1178
INDUSTRIAL AND ENGINEERING CHEMISTRY
I n the case of p-toluene methylene sulfonamide there was considerable peeling off of the film just before the film was rated as completely failed. It is somewhat difficult to interpret such exposure tests, because the weather resistance depends not only on the stability of the plasticizer, but on other factors such as the adhesion to the metal surface, etc. The following relationships appear to hold, however: (1) The ethyl derivatives show superior resistance to the methyl derivatives. ( 2 ) . The methylene sulfonamide shows a weather resistance superior to the simple alkylated derivatives.
Vol. 21, No. 12
Correlation between Various Properties
A study was made of Tables 11, 111, and IV in connection with Table VI to see if there was any relationship between the resistance to exposure and the retentivity, light fastness, or tensile strength. S o general relationship is apparent. The nearest approach to it is in the similarity between light fastness and resistance to exposure. That some rough relationship may exist is quite probable, because it is the actinic light rays which cause the breakdown in light fastness and which are also a major factor in the breakdown of exposed films.
Control of Viscosity of Solutions of Cellulose’” Fred Olsen3 and H. A. Aaronson CHEMICAL RESEARCH LABORATORIES, PICATINNY ARSENAL, DOVER,N. J.
I
N RECENT years much attention has been focused upon
~
that property of cellulose which is responsible for the consistency of dispersions of cellulose or its esters in various solvents. I n the manufacture of smokeless powder, for example, variations in ballistics have been found in lots of powder which were manufactured as nearly as possible in accordance with the same recipe and where the chemical analysis failed to reveal any difference between the patches of powder. Some of the variations have been traceable to some property of the original cellulose from which the nitrocellulose was made-namely, that property which apparently can be measured by determining the viscosity of solutions of that cellulose. When nitrocellulose is made from a sample of cellulose which yields cuprammonium solutions of relatively low viscosity, thin gels are produced when the normal amounts of solvent are employed; and similarly, when cellulose yielding cuprammonium solutions of high viscosity (so-called high viscosity cellulose) is used, stiff nitrocellulose gels will be produced with the same amount of solvent. The thin gels shrink more than the normal and the thick gels shrink less than the normal, so that the powder grains produced from these different specimens of nitrocellulose will be found to vary considerably in dimensions, a condition responsible for variation in ballistics. An effort has been made to correct for variations in the viscosity characteristics of cellulose and nitrocellulose by regulating the amounts of solvent used in the gelatinizing steps in the manufacture of smokeless powder, but this is a t best a very unsatisfactory condition. Present practice is to purchase cellulose under specifications which limit the viscosity variations of the cellulose. Much effort has been expended during the last few years in arriving a t appropriate limitations of viscosity of cellulose and of nitrocellulose for use in the manufacture of propellent powder and also in devising suitable means for measuring the viscosities of solutions of cellulose and nitrocellulose. Similar control is practiced by the manufacturers of nitrocellulose for use in lacquers, and it is understood that the control of viscosity of cellulose is an important feature in the manufacture of rayon and of other cellulose or cellulose ester products. 1 Presented before the Division of Cellulose Chemistry at the 78th Meeting of the American Chemical Society, Columbus, Ohio, April 29 t o M a y 3,1929. E Published by permission of the Chief of Ordnance, U. S. Army. a Present address, Western Cartridge Co., East Alton, Ill.
