C. J. MALM, J. W. MENCH, BRAZELTON FULKERSON, and G. D. HIATT N. Y.
Cellulose Acetate Development Division, Eastman Kodak Co., Rochester,
Preparation of Phthalic Acid Esters of Cellulose b Phthalic acid derivatives o f ethylcellulose and cellulose acetate can be prepared without the use o f pyridine b y substituting sodium acetate as catalyst and acetic acid as reaction solvent. A fact helpful for economical batch production is that the phthalyl content of the derivatives is inversely dependent on the reaction temperature, althoughthe rate of introduction is faster at high temperatures. Phthalyl content also depends on proportions o f acetic acid, sodium acetate, and phthalic anhydride.
THE
half esters of phthalic acid with cellulose are soluble in organic solvents but are quite resistant to water. Be. cause of their ability to form watersoluble salts readily with the alkali metal ions, ammonia, and the lower molecular weight amines, they have been found to be of interest as enteric coatings (7, 6, 8: 73), photographic film backings (4, 77, 79, 27, 22), antiabrasion and protective coatings (3, 24), for textile impregnation (23), and as components of photographic emulsions i(25) and water-base paints ( 5 ) . The preparation of the phthalate derivatives of cellulose has most commonly been accomplished by the reaction of partially substituted cellulose esters or ethers with phthalic anhydride in the presence of pyridine, the latter acting both as catalyst and reaction solvent (74, 78, 20). Variations have been described in which part or all of the pyridine is replaced with solvents such as dioxane (2, 7)! acetone (2), or methyl ethyl ketone (2, 72). The use of molten phthalic anhydride has also been proposed (9). Some of the most useful phthalate derivatives of cellulose are the acetate phthalates and the ethylcellulose phthalates, since both classes of compounds have wide ranges of solubilities in organic solvents. The ether phthalates are prepared by the phthalation of cellulose ethers. When attempts are made to prepare the cellulose acetate phthalates directly from cellulose, using acid catalysts and a mixture of the two anhydrides, the competition between acetic and phthalic anhydrides for the cellulose is so highly in favor of acetyl that negligible amounts of phthalyl are introduced, even
84
INDUSTRIAL A N D ENGINEERING CHEMISTRY
when phthalic anhydride is present in relatively large amounts. However, basic catalysts such as sodium acetate. rather than acid catalysts, promote the esterification of activated cellulose or partially substituted cellulose derivatives with phthalic anhydride when acetic acid is used as reaction solvent. There is negligible introduction of acetyl (70). This gives a convenient and less expensive method of preparing these materials. The effects of some sf the reaction variables upon the phthalyl contents of the resulting products are discussed here.
Ethylcellulose Phthalates Preparation. A commercial ethylcellulose containing 450/, ethoxyl was chosen as the starting material. The effects of varying the amounts of reaction solvent (acetic acid), phthalic anhydride, and sodium acetate were determined by using the following amounts of reagents: Amount, Parts/Part of EthylceIlulose 1.5, 2.5, and 3.5 0.1, 0.3, 0.8, and 1.5
Reagent Acetic acid Sodium acetate
Table I.
Reaction, Temp., OC.
25
Reaction Time, Hours 0.5
7
80
24 48 0.5 1 2 4 7 24 48 0.5 1 2 4
7 a
All possible combinations of the variables were made. A typical esterification was run as follows: Forty grams of ethylcellulose containing 45% ethoxyl, 15.5 grams of phthalic anhydride, and 32 grams of anhydrous sodium acetate were dissolved in 100 grams of glacial acetic acid in a 500-mL flask fitted with an eEcient stirrer. The reaction was conducted a t 95' C. with continuous stirring for 6 hours. 'The product was then isolated by dilution with acetic acid and precipitation into distilled water. The precipitate was washed with distilled water until the wash liquor was free of acidity, and the product was dried at 60" C. Analysis: 70phthalyl (direct titration), 13.1; yo total acyl, as phthalyl (saponification), 13.1. The phthalyl contents of the products were determined either by direct titration of the carboxyl or by the ultraviolet
Phthalation of Cellulose Acetate at Various Temperatures (10 parts of solvent)
1 2 4.5
40
Phthalic anhydride 0.388,0.728, 1.21, and 1.94 These correspond to 0.8,1.5,2.5,and4.0 times the theoretical amount required per mole of available hydroxyl.
24 48 Starting material.
