-Cellulosetion. The effect is pronounced: The intrinsic viscosity a t 13$% nitrogen is only about two thirds the value for the trinitrate and approximately one half a t 12%.
5
A relationship has been developed which permits the intrinsic viscosity for the trinitrate to be calculated from the experimentally determined viscosity ahd nitrogen content of any nitrocellulose. This relationship makes it possible t o compare the intrinsic viscosities, and hence the degree of polymerization, of nitrocellulose‘samples containing different amounts of nitrogen, so long as the latter is greater than 11.5%. The present best value of the Staudinger constant for cellulose trinitrate dissolved in acetone is 12 x 10-3 dl. per gram for polymer-homogeneous material. For unfractionated samples, the value is greater, depending upon the heterogeneity. ACKNOWLEDGMENT
n
The authors express their appreciation to the A4mericanEnka Corp. for permission t o publish this paper. LITERATURE CITED
(1) Alexander, W. J., and Nitohell, R. L., A?zuZ. Chenz., 21, 1497500 (1949).
(2) Blaker, R. H., Badger, R. XI., and Noyes, R. M., J . Phys. Chenz., 51,574-9 (1947). (3) Chbdin, J., and Tribot, A., Kolloid-Z., 125, 65-72 (1952). (4) Goldberg, A. I., Hohenstein, W. P., and Mark, H., J . Polymer SC~., 2,503-10 (1947). (5) Heuser, E., and Jorgensen, L., T a p p i , 34,450-2 (1951). (6) Husemann, E., and Schulz, G. V., 2. p h y s i k . Chem., B52, 1-22 (1942). (7) Jorgensen, L., “Studies on the Partial Hydrolysis of Cellulose,” Oslo, Trykt Hos Eniil hloestue A/S, 1950. ( 8 ) Jullander, I., Arkiv Kemi,M i n e d . Geol., 21A, No. 8 (1943). (9) Kuhn, H., and Kuhn, W., J . POlylneT Sci., 9, 1-33 (1952). (10) Lindsley, C. H., Ibid., 7, 835-52 (1951). (11) Munster, A., 2. physik. Chem., 197, 17-38 (1981); J . Polynzer SC~., 8,633-49 (1952). (12) Nioolas, L., Assoc. tech. ind. papetihre, Bull. 5, 427-35 (1951). (13) Spurlin, H. M., in “Cellulose and Cellulose Derivatives,” E. Ott, editor, pp. 920 et seq., New York, Interscience Publishers, 1943. (14) Wannow, H. A,, Kolloid-Z., 102,ZQ-34 (1943). (15) Wannow, H. A , , and Feickert, C., Ibid., 108, 103-13 (1944). RECEIVED for review March 30, 1953.
ACCEPTED August 17, 1953
Intrinsic Viscosity of Cellulose REPORT OF THE CELLULOSE DISPERSE VISCOSITY SUBCOMMITTEE A
study of the solvent power and stability of cupriethylene and cuprammonium solvents as a function of the amount of copper and of base has been completed. Work is being started on the preparation of cellulose solutions in the optimum solvents and on the viscosity behavior of such solutions. The Cellulose Disperse Viscosity Subcommittee is considering a tentative method in which results will be reported in terms of intrinsic viscosity and/or intrinsic fluidity. Factors for converting to degree of polymerization will be included. Viscosity measurements will be made at a concentration such that the product of concentration and intrinsic viscosity equals 3.0. Preliminary data indicate excellent reproducibility at a level within 10% of the true intrinsic viscosity. This tentative method is being tested in several laboratories, but a choice of solvent should be made before a standard method is published.
A. F. MARTIN, Chairman 1
Hercules Experiment Station, Hercules Powder Co., Wilmington, Del.
