Hvdrolvsis and Catalvtic Oxidation. of Cellulosic Materials J
J
J
Hydrolysis of Mercerized Cottons R. F. NICKERSON Mellon Institute, Pittsburgh, Penna.
The effects of mercerization on cotton are described in terms of hydrolysis rate data obtained by digestion of samples in hydrochloric acid-ferric chloride reagent and measurement of the carbon dioxide evolved. Mercerization ratios derived by this method are in agreement with those established by other means. The data indicate that both mercerized and unmercerized cottons consist of an easily hydrolyzed, or amorphous, component and a more acid-resistant component which may be the crystallites. Mercerization appears to increase the proportion of amorphous cellulose and to render the crystallites more susceptible to hydrolytic attack.
sodium hydroxide-1 per cent penetrant solution a t room temperature, and then through several changes of water until the swelling tension relaxed completely. Finally the skein was removed from the apparatus, washed thoroughly with water, subjected to 1 per cent acetic.acid for 10 minutes, washed again several times with water, and dried. Mercerization without tension was accomplished by agitation of loose dewaxed skeins of yarns for 3 minutes in a portion of the same alkali-penetrant solution. The washing and souring treatments were conducted in the manner described. The final step in the preparation of samples was purification to remove interfering pectates and other organic matter. Dry, loose, dewaxed skeins which represented each type of yarn and treatment were boiled simultaneously for 4 hours in a countercurrent of fresh, aqueous, 2 per cent sodium hydroxide. Air was excluded during this operation, and the solutions were preheated to expel dissolved oxygen. After the 4-hour scouring period, the samples were washed with boiling distilled water, placed in 1 per cent acetic acid for an hour, washed again, and air-dried. The procedures followed in the determination of rates of hydrolysis and hygroscopicity of cellulosic materials were given in detail in the previous papers (6, 7). The former Consists in refluxing a %ram cotton sample in 150 ml. of a stock mixture of hydrochloric acid and ferric chloride (2.45 N HC1 and 0.6 M FeCld, collecting and titrating the evolved carbon dioxide in barium hydroxide, and converting the rates of carbon dioxide formation to percentages of cellulose hydrolyzed to glucose* The hygroscopicity is m@3L3ured by the Percentage moisture uptake of a vacuum-dried sample exposed for 24 hours to atmospheric conditions of 21' C. and 65 per cent relative humidity.
RECEDING papers in this series described a method for the study of structure of cellulosic mat&& (6) and natuto gave data obtained from its ral cellulases and derived products (7). Rates of hydrolysis are calculated from carbon dioxide output of cel~u~osic materials in an aqueous acid-catalyst mixture. The present investigation is designed to show tile more or less well known effects of mercerieation in terms of measurements made by this method.
P
Materials and Methods
Mercerization Data
The cottons chosen for the investigation were raw P ~ Y yarns from commercial stocks: Designation
A B
c
D
Type of Cotton Egyptian North American North American
...
Growth Season
liiS 1937
..
