December 1949
INDUSTRIAL AND ENGINEERING
2831
ACKNOWLEDGMENT
(7) Hagedorn, M., and Guehring, E., U. S. Patent 1,846,524 (1932);
The authors are indebted t o W. A. Pons, Mrs. V. 0. Cirino, and Miss E. R. McCall of the analytical section of this laboratory for the analytical data, to Miss I. V. deGruy for the microscopical data, and to Edmund M. Buras, Jr., of the Cotkon Chemical Finishing Division for his interest and suggestions.
(8) Hagedorn, M., Reichert, 0.. and Guehring, E., U. 5. Patent
LITERATURE CITED
Burgess, Ledward & Co., Ltd., and Harrison, W., Brit. Patent 192,173 (1923).
Campbell, K. S., and Sands, J. E., Teztile W o r l d , 96, 118 (1946). Champetier, G., Compt. rend., 196, 930 (1933); Ann. Chim., 20, 5-96 (1933). d
CHEMISTRY
Coppiok, S., and Hall, W. P., in “Flameproofing Textile Fabrics,” by R. W. Little, A.C.S. Monograph 104, pp. 179 ff., New York, Reinhold Publishing Corp., 1947. (5) Federal Specification CCC-D-746 (1943) ; Jefferson Quartermaster DeDot. Saeoification 242 for Fire-, Water-, and Weather-R&istant Duck (1942). (6) Gerritz, H. W., J . Assoc. Oj%. Agr. Chemists, 23,321 (1940).
Brit. Patent 279,796 (1928).
2,002.81 1 (1936). (9) I. G. Farbenindustrie, Ger. Patent 547,812 (1932). (10) Ibid., 556,590 (1932). (11) Jurgens, J. F., Reid, J. D., and Guthrie, J. D., Testile Research J., 18, 42-44 (1948). (12) Leicester, J., and Wright, C. M., Brit. Patent 587,366 (1947). (13) Malm, C . J., and Fordyce, C. R., U.S. Patent 2,008,986 (1935). (14) Malm, C. J., and Waring, C. E . , I b i d . , 1,962,827 (1934). (15) Ibid., 1,962,828 (1934). (16) Nathansohn, Ibid., 1,891,829 (1932). (17) Popov, P. V., Compt. rend. acad. sci. U.R.S.S., 46,325 (1945). ENG.CHEM.,ANAL.ED., (18) Shirley, R. L., and Becker, W. W., IND. 17, 437-8 (1945). (19) Tanner, W. L., U. S. Patent 1,896,725 (1933). (20) Thomas, G. A., and Kosolapoff, G., Ibid., 2,401,440 (1946). (21) Weihe, A,, Ibid., 2,003,408 (1935). RECEIVED October 4, 1948. Presented before the Division of Sugar Chemistry and Technology and the Division of Cellulose Chemistry at the 114th CHEMICAL SOCIETY? Portland, Ore. Meeting of the AMERICAN
Composition of Two Types of Cellulose Phosphates J. DAVID REID, LAURENCE W. MAZZENO, JR., AND EDMUND M. BURAS, JR. Southern Regional Research Laboratory, New Orleans, La. This paper describes further experiments conducted in an effort to elucidate the structure of phosphates of cellulose prepared by the commercial urea phosphate method of preparing flameproofed cloth and by the pyridine-phosphorus oxychloride method. By electrometric titration it is shown that the combined phosphorus in cellulose phosphate prepared by the treatment of cellulose with urea phosphate is probably entirely in the form of a monosubstituted phosphate ester. There is no evidence of the formation of other, more highly substituted products. The structure of cellulose phosphate prepared by the treatment of cellulose with phosphorus oxychloridepyridine mixture is similar, except that, in a typical sample, approximately 23% of the phosphorus can be accounted for as a disubstituted phosphate ester. The chlorine also present in this product is probably attached directly to the carbons of the glucose units. A small amount of nitrogen is found in typical samples, presumably due to pyridine.
