688
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE x.
INTRINSIC \‘ISCOSITY OF DEACETYLATED CELLULOSE ACBTATEIK CUPRAMMONIUM SOLUTION
Concn., G./100 M I .
(Kramer) In V F / C
(Staudinger) Average
78dC
Vol. 43, No. 3
The above results indicate t h a t within esperiment,al error the esters fulfill the requirements set a t the beginning of the work. The properties of the triesters of similar degree of polymerization are described in the following paper (9). ACKNOWLEDGMEIYT
a
T h e authors wish t o express their appreciation t o ?*Ira. D. L. Kendall, who did much of the analytical work reported in this paper.
Extrapolated.
TABLE XI. INTRINSIC VISCOSITIESOF CELLULOSICS IS CUPRAMMONIUhC SOLUTION
LITERATURE CITED
Source of Cellulor e [?la Starting material 1.36 Acetate 1.17 Propionate 1.05 Butyrate 1.07 Valerate 1.10 Caproate 1.06 Heptylate 1.02 Caprylate 1.06 Caprate 1.02 Laurate 1.06 Myristate 0.99 Palmitate 0.72 a Determined a t 0 . 2 5 gram per 100 nil. Value reported is average of those calculated b y Kramer and Staudingei equations, which gives close approximation of value found b y extrapolation to infinite dilution by either equation.
monium intrinsic viscosities of the celluloses regenerated from the esters are shown in Table XI and Figure 4. These results indicate the acetate to be of slightly higher, and the palmitate of slightly lower degree of polymerization than that of the remainder of the series. All are lower than the starting material, giving a measure of the degradation occurring under the esterification and deacylation conditions employed.
Clarke, H. T., and Malm, C. J., U. S.Patent 1,880,808 (Oct. 4, 1932).
Genung, L. B., and hIallatt, R. C., IND. ENG.CHCM.,AKAL.ED., 1 3 , 3 6 9 (1941).
Greene, C. H., J . Am. Chem. Soc., 56, 1269 (1934). Hagedorn, M., and Moeller, P., Cellulosechemie, 12, 29 (1931). Hagedorn, M . , and Moeller, P., Veroffentl. wiss. Zentr-Lubs. phot., Abt. I . G.Fnrbenind. B.G. Agfa, 1, 150 (1930). Malm, C. J., and Fordyce, C. R., in Ott, E., “Cellulo3e and Cellulose Derivatives,” pp. 667-708, Xew York, Interscience Publishers. 1943. Malm, C. J.; Fordyoe, C . It., and Tanner, H. A , , IND.ENG. CHEM.,34, 430 (1942).
Malm, C. J., Genung, L. B., and Williams, R. F., Jr., IND. EKG. CHEX.,AKAL.ED., 14, 935 (1942). Malm, C . J., Mench, J. W., Kendall, D. L.. and Hiatt. G . D.. IND. ENG.CHEM.,43, 658 (1951). LIorey, D. R., and Tamblyn, J. IT., J . A p p l i e d P h y s , 16, 419 (1945).
Pringsheim, H., Lorand, E., and Kard, K., Jr., Cellulosechemie, 1 3 , 1 1 9 (1932).
Tagner, R. H., and Russell, J., A n d . Chem., 20, 151 (1948). RECEIVEDAugust 2 , 1950.
Presented before the Division of Cellulose CHEWCALSocriwr, Chemistry a t the 118th hleeting of the AMERICAN Chicago, Ill.
stem of
atic Aci
PRQPERTIES C. J. MALM, J. W. RIENCH, D. L. KENDALL’, AKD G . D. HIATT E a s t m a n IQodak Co., Rochester, N . Y .
Certain discrepancies are observed in the literature relating to the properties o€ homologous series of aliphatic acid esters of cellulose. This work presents data on melting point behavior, moisture sorption, density, tensile strength, refractive index, solubilities, and specific rotation for a series of cellulose esters from acetate through palmitate. The esters used were fully esterified and had substantially the same degree of polymerization. As the number of carbon atoms
in the acid increases, density, tensile strength, specific rotation, and moisture sorption decrease. The melting points pass through a minimum at the Cg ester, while maximum solubility is reached with the Cs or Cg esters. The refractive index varies only slightly throughout the series, The data may be considered comparable, because all esters studied were fully esterified and of uniform degree of polymerization.
