! i /( ,I I 0.11 O. J() i ,I O. 1,-, O.OJ 0.1.-, 0,0:; J.i ..i O. 1.-. 0.10 \1.0 14.;' \14 .0 4.0' 3.H O. 1.-, O.:?O 14 ..i o.::! O. J() l::?O W.O f).i.;i S.i 4.0 " :\qlll'OIi' PEL (I (';) wa" slowly added to aqueou" SX, with "tirring, until a prl' ,·ipitatt· wa~ fOrIUl"/. Sulfur ('ontent was determined withiu 1 hr after precipitatiou. h 1'1I1~'l'll'('trlllyte ('omplexes formed at pI! i. Yield = wt of preeipitate -;- wt (;-;X + PEli X 100. e Expl'riment wa" not made. d :'I iiik.\', uo prpl'ipitate. l'/tra\'i"lpt analyses of agp<! ~X-PEI ('omplpxP" illdicatt'd that rpaetioll" h:ld lI(·('lIrfl·d "imilar to tho"p ill aqupou" SX-PEI ;.;olutioll" at pH 10-1:2. Alkaline SX-PEI Solutions :\11 aqlll'lIl1'; "(,]utioll "f SX alld PEl at pH 11 was prqlar('(] that eOIl taill!'d :-:X of DS 0.:2:2 at ,jS~ C'"l('t'lltratioll alld pntJUgh PEl noo to gin a ratill "f al1lillP to xallthatp group" of:2: 1. conditiolls that WPrP prt'\'iou"ly r('pllrt('(P to yi('ld ··"tarch polyl'thykllimino thiour,thant·." all O-stareh PEl thiolll'arhamatt·. Oil al!illg. u/tra\'ioll't ab"orptioll of t.hi" alkalillP :-:X-l'EI ""Iutio!l gradually "hift<'d from it" xallthatp maximum at :30;j IIIll tCI :mo IIIll (1-:2 da~',,). :2\1:2 11m (;j day,,). and filially :2S\lllm (:2S dny::;) \\'ith t'oIlCUrr('lIt formati"l1 of a \\'('akpr 1I01l"hifting abmrptioll at ::WO Ilnl. Tlwfl' \\'a" poorly dplillt'd ah"orpt iOIl in thc' rpgion of :2:{;-)-:24;j nn1. \Vhpn a('id-trt'atpd (pH 1..-,), till' ag('d (.-,-:2,\ day,,) mixture' exhihitpd an ab"orptioll I)('ak at :2:{!I 11m hut 1I0tH' at :2(iO :\Ild :2,\\1 11m. :\t pH i-I:!, ab"orption b~' til!' :H'id-trpatpd Illixtllfl' "hiftpd ff(l1l1 :2:{\1 Ilm to :2:37 111l1. Ultraviol(·t ~I)('('tra of tilt' fl't'"h and :2,\-da~'-old Illixtuf(' hC'fOf(' and aftt:'f acid tr<'atment art· rc'produ("('d ill Figur(' 1. .-\I>"orption at :23:>-:24.'> nm is partially ob ,,('urt·d iJ~' m'('rlappillg: ab"orption" of alkali at lower wavl'!el1gths. SX ha" a \\'('ak ah"orptioll at :.?:.?i 11m. SX-PEI prodUt"l" in alkalillt' "olutiol1 wC'rp prC'cipitatC'd in C'thanol. iso !alt·d. and rpdi".,;olv(·d at pH 1:2. The ultraviolet spectra of these redi~ sol\'('d prt·('ipitatt·" \\,pre' ~imilur to tho:-:p of tIlt' solutions from which they \n'rp prc'l·ipitatPd. Dltravioll't spl'ctra of tIlt' SX-PEI solutions in Figure 1 \\'('f(' typical of :-:p('etra that contained initial xanthate DS of 0.1-0.5, SX 1444 CARR. HOFRElTER. A:\D RUSSELL 0.0,-------------------, --------- 02~ 2 .--- / ... --- r ~ 04f- I;/;/ I; ~ __ /I ' " /I ~ 4 .I' " /I 0 6f.- / , '/ '" , ,.... / ='" ~ 0 B - i .' -5 = I ' ..