Action of Acids o n Cellulose
The action of not only nitrating acids but of other acids upon cellulose has been studied a t Picatinny Arsenal for several years, and investigations have been conducted there on the action of sulfuric or hydrochloric acids upon cellulose with the purpose of making “hydrocellulose.” It was desired to obtain cellulose in the form of an extremely fine or even impalpable powder, and protracted digestion of cellulose with dilute sulfuric or hydrochloric acid was employed. The exceedingly low viscosity characteristics of solutions of this material are well known. Microscopic examination of the hydrocellulose shows that, although the cotton hairs have apparently been split up into a great number of pieces of very short lengths, yet nearly all of the physical appearance of the fibers has been retained. (Figure 1) Chemical analysis of hydrocellulose and of material from the intermediate stages in the preparation of hydrocellulose reveals the fact that degradation of cellulose has taken place, the alpha-cellulose content being very markedly reduced. The action of these acids was found, therefore, to be one in which the physical disintegration of the fiber and the corresponding chemical degradation of the cellulose occurred simultaneously. The hypothesis was formulated that the mechanism of the action between acids and cellulose comprised, first, the destruction of those forces which hold the cellulose molecules together in the form of aggregates of colloidal dimensions, and second, the chemical hydrolysis of cellulose. It is the present conception that the cellulose fiber is ordinarily made up of colloidal particles the size of which is not constant, but depends upon the kind of vegetable matter, the conditions under which the plant grew, and the subsequent processing steps. Upland cotton, for example, gives solutions of entirely different viscosity from lowland cotton when the solutions are prepared under identical conditions; ripe cotton differs from unripe cotton; and even if the original raw cotton was as nearly homogeneous as possible, the properties of dispersions of cellulose are found to vary with the conditions of processing, such as time, temperature, and concentration conditions in soda digestion, bleaching, etc. It was pictured, however, that whatever might be the size of the colloidal particle, the action of dilute acid appeared to be to sever with great readiness some of the bonds which held the cellulose aggregates together, and it was conceived that conditions ought to exist which would permit a severance of these bonds to any extent under conditions in which the
1
a
3
4
Flaure I-ERoct
of Acid on Cotton Fibers.
clicniicd dcgradntiori of tlre celliiluse would be i i iriini,liiim. A study vim therefore ninde of the action of acid iipoii ccllulose, the time of treatment, the teinper:iture, and the colicentratioii of the acid heiiig varied independcnt>ly. Cotton l i n k s were ordinarily used, biit the effects were fouiid t,o be similar witli wood or strnw cciliilose ( 1 ) . Experimental Results
Figures 2, 3, aiid 4 slms tlie cffcct (if time factors upon tire viscosity of cupr:inioioniiiin solutions of cellulose. Viscosity was determined by a Storimr viscoriieter at 20" C. using 2 grams of cot,toir in 100 gram3 of eupr:iiiirnoniuni solution eontaiiiiiig 3 per cent copper, 16.5 per writ amrrioni:i, and 1 pcr cent sugar. It, will be seen that :is tire concentrntiurr of acid is iiicrenscd up to 10 per cent tiit: As t,lietempcrature increases to 10 idly decrcases; and finally, as the time of t,reatmriit increases to 24 hours, the temperature being 50- 60" C. and the concentration of acid being about 5 per cent, the viscosity again rapidly decreases. Examination of the effect of tlrcse fiictors upoii the iilphacellulose coirtent, however, showed that it was possible to
x
50
operate under conditions which result in very little degradation of celliilase, and which nevertheless produce a very marked reduction in viscosity. Figures 5 , 6 , and 7 show the varixtioii in alplia-celiulose content with variations in concentration, tnnperat,ure, and time of treatment. From a study of tlrcse curves it is possible to pick out tlie ex& coiiilitions which will result iri a desired viscosity witti the iiiiniiriuru reduction in the clmnical purity of the material. It may be poiiitcd out that physical degradation of the cellulose may occur to a considerable extent without any visual chungt in form. Tlie action of tire acids reduces the size of the colloidal particles, so that the apparently uiichangcd fiber consists of a larger nuriiher of smaller colloidal particles, and is, of course, weakeiied thereby. Practical Considerations
Certain practical coilsiderations teiid toward the selection of soiiic of the conditions for viscosity control in preference to others. For rxtmiple, a 5 per cent sulfuric acid solution at 50" C. will cause a reduction in the viscosity of 2 per cent cuprarnnroniuni solutions of cellulose from, say, 4000
INDUSTRIAL AND ENGINEERING CHEMISTRY
1180
45
50
Figure 2
Vol. 21, No. 12
55
60
65
I 30
40
Figure 3
OFTME OFJT~EPIIYG CELLULOSE ln5%H2.30+ SOLUT/DN ON THEL/lSCOSlTY of A Z % CUPR4M M OIYIUM 50LUTlON OF THETEEaT€D CCLLULOJC. € C T
Q 70
0
IO
LO
30
40
50
Figure 5
Figure 4
45
,
so
TEMPERITURP 55