T
ment in high-boiling solvents containing acid catalysts. Obviously, this is a disadvantage if the properties of a series of esters are to be compared. Sheppard and Newsome (6) described a variety of properties of the fatty acid esters, and emphasized the necessity of having materials of comparable chain length and of uniform and high degree of esterification. They gave no data, however, t o show that these requirements were met, nor did they describe the method of preparing the esters. Certain properties of these esters were determined, and the results are summarized in Table I. The methods used and comments on the results are given below. BEHAVIOR ON HEATING. The melting behavior of the samples
H I S paper reports the properties of the series of cellulose esters whose preparation has been described ( 5 ) . The esters have been shown to be substantially fully esterified, and were prepared using pure reagents under conditions which minimized side reactions which cause combined impurities. The degree of polymerization is also relatively constant throughout the series. Hagedorn and Moeller ( 2 , 3 ) have reported tensile strengths and solubilities for a homologous series of fatty acid esters of cellulose. Most of their esters, however, were obtained in a fibrous, insoluble form and had to be solubilized by a heat treat1 Present address, Department of Chemistry, Purdue University, West Lafayette, Ind.
March 1951
INDUSTRIAL A N D ENGINEERING CHEMISTRY
689
TABLEI. PROPERTIES OF CELLULOSETRIESTERS Behavior on Heating Water% Moisture Regain ~ ~ C * Shrinking Melting Char Tolerance 25% 50% 75% Density, Strength, Ester Atoms point, ' C. point, ' C. point, ' C. Value R.H. R.H. R.H. G./Ml. Kg./Sq. Mm. 15.5 30.5 1.52 Cellulose0 0 5.4 10.8 2 366 315 54.4 2.0 7.3 Acetate 3.8 7.8 1.28 0.6 229 >315 2.4 234 26.9 1.5 1.23 0.1 0.5 4.9 3 Propionate 16.1 0.7 1.17 4 >315 178 1.0 183 Butyrate 0.1 0.2 3.1 0.3 119 122 10.2 1.13 5 >315 0.2 1.9 0 0.6 Valerate 0.2 1.10 >315 84 94 5.88 0.4 0.1 1.4 0 6 Caproate 82 88 3.39 0.4 290 0.2 1.07 0.1 0 7 1.1 Heptylate 82 0.1 86 1.14 0.2 315 1.05 0.1 8 0 0.9 Caprylate 87 88 1.02 0.1 0.2 0.5 310 10 0.7 0 Caprate 89 91 0.1 0.3 12 >315 0 0.1 ... 1.00 0.6 Laurate 87 0.1 0.2 14 315 M yristate 106 0 0.99 0.1 0.6 ... 0.1 0.2 315 105 90 Palmitate 0.1 0.5 16 ... 0 0.99 Starting cellulose, prepared by deacetylation of commercial, medium viscosity cellulose acetate (40.4% acetyl content).
95.3.
...
...
...
Specific ~ ~ Rotation i 25' c.8 589 mP CHCls CGHB
....
-20.9 -19.0 -15.7 -12.2 9.6 - 5.6 - 4.8 2.0 - 1.0 0 0
-
....
....
