July 1947
INDUSTRIAL AND ENGINEERING CHEMISTRY
929
boiling points, which svould make recovery of t h e solvent very easy. Several mixed solvents of this kind were 60. found which have high solvent power for t h e humic acids. For example, a mixture of 95% ethyl alcohol, henzene, and acetonitrile in a ratio of 2 : 2 : 1 gives a high extraction sield. These compounds boil at 78.5", 80.1", and 82" C., respectively, and probably would not undergo marked fieparation on distillation. Two other mixtures are 9570 ethyl alcohol, benzene, and ethylene dichloride and alcohol, henzene, and ethyl acetate, both mixtures in a 2 : l : l ratio. These mixtures phould be used to extract treated coal dehyPERCENT WAT€R IN TH€ SOL Vf N T drated to about 10% moisture. Since they tolerate litt,le water, more solvent Figure 1. Extraction of Humic -4cids from Coal with Water 3lixture.s Containing Acetone, icetonitrile, or Ethjl klcohol must he used than kvith the aaueous solvents described previously. However, t h e humic acids produced by these solvents would be dry; this n-ould offset the preliminary drying of greater initial cost of acetonitrile and its loss through hydro the treated coal. Also the quantity of mineral matter dihpersed Ethyl alcohol-water solution7 could be used also in extra along with t h e humic acids by the nonaqueous organic. solvents processes, but the yields would be less. is usually less than n i t h aqueous solvents. The acetone-n-ater solvents used in Table I' can be calculated t o . I n comparison with furfural, both the acetone-water and the contain over 15% humic acids. This is about the maximum convolatile solvents u e more easily and quantitatively recovered. centration t h a t can he centrifuged and filt,ered satisfactorily. For these reasons their use would be preferred t o that of furfural. More concentrated solutions may be made readily hut are much more difficult t o handle because of t h e finely divided fusain and miners1 matter. Based on there observations, t h e amount of LITERATURE CITED acetone required per ton of raw coal would be about 800 gallons. (1) Francis, IT., and Wheeler, 11. V., J . Chem. SOC.,127,223G (19'25). This is based on a yield of nitric acid-treated coal of 1.1tons, the ( 2 ) Fuchs, TY..U. S.Patent, 2,242,822 (Slay 20, 1941). use of 6070 acetone solution, and estracting in a countercurrent or (3) Fuchs. Tf-., Polansky, T. S.,and Sandhoff, A. G., ISD. I?XG. CHEM..35, 313 (1943). semicountercurrent batch procedure. T h e yield should he ( 4 ) Xarcusson. J., Chem-Ztg.. 42, 437 (1918). ahout 8570 of the treated coal, or 0.93 ton per ton of raw coal. ( 5 ) Smith, R. C . . and Howard, H . C., J . A m . C'hem. Soc.. 57, 512 The yields are also dependent upon the extent of the reaction (1935). with nitric acid ( 3 ) . ..inother procedure for the commercial extraction of the humic PRESESTED before t h e Dirizion of G a a and Fuel Cheniisrry a t the 109th acids i- based on the use of low hoiling organic solvents of similar N e e t i n g of thr, . ~ M E R I C . A S CHE>IIC.AL SOCIETT,Atlantic City, S . J .
Action of Acrylonitrile on Viscose d
CARBOXYLATED RAYONS J. P. HOLLIH.4S .AND S-AYFORD A. 310SS. JR. American
P iscose Corporation, Marcus H o o k , Pa.
Acrylonitrile reacts readily with cellulose xanthate when added to commercial viscose solutions. Cellulosic cyanoethyl derivatives are formed which hj-drolyze in the alkali riorrnally present to gis e carbosy- ether derivatives. These inodified celluloses are obtained as yarn suitable for the manufacture of specialized fabrics. The derivati\es differ from those previously obtained in that the modifying groups are evenly- distributed throughout and w-ithin the cellulose crystallites. The carbory ether ?;armare alkaline and water-soluble.
w
H E S acrylonitrile is added t o viscose, it reacts rapidly with the principal b>--product sulfur constituents, relensing carbon disulfide and raising the salt test C;i). Simultaneously t'he viscose becomes opaque as a result of the formation of a n insoluble thionitrile. On standing, the thionifrile hydrdyzes t o a eoluble thiocarboxy compound, and the opacity disappears.