.x
A
DDTTIONAL experiments conducted in an effort to elucidate the structure of the phosphates of cellulose and certain cellulose derivatives are described herein. The typical procedures for preparation of phosphorylated cellulosic materials by various methods, referred to below, were described in the preceding paper (12). Although the tensile strength of moderately phosphorylated cotton cloth is greatly reduced, the general appearance and feel are changed very little. The cloth will char while in a flame but will not continue to burn when the flame is removed, and afterglow is confined to the charred area. Samples of cloth containing 5% phosphorus were found t o dye brilliantly with methylene blue, very lightly with Celliton blue, and to be relatively little affected by direct cotton dyee, such as Solantine Blue, and wool dyes, such as Kiton Red. When cellulose is more highly phosphorylated, say above 6% phosphorus, the fibers are degraded to a light brown powder.
The degree of degradation cannot be determined by viscometric methods since the product is practically insoluble in water and cuprammonium solutions. This is also true of phosphorylated hydroxye thylcellulose. It was found preferable to dry phosphorylated cellulosic materials in vacuum at 60” C. or below, since many samples undergo further degradation a t higher temperatures. This was particularly true with phosphorylated cellulose acetate which released acetic acid on standing at room temperature, probably because of autocatalyzed hydrolysis. If the combined phosphorus in a cellulose phosphate is not triply bound, the substance should behave as a mono- or dibasic acid. Nuessle (10)has recently proposed the dibasic structure for cellulose phosphate prepared by the urea phosphate method. H e points out that urea is too weak a base t o form a stable compound with the combined phosphoric acid as postulated by Coppick and Hall (5). While not ruling out the possibility of amido forms being produced, he prefers the dibasic acid structure. In order to investigate the structures of such cellulose phosphates the authors have applied an electrotitrimetric procedure t o their compounds and found a marked difference between the cellulose phosphate prepared by the urea phosphate method and that prepared by the pyridine-phosphorus oxychloride method. Discussion of the results of these findings is presented below under suitable headings. PREPARATION OF CELLULOSE PHOSPHATE
PREPARED BY UREA PHOSPHATE. The titration of a sampIe of cellulose phosphate prepared by the urea phosphate treatment (11) resembles that of a relatively insoluble dibasic acid or acid salt, as shown in Figure 1. The p H was determined by the glass electrode using a continuous reading amplifier (4). Relative conductance was determined by a 1000-cycle alternating current resistance-balanced bridge using bright platinum elmtrodes. Both properties were observed during the course of a single titration with each alkali in a cell similar t o that described by Buras and Reid (3). Successive duplicate determinatims on
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INDUSTRIAL AND ENGINEERING CHEMISTRY
I
15 25 ml. o f alkali added
i
Figure 1. Acidity and Conductivity o€ Cellulose Phosphate (3.9% Phosphorus) Prepared by Urea Phosphate Method Points adjusted along abscissa to sample weight of . 1.7512 grams and alkali strength of 0.2105 N 1. pH us. ml. of NaOH added H us. ml. of Ba(0H)z added dative conductance us. ml. of NaOH added 4. Relative conductance us. ml. of Ba(OH)2 added
32: P
identical samples indicated that end points were precise to approximately 17,of the volume of alhali required, although the initial points on the p1-I curves, say for the first 2.5 ml., varied widely and irregularly. The equivalence points determined from the p H curves with barium hydroxide and sodium hydroxide were in agreement. occurring a t 10.4 and 20.8 ml , the second being exactly double rhe first. This indicates that the titratable phosphorus is singly bound to the cellulose chain, leaving two hydrogens available for titration. On this basis the phosphorus content of the sample was calculated to be 3.88 * 0.04%, which is in good agreement with 3.93 * O.OloG found by colorimetric analysis ( 7 ) . Thus. besides being singly hound, all of the phosphorus can be titrated, Only the first equivalence point determined from the conductometric curve obtained with this sample agrees with that determined from the p H curves. The second section of each relative conductance curve is somewhat longer than its first section. The slight difference may be due to unidentified nitrogen compounds present in the sample to the extent of 0.237, nitrogen. This was the amount retained by a sample which had been treated with urea phosphate for one-half hour a t 150" C., acidified with di1ut.e hydrochloric acid to form the.free acid, subsequently washed until it gave a negative chloride test when boiled with sodium hydroxide solution, followed by filtration. acidification, and treatment with silver nitrate.