-39.6 -37.4 -33.3 -30.0 -22.5 -19.6 -16.6 -13.0 -13.0 - 7.8
Q
was determined by heating the esters in a 4-mm. glass tube in a copper block whose temperature rise was controlled a t 5" C. per minute. Three distinct stages were observed: a shrinking point a t which t h e ester pulled away from the sides of the tube; a melting range which was fairly sharp-i.e., about 2" to 5 " C.; and a char point, which is the temperature a t which the sample turned black. Shrinking points varied, being in the range of 5' t o 15" C. lower than the melting points. The melting points decrease rapidly as the series is ascended, appearing t o reach a minimum with the caprylate, and then showing a slight increase t o the palmitate (Figure 1). High char points may be considered a n indication of quality, as low values indicate the presence of impurities which cause the ester t o be unstable t o heat. In general, this series of esters had char points in excess of 300" C. WATER-TOLERANCE VALUE. The decreasing tolerance of acetone solutions of the triesters t o the addition of water is shown in Figure 2. This test has been described (6). [The acetone solution of the triacetate was prepared by cooling t o -70" C. ( I ) . ] MOISTUREREGAIN.The per cent moisture sorption of the dry cellulose triesters was determined by placing the samples in
weighing bottles held i n desiccators containing aqueous sulfuric acid of the concentrations required to obtain the desired relative humidities (7). These values decrease rapidly from the acetate t o the valerate, and show a continuing but low rate of decrease from this point, as indicated in Figure 3. DENSITY.Densities were determined on the series of esters by the method of Archimedes as described b y Malm, Genung, and Fleckenstein ( 4 ) . T h e measurements were made on films coated from chloroform, and special precautions were taken to remove residual solvent from the films. Carbon tetrachloride was used as the liquid medium for the acetate, and distilled water containing a small amount of a commercial detergent was used for the other members of the series. T h e values obtained are shown in Figure 4 and are compared with the corresponding values calculated as described in the literature ( 4 ) . The agreement is good when the assumptions involved in the calculated values are considered. TENSILE STRENGTH.T h e tensile strengths of the esters are shown in Figure 5. These were determined on films coated onto glass plates from filtered chloroform solutions. The stripped films were cured for 24 hours in a current of air a t 60" t o 70" C. t o decrease residual solvent content t o a minimum. T h e tests were conducted on strips cut t o 15 X 180 mm. with a thickness of
30C 280 260 240
220 0 0
.-E0
200
n
: 180 ._ f m
160 I40 120
IO0
80 0 1 2 3 4 5 6 7 6 9 1 0
12
14
Number of corbon atoms in esterifying acid
Figure 1.
Melting Points of Triesters
16 Number of carbon otoms i n esterifying acid
Figure 2.
Water-Tolerance Values of Triesters
l
~
INDUSTRIAL AND ENGINEERING CHEMISTRY
690
Vol. 43, No. 3
Table 11.
Solubilities of Cellulose Triesters of n-Fatty Acids Solvent-solid 9 to I by weight Solid black. Grain-free solutiou at 25' C.
Cellulose T r i r s t r r
I
Cross hatched. Grainy or swollen at 25' C.; grain-free at 100' C. or at boiling point of solveut White. Insoluble at 25' C. and at 100' C. or a t boiling point of solvent
SOLVENT
I 2
II)
1 4
5 6
76
2-Ethylhe
IO
8 &the r-Alc ohol I @-Methoryethan B-Ethoxyerhanoi 8-Butoryetha I2 Ethyl Carbitol I 1 Butyl Carbit01
9
9 10
9 10 I 1
I1 I2 13
E t h e r . and A c e t a l s I4 Ethyl E t h e r 1 5 Isopropyl E t h e r 16 Diethyl Cellosolve
I4
15
8 *
7
I6
I7 I8
17 18 Tetrahydroiurnn 19 Ethylene Formal
19
Keloncr
20
Al.to.
20
L!
h!r'ky.
2.' 2, 24
MCII,!
21 2:
C) tlonPXdnore
I1
Isaphoronc
24
Esters 2 5 MethylFarrnate 26
Methyl Acetare
3
2 I I.5
Halogenated Compounds Methvlrne and .. ,.. . C . .h.l . .s
35 10
Propy:er. J8 Cnlorolor 39 C s r b o r T 40 Titch'oroe. 4 1 s-Te!roch:o 4 2 ~ - A m >Cl h : o r . d e 4 3 ?tloroberzrne 64 F ' m r o b c r r s n c 4 5 E:hylene Chlor 4 b D P'-Dtch!oroc. 37
0
38 'Y
.)
Number of carbon atoms in esterifying acid Per Cent Moisture Sorption of Triesters
O.
.: 41
Figure 3.
25' C.
.L .i .c
47 48 40
51
10 11 52 53 54
NIIrornelha
55 Formic A C L 56 k t t l c Aerd
55
5b
1.08 1.06 1.04 -
1.12
-
68
(1:4)
69 Ethyl A c c t a f c . E t h a n o l ( 7 0 . * (1.1) 71 Methylene C h 1 a n d e : M e t p n o 12
71 14
-
* Ethylene C h l o r i d e . M e t h a n o t ( 4 ~I i
75 76 17 P r o p y l e n e Chlonde.Methanol(4.