Analysis of Products, % Total Comacyl as bined Phthalyl acetyl acetyl
Groups/Anhydroglucose Unit Phthalyl Acetyl Hydroxyl
..
32.Za
32.Za
..
1.77"
1.23a
0.9 2.0 4.0 7.8 10.8 20.9 24.7
32.5 32.5 33.0 33.9 34.6 37.6 38.2
32.0 31.4 30.7 29.4 28.4 25.5 24.0
0.02 0.03 0.07 0.13 0.19 0.42 0.52
1.78 1.76 1.75 1.74 1.74 1.78 1.79
1.20 1.21 1.18 1.13 1.07 0.80 0.69
4.5 6.6 11.1 16.2 19.9 25.5 26.9 17.1 18.9 20.6 22.0 22.5 22.2 21.7
33.1 33.9 34.7 36.0 36.3 38.1 37.9
30.2 30.1 28.3 26.7 24.8 23.4 22.4
1.72 1.77 1.74 1.74 1.67 1.70 1.65
1.21 1.11 1.06 0.96 0.94
36.3 37.0 37.1 37.0 37.8 38.2 37.3
26.4 26.1 25.2 24.3 24.8 25.4 24.8
0.07 0.12 0.20 0.30 0.39 0.53 0.57 0.32 0.37 0.41 0.44 0.46 0.45 0.44
1.74 1.77 1.73 1.69 1.75 1.80 1.73
0.94 0.86 0.86 0.87 0.79 0.75 0.83
0.77 0.78
CELLULOSE D E R I V A T I V E S
a
0.1 port o f sodium acetate >-
,
1
1
I
I
l
,
0.3 part o f sodium acetate I
l
l
I
I
I
l I
1 ,
1
-
2
20-
Q
a"
_-
15-
IO
0 8 port of sodium acetate --
I
02
0.6
1
1.0
sodium acetate -
I
1
,
1.4
1.8
0.6
1
I O
1
1.4
1
I 8
Ports phthalic anhydride/par' etnylcellulose
Figure 1. Effect of variation of phthalic anhydride, sodium acetate, and acetic acid in phthalation of ethylcellulose
0 1.5 A 2.5 0 3.5
parts AcOH partsAcOH parts AcOH
absorption of solutions a t 275 mp (75). Values determined in this manner were also verified by determination of total acyl contents by saponification (75) to verify the absence of appreciable amounts of acetyl. The data obtained are shown in Figure 1 and may be summarized as follows.
The use of increasing amounts of acetic acid solvent gives products of lower phthalyl contents. This is true at all levels of sodium acetate and a t all levels of phthalic anhydride. This could be explained by assuming that phthalation is an equilibrium reaction whose position is affected, not only by the relative amounts of reagents, but also by their concentration in the reaction mixture. Since the use of excessive amounts of acetic acid requires the use of increasing amounts of the other reagents to attain a given phthalyl content, it should be kept at a minimum. Increasing amounts of phthalic anhydride give increasing amounts of combined phthalyl in the products. The effect, however, begins to level in the range of 2.5 times the theoretical amount of anhydride at the higher levels (0.8 and 1.5 parts) of sodium acetate, even though complete esterification was not attained. Increasing amounts of sodium acetate also gave increased phthalyl contents of the products. This is true for all levels of anhydride and acetic acid. The choice of formula will depend on the amount of combined phythalyl desired in the product, the equipment available, and on the particular reagent most desired to be in excess because of cost considerations. The range of formulas available is summarized in Figure 2. This figure is valid only for use on the 1.5-parts level of acetic acid, which is about the minimum which may be employed to give reaction mixtures capable of being stirred a t 95" C. in laboratory equipment.