The salt test also decreases more or less normally during this reaging process. All of these changes can be esplained satisfactorily by reactions involving the by-product sulfur. I n addition it i- evident t h a t reactions occur which involve the cellulose .itself. Thus ~ r h e n viscose which has been treated with acrylonitrile is spun into rayon, a product differing considerably from the normal is ohtained. I n general, i t may be said that the n:itiue :ind extent of this alteration in cellulose properties depend both upon the amount of acrylonitrile added and also upon the extent t o which the viscose has been allowed t o re-age before being spun. In the present discussion the authors are concerned almost entirely with the latter case-that is, the viscoses were allowed t o re-age complet ely. IVhen small amounts of acrylonitrile (up t o 3 5 of the weight of the viscose) are added t o viscose spun under masimum stretch, the effect of the addition of the acrylonitrile on the cellulose itself
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INDUSTRIAL AND ENGINEERING CHEMISTRY
become$ apparent in that the u e t strengths of the resultant rayons are reduced, although the d r trengtlir are substantially normal. Both dry and wet estcnsib ies at break, as deterniined on a Scott tester, are somewhatl lon-er thari normal. Alternatively, when the viscose is spun a t a stretch aomrwhat belon. masimum, both dry as ivcll as \vet st'rengt'hs are retlucrd. The dry estensibilit,y is reduced below what ivould be espected at low strrtch, but the \vet' extensibility is now substantially increased. Stsmewhat different results are obtained when larger anmints of acrylonitrile are added. The dry strengths :Ire noiv lubstantially affected, and the \vet strengths decrease regularly and markedly with increasing acrylonitrile content, as do both wet and dry extensihilitiei. Some of these relations :irr shorn-n i n Tahlr I over the range 1-cr; ncrylonitrilr.
Ariylu-
Glucorr
nitrile Units ' Added". Carboxyl Group5 "c Zone 240 1 110 2 45 20 3 4 16 5 6
s1+-
mng
Stretch, c /r
9 1
55 36
31 44 $59 43
' r e r i d e Strength, G./Denier ._____
Dry "75
TVe t
1.75
2.36 2 32 2.32
1 .37 1.0s 0 99
2.36
0.9:i 0.48
20,8 14 3
30.0
17.3 10 6
26.1
7 7
23.2
16.3' 9.6
1.54 8 4 108 7 4 85 1 68 0.57 3 8 4 8 Acrylonitrile added by simple stirring into riarose. b Carboxyl r o n t e n t s drrermined by rnodifiratinn of Ludtkc's IcIerllod $4)
I n all ctises the treated fihers have a greater sn-elling capacity ill water than does normal rayon, and the higher members of this Eeries are iilkali-soluble. Further, if successive addition> of acrylonitrile are carried out a t low temperatures, prodncts Rre obt,ained which are water-soluble. This change in the fundamental nature of the cellulose c n i i fiatisfactorily he esplained by the wsuniptiori of a hlichael-t,ype addition of the cellulose residue to the ronjugat,ed douhle bond system of the acrylonitrile. The following reaction would apply:
OH
+ CH,=CHCS
+R.. . . .OCHrCH?CS
(1)
where R is the cellulose santhate residue, kitid the active hydrogen required for the reaction is supplied by t,he li),drosy groups of the pyranose ring. This will be recognized :is a specific example of the reactions of acrylonitrile with compounds containing a labile hydrogen, as described by Hriison ( 2 ) , Rriison and Rienrr ( 3 ) , and Koelsch (6). The cyanoethyl derivative obtained in reaction 1 \vould be expected to hydrolyze in t h r presence of t,!ie approsiniatrly 3% sodium hydrositlr normnlly prwent i n viscose, as indic:ited in Equation 2:
R . . . .OCHyCHrCS
+ H,O + K .
,
.
.OCH,CH,CONHY
of the modified rayons showed the hydrolysis her group to be substantially complete vithin the time required t o re-age the viscose t o n normal salt indexthat is, within nhout 70 hours. Although these modified rayons are cnrbosy ether rather than carbosyl derivatives, they 1%-ouldbe expected t o have properties similar in many respects t o the carbo. ited celluloses prepared by Yackel and Iieri~-on( 7 ) and others. Solubility in 11-ater and in alkali have already been mentioned. In addition the presence of the carbosy ether groups would be espected t o enhance the pickup of basic dyes. This occurs as espected, test dyeings on knitted fabrics showing a pronounced and regular increase in dye pickup with increasing acrylonitrile content. Reaction 1 is analogous t o the reaction descrited in the patent literature (1) as a reaction b e b e e n acrylonitrile and cellulose when the cellulose is in the form of a fibrous suspension, and in the presence of high concentrations of a strongly basic hydroside.