PREPARED BY PHOSPHORUS OXYCHLORIDEAXD PYRIDINE MIXTURE. Similar titrations were conducted on a typical sample of cellulose phosphate prepared by the phosphorus oxychloride-pyridine treatment (11 ) with the results shown in Figure 2. The equivalence points drawn in a t maximum slopes of the pH curves and determined from all four curves are in mutual agreement, occurring at 13.0 and 29.2 ml., but the second section of each curve is approximately 1.25 times the length of its initial section. One might assume that this effect is due to doubly bound phosphorus to the extent of about 2001, of the titratable phosphorus.
VoL 41, No. 12
except that Bumler and Eiler (9) have iound that the remaining hydrogens of organic phosphate esters are progressively more ionized than the initial hydrogen of phosphoric. acid. If this 16 true when cellulose is the alcohol involved, then if doubly hound phosphorus were present, the initial rathrr than the second section of the curves would be lengthened I n a qualitative test in which this cellulose phosphate ir boiled with sodium hydroxide solution the presence of pyiidine is read$ detected, whereas washing with a dilute solution of sodium hydroxide, a t room temperature, does not release additional pyridine. A Kjeldahl analysis gave 1.4576 nitrogen u hich calculated as pyridine, would correspond t o 7.94 ml. of base used in titration. If the 7.94 ml., equivalent to the pyridine rontent, is added t o the volumes obtained directly (Figure 2), one would ohtair equivalence points a t 20.94 and 39.14 ml. On the basis of increasing dissociation of phosphate hydrogens as ester ificatioi becomes more complete, the difference between these figures, oi 16.20 ml., represents 1 hydrogen of singly bound phosphate Twice that figure subtracted from the second equivalence point or 4.74 ml. represents the remaining hydrogen of doubly bouno phosphate. These calculations accounb for 8-47y0 phosphorub of which 1.92% (22.6% of the total) ~ o u l dbe doubly bound and 6.55Y0 (77.47, of the total) singly bound. The total phosphoru. content thus calculated from the nitrogen analysis and titratior curves is in excellent agreement with the colorimetric analyair 8.48 * 0.01% phosphorus. An attempt was made to verify the bupposition that the preqence of pyridine shortens the initial section of the titration curves. Pyiidine, in an amount equivalent to 3.1 ml. of 0 2105 N base, was added to a sample of cellulose phosphate prepared by the urea phosphate method. The curves obtained by titration of this mixture are shown in Figure 3 together with thr curves obtained without addition of pyridine. The initial section of t h e curve was shortened in accord with the suppnsition.