T
HE need for simplification and standardization of methods for determining cellulose disperse viscosity is apparent to all
those working with cellulosics. The Cellulose Disperse Viscosity Subcommittee, now sponsored jointly by the Division of Cellulose CHEMICAL SOCIETY, the TAPPI Chemical Chemistry, AMERICAN Methods Committee, and ASTM Subcommittee D-23, feels that no present standard method is well adapted to the diverse needs of the cellulose industry. Methods suitable for infrequent use in a referee laboratory are too awkward and expensive for use in routine testing in cellulose manufacturing operations. The present methods differ greatly in such features solvents, concentrations, and techniques of measuring viscosity. This report summarizes the committee’s efforts t o date on standardization, emphasizing in particular the necessity for ensuring wide applicability while retaining operating simplicity. The method under development differs SO greatly from present methods that it will supplement rather than completely rep]ace them. The subcommittee must now make a decision concerning the merits of immediate revision and republication of the standard
November 1953
ACS method. This report is concerned entirely with the progress on the new method, The new method will undoubtedly follow in general the standard outline given in Table I, each topic of which has been the subject of correspondence among the members of the subcommittee, DETERMINATION OF VISCOSITY
REPORTING RESULTS. Opinion of committee members is almost unanimous that cellulases be characterized by the fundamental characteristics intrinsic viscosity, ], degree of polymerization (Dp), or intri,?sic fluidity, The method under consideration will give intrinsic viscosity directly. Degree of Polymerization can be determined by multiplying by a factor of about 200, while intrinsic fluidity is merely the reciprocal of intrinsic viscosity. Degree of polymerization is a concept easily understood by nontechnical people who must interpret technical
INDUSTRIAL AND ENGINEERING CHEMISTRY
2491
APPARATUS.Because the final measurements will all be made a t approximately the same viscosity and therefore a t the same INTRIXSIC VISCOSITYAND DEGREE OF POLYXIERIZATION OF velocity gradient (rate of shear), a choice of viscometer is priCELLULOSE marily a matter of cost and convenience. Referee laboratories I. Scope which make infrequent measurements are primarily interested in a 11. Preparation of Cellulose Sample low-cost, accurate instrument, while for routine use the cost of 111. Preparation of Solvent an elaborate viscometer can more than be repaid by increases in a. Apparatus b. Reagents operating efficiency. I t is probable, therefore, that two viscomc. Procedure eters should be specified t o meet the diverse needs. Both d. Analysis should have the same rate of shear a t the 11-cp. observed visIV. Preparation of Cellulose Solution cosity. a. Apparatus For routine use a Brookfield Synchrolectric viscometer (Broolcb. Reagents c. Procedure field Engineering Laboratories, Inc., Stoughton, Mass.) with a 1'. Determination of Viscosity shear rate of about 50 reciprocal seconds appears indicated. a. Apparatus The second viscometer, preferably a capillary instrument, should b. Procedure operate a t this same low shear rate. This qualification rules out c. Reportingrwults the usual Ubbelohde and Cannon-Fenske viscometeI s. However, a modification of the Kagner-Russell viscometer, recently adopted as standard by the Swedish cellulose industry (8), should give satisfactory results. Accuracy within 27, should data (9). Intrinsic fluidity is 3 linear fmction of tei:sile stlength be easy to obtain with both viscometers. Greater accuracy is and other strength properties (9) not warranted because of the other errors inherent in a deterViscosity mensuiements rsill be made at a conPROCEDURE. mination of intrinsic viscosity (6). centration such that the product of concentration and inti irsic With both viscometers it is expected that measurements can be viscosity equals 3.0. Under these conditions, tlir measured viscosity will always approximate 11 cp. (6). In most cases the , obtained by immersing the instrument in the cellulose solution in the bottle in which the solution was made up. The solution conrentration to be used for measurement will be known, because should not have to be protected from oxidation through the use the cellulose has been made to have a specified intrinsic viscosity. of an inert atmosphere duxing viscosity determination. All For celluloses of unknown intrinsic viscosity a pi eliminary determeasurements will be made a t a constant temperature of 25' C. mination will probably be necessary to deternii1.e the correct Concentration for the final measurement.
TABLEI. TENTATIVE ST.4XDARD -4si L Y T I C A L
RIETHOD
FOR
PREPARATION OF CELLULOSE SOLUTION
Prepare a solution of the cellulose in the standard solvent a t an) convenient concentration, using a value of 1% if knowledge of the sample does not suggest a different value. Measure this solution in the standard viscometer (to be chosen). From Table I1 determine an approximate value of [?IC which corresponds to the observed viscosity. Calculate an approximate intrinsic viscosity from this value of [TIC and the concentration that was used. The exact concentration to be used in the final viscosity measurement is obtained by dividing the constant 3.0 by the approximate intrinsic viscosity. Make up a new solufion a t this derived concentration and measure the viscosity again. Calculate a revised intrinsic viscosity from the table. The second viscosity measurement need not be made if the first one is within 2073 of the standard value of approxirnat~ly11 cp.
