SULFITE PULPS FROM SEVERAL SOUTHERN HARDWOODS

Transcription

1 AGRICULTURE RM SULFITE PULPS FRM SEVERAL SUTHERN HARDWDS July 1942 (RP UNITED STATES DEPARTMENT F AGRICULTURE LFREST SERVICE, FREST PRDUCTS LABRATRY L;-- Mdison, Wisconsin In Coopertion with the University of Wisconsin

2 SULFITE PULPS FRM SEVERAL SUTHERN HARDWDS By J. N. McGVERN, Associte. Technologist nd E. L. KELLER, Junior Chemist Introduction The sulfite pulping experiments on southern cottonwood (Populus deltoides virginin), blck willow (Slix nigr), nd sugrberry (Celtis levigt) described in this report were mde s prt of generl investigtion of the preprtion nd properties of wide vriety of pulps from hrdwoods grown in the Arknss Delt region. The objective of the generl investigtion ws to develop possible uses s pulpwood for the lrge supply of hrdwoods from this region. A study llied to the present experiments ws reported previously concerning neutrl nd cid sulfite semichemicl pulps from number of the Delt hrdwoods, including the bove species (1). ne of the woods, sugrberry, ws lso pulped in connection with the prepr rtion from hrdwoods of sulfite pulps suitble for purifiction to ryon pulps (2). f the three species studied, only the cottonwood hs received ny considerble ttention. Crpenter nd McCll (2) found southern cotton.. wood to be redily pulped by the sulfite process to produce low bleching pulp high in lph cellulose: the purified product prepred from this pulp, however, showed some limittions during conversion to viscose derivtives. This species ws considered by Rue nd Wells (4) to be similr to spen in its pulping chrcteristics. Rue nd Wells-(45- found blck willow to be esily reduced to low.bleching sulfite pulp in yields of 5 to 55 percent; the pulp, however, ws specky. The pulping of sugrberry by the sulfite process hs pprently not been reported, lthough Rue nd Wells (4) found the closely relted hckperry (Celtis occidentlis) to produce light colored, esily bleched sulfite pulp. The objectives in the present study were (1) to prepre sulfite pulps by conventionl mens from southern cottonwood, blck willow, end sugr berry, nd to determine their properties; (2) to compere the southern hrdwood pulps with previously prepred birch (Betul ppyrifer) nd spen (Populus tremuloides) sulfite pulps; nd (3) to Compre the yields end properties of sugrberry sulfite pulps rnging from high yield semichemicl to low bleching pulp. R1149

3 Experimentl Prt The three hrdwoods selected for the sulfite pulping experiments were included in shipment of six Arknss delt species supplied by the Phillips County Chmber of Commerce, Helen, Arknss, nd cut in tht county. The physicl nd chemicl properties of the whole shipment hve been described in detil elsewhere (1, ). Averge vlues for the cottonwood, willow, nd sugrberry re given in tble 1. Representtive logs from ech of the three species were converted into stndrd 5/8-inch chips for the digestions. The sulfite cooking cid used for digesting the chips ws prepred s usul by pssing sulfur dioxide from cylinder into led-lined tnk contining milk of lime. The digestions were mde in stinless-steel cld, stem-jcketed utoclve hving cpcity of 1.5 cubic feet. The pulped chips were defibered with stirrer nd screened through diphrgm screen with.12 inch slots. The conditions for the digestions of the three southern hrdwoods re given in tble 2. Conditions for birch nd spen digestions tken from Previous report (2) re lso included for comprison. All the digestions were mde with indirect stem. ' The results from the southern hrdwood digestions, s well s those from the northern hrdwoods, re found in tble 3. These results include yields, pulp blech requirements, strength, vlues, nd chemicl nlyses of the pulps. In the cse of the southern hrdwoods the results re verges from two digestions for ech species, wheres only one digestion ech is represented by the northern hrdwoods.. The blech requirement vlues re the verge of dt from permngnte number nd single stge hypochlorite determintions, expressed in terms of stndrd blech powder. The strength vlues re given for two freeness vlues, 5 nd 55 cc. (Schopper- Riegler), s interpolted from strength-freeness reltions obtined by beter processing. Stndrd Forest Products Lbortory methods were used throughout. Discussion of Results The Wood The chemicl nd physicl properties of the three southern hrdwoods given in tble 1 indicte certin differences between the cottonwood nd willow on one hnd nd the sugrberry on the other. These differences, s will be shown lter, reflect on the qulities of these species s pulpwood. The cottonwood nd willow were very rpid-growing nd hd reltively low densities but high totl nd lph-cellulose contents. The sugrberry, in contrst, hd medium growth rte nd density, but rther low contents of lph nd totl cellulose. The sugrberry, nevertheless, hd slightly lower lignin content thn the others, lthough it ws somewht high in pentosns nd mteril soluble in 1-percent sodium hydroxide. None of the three woods ws high in mteril soluble in ether. R149-2-