aJ 0
c 0 + V
3
U
c
0
V
tu
.->
0
LE U
c E)
I a
I
1
IO 28 30 ml. of alkali added Figure 2. Acidity and Conductivity of Cellulose Phosphate (8.48qo Phosphorus) Prepared by Phosphorus OxychloridePyridine Method Points adjusted along abscissa to &leweight of 1.6142 grams and alkali strength of 0.2105 N 1. _ nH. m. of . . .. ml. ~~... . .NaOH ..-- added 2. pH c's. ml. of Ba(0H)n added 3. Relative conductance us. ml. of NaOH added a. Relative conductance us. ml. of Ba(0H)t added ~
December 1949
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t
INDUSTRIAL AND ENGINEERING CHEMISTRY
2833
On the other hand, the pyridine was OF PHOSPHORYLATED CELLULOSIC MATERIALS IN ACIDAND TABLE I. HYDROLYSIS not retained throughout the titration of ALKALINEMEDIA the urea phosphate sample to which Weieht % Chlorine onLoss R ~ this base had been added (Figure 3). '$6 Phosphorus Equivalence points drawn a t maximum Material Reagent Before After Before After fluxing, % slopes of p H curves occurred a t 6.9 Cellulose phosphate 1 % HC1 7.19 7.11 6.7 7.66 15.27 Cellulose phosphate 1 % NaOH 7.19 6.62 6.7 6.00 7.52 and 20.4 ml., as compared t o 10.4 and Hydroxyethylcellulose phosphate 1% HC1 8.90 8.56 11.1 11.12 26.74 20.8 ml. when pyridine was not added. Hydroxyethylcellulose phosThe second equivalence points of the phate 1% NaOH 8.90 8.68 11.1 8.82 18.11 two curves were approximately the OF CELLULOSE PHOSPHATES ON IODINATIOX same, showing nearly complete displaceTABLE 11. CHANGEIN COMPOSITION Phne. ment of the pyridine by the stronger ph&y1aAnalysis before Analysis after base, barium hydroxide. Therefore, it tion Iodination Iodination Time, Tzrnd., would seem evident that pyridine is Material Hr. P, % C1, % N, % P, % C1, % N, % I , % bound differently in the cellulose phosPhosDhorvlated cellulose a 120' 8 . 4 8 9.96 1.45 3 . 8 1 1 . 7 3 1 . 2 0 19.36 PhoLphoFylated hydroxyethylcelphates prepared by the two different lulose 3 120 0.45 9 . 9 8 1.66 3.87 2.91 1.51 24.95 methods. Phosphorylated hydroxyethylcellulose 864 26-30 9 . 7 3 6 . 4 7 1 . 0 4 6 . 8 1 0 . 1 8 0 . 9 7 14.29 The observation has been made above Cotton (control) ... ,.. 0 . 0 5 0 . 0 0 0 . 0 4 0 . 0 5 0.00 0 . 0 4 0.00 that pyridine cannot be removed completely from the phosphorus oxychlorideprepared cellulose phosphate by treatit may be concluded that the chlorine is attached t o the carbon ment with dilute sodium hydroxide a t room temperature. If, of the glucose residue rather than t o an unhydrolyzed residue of for the sake of argument, it is postulated that pyridine is disphosphorus oxychloride. Such stability is not surprising since placed during titration before the second equivalence point is Allison and Hixon (1) found that 3-chlorodiacetoneglucose was reached, calculation of the phosphorus content of the sample from stable toward the action of 6 N sodium hydroxide at reflux temthe data in Figure 2 would also give 8.47% phosphorus; but-this perature. They used phosphorus pentachloride t o prepare this postulation would necessitate 60.6% of the phosphorus being compound since phosphorus oxychloride gives only "easily doubly bound, which is, t o the authors, unreasonable. hydrolyzable phosphoric acid esters." The mechanism of the I n addition t o the phosphorus, nitrogen, and cellulosic coninteraction of phosphorus pentachloride and phosphorus oxystituents, this sample contained a considerable amount of chlochloride with (+)2-octanol in the presence of pyridine to produce rine, 9.96%. Both the chlorine and the phosphate constituents ( -)2-chloro-octane and phosphoric esters has been discussed were quite stable t o mild acid and alkaline hydrolysis, even after by Gerrard (6). 