Yarn
Construction
42/3 3612 36/2 60/2
A number of 10-gram skeins of each of these yarns was extracted (Soxhlet), first with ethyl alcohol for 6 hours and then with benzene for a similar period. The dewaxed skeins were air-dried. Mercerization with tension was effected in the following way: a dewaxed skein, held fixedly at its original length between two pulleys in a laboratory mercerizing apparatus, was passed as a belt rapidly for 3 minutes through a 25 per cent 85
carbon dioxide evo~ution-time data for glucose and a soda-boiled cotton (B) are plotted in Figure 1. After an initial induction period, glucose evolves carbon dioxide rapidly and, for practical purposes, in a linear fashion. Previous work showed that a similar lag between the addition of glucose and the appearance of carbon dioxide occurs even when glucose is introduced in the course of a run. Consequently, additions of glucose precede the appearance of carbon dioxide by a time interval for which correction can be made in the calculation of results. The curve of a typical cotton cellulose under identical conditions is included in Figure 1 for comparison. Raw data corresponding to unmercerized and mercerized samples of one of the cottons (A) are also presented in Figure 1. It is clear that the carbon dioxide output is least for the unmercerized, is considerably greater for both the mercerized
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INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 34, No. 1
OF D I G E S T I O N
FIGTJR~: 1 (Above). DIRECTPLOTOF CARBON DIOXIDE-TIME DATA FIGURE 2 (Right). CARBON DIOXIDE EVOLUTION DATAFOR Two DIFFERENT COTTONS PLOTTED AGAINST A POWER FUNCTION OF TIMECORRECTED FOR AN IKDUCT~ON PERIOD
types, and, by a small margin, is greatest in the case of the sample mercerized without tension. The same relation among the differently treated cottons was observed in all four cases studied. The raw data shown in Figure 1 (upper) are corrected and presented in Figure 2, a more useful form for calculation. Correction involves the subtraction of the induction period from each time of observation. The carbon dioxide totals are then plotted against a power function of the corrected time. As Figure 2 shows, this treatment yields an approximately linear
relation over a considerable part of the breakdown period. The last part of the relation is indicated by a dotted line to emphasize its rapid divergence from linearity. A similar plot for one of the other cottons (C) is shown in Figure 2 also. The same relation obtains again, but the divergence from linearity toward the end of the digestion period is less rapid than in the previous case. These two sets of data represent the extremes; the two cottons (B, D) not shown in Figure 2 gave qualitatively the same types of curves with intermediate degrees of divergence.
January, 1942
INDUSTRIAL AND ENGINEERING CHEMISTRY
It has been demonstrated that, corrected only for the induction period and plotted directly as in Figure 1, glucose yields essentially straight lines whose slopes are directly proportional to the glucose concentration in the system (6). By means of this relation the glucose set free during the acid digestion of cellulose can be estimated readily. The slope of the cotton curves at any time in the linear interval (Figure 2) is the first derivative of the function plotted; that is, = 1.5 K d T 7 dT where T = observed time = induction period for acid-catalyst solution 01
Slopes of the nonlinear portions of the curves can be approximated by the direct methods of analytical geometry. The apparent percentage of cellulose converted to glucose is given by 100 times the ratio of the observed slope, corresponding to 1 gram of cellulose, and the slope for 1.11 grams of glucose under identical conditions-i. e., the observed slope to the slope for the complete breakdown of anhydroglucose to glucose. This relation over the linear interval then takes the form:
% cellulose hydrolyzed
=
[l.;"l"sJ [1.5K 4-1
87
also that the instantaneous rates of hydrolysis decrease rapidly with time and finally become very slow. The behavior of the other cottons (B, D) is of the same general nature. Thus, regardless of treatment, the cottons act as if they were constituted of two fractions, a more or less readily hydrolyzable part and an acid-resistant residue. Mercerination appears to increase the readily available fraction. The K values, corresponding to the velocity constants for the linear hydrolysis in Figure 2, were calculated and are given as ratios in Table I. The relative effects of mercerization, with and without tension, on the velocity constants of the untreated cottons are clearly demonstrated. It can be seen that, despite the fact mercerizing conditions were held as uniform as possible, considerable differences in ratios develop among the individual cottons with either type of mercerization. On the other hand, the without-tension to with-tension ratios of the mercerized cottons appear to be constant within the experimental error and indicate that tension has a relatively fixed effect. TABLEI. RATIOSOF K VALUESOF MERCERIZED AND UNMER-
(2)
CERIZED COTTONS Mercerized (Mercerized (Mercerized wit6out Tension)/ with Tension) without Tension)/ (Mercerized with Unmercerized Unniercerized Tension)
Yarn
where So = slope for 1 gram of free glucose The remaining nonlinear interval can be converted similarly by substituting the estimated slopes for the second bracket in Equation 2. The percentages so calculated are plotted against (T - a),the corrected time. Apparent percentages of cellulose hydrolyzed to glucose, obtained in the manner just described, are shown in Figure 3. These curves arise from the carbon dixoide-time data of Figure 2. The asymptotic character of the time-percentage breakdown relation is indicated both by the ultimate straightening of the raw data curve (Figure 1) and by the divergence from linearity of the power function (Figure 2). It is evident
The variation of velocity constant, K , with hygroscopicity is given in Table 11. I n the determinations of moisture the twelve samples were kept in parallel throughout and, consequently, are strictly comparable. The absolute values of K depend upon the acid-catalyst concentrations but, since this factor was a constant for the series, these results also are comparable within the experimental error.