-
-
lI'4! To!uenr Methanall4.1) 86 * ( I I, * (I:4j 87 88 ) . b ' - D l c b l o r o e i h y l Eth
84
85
--
b8 69 70 71 72 73 74 75 76 77 78
84 85
8) 88
I. I O
1.02 1.00 0.98 0.96 -
%-
I I I I I I I I 0 1 2 3 4 5 6 7 8 9 1 0
0.94
1
I
-a\... I
I2 14 Number of carbon atoms in esterifying a c i d Figure 4. Densities of Triesters 25' C.
March 1951
691
INDUSTRIAL AND ENGINEERING CHEMISTRY -"
- 40 - 35
- 30
0
I 2 3 4 5 6 7 8 9 1 0 12 14 Number of carbon atoms in esterifying acid
Figure 5 .
1
16
Tensile Strengths of Triesters
0.0055 inch, and the results have been calculated in terms of kilograms per square millimeter of starting cross-sectional area. A Schopper tensile tester with a cross-head speed of 4 inches per minute was used. Physical properties of films are dependent on the coating conditions-i.e., solvents used, coating humidity and temperature, and degree of wring. The curve, therefore, shows only the general trend. REFRACTIVEINDEX.Refractive index measurements were made on the films coated from chloroform, and on sheets formed by pressing at elevated temperatures and pressures. All values were in the same order of magnitude and were somewhat erratic, ranging from 1.47 t o 1.48 throughout t h e series, with the lower value predominating. These determinations were made with a n Abbe refractometer, using a variety of nonsolvents of high index of refraction as contact media. SOLUBILITY.Solubility determinations were made in a wide variety of solvents and solvent mixtures at a solvent-solid ratio of 9 t o 1. Samples insoluble at room temperature were heated t o 100" C. or t o the boiling point of the solvent if the latter value lyas lower. T h e results are shown in Table 11. The effect of the decreasing cellulosic content of the esters as the proportion and length of the hydrocarbon side chains increases is apparent from the trends in solubilities. Maximum solubility (as measured by the number of solvents for the ester) is obtained a t the valerate or caproate level, depending on whether results a t room temperature or elevated temperatures are considered. I n general, the chlorinated solvents show the widest range of solvent power. Methylene chloride, chloroform, and s-tetrachloroethane are the only compounds which are solvents throughout t h e entire series. Solvents for the triacetate are limited in number.
Number of carbon atoms in esterifying acid
Figure 6.
Specific R o t a t i o n s of Triesters 25'
C., 589 m
p
OPTICALROTATION(determined through the courtesy of the High Polymer Division of the Kodak Research Laboratories). The specific rotations of the esters were determined in benzene and in chloroform a t a concentration of 1.0 gram per 100 ml. of solution. The measurements were made in a 1-dm. tube a t 25 C. using light of 589 mp wave length. These data are shown in Figure 6. I n both solvents, the trend is for the rotation t o become less negative as the series is ascended. O
LITERATURE CITED
(1) Baker, W.O.,U. S. Patent 2,362,182(Nov. 7, 1944). (2) Hatgedorn, M., and Moeller, P., Cellulosechemie, 12,29 (1931) (3) Hagedorn, M., and Moeller, P., Verofentl. 7uiss. 2entr.-Labs. phot., Abt. I . G. Furbenind. A.G., A g f u , 1, 150 (1930). (4) Malm, C. J., Genung, L. B., and Fleckenstein, J . V., IND.ENO. CHEM., 39,1499 (1947). (5) Malm, C. J., Mench, J. W., Kendall, D. L., and Hiatt, G. D., Ibid., 43,684 (1951). (6) Sheppard, S. E.,and Newsome, P. T., J. Phys. Chem., 39, 143 (1935). (7)Wilson, R. E., IND.ENG.CHEM.,13,326 (1921). RECEIVED August 2, 1950. Presented before the Divisioa of Cellulose CHEMICALSOCIBTY, Chemistry at the 118th Meeting of the AMERICAN Chicago, Ill.