Per cent phthoiyi in product
1
I
5
IO
I
2.0,
I
oi
012
,
,
I
d 4
d.6
OI.8
,
1
,
i
I(0
1'2
114
1'6
Parts sodium ocetote / p o r t ethylcelluiose
-1
'
Figure 2. Relation of phthalation bath composition to phthalyl content of ethylcellulose phthalate 1.5 parts of acetic acid solvent and ethyicellulose of 45% ethoxyl content
The range of phthalyl contents obtained with this starting material was 9 to 26%. Complete phthalation was not attained; about 0.2 hydroxyl group per anhydroglucose unit remained unesterified in the product containing 26% phthalyl. Using similar reaction procedures, phthalates having combined phthalyl contents of 9 to 1670 were also prepared from a commercial ethylcellulose containing 47.7% ethoxyl, and products of 7 to 14% phthalyl from an ethylcellulose containing 49.570 ethoxyl. In no case were fully substituted products obtained. Solubility Properties. The ethylcellulose phthalates have organic solvent solubilities which do not vary greatly
I
I
I
I
35
40
45
30 c
u
U 3
25 Q
E
0 f r
. 2
20
a 15
0
27 5 % 25.0%
0 060
r
&04-
a B
J
0.2
a
, L L '0
0 2
04
06
08
I O
P o r t s sodturn acetote/port cellulose acetate
'0
20 25 30 Reaction tlme ( h o u r s )
15
'
Figure 3. Relation of phthalation bath composition to phthalyl content of cellulose acetate phthalate
Figure 4. Effect of time and temperature on phthalyl content of cellulose acetate phthalate
2.0 parts of acetic acid solvent and cellulose acetate of 32.2% acetyl content
10 parts of acetic acid solvent, 1 .O part of sodium acetate, 1 .O part of phthalic anhydride, cellulose acetate of 32.2% acetyl content VOL. 49, NO. 1
JANUARY 1957
85
from those of the parent ethylcellulose, although there is some tendency toward decreased solubility in the aromatic hydrocarbons as the phthalyl content in-? creases. Both the ethoxyl content of the starting material and the degree of phthalation influence the solubilities of the products in aqueous alkalies. For example, all of the phthalate esters prepared from the 45% ethoxyl ethylcellulose (in the range of 10 to 267" combined phthalyl content) are readily soluble in 5% aqueous ammonia. The products containing above 17 to 1870 phthalyl are soluble at room temperature, whereas cooling is required for the samples below this phthalyl content. This inverse solubility with temperature in aqueous solutions is similar to that observed with cellulose ethers themselves. The phthalate esters prepared from the 47.7y0 ethoxyl ethylcellulose, containing 10 to 16% phthalyl, all required cooling for solubility in 5% aqueous ammonia; none dissolved at room temperature. The esters prepared from the 49.5'30 ethoxyl ethylcellulose also dissolved in cold 5% aqueous ammonia, if the phthalyl contents were above 11%. Cellulose Acetate Phthalates
Preparation. A set of experiments similar to that described for ethylcellulose phthalates was made using a cellulose acetate starting material containing 32.27, acetyl. Since the previous runs indicated the desirability of using the least possible amount of acetic acid solvent, a level of 2 parts of solvent was selected as being about the amount leading to reaction mixtures which could be readily stirred in laboratory equipment. All combinations of the following reagent amounts were employed.
Reagent Acetic acid Sodium acetate Phthalic anhydride
Amount, Parts/Part of Cellulose Acetate 2.0 0.1, 0.25,0.5, and 1 . 0 0.57, 0.96, and 1.92 These correspond to 0.75, 1.25, and 2.5 times the theoretical amounts required per mole of available hydroxyl
3
Reaction time (hours) Figure 5. Effect of time and temperature on phthalyl content of cellulose acetate phthalate 2.0 parts of acetic acid solvent, 0.2 part of sodium acetate, 1 .O part of phthalic anhydride, cellulose acetate of 32.2% acetyl content
of either anhydride or sodium acetate leads to increased amounts of combined phthalyl in the products, although complete esterification is not attained. Effect of Temperature. During the course of the work, reaction mixtures which were allowed to cool overnight to room temperature before dilution and precipitation frequently gave products having more combined phthalyl than those which were isolated at the end of the reaction period. Since it was already known that prolonged reaction at 95" C. would not lead to increased phthalyl contents, the effect of reaction temperature was investigated. Temperatures of 25", 40°, and 80" C. were chosen, and a reaction mixture utilizing a large amount of solvent was selected for ease
As in the case of the ethylcellulose phthalate preparations, these esterifications were made on a laboratory scale in 500-ml. flasks using 40 grams of the cellulose acetate starting material. Reactions were run for 6 hours at 95" C. with continuous stirring. The products were isolated and analyzed as described for the ethylcellulose derivatives. The relationships between varying amounts of phthalic anhydride and sodium acetate on the phthalyl contents of the products are shown in Figure 3. The range of variables selected gave products containing from 21 to 38% of combined phthalyl. As with the ethylcellulose derivatives, the use of increasing amounts
86
3 30
5
INDUSTRIAL AND ENGINEERING CHEMISTRY
Reaction Temp.,
Reaction Time,
OC.