TABLE 11. VARIATION OF K VALUES WITH MOISTURE UPTAKE Unrnercerized Moisture uptake,
I
40 COTTON A
Yarn
K
%
A B C D
0.081 0.069 0.061 0.063
7.68 7.72 7.75 7.65
Merperized ,with Tension Moisture Moisture uptake,
K
0.105 0.095 0.093 0.101
% 9.05 9.58 9.57 9.70
Mercerized w,ithout Tension Moisture Moisture uptake,
K
0.113 0.103 0.100 0.108
% 10.24 10.58 10.74 10.83
It has been found that the actual amounts of undissolved cellulosic residue recoverable a t the end of the digestion period agree favorably with the amounts calculated from the foregoing relations. Discussion of Results From Figures 1 and 2 it is apparent that mercerization efCOTTON C fects a substantial increase in rate of evolution of carbon dioxide from cotton cellulose. Since this increase probably originates in a greater availability of glucose, these observations indicate that strong alkali converts acid-resistant cellulose of native cotton to a more easily hydrolyzed form. This conversion could represent either an increase in amount of less dense, amorphous cellulose, a greater chemical reactivity of the denser crystalline cellulose, or both. The evidence suggests that both of these changes occur. It is assumed that the initial rapid hydrolysis of celluloses involves principally the amorphous or finely divided fraction H O U R S OF DIGESTION which presents maximum surface per gram to the hydrolyzing medium, and that the subsequent slower breakdown depends CURVESOBTAINEDBY CALCUFIGURE 3. HYDROLYSIS-TIME upon the more resistant, more protected crystalline aggreLATION INDICATE TEE NATURE AND EXTENT OF BREAKDOW~ gates of cellulose. Larger amounts of amorphous cellulose BEFORE AND AFTER MERCERIZATION a 0 >
I
0
i
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INDUSTRIAL AND ENGINEERING CHEMISTRY
in the mercerized cottons are indicated by the upward displacement of the “knee” of curves in Figure 3 and by the greater intercepts obtained upon extrapolation of the flattened portions of these curves to zero time. Sisson and Saner (8) observed that a crystallite-to-amorphous conversion may occur during mercerization. It is possible, therefore, that new amorphous cellulose may be formed as a result of incomplete reversion to the original amorphous-crystallite distribution. An enhanced chemical reactivity of the crystalline component of cotton cellulose would explain the progressive divergence of curves for mercerized and unmercerized cottons in Figure 3. After 4 hours of acid digestion about 80 per cent of the unmercerized and about 70 per cent of the mercerized cotton appear to remain unhydrolyzed, yet the smaller residue breaks down the more rapidly. This suggests that mercerization increases the susceptibility of native crystallites to acid attack. X-ray evidence has shown that mercerization alters the native crystalline pattern and produces slightly expanded crystals. These lower density crystals and the new amorphous cellulose formed as a result of the process would account for the higher specific volume of mercerized cotton as compared with native fiber (1). Measurements by the present method indicate that tension retards or inhibits the development of maximum effects. This is shown by both the various hydrolysis curves and the data in Tables I and 11. Apparently, tension opposes the tendency of the fibers and yarns to shorten and restrains the lateral swelling of fibers. I n other words, the separation of anhydroglucose chains in a direction perpendicular to the fiber axis is limited; as a result, a higher density, more acid-resistant, and less hygroscopic product is obtained than in free swelling. One effect of tensions of the order employed may be to restrict the formation of amorphous cellulose, but there may be others.