'c. 60
65
I /O
I 20
I
Figure 6
Figure 7
centipoises (about the highest value for high-grade linters) down to about 50 centipoises in times up to 16 hours. This is approximately an overnight soaking and one hour more or less does not produce any marked effect. This, of course, means an easier plant control than would be possible if higher temperatures and stronger concentrations were employed for very short times. If the period of treatment is very short, there is usually an appreciable difference in time between the removal of the first and last portions of cellulose from the tub in which the soaking has taken place, resulting thereby in less uniform conditiom of viscosity. If, however, equipment is available in which a continuous processing could take place, such as a screw conveyor, in the course of a reasonably short time the cellulose could be passed through an acid bath and discharged to a continuous centrifuge which will rapidly remove the
acid liquors. With such equipment more drastic conditions of temperature and concentration could be employed if the necessary close control of these conditions could be provided. Since it has been pointed out that cotton from various localities, and grown under various climatic conditions, produces cellulose of varying viscosity characteristics, it is necessary, in applying the time, temperature, and concentration conditions to effect the desired control of viscosity, to determine previously the character of the cellulose being processed by tests upon a carefully selected representative sample. Because of these variations in the character of the raw cotton, it is usually more convenient to keep the temperature and concentration conditions constant and to bring about the desired control of viscosity by varying the time of the treatment, and for purposes of convenience to have this time ap-
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1929
1181
has been studied, and it has been found that the action of acid is such that the colored matter is very much more readily removable in the subsequent bleaching steps so that more brilliant whites are secured with less drastic bleaching and, hence, with a lower degree - of degradation of the cellulose.
proximately 16 hours, since in a processing step of this duration small changes in time are not significant, and control is thereby more easily effected. Effect of Acids on Colored Matter i n Cellulose
I
Concurrently with these investigations the effect of acids upon the colored matter in cellulose, especially in cotton linters which had been purified by the customary soda boils,
Literature Cited (1) Olsen a n d Aaronson, U. S. Patent 1,615,343 (January 25, 1927).
Fermentation Products of Cellulose' C. S. Boruff with A. M. Buswell ILLINOISSTATEWATBESURVEY DIVXSION,UREANA,ILL.
I
N WORKING on the products resulting from the anaerobic
As a gas containing 50 per cent methane has a calculated heat value of 500 British thermal units per cubic foot (coal gas runs 525-550), it seemed worth while to see whether or not crude plant material could be converted into gas in sufficient quantities to be of practical importance. Naturally, being in the heart of the Corn Belt, the material selected was cornstalks. The results were favorable (Table 111). Four digestion mixtures were prepared with cornstalks which had been shredded, soaked, boiled, and soaked in lime, respectively. The cornstalks were decomposed to the extent of 35 to 50 per cent and an equivalent weight of gas was produced. The rate of gas evolution from the eight grams
decomposition of biologic waste material, the writers, with others ( I ) , have observed that the reactions, which are brought about by bacteria, cause the formation of considerable amounts of gas. This gas is principally methane and carbon dioxide, with small amounts (3-5 per cent) of hydrogen and nitrogen, the latter probably from solution in the liquor. The ratio between COZand CHd varies from about 1:lO to 1 : l when air is excluded and sugars are absent. In attempting to explain this variation in gas composition we have carried out experiments using various selected materials of known composition. T a h l e I-Cellulose
Digestion Balances
1
VOLATILEMATTER DIGESTIONCOMPOSITION
+ ++ + +
Filter paper (inoculum 9.56 grams, d r y basis) 1 0 . 4 2 9 grams, dry basis) Cotton (inoculum 9.3 grams, d r y basis) Toilet paper (inoculum 10.12 grams, d r y basis) Wood pulp (inoculum 13.777 grams, d r y basis) Kotex (inoculum 2460 cc. Inoculum (200 cc. digested sludge settled sewage)
+
I
A t close
Gasified
Grams 15.447 16.316 14.807 15.855 19.5676
Grams 6.515 7.00 9,051 12.983 6.5611
Grams 8.932 9.316 5.756 2.872 13.0065
7.038
5.804
1.234
Our preliminary work on the digestion of cellulose, summarized in Table I, showed that the material decomposed or digested was converted practically quantitatively into gas and that the ratio between COZ and CH4 was about 1:1,5, except in the blank where it was 1:8.3. The simplest equation for the decomposition of cellulose would be C6H1008
+ HzO ---f 3COz + 3CH4
According to this equation, the C02:CH4 ratio should be 1 : l . When the organic matter in inoculating material is reduced to a relatively small value, this ratio becomes practically the theoretical for the equation given (Table 11).
