INDUSTRIAL A N D ENGINEERING CHEMISTRY
1176
Vol. 21. No. 12
Sulfamide Derivatives as Plasticizers for Acetyl Cellulose' T. S. Carswell MONSANTO CHEMICAL WORKS,S T . LOUIS, M o
HE increasing use of Acetyl cellulose films, plasticized with eight different It is obvious that a certain acetyl cellulose f o r aryl sulfonamide derivatives, have been studied with degree of retentivity is essenmolded articles and for respect to retentivity, light fastness, tensile strength, tial for a substance to be a lacquers makes the developand weather resistance. Where possible, conclusions plasticizer at all. A very low ment of suitable plasticizers have been drawn as to the effect of substituents in the retentivity means that the plasticizer on the plasticizing action. a problem of increasing imsubstance which is intended portance. The two standard to be used as a plasticizer is nitrocellulose plasticizers, camphor and dibutyl phthalate, are actually incompatible with the cellulose acetate. of no value, as neither is compatible with the acetyl cellulose. The retentivity was determined by making up a series of The aromatic sulfonamide derivatives form a very important solutions corresponding to the formula: 20 grams of cellulose class of acetyl cellulose plasticizers, and in this paper varia- acetate (15-second viscosity), 95 cc. of acetone, and a varying tions in the physical properties of acetyl cellulose films which amount of plasticizer, to give the desired film concentration. have been plasticized with different sulfonamide derivatives This solution was spread on glass plates and dried in an will be described. oven a t 50-60" C. When dry, the films were stripped from The first mention in the literature of sulfonamide deriva- the plates and allowed to age. When the plasticizer content was higher than the maximum tives as plasticizers occurs in U. S. Patent 1,041,113 under date of October 15, 1912, issued to William A. Lindsay. retentivity, separation took place. I n some cases the sepaSince that time the use of many such derivatives as plasti- ration took place immediately; in others, particularly when cizers has been described. Since i t would be an almost hope- the concentration of plasticizer was only slightly in excess less task to test the value of all these derivatives, these of the maximum retentivity, the separation occurred only studies have been confined to the typical compounds listed in after standing for a week or more. The separation of solid Table I, which have been selected with the view of providing substances usually takes place in the form of microscopic homologous series in which the effect of different substituents, crystals, which appear as fine dust on the surface of the film. both in the nucleus and on the sulfonamide nitrogen, could The separation of liquid substances takes the form of minute globules. Table I1 shows the retentivity in 15-second acetyl be studied. All the compounds studied were commercial products and, cellulose.
T
Table I-Sulfonamide
Derivatives Studied MELTINGPOINT
DERIVATIVE
CHEUICAL FORMULA
Pure product 0
+Toluene sulfonamide Benzene methyl sulfonamide Benzene ethyl sulfonamide p-Toluene methyl sulfonamide $-Toluene ethyl sulfonamide Xylene methyl sulfonamide +Toluene sulfonanilide #-Toluene methylene sulfonamide
CHs. CaHd. SOzNHs CaHaSOzNHCHa CsHsSOzNHCiHa $-CHI. CaH4SOzNHCHs p-CHsCsH4SOzNHCaHs (CHdrCaHaSOaNHCHa ~-CH~C~H~SOZNHC~HI (9-CHsCsHBOaN:CHi)n
with the exception of the p-toluene sulfonanilide, contained about 15 per cent of the unalkylated amide. The p-toluene sulfonanilide is a practically pure compound in its commercial form. Xylene methyl sulfonamide was a mixture of the various isomers which are produced when xylene is chlorosulfonated and converted to the methyl sulfonamide. The p-toluene methylene sulfonamide is obtained by condensing p-toluene sulfonamide with formaldehyde. It is a rather highly polymerized substance with a resinous appearance. Retentivity in Acetyl Cellulose
By ((retentivity" is meant the amount of plasticizer which can be incorporated in the film with respect to the amount of cellulose ester present. I n this paper retentivity is expressed as percentage calculated from the following formula: Weight of plasticizer X 100 Weight of cellulose acetate 1 Presented before the Division of Paint and Varnish Chemistry at the 78th Meeting of the American Chemical Society, Minneapolis, Minn., September 9 to 13, 1929.
c.