1 hour a t reflux temperatures as shown in Table I. From this Cellulose phosphates cannot withstand the rigorous treatment of 6 N sodium hydroxide at reflux temperature. If the strength of the sodium hydroxide solution is 5% and the cellulosic phosphate refluxed in it for 1 hour, the phosphorylated material is solubilized. Barham, Stickley, and Caldwell (8) have recently reported that pentachlorostarch and pentachlorocellulose are inert even to 50% sulfuric acid solutions. These compounds, prepared by the action of phosphorus pentachloride on cellulose and starch at temperatures up t o 170" C. for 8 hours, "contained an appreciable quantity of bound phosphorus." This was probably due to the action of the phosphorus oxychloride, produced in the original reaction, on the chloro compound first formed. As was noted previously (11),sample 30 of Table I1 of the reference (11) was prepared a t 25" to 30" C. and had 4.89y0 phosphorus and 1.71% chlorine, whereas sample 32, prepared at 120' C., had 2.77% phosphorus and 4.31% chlorine. This was taken t o mean that at the higher temperature the phosphate group was being replaced by chlorine. Preparation of a sample a t 25" to 30" C. followed by retreatment with the phosphorylation mixture a t 120" C. confirmed this. The reaction may be analogous to that observed by Hess and Stensel (8) who substituted both the 4 and 6 positions in glucose with chlorine by t l i 4 l I treating tetratosyl-a-(or) p-methylglucoside with pyridine hydroI I chloride. The tosyl group on the primary hydroxyl may 15 25 be easily replaced by iodine by treatment of the material with ml. of alkali a d d e d sodium iodide in acetone a t about 100"C. When phosphorylated cellulose was treated similarly with sodium iodide in acetone Figure 3. Acidity and Conductivity of Cellulose Phosphate (3.99'0 Phosphorus) a t 110" C. for 1 hour in an autoclave, it was found t h a t some Prepared by Urea Phosphate Method, of the phosphorus as well as part of the chlorine was replaced Showing Effect of Added Pyridine with iodine. If the replacement of phosphate groups is analogous Points adjusted along abscissa to sample weight of to the tosyl replacements of Hess and Steneel it indicates that 1.7512 grams and 0.2105 N Ba(0H)a 1. pH US. ml. of Ba(0H)z added, following addition some of the phosphorylation occurred on the primary hydroxyl of pyridine 2. pH ua. ml. of Ba(0Hh added, no pyridine added and was subsequently replaced by chlorine. The reaction pro3. Relative conductance us. ml. of Ba(0H)a . . added. n o pyridine added ceeds equally well using acetonyl acetone as solvent and elimi4. Relative conductance US. ml. of Ba(0H)z added, nates the need for an autoclave. Full benefit of the high boiling following addition of pyridine
1
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INDUSTRIAL AND ENGINEERING CHEMISTRY
point of acetonyl acetone cannot be utilized, however, because of the acidity of the phosphorylated compounds. This acidity is sufficient to cyclicize the compound to 2,5-dimethylfuran and hence the reaction temperature must be kept a t 90” to 100” C. Table I1 shows result’s of treatment of phosphorylated materials with sodium iodide in acetonyl acetone. Sample 3 was prepared by treatment of hydroxyethylcellulose with phosphorus oxychloride in pyridine a t room temperature for 35 days. The product contains 9.7% phosphorus which is approximately 9 times that contained in a phosphorylated cellulose prepared in the same manner. This may be dne to the phosphorylat,ion occurring in the hydroxyl group of t’hehydroxyethyl chain, which should be the most easily accessible. Since all samples underwent a replacement of part of the phosphorus and part of the chlorine, it appears probable that some of each is attached in the primary position. CONCLUSIONS
The combined phosphorus in cellulose phosphate prepared by treatment of cellulose with urea phosphate is probably entirely in the form of a monosubstituted phosphate ester. There is no evidence of formation of other, more highly substituted products, as presumed by Coppick and Hall ( 5 ) . The structure of cellulose phosphate prepared by the treatment of cellulose with phosphorus oxychloride-pyridine mixture is similar, except, that in a typical sample approximately 23y0 of the phosphorus can be accounted for as a disubstituted phos-
Vol. 41, No. 12
phate ester. The chlorine also present in this product is probably attached directly to carbons of the glucose units. Nitrogen is found in typical samples, presumably due to pyridine. ACKNOWLEDGMENT
