"March 15, 1967.""Institute of Paper Chemistry ... George E. Lauterbach ... Edward J. Jones ... John W. Swanson.

Jones, Edward Jesse.

Lauterbach, George E.

Swanson, John W.

"June 17, 1966.""Institute of Paper Chemistry ... George E. Lauterbach ... Edward J. Jones ... John W. Swanson.

Scholarly Materials And Research @ Georgia Tech

Studies on the factors governing retention and effectiveness of starch xanthates and xanthides by wood pulp in papermaking. Project 2580, report three : a quarterly report to Agricultural Research Service United States Department of Agriculture

"June 15, 1967.""Institute of Paper Chemistry ... George E. Lauterbach ... Edward J. Jones ... John W. Swanson.

Studies on the factors governing retention and effectiveness of starch xanthates and xanthides by wood pulp in papermaking. Project 2580, report seven : a quarterly report to Agricultural Research Service United States Department of Agriculture

"September 28, 1967.""Institute of Paper Chemistry ... George E. Lauterbach ... Edward J. Jones ... John W. Swanson.

Studies on the factors governing retention and effectiveness of starch xanthates and xanthides by wood pulp in papermaking. Project 2580, report eight : a quarterly report to Agricultural Research Service United States Department of Agriculture.

"March 28, 1968.""Institute of Paper Chemistry ... George E. Lauterbach ... Edward J. Jones ... John W. Swanson.

Studies on the factors governing retention and effectiveness of starch xanthides by wood pulp in papermaking. Project 2580, report twelve : a final report to Agricultural Research Service United States Department of Agriculture

Studies on the factors governing retention and effectiveness of starch xanthates and xanthides by wood pulp in papermaking. Project 2580, report six : a quarterly report to Agricultural Research Service United States Department of Agriculture

"March 17, 1966.""Institute of Paper Chemistry ... George E. Lauterbach ... Edward J. Jones ... John W. Swanson.