127
36131 57-58 78-79 63.2
io3
...
Commercial product 0
I
SOLUBILITY IN: Benzene
Acetone
Alcohol
Slight Good Good Good Good Good Good Good
Fair Good Good Good Good Good Good Good
Slight Good Good Good Good Good Good Good
c.
127
Ab-o-ut 30 About 45 About 40 About 45 Liquid 101-102 70-75
Table 11-Retentivity of Plasticizers i n 15-Second Acetyl Cellulose PLASTICIZER MAXIMUM RETENTIVITY Per cent #-Toluene sulfonamide 30 Benzene methyl sulfonamide loo+ Benzene ethyl sulfonamide 100 $-Toluene methyl sulfonamide 40 p-Toluene ethyl sulfonamide 40 Xylene methyl sulfonamide 100 @-Toluenesulfonanilide 70 p-Toluene methylene sulfonamide 200
+
The work was repeated on lacquer viscosity acetyl cellulose and in every case the figures were the same as those given in Table 11. It is hard to draw definite conclusions from these figures. It seems to make no difference whether the alkylating group on the nitrogen is ethyl or methyl. Substitution of the methylene group, however, greatly increases the affinity for acetyl cellulose. On the other hand, it must be considered that the methylene compounds are polymerized compounds of a resinous character, and perhaps they are not strictly comparable with the other derivatives. Substitution of the
INDUSTRIAL A N D ENGINEERING CHEMISTRY
December, 1929
phenyl group on the nitrogen increases the retentivity, as shown by the difference between p-toluene ethyl or methyl sulfonamide and p-toluene sulfonanilide.
exposed portion could be seen on holding the film against B white surface. The time of exposure up to this point was then taken as the light fastness.
Tensile S t r e n g t h
T a b l e 111-Tensile S t r e n g t h T e s t s on Plasticizers (Results after 7 days)
PLASTICIZER
PLASTICIZER IN FILM 26 PER CENT
100 PER CENT
T, S, Elonga
T, S, Elonga-
tion
Kg./ cm. 408 453 414
Per cent 3 7 10
460 380 475 335
4 6 S 10
660 355
2 0
sq.
#-Toluene sulfonamide Benzene methyl sulfonamide Benzene ethyl sulfonamide 9-Toluene methyl sulfonamide p-Toluene ethyl sulfonamide Xylene methyl sulfonamide #-Toluene sulfonanilide +Toluene methylene sulfonamide No plasticizer
tion
Kg./
Kg./
sq. cm.
Per cent
q. cm.
Per cent
320 290
12 10
80 115
40 50
...
...
..
..
360 350 383
8 10 6
408
3
...
F a s t n e s s of Plasticizers TIMEIN F A D E - O - M ~ T B R Hours 630 Benzene methyl sulfonamide 724 Benzene ethyl sulfonamide 1140 p-Toluene methyl sulfonamide 1534 p-Toluene ethyl sulfonamide 532 Xylene methyl sulfonamide 39 +Toluene sulfonanilide About 2000 p-Toluene methylene sulfonamide T a b l e IV-Light
In order to determine whether the constitution of the plasticizer had any effect upon the tensile strength and elongation, films were prepared and tested for these properties by the H. A. Gardner Laboratory of the Institute of Paint and Varnish Research. The acetyl cellulose and the plasticizer were dissolved in a mixture of acetone and ethyl lactate, and a film 0.04 mm. thick was made by a spinning device. The films were aged under constant humidity conditions, and the tensile strength and elongation determined. In Table I11 only the results of the 7-day test are given, as these are regarded as the most important. All the figures represent the mean of three closely checked determinations.
I
..
...