Vol. 33. No. 7
Under t l i t v ronditiou. wti.stitntioti t o tlw estent of one cy;t110ethyl or cartiosj- ether grcruli p ~ glucose r iinit has been reported Somewhat lrsi suhstitiition i. ii*ri;illy ohtuined when acrylonit,rilr ri proceeds more is reacted with viscose, but tlw i ~ ~ i r t i oapparently rapidly in thi. ewe. Thus the rwctioii 1ietn.een 1--6ri :mylonitrile anti crlluloic pulp suspended in 3' mcIium Ilydroside is a l o ~ ,\rherc:as I ' R ~ O I I S w r e ohtailled n.liic11 were conaitler,:il)ly modified from viscoses spun :is soon :IS ponsihlo after the addition et1 reE1ctivit.v i-. nttrihited t(J is in :I tlis~olvcdcondition. t>hefnrt t h i t t h e rellu1~~i.c ;is :I t'urtliw po>sitJk rwiilt o f this tli-mlvcd cotiditi~~n, tlie fundaniental iinturr of thc crllulohe i-. con:.iclerahly modified liy the action of the aciylonitrilr. Conqinrison of tlie s-rxy dingrams of :icr~loriitrile-treatedfilwrs n-ith normnl fiber diagram;. e:idinp or forcing a p r t of the cellulose ch:iins i n the 1:itw:II tlirwtion irithin the crystalline areas. It is rvident that, the niodifyiilg ~ X J Uis~ evenly distributed throughout thp crystal lattice. l'hi. is understandahle, zince the reaction of the :icrylonitrile \Tit11 the dissolved cellulose precedes the forni:ition of rry,st:illin(xrrgcnrrntad cellulose during the spinning operation. If tlie al)ov(' suppusition ia corrwt, evidrnces should tic found of interilnl plnstirizing during spinning, a-: n result of t,he presence rif the liulliy cide group^. There is some evidence for t h i , ~sincc. , ndditinn l i t ' 6 7 acrylonitrile allo~v-a considerable i n c ~ e w rin stretch during spinning (Tahle I). .Us0 the forcing apart of the cellulii>c~cli:iins in the cry-tu1 1:ittice w i u l d be e z p e c t d t o increase thcx rexctivity of the wlliilo-e, i i i t h r Pense that easier w t r y of rrapriitb ahould tir p w h i h l t , . Thi- i. confilmed by tlic. fact that, wit11 wveral rrnction+,t h e nicidified yarns consistently d i o v an iiicrc:iw! reactivity, tn tlir estrnt of :ihout -lorc for tho 6 7 acrylonitrile simples. The drcrrase in wet strength of the rnrbosylated samples listed in T:thle I i.; iindeist:mdahle, hut tlie C R W P for the great, reduction in estensibility on the introduction of carbosy et,her groupis nut so re:idily apparent. This hrittleness may be due, however, to the iorination of strongly polar linkages tietn-een t h r carboxyl g r o u p lit' cine wllulnk chain rind the hydrosyl groups on a neighboring eli:iin. Siicli strongly pcil:ir or salt-type linkages might approncli t Iw conditio11 ohtained n-hen liiienr polymers are crncblinked 11y 1cwction. involving primary valences; and since thia salt-tyiitl t)i,idge rorrespotid~t o a short bridging unit, rigidity ani1 hrittlenrs> nwnld Iir rspected. 111 partial confirmation of this concept riniple linear function is obtained n.hen the elongat,ion a t cnnst:riit lond is plotted against the carbosyl content of thr. various mnples (T:il)lr I). That i-, the decrease in dry eloiigation at, conatant load is directly proportional t o the nunihrr carhoxy ether group. present. So cquipnient is needed for the production of tlie c:trlios~. ether derivative other thnn that used in normal rayon production. The r)rwetiurr is comriatible Tvith normal visenough t o affect either filtmtion or spinning. Hence the derivative i-: easily olitnined :ind in yarn form. The derivative niny poshibly he useful for cro~a-linl;ing rea(*tions involving tlie carbosyl group, particularly since the cnrhosy ether g r o u p are cveuly di.;triliutrt! tliroiighout :md viithin the cellulose micellri. It may :ilso lie ti-eful i n t h r prodiiction of qoluble yarns. L I T E R i T U R E CITEI)
Haa5 (:o., L. S. Patents 2,332,048-9 (Oct. 19, 1944). ( 2 ) Bruson, H. -4.. 6.d m .Chem. SOC.,64, 2457-01 (1942). ( 3 ) Bruwn, H . -I., and Rimer, T. TY.,Ihiri.. 64, 2850-F (I949) : 65, 11) Bock. L.
H., and Houk, -1.L. ( t o Iiohiii 6
18-27 (1943). (4) Ho!Iiliaii, J . P..Te'.di{f f f r w w c h . I . , 16, 487-9 ( 1 9 4 j I . (5) Hollihaii. J? P., and N m n . 9 . A , , J r . , ISD. ESG. CHEY.,39, 222 (1947). (6) Koelsch, C..F., J . Am. C'hem. S o c . , 65, 437-9 (1943). ( 7 ) Yarkel. E. C.. and Kenyon, W O., Ihiil.. 64, 121-7 (1942).