Institute of Paper Science and TechnologyCentral FilesSTUDIES ON THE FACTORS GOVERNING RETENTIONAND EFFECTIVENESS OF STARCH XANTHATES ANDXANTHIDES BY WOOD PULP IN PAPERMAKINGProject 2580Report TwoA Quarterly ReporttoAGRICULTURAL RESEARCH SERVICEUNITED STATES DEPARTMENT OF AGRICULTUREMarch 17,1966THE INSTITUTE OF PAPER CHEMISTRYAppleton, WisconsinSTUDIES ON THE FACTORS GOVERNING RETENTION AND EFFECTIVENESS OFSTARCH XANTHATES AND XANTHIDES BY WOOD PULP IN PAPERMAKINGProject 2580Report TwoA Quarterly ReporttoAGRICULTURAL RESEARCH SERVICEUNITED STATES DEPARTMENT OF AGRICULTUREMarch 17, 1966I-TABLE OF CONTENTSPageSUMMARY 1INTRODUCTION 2EXPERIMENTALStarch Xanthate 3Sodium Hypochlorite 3Electrometric Titration 3Reaction of Starch Xanthate With Sodium Hypochlorite 4Titration of Starch Xanthate With Sulfuric Acid 4Titration of Hylex With Sulfuric Acid 6Estimation of pKa 7DISCUSSION 8FUTURE WORK 10LITERATURE CITED 10THE INSTITUTE OF PAPER CHEMISTRYAppleton, WisconsinSTUDIES ON THE FACTORS GOVERNING RETENTION AND EFFECTIVENESS OFSTARCH XANTHATES AND XANTHIDES BY WOOD PULP IN PAPERMAKINGSUMMARYThis is the second quarterly report for Project 2580 undertaken incooperation with Agricultural Research Service. The conversion of starch xanthateto starch xanthide appears to be involved in the critical step of the chain ofevents leading to the retention of starch xanthide by wood fibers. Absorption ofthe xanthate form is not a significant factor. This report describes exploratoryinvestigations into the stoichiometry and pH dependency to increase our own under-standing of the xanthate to xanthide conversion.Page 2 Agricultural Research ServiceReport Two United States Department of AgricultureProject 2580INTRODUCTIONThis project was established with the Agricultural Research Service, UnitedStates Department of Agriculture to obtain the basic information that discloses themechanisms governing the absorption of starch xanthate and starch xanthide by woodfibers used in papermaking. We are presenting the second quarterly report of thework undertaken to achieve this goal in accordance with the terms of the contract.The preliminary experiment described in Report One established that starchxanthate is not absorbed by bleached, fines-free, softwood kraft fibers during con-tact times including up to one hour. At the time that report was presented, theanalytical data for the highest fiber constency (1.0%) had not been completed. Thesedata are now available and show no retention of starch xanthate, either with orwithout alum or at acidic or basic pH values.These results are not too surprising in view of the experience in theCereal Products Laboratory of the Northern Utilization Research and DevelopmentDivision. However, these workers do report starch xanthate absorption on unbleachedkraft fibers in the presence of alum (1).The absence of xanthate sorption simplifies the retention study and allowsus to concentrate on the factors involved in oxidizing starch xanthate to xanthideand its absorption on the fibers. The work reported here was undertaken in orderto become acquainted with the conversion of starch xanthate to starch xanthide. Itis our aim to isolate the critical rate-controlling step so that rate studies ofxanthide sorption can lead to deductions concerning the retention mechanisms.Agricultural Research Service Page 3United States Department of Agriculture Report TwoProject 2580EXPERIMENTALSTARCH XANTHATEThe material used for this report came from Ko-Kneader Runs No. 414 and415. It was provided by the cooperator along with the following information:Run No. 414 415Starch g./100 g. 10.1% 9.96%Starch xanthate g./10O g. 10.8% 10.74%D.S. (meq. xanthate/meq.anhydroglucose unit) 0.114 0.122Mole reactants/moleanhydroglucose unit:NaOH 0.508 0.4.94CS2 0.157 0.155SODIUM HYPOCHLORITEA proprietary product, Hilex, containing 5.25% sodium hypochlorite wasused in this work. The stated concentration equals 0.704 molar sodium hypochlorite.ELECTROMETRIC TITRATIONA model N Beckman pH meter was used with the model 41263 glass electrode.The meter was standardized against pH 10 and pH 7 buffers at room temperature. The1.OOON sulfuric acid or Hilex was mixed into the sample by a magnetic stirrer oper-ating at a speed just sufficient to form a vortex "dimple" about a quarter of aninch deep. No provision was made to prevent the escape of gaseous products duringthe titrations.Page 4 Agricultural Research ServiceReport Two United States Department of AgricultureProject 2580REACTION OF STARCH XANTHATE WITH SODIUM HYPOCHLORITEA sample of starch xanthate was neutralized to pH 5.5 and titrated withsodium hypochlorite in the presence of potassium iodide until the persistence ofthe blue starch iodine complex indicated the presence of an excess. This quantityof hypochlorite was the basis for subsequent experiments.When 60 and 100% of the hypochlorite required for the blue end point atpH 5.5 were added to 10% xanthate solutions no blue color appeared at the high pHor after acidification. More hypochlorite was required at acidic pH values for theend-point reaction. It was almost as if the