I
JOHN E.
KIEFER, GEORGE P. TOUEY, and JOHN R. CALDWELL
Research Laboratories, Tennessee Eastman Co., Division of Eastman Kodak Co., Kingsport, Tenn.
New Nitrogen-Containing Cellulose Esters from
Cellulose Acetate Succinamates The behavior of succinamic acid derivatives is unique and may lead to a new synthetic yarn that can be dyed with acid wool dyes
A of methods have been devised for producing cellulose derivatives NUMBER
containing amino or amido nitrogen substituents. These methods usually involve etherification rather than esterification; the few esterification methods are either complicated or expensive. I n the present study, amido nitrogen \vas introduced into cellulose by esterification with a n .\--substituted succinamic acid in the presence of a n aliphatic anhydride. 'The reactivity of some succinamic acids xrith cellulose was compared with that of several other amic acids, acetylated amino acids, monoethyl succinate: benzoic acid, and butyric acid. T h e almost quantitative reaction of 11*substituted succinamic acids with cellulose in the presence of a simple acid anhydride is believed to be unique. I t offers a simple method for introducing a variety of .V-alkylamido and JV-arylamido groups into common cellulose esters. Succinamic acid esters of cellulose having a wide range of properties can be prepared. T h e addition of .Y?,V-dimethylsuccinamic acid to a cellulose acetylation formula results in a cellulose acetate with improved dyeing properties. T h e *V,>\-dimethylsuccinamate group has little effect on the solubility or melting properties of the cellulose acetate; however. if the methyl groups on the succinamic acid are replaced by a larger alkyl group or a n aryl group, the cellulose esters have increased solubility in organic solvents and a lower melting point. Experimental
Preparation of Amic Acids. T h e .V-substituted amic acids were prepared from anhydrides of succinic, maleic: glutaric, and phthalic acids using a method similar to that described by Bryden and Pauling (2). T h e anhydride was dissolved in 1.5 parts by weight ofp-dioxane, and a molar amount of a primary or secondary amine was then added as the solution was heated to 75' C. After 2 to 3 hours, the p dioxane was distilled off and the products were purified by crystallization. Amic acids were prepared from dimethylamine: diethylamine, dibutylamine, iso-
butylamine, aniline, and morpholine. T h e yields were almost quantitative. Preparation of Cellulose Esters. T h e reactions of cellulose with acetic anhydride and n'substituted amic acids, acetylated amino acids, monoethyl succinate, benzoic acid, and butyric acid were carried out as follows: Wood pulp (1 mole) was activated by soaking in water for 1 hour. T h e water \vas then replaced by p-dioxane. T h e activated wood pulp was then heated a t the proper temperature with 0.3 to 3.0 moles of acid, 4 moles of acetic anhydride, 20 moles of p-dioxane, and 0.09 mole of sulfuric acid until the pulp dissolved to make a smooth, grain-free dope. The catalyst was then neutralized with aqueous magnesium acetate solution, and the ester was precipitated in water. Esters prepared from water-soluble acids were washed with water, and those prepared from water-insoluble acids were washed with isopropyl alcohol. Cellulose propionate S~.V-diethvlsuccinamate and cellulose butyrate lV,.Vdiethylsuccinamate were also prepared : Water-activated wood pulp (1 mole) was heated to 100' C. with 0.5 mole of .V,LV-diethylsuccinamic acid, 4 moles of propionic or butyric anhydride, 8 moles of propionic or butyric acid, and 0.09 mole of sulfuric acid until the pulp dissolved to form a smooth dope. T h e catalyst was neutralized with aqueous magnesium acetate solution and the ester precipitated in 30% aqueous acetic acid. T h e product was washed in 50% aqueous isopropyl alcohol. Analytical Procedures. Nitrogen was determined by the Kjeldahl method,
loor
P
y
N. N D ~ m o t h ~ l i u c i 8 n o moi8d lc N Irapropylsucc~nomir ocsd N. N-Diethyliucrinomic ocsd
i
\b
601
- -1
50;--____
05
10
15
10
-
25
IO
ACID USED, MOLEWMOLE OF CELLULOSE
Figure 1. Esterification efficiency declined with increasing N-substituted succinamic acid concentration
and total acyl was determined by the Eberstadt method. T h e inherent viscosities were measured with a modified Russell-LYagner viscometer, using a concentration of 0.23 gram of ester in 100 ml. of 90%, methylene chloride-lOyc methanol a t 25" C. Discussion of Results
Comparison of Acids as Esterifying Agents. All products obtained from *Y-substituted succinamic acids and acetic anhydride Irere mixed triesters containing acetyl groups as the major substituents (Table I). O n e surprising result was the high reactivity of these substituted succinamic acids wirh the cellulose. .Although only 0.3 mole of th? acid was used: compared to 4 moles of acetic anhydride, nearly all of the acid combined Tvith cellulose. T h e high temperatures required for esterifications were also unexpected. When these reactions were carried out a t temperatures usually used in sulfuric acid-catalyzed esterifications, little acylation occurred. Although high temperatures were used, the products were not highly degraded as they had inherent viscosities of 1.5 to 2.1. \Yhen another acid was used, the product was substantially cellulose triacetate, indicating that only a small amount of the acid had combined with cellulose. T h e low degree of substitution with 4-acetamidobutyric acid was unexpected as it is a n isomer of ,V>.'l'-dimethylsuccinamic acid, M-hich reacted almost quantitatively with cellulose. T h e high temperatures required for the reaction of substituted amic or substituted amino acids with cellulose may be due to the formation of complexes of the acids with the catalyst through their amino or amido groups. T h e complex, in turn, may retard the hydrolytic action of the catalyst. Cellulose propionate h:L\7-diethylsuccinamate was prepared using 0.5 mole of .V,,\-diethylsuccinamic acid. T h e degree of substitution of 0.43 of succinamoyl group per Cs unit shows that 80% of the available acid combined. A rather high temperature (100' C.) was required to produce cellulose propionate succinamate; however, the use of propionic acid as a diluent offers a n VOL. 5 1 , NO. 12
DECEMBER 1959
1481
Pertinent Literature
Table 1.
Etherification
+ HO~SOCHZCHZNHZ xH (Ce1l)OCHzCHzNHz (Cel1)OH + CHz-CHz NaoH* (Ce1l)OCH~CHzNHZ
(Cel1)OH
+
\ /
Ref. (6)
(4)
O
NH CHI = CHCONHz NaOH -* (Cell)OCHzCHzCONH2 (1)
+ (Cel1)OH + ClCHzCO-
(Cel1)OH
(8)
Esterification
/OAC Cell-OH \OAc
+ RNHz
-+
(3)
Cell-OOCCHzNHR /OAC \OAc
zO+ + CH3CONHCHzCOOH (CICHzCO) ,OAc Cell- OOCCHzNHCOCH3 (5) \OAc 0
I1
C
~ ~ \OAc
~-/
Succinamic acids (CHs)zNCOCHzCHzCOOH (CzH5)zNCOCHzCHzCOOH
84 77 90
70 90 70 100 80 70
3 5 3 6 3