Hours
Phthalyl
25
1 2 4.5 7 24 48 0.5 1 2 4.5
12.0 17.1 23.4 26.0 29.5 30.5 17.7 23.4 26.6 29.3 30.5 32.0 33.0 20.3 25.0 25.8 26.8 25.2 21.9
7 80
24 48 0.5 1 L
a
The data are shown in Table I and in Figure 4. The runs at 25" and 40" C. both gave products of higher combined phthalyl contents than the maximum obtained in the run made at higher temperature, although the rates of in-
Phthalation of Cellulose Acetate a t Various Temperatures (2 parts of solvent) Analysis of Products, %-
Table II.
60
of handling of the lower temperature runs. The esterifications were run in the following manner: Portions of 150 grams of a cellulose acetate containing 32.2Y0acetyl were placed in 3-liter flasks fitted with efficient stirrers, and were dissolved in mixtures consisting of 1500 grams of acetic acid, 150 grams of phthalic anhydride, and 150 grams of anhydrous sodium acetate. The flasks were then placed in oil baths controlled a t the desired temperatures, and samples were isolated at intervals.
7.5 24 48 Starting material.
..
Total acyl as acetyl 32.2Q 34.5 35.5 37.6 38.1 39.0 39.4 35.9 37.7 38.4 39.4 39.4 40.7 40.8 36.5 37.8 37.9 38.6 38.4 38.3
Combined acetj-l 32.2" 27.6 25.6 24.1 23.1 22.0 21.8 25.7 24.2 23.1 22.5 21.8 22.2 21.8 24.8 23.4 23.0 23.1 23.9 25.9
Groups/AnhydroglucoaeUnit Acetyl Hydroxyl
Phthalyl
-.
0.21 0.32 0.48 0.55 0.65 0.68 0.34 0.48 0.57 0.65 0.68 0.75 0.78 0.40 0.52 0.54 0.57 0.53 0.41
1.77' 1.70 1.67 1.71 1.69 1.69 1.68 1.69 1.72 1.71 1.74 1.70 1.80 1.79 1.68 1.69 1.67 1.72 1.75 1.83
1.23" 1.09 1.01 0.85 0.76 0.66 0.64 0.97 0.80 0.72 0.61 0.62 0.45 0.43 0.92 0.79 0.79 0.71 0.72 0.76
CELLULOSE D E R I V A T I V E S troductions were slower a t the lower temperatures. The lower degree of phthalation observed in the run made a t 80" C. is not due to a decrease in available hydroxyls because of acetylation, since Table I shows that the number of acetyl groups per anhydroglucose unit remains fairly constant and comparable with that of the starting material. Because of the unexpected effect of temperature on the phthalyl contents of the products, this experiment was repeated using a more concentrated formula and equipment suited for large scale runs. Six pounds of cellulose acetate (32.2% acetyl), 12.0 pounds of acetic acid, 6.0 pounds of phthalic anhydride, and 1.2 pounds of anhydrous sodium acetate were charged into a 5-gallon WernerPfleiderer-type jacketed mixer. Runs were made a t 25", 60°, and 80" C. with sampling a t appropriate intervals. Results from these experiments are shown in Table I1 and in Figure 5. AS in the case of the previous experiments, the products from the lower temperature runs attained higher phthalyl contents than those from the phthalation conducted a t 80" C. That this effect of temperature on the phthalyl contents of the products is reversible in the early heating stages is shown by the following experiment: A reaction mixture was made of 200 grams of cellulose acetate (32.2% acetyl), 200 grams of phthalic anhydride, 40 grams of anhydrous sodium acetate, and 400 grams of acetic acid. The reaction was run for 2 hours at 95" C. and sampled. The remainder of the reaction mixture was cooled to 40" C., held at this temperature for 24 hours, and sampled again. This cycle was repeated four
3 5 5
C
:I O -
5t I
I
I
I
I
5
IO
15
20
I
I
I
I
1
30
35
40
45
50
1
R e o c t i o n t i m e (hours)
more times, heating for 2 hours a t 95' and sampling, then cooling for 24 hours to 40" C. and sampling. The results are shown in Table 111. The phthalyl and hydroxyl contents alternate inversely with each other, and both analyses alternate with the temperature of reaction. Although there is variation in the numbers of acetyl groups per anhydroglucose unit, no such pattern is observed. Most of this variation is due to the degree of precision of the total acyl analysis (3~7 limits = f 0 . 3 % , calculated as acetyl) and to the sensitivity to small variations of the equations for calculation of acetyl substitution per anhydroglucose unit. I t was a t first considered that the lower phthalyl contents obtained in hightemperature reactions might be caused by a decrease in phthalic anhydride concentration by partial reaction
i-
5-
25
-
Figure 6. Reversible effect of amount of reaction diluent on phthalyl content of product
30
Q
-
0 IO p o r t s of ocetic o c i d 0 5 p o r t s of ocetic o c i d initialiy, with 5 oddltiona-l p o r t s added a t 4 hours r e o c t l o n time