4 Sulfite Pulps from the Southern Hrdwoods Appliction of the pulping conditions outlined in tble 2 to the three southern hrdwoods resulted in the production of sulfite pulps hving blech requirements of pproximtely 12 percent, s shown in tble 3. The pulping conditions to obtin the sme degree of pulping were the sme for the three species except for slightly shorter time, 9.5 compred to 1 hours, for the sugrberry. The shorter time my possibly hve been result of the somewht lower lignin content of the sugrberry in comprison with the other two species. The pulp yields from the cottonwood nd willow were pproximtely the sme high vlue of 52 percent, wheres tht from the sugrberry-ws lower by nerly 1 percent. The lrge difference in pulp yield cn be trced to the sme reltive difference between the woods in their cellulose contents. The chemicl nlyses of the three pulps, nevertheless, showed them-to be very similr in their composition..the, sugrberry pulp hd slightly higher lignin content thn the thers, rheres the willow pulp ws slightly lower, in lph cellulose nd pentosn g.' The chemicl composition of ll the pulps ppered to be typicl for hrdwoods pulped under, the specified conditions. The strength vlues of the equl bleching pulps from cottonwood, nd sugrberry, s shown in tble 3, were the sme for ll the strength chrcteristics, while the sme bleching pulp from the willow hd strength vlues lower throughout thn the others. The low vlues for the willow pulp cn not be explined by ny differences in the chemicl composition of'the three pulps or the originl chips. The strength vlues of the pulps on the whole were perhps somewht low for hrdwood sulfite pulp in generl nd certinly considerbly below the strength of softwood sulfite pulps. The reltively high density of the sugrberry permitted lrger chrge of chips thn possible with the cottonwood or willow. The volume of cooking liquor chrged for unit weight of. chips ws therefore pprecibly lower for the sugrberry thn the others, s indicted in tble 2. The low percentge yield of pulp from the sugrberry, on the other hnd, offset to lrge extent the dvntge of high density. Thus, the yield of pulp for given digester volume would be bout the sme for ll three species. Comprison with. Birch nd Aspen Sulfite Pulps Birch nd spen pulps prepred for purifying to ryon pulps (2) showed certin similrities nd dissimilrities to the southern hrdwood sulfite pulps, s indicted in tble 3. The pulping, conditions for the northern nd southern hrdwoods were the sme except for the low combined sulfur dioxide in the cooking liquor used to digest the birch nd, spen. Apprently, becuse of the low combined sulfur dioxide, the pulping time for the birch nd spen ws considerbly less thn for the southern hrdwoods. The blech requirement of the birch pulp ws the sme s tht of the southern hrdwood pulps, but its yield ws 4 percent lower thn tht of either cottonwood or willow, lthough 6 percent higher thn tht_of the sugrberry. The spen pulp hd very low blech requirement but ws produced in bout the sme yield s were the cottonwood nd willow pulps