The authors are indebted to W. A. Pons, Mrs. V. 0.Cirino, and Miss E. R. McCall of the analytical section of this laboratory for the analytical data given. LITERATURE CITED
(1) Allison, J. B., a n d Hixon, R. M., J . Am. Chem. Soc., 48, 406 (1926). (2) B a r h a m , H . N., Stickley, E. S., a n d Caldwell, M. J., Ibid.,68, 1018 (1946). (3) Buras, E. M., and Reid, J. D., IND.ENG.CHEM.,ANAL.K D . , 16, 591 (1944). (4) Ibid., 17, 120 (1945). (5) Coppick, S.,a n d Hall, TT. P., in “Flameproofing Textile Fahrics,” by R. W. Little, A.C.S. Monograph 104, pp. 182-3, New York, Reinhold Publishing Corp., 1947. (6) Gerrard, W., J. Chem. Soc.. 1946, 741. (7) Gerritz, H . I\’., J . Assoc. 0&. A y r . Chemists, 23,321 (1940). ( 8 ) Hess, K . , a n d Stcnzol, H., Ber., 68,981 (1935). (9) Kumler, W.D., a n d Eiler, J. J., J . Am. Cham. Soc., 65, 2355 (1943). (10) Nuessle, A. C., J . SOC.D y e i s Colourists, 64,342 (1948). 1 x 1 . ENG.CHEM.,41, 2828 (11) Reid, J. D., a n d M a m e n o , L. W., (1949).
RECEIVED October 4, 1948. Presented before the Division of Sugar Chemistry 5nd Technology and the Division of Cellulose Chemistry a t the 114t,h Meeting of the . ~ M E R I C A X CHEMICIL S O C I ~ T PPortland, Y, Ore.
J
L. $1. WELCH, J. F. NELSON, AND H. L. WILSON Esso Laboratories, Standard Oil Development Company, Linden, N . J .
The physical properties of Butyl type vulcanizates are discussed, pointing out the variation between polymers containing a wide concentration range of isoprene, butadiene, piperylene, and dimethylbutadiene as diolefins.
A
LTHOUGH Butyl polymers can be made by copolymerizing isobutylene with a variety of diolefins ( 4 ) ,isoprene is the diolefin used in the commercial production of Butyl rubber (GR-I). The choice of isoprene as the diolefin was based on its availability, the polymer quality, and its applicability in the process. At the present time the major part of GR-I production goes into inner tubes, primarily because of its air-holding properties and excellent tear resistance. However, there is a growing market for Butyl in mechanical goods, curing bags, proofed goods, and farm tractor tires. McKinley ( 3 ) has reported that Butyl is a n outstanding polymer for use in wire insulation. This results from its good age resistance, low moisture retention, and good electrical properties. The other uses mentioned require good aging properties above all else. The well-known superior aging properties of Butyl are attributed to its low unsaturation, but low unsaturation results in an inherently slow cure rate which has, in some instances, limited its use.
Since the unsaturation in Butyl is a variable which can be adjusted a t viill, within rather wide limits, the manufacture of different grades of polymer has been a logical step in supplying the rubber industry with the polymer which suits its needs best Table I lists three of the grades of Butyl which are manufactured a t the prescnt time: GR-I, GR-1-18, GR-1-25, having unsaturations ( 1 ) of approximately 1.1, 1.6, and 2.2 mole 7 0 ,respectively. The specifications for GR-I, GR-1-15, and GR-1-25 illustrate the range of properties obtained in a 50-part easy processing carbon black (EPC) formulation. Of particular interest hero is the increasing cure rate as evidenced by the 300% moduli. The production (or consumption) trend established by the rubber industry as a whole is toward polymers of higher unsaturation. Although only 1.6% of the United States Butyl production was GR-1-15 in 1946, this increased to 32.0% in 1947 and to 75.0y0 in 1948. This trend results from the advantages of GR-I15 for inner tubes-namely, faster cure rate with attendant higher state of cure which isdesirable for better inner bube performance. The volume of GR-1-25 remains low because GR-1-25 compounds either tend to scorch or precure duringinner tube processing, or the over-all physical properties of a pncessable compound are unsatisfactory. From this it is evident that the proper balance between polymer unsaturation, acceleration, and physi-