a
'0
o d d i t i o n o l p o r t s of o c e t i c o c i d o d d e d
2.0% water in acetic acid (equivalent to 164% of the phthalic anhydride u s e d )
with acetic acid. However, similar alternations of phthalyl content with temperature of reaction occur also in reaction mixtures utilizing acetone as solvent and pyridine as catalyst. The reaction, thus, is apparently an equilibrium reaction which is dependent on temperature as well as reagent concentrations. This fact has proven useful in the production of these materials, in that higher phthalyl content products can be made by employing a relatively short high-temperature reaction followed by cooling before dilution and isolation, eliminating the necessity of using larger amounts of reagents to obtain the higher phthalyl contents. The reversibility of the phthalation equilibrium with reagent concentration was confirmed. Two reaction mixtures were made consisting of 1 part of cellulose acetate (32.8% acetyl), 1 part of phthalic anhydride, 1 part of anhydrous sodium acetate, and either 10 parts or 5 parts of acetic acid. The run with 10 parts of solvent was sampled over a period of 48 hours, whereas the other run was sampled until the phthalyl content had essentially reached a maximum (4 hours), and then was diluted with additional acetic acid so that the equivalent of 10 parts was present. These data (Figure 6) show that, upon continued sampling, the phthalyl contents of the products from the diluted run rapidly approach those attained in the experiment using 10 parts of acetic acid from the start. During the course of the work it was occasionally observed that the phthalyl contents would reach a maximum and then, upon prolonged reaction time, decrease-e.g., the 80" C. run of Figure 5. It was suspected that if water was present, the phthalic anhydride might react preferentially with the cellulose ester and that later reaction of the anhydride with water, reducing the anVOL. 49, NO. 1
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JANUARY 1957
87
Table 111.
Phthalation of Cellulose Acetate: Alternation of Reaction Temperature Analysis of Products, % ' Reaction Time, Total ComHours at acyl as bined Groups/Anhydroglucose Unit 95' C. 40' C. Phthalyl acetyl acetyl Acetyl Phthalyl Hydroxyl 2 24 2 24 2 24 2 24 2 24 Av. of 40" runs Av. of 95O runs
28.3 30.9 28.2 31.2 28.1 30.2 27.7 31.7 26.6 29.9 30.8 27.8
39.1 40.1 39.0 39.6 39.3 39.6 38.6 39.6 38.8 39.5 39.7 39.0
hydride concentration, would cause a shift in the equilibrium and a decrease in the phthalyl content of the product. This hypothesis was tested by phthalations run with 10 parts of acetic acid as described above, using acid containing 1 and 2% of water. These amounts are equivalent to 82 and 1647,, respectively. of the phthalic anhydride employed. The results, shown in Figure 7, are compared with a normal run in which the moisture content of the acetic acid was 0.27c. The phthalyl contents of the products rapidly reach a maximum and then decrease. Apparently the anhydride reacts more rapidly with the cellulosic hydroxyls than with water, since considerable phthalation of the cellulose acetate occurred even in the experiment which contained more than enough water to destroy all of the anhvdride.
1.74 1.77 1.72 1.71 1.76 1.73 1.69 1.69 1.75 1.72 1.73 1.72
22.8 22.3 22.7 21.6 23.1 22.2 22.6 21.3 23.5 22.2 21.9 22.9
0.62 0.71 0.62 0.71 0.62 0.68 0.60 0.72 0.57 0.67 0.70 0.61
0.64 0.52 0.66 0.58 0.62 0.59 0.71 0.59 0.68 0.61 0.58 0.66
Solubility Properties. To study the solubility of a wide range of cellulose phthalates and acetate phthalate compositions, a regenerated cellulose and cellulose acetates having various acetyl contents were phthalated by procedures described here, using a variety of reagent levels and reaction times. These compositions are shown in Figure 8. T h e solubilities of the cellulose acetate phthalates in organic solvents approximate those of the simple cellulose acetates having comparable degrees of substitution. The enhanced solubility imparted to cellulose esters by the presence of a higher aliphatic acid ester grouping-i.e. , butyr yl-is not observed with the phthalyl group. Moisture resistance and water tolerance values (16, 17) are also similar to those of cellulose acetates of comparable hydroxyl contents.