The method will undoubtedly contain a two-step dissolving procedure in order to cut solution time to 0.5 hour or less. The first liquid to be added to the cellulose will probably be water if a cupriethylenediamine system is chosen or ammonium hydroxide if a cuprarnmonia system is used, A wetting agent will probably be beneficial in either case (a). The second liquid will be concentrated cupriethylenediamine or cupr.ammonium. No precautions will be required to e ~ c l u d eoxygen in the wetting-out stage, but oxidation must be prevented after the strong solvent is added. Oxygen may be removed through the use of an atmosphere of pure nitrogen, but a less complicated
BETWEEX RELATIVE VISCOSITY TABLE 11. RELATIOX
AXD
IXTI~ISSIC VISCOSITY ( [? I )
(e = concentration in grams/100 ml.) [?IC
1
2.350 4.644 8.379 14.280 23.409 37.298 58.163 89.184 134.92
2
3 4 5 6 7 8 9 17
0.0
1.
2.5 2.6 2 7 2.8 2.9 3.0 3.1 3.2
3.3 3.4
2498
0.00
6,2925 6.6719 7.0693 7.4859 7.9220 8.3788 8.8570 9.3574 9.8810 10.4289
0.1
0.2
0 3
2.720 5 257 9.357
2.920 5.586 9.851 16 621 26.990 42,702 66.227
2.530 4.943 8.857 15.027 24,553 39.027 B O . 746 93,008 140.53
2.5,746 40 827 63,432 96.981 146,36
0.01
0.02
6.3297 6.7107 7.1102 7.5285 7.9668 8.4257 8.9059 9,4086 9.9347 10.4849
16,807
6.3668 6,7499 7.1510 7.5714 8.0118 8.4727 8.9554 9,4602 9,9886
10.5416
101.10
132.41
0.03 6.4043 6,7892 7.1922 7.6146 8 0569 8.5199 9.0047 9,5120 10.0429 10.5982
0.5 Values of qrel 3.131 3.3a 6.293 5.931 10.423 11.002 17.471 18.358 28.287 29.639 44.654 46.687 69.134 72.158 105.40 109.86 158.70 165.24 0.4
0.04
0.05
Values of qrel 6.4422 6.4800 6.8286 6.8682 7.2752 7.2336 7.6578 7.7015 8.1478 8.1022 8.6152 8.5674 9.1043 9.0544 9.5640 9.6164 10.0972 10.1619 10.7121 10.6550
0.7
0 6
0.8
0.9
3.586 6,672 11.601 39.285 31.047 43.802 75.303 114.49 172,Ol
3.831 7.069 12.227 20.231 32.516 51.004 78.570 119.31 179.06
4.089 7.486 12.882 21.259 34.044 53.296 81,372 124.31 186.38
4.360 7.922 13.566 23.311 35,638 55,681 85.506 129.32 193.97
0.06
0.07
0.08
0.09
6.5948 6.9885 7.4010 7.8331 8.2868 8,7594 9,2636 9,7743 10.3173 10.8853
6,6330 7.0288 7,4432 7.8776 8.3321 8,8081 9.3064 9,8277 10.3730 10.9434
6.5181 6.9081 7.3168 7.7450 8.1937 8.6632 9.1544 9,6687 10.2067 10.7697
6.5S61 6 . 9482 7 3588 7.7890 8.2397 8.7112 9.2043 9.7214 10.2618 10.8270
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 45, No. 11
Cellulose technique under consideration involves the use of a solution bottle completely full after the second liquid is added (7). I n such a case agitation can be provided by pieces of copper metal, as is specified in the new Swedish viscosity method (8). All solutions will be fluid enough t o make use of a reciprocating-type shaker practical, PREPARATION OF SOLVENT
The choice of solvent is proving t o be the most difficult part of the work of the subcommittee. Both cuprammonium and cupriethylenediamine solvents have favorable and unfavorable characteristics. Because of this choice a n investigation of the problem has been given to a n impartial experimenter, B: L. Browning, Institute of Paper Chemistry, whose work is being sponsored by financial grants from TAPPI.