first addition of hypochlorite haddisappeared. The amount of sulfuric acid required for acidification to pH 5.5 wasa little less than would have been required if no oxidation had been attempted.This is reasonable only if hypochlorite is consumed in some way at the high pH levels.The end-point reaction was obtained at high pH (9 to 11) when 500% of thetheoretical amount for xanthide formation was added slowly. This result agreeswith the total amount of sulfur in the sample, including by-products, if it isassumed it all disproportionates to sulfide. Hypochlorite is used for total sulfurdeterminations with cellulose xanthate [(2) p. 998].There was no odor of hydrogen sulfide during most of these titrations.Occasionally the odor associated with carbon disulfide was noticed.These experiments are summarized in Table I.TITRATION OF STARCH XANTHATE WITH SULFURIC ACIDPotentiometric titration of xanthate solutions with acid followed by back-titration with base is a means of estimating the degree of substitution of starchTABLE IOF STARCH XANTHATE WITH SODIUM HYPOCHLORITEKo-KneaderRunNumber414414414414415415415415415StarchXanthateConcn.,%5pHBeforeNaOC15.5pH RangeDuring NaOC1Addition10 12.4 (12.4-12.2)(4.9-6.3)10 12.4 (12.4-12.0)(4.3-6.3)10 5.0 4.7-6.22 8.0 11-72 7.5 (10-9)(7-6)2 5.2 (9-8) (9-8)2 10.6 11.0-8.72 6.2 (11-10)(5.-6.5)NaOCl(%Theory forXanthide)0(100%) Fast(170%) Fast00(116%) Fast(115%) Fast0(100%) FastAdditionTo BlueEnd-PointFastSlowSlowSlowSlowSlowSlowSlowSlowPercent Theoretical NaOClConsumedXanthide Total Sulfur167 30247 452732253102302 8 7 a50019850416246579939aContained 0.25% alum, coagulated at 172% theoretical OC1-.TITRATIONNote-bookPageNo.5458637173757682Page 6 Agricultural Research ServiceReport Two United States Department of AgricultureProject 2580xanthate (3). Our interest in these experiments was not centered on this aspect ofthe procedure. It was hoped that the pH of the half-equivalence points could berelated to the pKa of ionic species possibly involved in xanthide formations.Forty to ninety grams of xanthate solutions were titrated with 1.OOONH2SO4 at 19 to 25°C. The pH of the solution was found to vary with time after eachaddition of acid. Consequently, a schedule for reading pH was established.The potentiometric titration curves usually displayed the double inflectionshown in the description of the analytical procedure (3). However, when using smallincrements of acid and reading the pH just after, and one minute after adding theacid, a third equivalence point was detected at about pH 2.9.The first equivalence point is believed to be due to strong bases, suchas excess NaOH, and the second equivalence point to xanthation by-products (3). Thethird equivalence point at pH 2.9 we attribute to the xanthate groups. It probablyrepresents the completion of the hydrolysis of these groups from the starch. In anyevent, 5.9 milliequivalents of acid were consumed between the second and third points.This can be compared with the 6.2 milliequivalents of xanthate calculated from thedata provided with the sample (Ko-Kneader Run No. 415, four days old). A pKa ofabout 3.5 for starch dithiocarbonate groups can be estimated from the bufferingeffect observed between the equivalence points.TITRATION OF HILEX WITH SULFURIC ACIDThe sodium hypochlorite solution being used in this work (25.0 ml.) wastitrated with l.OOON sulfuric acid at room temperature. An average of 2.0 milli-equivalents of acid were required to reach the first inflection at pH 10.5 and15.5 milliequivalents additional were required to produce the second inflectionAgricultural Research Service Page 7United States Department of Agriculture Report TwoProject 2580at pH 5.1. The observed half equivalence pH is high for sodium hypochlorite andmay reflect the presence of undetermined additives in a proprietary product.ESTIMATION OF pKaThe pKa, or acid hydrolysis constant expressed in reciprocal logarithmicunits, is relatively independent of concentration and corresponds approximately tothe half-equivalence point in acid-base titrations. The estimates of pKa obtainedby titrations are shown in Table II along with some values obtained from the lit-erature.TABLE IIESTIMATED pKa VALUES AND CERTAIN PUBLISHED VALUESCompound pKa 95% Confidence Level aBy-products, xanthation 7.0 + 0.2Starch xanthate 3.5 ?By-products, after Hilex 6.4 + 0.1Hilex 7.5 + 0.1HOC1 7.25H2CO3 first 6.36second 10.25 -H2S first 7.04second 14.92 -Based on range.Page 8 Agricultural Research ServiceReport Two United States Department of AgricultureProject 2580DISCUSSIONA reaction scheme is presented by Ingram and Toms [(4) p. 4336] whichdescribes the decomposition of organic xanthates in the presence of base and tri-thiocarbonate ions to organic alcohol, carbonate ions, and sulfide ions. This schemeis not accepted by some authorities (5). However, we have found it useful in gainingan understanding of the system we are working with.Our data suggest that the ionic species titrated in the by-productsportion of the xanthate curve is sodium hydrogen sulfide rather than sodium tri-thiocarbonate, in agreement with Ingram and Toms (4) and the published pKa values.Treatment of starch xanthate solution with hypochlorite above pH 7apparently removes free hydrosulfide ions since the by-product pKa is lower in sub-sequent titration. The species titrated then is probably the bicarbonate ion.According to Ingram and Toms data (4), mixtures of sodium bicarbonate and sodiumhydrogen sulfide give titration curves more like sodium hydrogen sulfide than likesodium bicarbonate. Consequently, we should not expect to detect both bicarbonateand acid sulfide ions in a mixture by acid titration.If starch xanthide is formed at high pH, then more hypochlorite would berequired than at pH 5.5 specified in the standard procedure for xanthide preparation(6). At higher pH, all the by-product sulfur is present mainly as sulfide or aspotential sulfide by hydrolysis, whereas at low pH varying amounts are lost by theescape of gaseous hydrogen sulfide.If xanthate is to be converted to xanthide, all of the xanthate must reactor it will disproportionate to form carbon disulfide and subsequently trithiocarbonateand then sulfide ions. On the basis of the total carbon disulfide added to theAgricultural Research Service Page 9United State Department of Agriculture Report Tworeaction and the amount of starch xanthate formed, 251% (Run 414) andof hypochlorite needed on the basis of starch xanthate to xanthidebe added to satisfy all the reactive species. This is based on thethat each xanthate equivalent will consume one equivalent of hypochloritemole of carbon disulfide added, but not present as xanthate, will requireequivalents of hypochlorite.Another factor to be considered is that,if sodium trithiocarbonate israpidly with dilute acid, carbon disulfide and hydrogen sulfide are formedinstant of hydrogen sulfide and carbon dioxide (4). This will reduce the amount ofrequired by trithiocarbonate sulfur to 20% of that at high pH. Thus,whe atarch xanthate is neutralized to pH 5.5 (6) before cross-linking, the rate ofacidification can change the amount of hypochlorite consumed by affecting the de-componition of the by-products. It is conceivable that starch xanthate concentrationcould also have an affect by changing equilibrium positions by mass action.The reactants in cross-linking at pH 5.5 may be deduced from pKa valueswith the constituents. Starch xanthate groups (pKa ca. 3.5) are probablyThe hypochlorite is probably present as hypochlorous acidand about 6% hypochlorite. Hydrogen sulfide (pKa 7.04) would be aboutt acid sulfide ion.The question of why pH 5.5 has become established by practice (6) as thefor cross-linking with hypochlorite is puzzling. Not that it has beenthe basis of experience but from the standpoint of what is involved to makedesirable. None of the expected ionic species has a significant bufferingcapacitythis range. Rather it is about half-way between the pH values wherecould be expected. For this reason, acetic acid is specified in the pro-xanthide preparation (6).Page 10 Agricultural Research ServiceReport Two United States Department of AgricultureProject 2580FUTURE WORKWe shall continue to develop our understanding of the conditions peculiarto xanthide formation by hypochlorite oxidation. This will be done to the extentthat is consistent with the needs of the project.LITERATURE CITED1. Swanson, C. L., and Stout, E. I. First report - study of the absorption ofstarch xanthate onto unbleached kraft pulp. Northern Utilization Research andDevelopment Division Report, Jan. 25, 1965.2. Kline, Emil. Cellulose. Ott, Spurlin, and Grafflin Eds. High Polymers. Vol. V.p. 959-1018. New York, Interscience, 1954.3. Swanson, C. L. Procedures for determination of degree of substitution of starchxanthate by strong acid titration. Northern Utilization Research and DevelopmentDivision Report, March 11, 1964.4. Ingram, G., and Toms, B. A. The hydrolysis of sodium trithiocarbonate and itsreactions with ethanol. J. Chem. Soc. 1957; 4328-44.5. Vermaas, D. The xanthations reaction and the ripening of xanthates. Proc.Cellulose Conf., 2nd, Syracuse, 1959. p. 110-26.6. Hofreiter, B. T. Establishing of "Standard" xanthate cross-linking and hard-sheet procedures for NU and Battelle. Northern Utilization Research andDevelopment Division Report, Feb. 27, 1964.THE INSTITUTE OF PAPER CHEMISTRYGeorge E. LauterbachResearch AssociateEdward J. JonesChief, Colloid Chemistry GroupJohn W. SwansonChairman, Physical Chemistry Section

Studies on the factors governing retention and effectiveness of starch xanthates and xanthides by wood pulp in papermaking. Project 2580, report two : a quarterly report to Agricultural Research Service United States Department of Agriculture

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Studies on the factors governing retention and effectiveness of starch xanthates and xanthides by wood pulp in papermaking. Project 2580, report six : a quarterly report to Agricultural Research Service United States Department of Agriculture

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Scholarly Materials And Research @ Georgia Tech

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