... ... 349 ... 350
PLASTICIZER
A study of Table IT.' brings out the following: (1) The toluene sulfonamide derivatives are superior in light fastness to either the benzene or xylene sulfonamide derivatives. (2) The derivatives in which the ethyl group is substituted on the nitrogen have better fastness than those in which the methyl group is substituted. (3) The substitution of the phenyl group on the nitrogen has a marked effect in decreasing the light fastness.
The fact that the ethyl group in the nitrogen increased the light fastness as compared to the methyl group naturally suggested the thought that the higher alkylated derivatives might show even better light fastness. Accordingly, a number of these were tested with the results given in Table V. Table V-Light F a s t n e s s of Alkylated S u l f o n a m i d e s PLASTICIZER TIMEIN FADE-0-METER Hours +Toluene methyl sulfonamide 1140 $-Toluene ethyl sulfonamide 1534 Not tested $-Toluene n-propyl sulfonamide p-Toluene n-butyl sulfonamide 1155 $-Toluene n-amyl sulfonamide 981
..
ib *.
5
..
A study of this table indicates that the following relationships hold: (1) p e n ethyl is substituted for methyl on the nitrogen, the tensile strength decreases and the elongation increases. (2). As the number of methyl groups in the nucleus increases -as in the series benzene methyl sulfonamide, p-toluene methyl sulfonamide, xylene, methyl sulfonamide-the tensile strength increases. There is no significant variation in the elongation. (3) Substitution of a heavy group, as the phenyl group in p-toluene sulfonanilide, results in a marked decrease in tensile strength. (4) When the plasticizer contains a methylene group substituted on the nitrogen, the tensile strength is remarkably increased.
It can be seen that increasing the length of the alkylating group beyond a certain point decreases rather than increases the light fastness. It is probable that the light fastness is associated with the stability of the molecule, and the long side chains may tend to decrease the stability. The same tendency is shown in the case of the sulfonanilide, where the phenyl group is substituted on the nitrogen. Outdoor Exposure Tests
In order to determine the relative weather resistance of the sulfonamide plasticizers, clear lacquers were made up according to the following formula: Lacquer viscosity acetyl cellulose Plasticizer Methyl Cellosolve Alcohol Acetone Toluene
Light Fastness
When the product is to be used in clear or light-colored lacquers, in non-shatterable glass, or any other purpose which requires continued exposure to the light, the plasticizer must be fast to light. To test this property films of a uniform thickness of 0.4 mm. ('/64 inch) were made up, containing 25 per cent of the plasticizer on the weight of the acetyl cellulose present. After thorough drying, these films were exposed in the Fade-0-Meter in such a way that one half of the film was subjected to the light while the other half was protected, and were observed a t frequent intervals. Note was taken of the time when the slightest discoloration of the T a h l e VI-Outdoor
10 grams 5 grams 40 cc. 16 cc. 16 cc. 24 cc.
After evaporation of the volatile constituents, this solution leaves a film containing 50 per cent of plasticizer on the weight of the acetyl cellulose. These lacquers were flowed onto clean black iron panels and exposed to the weather in St. Louis during July and August. Exposure was made with the panels facing south and tilted a t an angle of 45 degrees. Table VI shows the rate a t which the films deteriorated. The type of failure was practically the same in every case, and was due to the formation of small blisters, under which the film separated from the iron panel. Rusting then took place under these blisters, followed by flaking off of the film. Exposure T e s t s APPEARANCE O F FILM AFTER:
PLASTICIZER
4 weeks
5 weeks
Starting to rust Good Poor Fair Quite rusty Elistering and rusting
Poor Fair Failed Starting to rust Failed V_ery,dull, rusted in spots
3 weeks Benzene methy1 sulfonamide Benzene eth.yl sulfonamide #-Toluene uiethyl sulfonamide $-Toluene ethy1 sulfonamide Xylene methyl sulfonamide $-Toluene sulfonanilide #-Toluene methylene sulfonamide
1177
Fair
I
Starting to rust Good Good
IJooa
,
6 weeks
7 weeks
Failed Fair
Failed
Quite rusty
Failed
......
F_i!:d
....
. .. .
9 weeks
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