ethylenediamine t o copper is in the range of 1.92-2.0 to 1. None of the solvent compositions used by Browning satisfactorily dissolved cotton of a high degree of polymerization and cellulose with high hemicellulose content. Further work with cupriethylenediamine seems indicated in the restricted area of solvency. The advocates of cuprammonium solvents recommend consideration of simple preparative methods such as those of Launer and Wilson ( 4 ) . This latter method, however, will not produce copper contents higher than about 10 grams per liter. Modification of the Launer and Wilson method to obtain higher copper contents will be part of Browning’s work during the next year. Other aspects of his work will be a study of the effect on the viscosity of cellulose solutions of small changes of copper and base contents within the optimum areas. Once the choice of solvent is made, it is expected that the analysis and standardization of the solvent will follow the standard well-developed techniques. PREPARATION OF CELLULOSE SAMPLE
COOP.‘
unI t
.
solrent hI e
Two-stage dissolving techniques give latitude in regard to t h e physical form of the cellulose and make reactivity of the cellulose relatively unimportant. The use of oven-dry cellulose will probably be specified. The usual types of cellulose need only to be partially defibered. Exceptionally harsh celluloses may have to be wetted with water and then dried by solvent displacement. SCOPE
COPPER, G R A M S PER LITER
Figure 1. Solvency and Stability of Cuprammonium Hydroxide
U p to the present Browning has studied the behavior of both cuprammonium and cupriethylenediamine solvents as a function of copper and base contents ( 1 ) . The results with cuprammonium are summarized in Figure 1. At high copper and high ammonia contents cuprammonium is unstable even after the addition of sucrose, the usual stabilizer. At copper contents of 20 grams per liter or less, solvent power is poor, so that cottons of a high degree of polymerization and celluloses containing large amounts of hemicellulose are not completely soluble. The optimum area appears t o lie between 22 and 30 grams per liter of copper and below 200 grams per liter of ammonia. I n a two-stage dissolving procedure the final solvent will be weaker in copper content than the second liquid added. As this second liquid added i n the cuprammonium system cannot contain more than 30 grams per liter of copper, it is likely that the optimum solvent will be near 22 grams per liter. Browning’s work has verified the previous conclusion that cupriethylenediamine is a solvent for cellulose only over extremely narrow ranges of copper and base content. Stability is no problem. A plot such as Figure 1 for copper and ethylenediamine would show solvency only in the lower right-hand corner. Solvent power is reasonably high only when the molar ratio of
November 1953
At the present stage of development it appears that the proposed method can be used with celluloses varying widely in degree of polymerization and in hemicellulose content. The physica3 form of the sample is relatively unimportant. The dissolving time can be made so rapid that the method is suitable for both routine and referee use. Two different viscometers can be specified to give identical results and yet fill the needs of many segments of the cellulose industry. Reporting in terms of intrinsic viscosity appears t o satisfy all major users. The error in estimating intrinsic viscosity will be the same for all celluloses, regardless of chain length. Reasonably satisfactory methods could be written in the near future if either cuprammonium or cupriethylenediamine were chosen as the standard solvents. The chairman of the subcommittee recommends that the drafting of this method be delayed until it is sure that the best choice of solvent is made. The possibilities are good of finding a new solution technique which can combine the solvent power and economy of cuprammonium with the convenience of cupriethylenediamine. LITERATURE CITED
(1) Browning, B. L ,Progress Report 1 to TAPPI Chemical Methods Committee, Project 1592 (June25, 1952). (2) Cox, L. A., and Battista, 0. A., IND.ENO.CHEM.,44, 893-6 (1952). (3) Flory, P. J., J . Am. Chem. SOC., 67,2048-50 (1945). (4) Launer, H. F., and Wilson, W. K., Ana2. Chem., 22,455-8 (1950). ( 5 ) Lindsley, C. H., Teztile Research J . , 21, 286-7 (1951). ( 6 ) Martin, .4.F., T a p p i , 34,363-6 (1951). (7) TAPPI, Analytical Method T 206 b9-44. (8) Wilson, Karin, Svensk Papperstzdn., 55, 125-32 (1952). RECEIVED for review March 30,1933. ACCEPTEDJuly 27, 1953.
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