Vol. 34, No. 1
The ratios in Table I are derived from K values which are directly proportional to initial breakdown velocities. A survey by Neale (5) suggests that the measurable properties of cellulose, except strength and cuprammonium viscosity, are increased by mercerization in about the ratio 1.5 to 1. The present values do not differ greatly from this more common ratio. A fair correlation between K values and moisture-regain percentages is evident from the data in Table 11. This indicat’esa parallelism between the entrance of water vapor and hydrolytic liquid into the fiber, and may mean that hydrolytic attack involves mainly the surfaces and capillaries where moisture is adsorbed. There are reasons for supposing that continuity of fiber structure is supplied by amorphous links between the discontinuous crystallites (2, 3, 4 ) . The present observations suggest that the amorphous links are augmented by mercerization. The dependent properties may be increased in proportion. A more complete characterization of different celluloses by means of the hydrolysis-oxidation method is in progress.
Literature Cited (1) Davidson, G. F., J . Tertile Inst., 18, 175T (1927). (2) Frey-Wyssling, A., “Submikrosoopisohe Morphologie”, Berlin,
(3) (4) (5) (6) (7) (8)
Gebruder Borntraeger, 1938. Kratky, O., Silk and Rayon, 13, 480, 571, 634 (1939). Mark, H., J . Phys. Chem., 44, 764 (1940). Neale, S. M., J. SOC.Chem. Ind., 50, 177T (1931). Nickerson, R. F., IND.ENQ.CHEM.,ANAL.ED., 13, 423 (1941). Nickerson, R. F., IND. ENQ.CHEM.,33, 1022 (1941). Sisson, W. A., and Saner, W. R., J. Phys. Chem., 45, 717 (1941).
PRESENTED before t h e Division of Cellulose Chemistry at t h e lOlst Meeting of the AMERICAN CHEMICAL SOCIETY, S t . Louis, Mo. Contribution X X X I V from t h e Cotton Research Foundation Fellowahip, Mellon Institute.
Patent Liti ation in 1940 an NELSON LITTELL Hammond & Littell, New York, N. Y.
T
HE last two years in the field of litigation concerning patents and their uses have been characterized by numerous suits and prosecutions under the antitrust laws to stop alleged improper uses of patents for the control of prices and competition. The effect of this litigation has been to clarify somewhat the border line between lawful and unlawful exercises of patent rights under the antitrust laws, but it may be said that there still remain many conflicts between existing “court law” and the attitude of the government departments charged with the enforcement of the antitrust laws as to what may be done lawfully in the exploitation of patent rights. In the case of Ethyl Gasoline Corporation v . United States of America (309 U. S. 436) the Ethyl Gasoline Corporation had made license agreements with most of the principal producers of gasoline for the production of gasoline treated with tetraethyllead under its various patents. It had also made license contracts with approximately 11,000 of 12,000 jobbers handling gasoline throughout the United States, the effect of which was to license the jobbers to sell “Ethyl” gasoline purchased from licensed refiners and to subject the jobber to possible cancellation of his license contract in the event of violation of the terms of the license contract. While the jobbers’ licenses were not shown to have been canceled because
of failure to maintain the policies and prices of the refiners, the effect of the jobbers’ license contracts was to give the Ethyl Gasoline Corporation the right to cancel the contracts for failure to observe any conditions specified therein. The Court held that the license to the refiners to produce “Ethyl” gasoline had exhausted the patent rights, that the license to the jobbers to sell the gasoline which had been produced by the refiners under the license was beyond the scope of the patent monopoly, and that the jobbers’ licenses were therefore a n illegal extension of the monopoly. The Court, however, set forth (page 456) the criteria which distinguish between the proper and improper uses of a patent under the antitrust laws in the following language: The patent law confers on the patentee a limited monopoly, the right or power to exclude all others from manufacturing, using or selling his invention (Rev. Stat. See. 4884, 35 USCA Sec. 40). The extent of that right, is limited by the definition of his invention, as its boundaries are marked by the specifications and claims of the patent (Motion Picture Patents Company u. Universal Film hIanufacturing Company 243 US 502, 510, 61 L. ed 871, 876, 37 S Ct 416, LRA1917E 1187, Ann Cas 1918A 959). He may grant licenses to make, use or vend, restricted in point of space or time, or with any other restriction upon the exercise