Cellulose
'
0
)
\
Proper balance of acetyl, phthalyl, and unesterified hydroxyl groupings gives cellulose acetate phthalates which may form water-soluble salts with alkali metal ions, ammonia, and the lower weight aliphatic amines. Compositions yielding water-soluble sodium salts with 1.5Tc sodium bicarbonate are shown in Figure 8. As would be expected, large amounts of combined phthalyl are required for solubility of samples having a high degree of total substitution (low in unesterified hydroxyl), whereas compositions having a low degree of substitution require only small amounts of phthalyl to yield water-soluble sodium salts.
Literature Cited
(1) Bogin, H. H., U. S. Patent 2,491,475 (Dec. 20, 1949). (2) Crane, C. L., Blanchard, L. W., Zbid., 2,183,982 (Dec. 19, 1939). (3) Fiedler, S. O., Bjorksten, J., Yaeger, L. L., Zbid., 2,578,683 (Dec. 18, 1951'1. (4) Fordyck, C. R., Zbid.,2,000,587 (May 7, 1935). (5) Ibid.,2,338,580 (Jan. 4, 1944). (6) Fox, S. H., Opferman, L. P., Zbid.. 2,390,088 (Dec. 4, 1945). ( 7 ) Genung, L. B., Zbid.,2,126,460 (Aug. 9, 1938). (8) Hiatt, G. D.: Zbzd.,2,196,768 (April 9, 19401 - ,(9) Hiatt, G. D., Emerson, J., Zbid., 2,352,261 (June 27, 1944). (10) Hiatt, G. D., Mench, J. W., Emerson, J., Brit. Patent 722, 594 (Jan. 26, 1955). (11) Malm, C. J., U. S. Patent 1,884,035 (Oct. 25. 19321. Malm, C. 'J., Bearden, L. D., Ibid., 2,379,309 (June 26, 1945). Malm, C. J., Emerson, J., Hiatt, G. D., J . Am. Pharm. Assoc., Sci. Ed. 40, 520-5 (1951 ). Malm, C. J., Fordyce, C. R., IXD. ENG.CHEM.32.405 (1940). (15) Malm, C. J., Genung, L. B., Kuchmy, I V . . Anal. Chem. 25,245 (1953). (16) Malm, C. J.. Mench, J. \Ir., Kendall, D. L., Hiatt, G. D., IND.ENG. CHEM.43, 684 (1951). (17) Malm, C. J., Tanghe, L. ,J., Laird, B., Smith. G. D., J . Am. Chem. SOC. 75, 80 (1953). Malm, C. J., Waring, C. E., U. S. Patent 2,093,462 (Sept. 21, 1937). Nadeau, G. F.,Zbid., 2,211,346,2,211,347 (Aug. 13, 1940); 2,289,799 (July 14, 1942); 2,326,056, 2,326,057 (Aug. 3, 1943); 2,333,809 (Nov. 9, 1943); 2,376,175 (May 15, 1945).
Schulze, P., Zbid.,2,069,974 (Feb. 9, 1937'1. (21) Simmons, N. L., Zbid., 2,327,828 (hug. 24, 1943). (22) Staud, C. J., Ibid., 1,954,337 (April 10, 1943); 2,271,234 (Jan. 27, 1942). (23) Stone, H. G., Malm, C. J., Zbid., 2,108,455 (Feb. 15, 1938). 124) Talbot, R. H., Zbid.,2,331,746 (Oct. . . 12, i943). . (25) Talbot, R. H., McCleary, T. J.. Brit. Patent 724,827 (Feb. 23, 1955). ~I
~~
Figure 8. solution
Solubility of cellulose acetate phthalates in 1.5% sodium bicarbonate
0
0 Q
88
Soluble in 1.570 N a H C 0 3 Insoluble in 1.5% N a H C 0 3 B o r d e r l i n e solubility
INDUSTRIAL AND ENGINEERING CHEMISTRY
RECEIVED for review March 13, 1956 J u n e 20, 1956ACCEPTED