I
HI
CH4
C%:CH4:Ha
GAS
N2
COz:CH4
Cc.
Cc.
Cc.
2864 2961 1786 733 4756
3953 4440 2835 2083 5710
223 320 233 99 26
Grams 8.48 9.019 5.562 2.946 13.4534
12.9:17.7:1 9.3:13.9:1 7.6:12 2:l 7.4:21.0:1 18.2:21.8:1
1:1.4 1:1.5 1:1.6 12.8 1:1.2
114
944
38
0.90
3 . 0 : 2 4 , 8 :1
1:8.3
of cornstalks used is shown in Figure 1. The best results were obtained with material which had been soaked in lime water. T a b l e 11-Cellulose
DIGESTION COMPOSITION
0
b c
D i g e s t i o n B a l a n c e Sheet
Lz&?'Dk5h2coz: GAS
VoLATILE
At start
At close
I
+
Inoculum filter paper Inoculumb f toilet paper
1 Presented before t h e Division of Agricultural and Food Chemistry a t t h e 78th Meeting of t h e American Chemical Society, Minneapolis, Minn., September 9 t o 13, 1929.
T a b l e III-Di-2estion
1
COS
Gasified -
COz.
CHa:Hz
cot: CHI
1
Grams Grams Grams
Cc.
12.950''
Grams
2.466
10.484
7734
9.367
12:ll:l
1i0.94
1 2 . 3 1 3 ~5 . 5 4 4
6.769
5560
6.728
12:12:1
1:l
-
Of this, 3 . 3 9 0 grams are inoculum and 9 . 5 6 0 grams are paper.
H g from gas seal sucked into digestion bottle. Digestion not complete. Of this, 3 . 3 9 0 grams are inoculum and 8 . 9 2 3 grams are paper.
of C o r n s t a l k s
DIGESTIOKMIXTURE ~
-4
Inoculum S grams cornstalks Inoculum 8 grams cornstalks Inoculum 8 grams cornstalks Inoculum S grams cornstalks Inoculum comoosition i
+ +
Shredded Shredded, 4-day water !:oak Shredded, %hour water boil Shredded, 4-day lime soak, neutralized
......
Grams 14.006 14.006
14,006 , ,
fi
..
onoc
Grams 4.275 4.597
4,904
...
1 21
Grams 3.974 4.710 5,068 6.732 1 21
~~~
cc. 3282 3870 4057 5600
1026
Grams 2.691 2.833 2.848 4.688
These weights are all too low owing t o difiiculty in completely separating the fibers from the sludge, b Inoculum composition: 50 cc. active sewage sludge, 650 cc. settled sewage, 300 cc. distilled water, and 0.75 gram each of S a H S H i P O I and K I H P O ~ . 49.6 per cent volatile m a t t e r . c Calculated on t h e basis t h a t initial total soiids are equivalent t o t t e final total solids plus weight oi gas collected.
