A M I N A T I O N OF CELLULOSE A C E T A T E CH L O R O A C E T A T E Preparation and Properties of Cellulose Acetate N , N - Diethylaminoacetate G. D . H I A T T ,
J. W .
MENCH, A N D B. FULKERSON
Cellulose Technology Division, Eastman Kodak Co., Rochester, N . Y . A new acid-soluble cellulose derivative, cellulose acetate N,N-diethylaminoacetate (CADA), has been prepared b y the reaction of diethylamine with cellulose acetate chloroacetate. The CADA i s soluble in many organic solvents and in dilute aqueous acid solutions below a pH of 5.4 but i s insoluble in water. It i s com-
patible with many synthetic resins, cellulose derivatives, and plasticizers, and dilute acetic acid solutions of the ester are compatible with many water-soluble polymers. When coated from proper solvents CADA gives clear, self-supporting films. Other secondary omines also react with cellulose acetate chloroacetate to yield the dialkylarninoacetate esters, but reaction with primary amines results predominantly in removal of the entire chloroacetyl grouping b y aminolysis. HE
need for cellulose derivatives which are insoluble in
Twater but soluble in organic solvents and in dilute, aqueous alkalies has been met by the preparation of cellulose esters of dicarboxylic acids (5). There are also specialized uses for cellulose derivatives which are insoluble in water but soluble in organic solvents and in dilute, aqueous acid. This paper describes a method for the preparation of such an ester? consisting of the amination of cellulose acetate chloroacetate with diethylamine, and describes some of the properties of a typical product. Amination of cellulose derivatives containing readily replaceable halogen has been but little exploited, although one typical patent shows the preparation of cellulose chloroacetate esters followed by amination of the products with ammonia or amines ( 7 ) . Few or no data, however, are available on the composition or properties of the products. A previous paper from this laboratory (7) has described the quaternization of cellulose acetate chloroacetates with the tertiary amine pyridine to yield water-soluble products. Preparation of Cellulose Acetate Chl6roacetate
Previous publications (,?, 7) describe a variety of methods for the preparation of the acetate chloroacetates, any of which may produce esters suitable for amination. Those methods utilizing chloroacetic anhydride yield products relatively high in viscosity, whereas those using chloroacetic acid are more economical but in general require long reaction times and give products of lower viscosity. A more convenient method of preparing high viscosity cellulose acetate chloroacetate, recently described (8),consists of "impelling" chloroacetic acid onto hydrolyzed cellulose acetate by means of acetic anhydride in the presence of relatively large amounts of a basic catalyst such as sodium acetate. By this method chloroacet),l is introduced almost exclusively without the use of chloroacetic anhydride and without requiring long reaction times. Typical Preparation. Fifty pounds of a cellulose acetate containing 32o/G acetyl [1.75 acetyls per anhydroglucose unit (a.g.u.)] was placed in a Werner-Pfleiderer mixer with 150 pounds of chloroacetic acid and the mass was mixed a t 60' to 70 ' C. until the acid melted and dissolved the cellulose acetate. At this point the mass was cooled to 55' C. and 25 pounds of
anhydrous sodium acetate was added, followed by 30 pounds of acetic anhydride over a period of 15 minutes. After 5 hours' reaction time a t 80 ' C. the reaction mass was cooled to 60' C. and the product precipitated by adding water while mixing continued. At the point of partial precipitation the supernatant liquid was decanted and replaced with fresh water. The granular product obtained was further ground to 40-mesh and washed free of acid with distilled water. After centriIt had the following fuging, the product was dried a t 60" analysis: 7 0 chloroacetyl, 21.7 (0.85 group per a.g.u.); yo combined acetyl, 25.9 (I .85 groups per a.g.u.); and inherent viscosity in acetone, 0.81,
c.
Amination of Cellulose Acetate Chloroacetate
With Diethylamine. I n the reaction of a secondary amine with cellulose acetate chloroacetate, I mole of hydrogen chloride is liberated for every equivalent of chlorine reacting. This immediately reacts with a second mole of amine to form the hydrochloride and makes necessary the use of at least 2 moles of amine per equivalent of chlorine in the chloroacetate. When acetone, methyl ethyl ketone, or dioxane is used as reaction solvent, the amine hydrochloride is insoluble and can be seen as crystals soon after the reaction starts.