5 Although the birch nd spen pulps were mde with n cid low in combined sulfur dioxide, condition fvoring production of pulp with high lph-cellulose nd low pentosn content, they contined bout the sme generl percentge of lph cellulose nd higher percentge of pentosns thn the southern hrdwood pulps mde with conventionl cid. Further, the southern hrdwood pulps hd less thn hlf the mteril soluble in ether contined in the birch nd spen. n the bsis of the chemicl chrcteristics shown in tble 3, the cottonwood, willow nd sugrberry pulp would pper to be more promising pulps for purifying to ryon-type pulp thn the birch or spen pulps. The strength vlues of the willow pulp were pproximtely the sme' s the low bleching spen pulp, wheres those of the cottonwood nd sugrberry pulps were intermedite to the spen nd birch pulps. As might be expected the botniclly relted species, southern cottonwood nd spen, gve pulps in similr yields nd hving firly similr properties. A hrder bleching spen pulp would perhps hve strength properties nerly the sme s the cottonwood pulp. An importnt difference did exist, however, in the mount of mteril soluble. in ether; this vlue ws reltively high in the spen pulp. Sugrberry Sulfite Pulping Cooking conditions for producing sugrberry pulps rnging from well-cooked pulp to prtilly delignified semichemicl pulp nd the properties of these pulps re given in tble 4. The results for the most delignified pulp, number 1, were tken from tble 3; the results for the other pulps were reported previously (1, 2). Although the combined sulfur dioxide in the cooking cid used for number 1 ws higher thn for the others nd the mximum temperture for numbers 3 nd 4 ws lower thn for the others, the min independent cooking vrible connecting these dt ws the cooking time. The effect of cooking time on the yields nd properties of the pulps is plinly evident from the figures in tble 4. The yields nd some of the chemicl nd physicl properties vlues were lso plotted ginst cooking time to furnish the curves in figure 1. There were definite reltions between cooking time nd yield nd mny of the, pulp properties, s shown by the curves in figure 1. The totl yield decresed nd the cellulose contents incresed rther shrply with n increse in cooking time from 4-to bout g 'hours. The chnges were more grdul with cooking time longer thn hours. The lignin nd pentosns contents decresed grdully with cooking time, the over-ll chnge being less thn for yield or cellulose contents. The bursting nd tensile strength nd solid frction vlues incresed shrply s the cooking time incresed from tht producing n undefibered chip to tht producing mteril pproching the defibering point. The chnges in these strength chrcteristics with cooking times corresponding to yields of 55 percent or less were reltively smll. The tering strength vlues nd the times required to ttin certin freeness levels showed no definite reltion to cooking time. It is interesting to note tht digestion number 2, tble 4, ws crried considerbly beyond the point ef, exhustion of the bse in the cooking liquor, but the pulp from it hd considerbly higher blech. requirement R149

6 nd ws less purified thn the pulp from number 1, which ws crried just to the point of,exhustion. It ppered tht n insufficient mount of chemiclws present in number 2 to, omplett the delignifiction nd puri-, fiction before the bse ws exhusted. Summry (1) Sulfite pulps hving blech requirements of pproximtely 12 percent stndrd blech powder nd n verge lph cellulose content of 82.5 percent were prepred by conventionl pulping procedures from southern cottonwood, blck willow, nd sugrberry. The pulp yield from the cotton- -wood nd willow ws 52 percent, wheres tht from the sugrberry ws lower by 1 percent. The strength properties of the cottonwood nd sugrberry pulps ws somewht superior to those of the willow pulp. (2) Comprisonf the-southern hrdwood pulps with birch nd spen sulfite pulps prepred for 'purifying to ryon pulps showed the former to hve the sme lph cellulose content, lower pentosns content, nd lower mounts of mteril soluble in ether thn the ltter. The cottonwood nd willow pulps were produced in the sme yield s the somewht lower bleching spen pulp, but in higher yield thn the birch pulp. The birch pulp showed higher vlues for strength properties thn the others. (3) Sugrberry sulfite,pulps tovering the rnge from semichemicl pulp produced in 4.2 hours to ' low bleching pulp produced in 9.5 hours showed consistent reltions between pulping time nd yields nd properties of the pulps. An increse in pulping time cused decreses in pulp yield nd lignin nd pentosns contents nd increses in the totl nd lph cellulose content of the pulps nd their bursting nd tering strength nd solid frctions. The lrgest prt of the chnges occurredwhen the time ws incresed from 4.2 to 6.5 hours. References (1-) McGovern, J. N. nd Chidester, G. H. Semichemicl pulps from Arknss Delt hrdwoods. Problem B-2; project Mimeogrphed report. (2) Nihl4n, Hugo. Preprtion of ryon pulp from hrdwoods. Problem B-22; project Mimeogrphed report. (3) Crpenter, Chrles nd McCll, Frnk. Progress in hrdwood pulping for viscose ryon.. Ryon Textile Monthly 19 (9, 1): 538-9, (Sept., ct. 1938) (4) Wells, S. D. nd Rue, J. D. The suitbility of Americn woods for pper pulp. U.S.D.A. Bull (1927) (5) Pew, J. C. nd Schfer, E. R. Physicl nd chemicl properties of Arknss Delt hrdwood pulpwoods: sugrberry, sh, bitter pecn, cottonwood, willow, nd elm. Problem D-189; project Mimeogrphed report. R1149

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