EFFECTOF TIMEON AMINATION REACTION.Twenty-gram portions of a cellulose acetate chloroacetate containing 20,3y0 chloroacetyl were dissolved in 100 ml. of 1,4-dioxane with stirring and made to react with 11.62 grams of diethylamine (2.8 moles per mole of chlorine) at steam bath temperature. Reaction times were varied from 0.5 to 24 hours, the samples being isolated by dilution of the reaction solutions with acetone, followed by precipitation into water. After thorough washing with distilled water, the esters were dried at 60' C. Kitrogen contents were determined by the micro-Dumas method and residual chlorine contents by a saponification procedure (7). The data obtained, shown in Figure 1, indicate that under these reaction conditions the maximum nitrogen content is attained in about 1 hour, but the minimum residual chlorine content is not reached until about 4 hours. Cellulose acetate chloroacetates containing smaller amounts of chloroacetyl than the previously described samples were prepared and aminated with diethylamine to determine the minimum chlorine content required to give a n aminated product soluble in dilute acid. These data, shown in Table I, indicate that a minimum of about 11% chloroacetyl is VOL. 3
NO. 4
DECEMBER
1964
295
Table 1.
o/o
I
Sample
Dilute Acid Solubility of Cellulose Acetate N,NDiethylaminoacetate Analysis of cellulose Acetate Chloroacetate Aminated Product Groups/A.G.C. - __ Solubility Chlorobined Chloro- Nitroin 0.5C;l, acetyl, % acetyl, % Acetyl acetyl gen, % acetic acid
corn-
1 2 3
7.9 8.7 10.7
Table II. 0
2
4
6
a
24
Reaction time (hrs.) Figure 1. Reaction of diethylamine with cellulose acetate chloroacetate
necessary to yield aminated products (with diethylamine) showing solubility in dilute acetic acid. With Other Secondary Amines. Table I1 shows the result obtained on the aminat'ion of a cellulose acetate chloroacetate chloroacetyl with various secondary amines. containing 21 .'i% All reactions were run using 1 part of chloroacetate, 4 parts of 1,4-dioxane solvent, and 2.5 moles of amine per mole of chlorine. Reaction conditions were 4 hours a t steam bath temperature. Nitrogen and residual chlorine contents OP the products indicate that reasonably complete amination is attained with all of the amines except diisopropylamine. T h e difference between the theoretical and observed nitrogen contents, except with diisopropylamine, is a measure of aminolysis of the entire chloroacetyl group. With Primary Amines. All of the isomeric primary butylamines were made to react with a cellulose acetate chloroacetate of 21.7y0 chloroacetyl content, using 4 parts of 1,4dioxane Solvent along with 2.6 moles of amine per mole of chlorine and running the reactions for 6 hours at 60" C. T h e nitrogen contents varied from 0.2 to 0.570, indicating that only minor amounts of amination are attained. Instead, there is substantial removal of the entire chloroacetyl groupings as evidenced by residual chlorine contents of O.lyOand combined acetyl contents which approximate the 32% acetyl content of the cellulose acetate from which the chloroacetate was prepared. Preparation of Cellulose Acetate N,N-Diethylaminoacetate (CADA)
T h e amination of cellulose acetate chloroacetate with diethylamine using methyl ethyl ketone as reaction solvent in a more practical and concentrated reaction mixture is shown in the following example : Seven pounds of a cellulose acetate chloroacetate containing 1.84 acetyl and 0.85 chloroacetyl groups per a.g.u. was dissolved in 1 4 pounds of methyl ethyl ketone with stirring in a 22-liter fiask and heated to refiux temperature. Diethylamine (3.62 pounds, 2.5 moles per mole of chlorine) was added slowly over a period of 1 . 5 hours, and the reaction mixture was held a t reflux for a total of 7 hours. After suitable dilution with acetone. the product was isolated by precipitation into and washing \zith distilled izater. It contained 3.36y0nitrogen (Kjeldahl) a n d had a combined acetyl content of 25.1y0 and a residual chlorine content of 0.06%. T h e product thus approximated 0.80 ,Y.,Y-diethylaminoacetyl: 1.9 acetyl, and negligible chloroacetyl groups per a.g.u. in composition. 296
I&EC
PRODUCT RESEARCH A N D DEVELOPMENT
35.6 33.8 32.8
2.34 2.18 2.15
0.29 0.31 0.39
1.O 1.2 1.6
Insoluble Insoluble Soluble
Amination of Cellulose Acetate Chloroacetate with Secondary Amines
Secondary Amine
Nitrogen,
Residual Chlorine, %
DimethylDiethylDiisopropylDi-n-butylDibenzylMorpholine
2.1 2.9 0.6 2.8 2.5 2.5
