Reactions of Cellulose With Amic Acids and Anhydride-Ammonia

11 Reactions of Cellulose With Amic Acids and Anhydride-Ammonia

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Part VI: Reaction Stoichiometry B. G. BOWMAN☼and JOHN A. CUCULO Dept. of Textile Chemistry, North Carolina State University, Raleigh, N.C. 27607

The c h e m i c a l and p h y s i c a l p r o p e r t i e s of cellulosic fabrics can be m o d i f i e d i n a pad-bake r e a c t i o n with s o l u t i o n s of c e r t a i n h a l f - a m i d e s of d i c a r b o x y l i c a c i d s (amic a c i d s ) (1, 2, 3). The p r o d u c t s o f the r e a c t i o n are ammonia and cellulose half-acid esters (Equation 1 ) . Woven and nonwoven f a b r i c s composed of

e i t h e r v i s c o s e rayon or c o t t o n (1, 2, 3) and wood p u l p mats (4) have been m o d i f i e d by t h i s p r o c e d u r e . The r e a c t i o n is specific f o r amic a c i d s d e r i v e d from dicarboxylic a c i d s which form i n t e r n a l p e n t a c y c l i c anhydrides (e.g., s u c c i n i c , maleic, p h t h a l i c a c i d s , e t c . ) ( 3 ) . The r e a c t i o n a l s o o c c u r s when s o l u t i o n s of a n h y d r i d e s and aqueous ammonia are r e a c t e d with the cellulosic f a b r i c s ( E q u a t i o n 2) (5). The r e a c t i o n is m o d e r a t e l y c a t a l y z e d by s m a l l amounts of a v a r i e t y of compounds and may be s u c c e s s f u l l y completed when the pad-bath s o l v e n t i s e i t h e r water or formamide (4). The r e a c t i o n does not appear to be s u c c e s s f u l when the pad-bath s o l v e n t i s an a p r o t i c medium such as N,N-dimethylformamide or N-methylpyrrolidone (4). •Present Address: High P o i n t C h e m i s t r y , H i g h P o i n t , Ν. C. 27262

College,Department

152

In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977.

of

11.

B O W M A N AND cucuLô

153

Reactions of Cellulose υ

ο

C

c ' Ç

c )

0

+

N H

C

^ O H O

H

A

+ CellOH

*·

3(a .) q

C

Ο

II

0

2

in s i t u Ο

Ο


CellOC-

COH + N H -

The pad-bake p r o c e s s i n v o l v e s the a p p l i c a t i o n o f the amic a c i d and c a t a l y s t i n s o l u t i o n to the f a b r i c , squeezing to a predetermined p i c k - u p , and p l a c i n g i n a hot oven to remove the s o l v e n t and to e f f e c t the reaction. The s o l v e n t i s r a p i d l y removed as vapor, t y p i c a l l y i n about two minutes, l e a v i n g behind a s o l i d or l i q u i d r e s i d u e on the f a b r i c . The r a p i d removal o f the s o l v e n t , water, has been shown to be important (4^) The f a b r i c m o d i f i e d by the pad-bake r e a c t i o n w i t h α , 3 -amic a c i d s has i n c r e a s e d base combining c a p a c i t y and water s e n s i t i v i t y . T h i s i n d i c a t e s t h a t a c i d groups are indeed p r e s e n t on the f a b r i c . The s a p o n i f i c a t i o n e q u i v a l e n t o f the f a b r i c i s g e n e r a l l y twice the n e u t r a l i z a t i o n e q u i v a l e n t i n d i c a t i n g the presence of e q u a l numbers o f a c i d and e s t e r g r o u p s . Longer r e a c t i o n times or h i g h e r temperatures g i v e r i s e to the f o r m a t i o n of d i e s t e r c r o s s l i n k s ( E q u a t i o n 3) U , 4 i ) . Under these c o n d i t i o n s the s a p o n i f i c a t i o n e q u i v a l e n t i s more than twice the n e u t r a l i z a t i o n e q u i v a l e n t . There i s some e v i d e n c e t h a t a s m a l l amount o f h a l f - a m i d e o

o

o

Cell0CCH CH C0H + CellOH 2

2

^

o

CellOCCH CH COCell 2

2

(3)

e s t e r i s formed (3, 4 ) . S p e c t r o s c o p i c e v i d e n c e f o r the f o r m a t i o n o f the ïïalF-acid e s t e r o f c e l l u l o s e by the pad-bake r e a c t i o n w i t h a , 3 - a m i c a c i d s i s g i v e n i n F i g u r e 1. These i n f r a r e d s p e c t r a were o b t a i n e d from cupraphane f i l m which was m o d i f i e d i n the pad-bake r e a c t i o n with s u c c i n a m i c a c i d . Spectrum A r e p r e s e n t s i n f r a r e d a b s o r p t i o n o f the unmodified c e l l u l o s e i n the c a r b o n y l a b s o r p t i o n r e g i o n . There i s one weak d o u b l e t near 1650 cmwhich i s due to the presence o f water. The c a r b o n y l a b s o r p t i o n r e g i o n of the c e l l u l o s e h e m i s u c c i n a t e i s shown i n spectrum B. The s t r o n g a b s o r p t i o n at 1730 cm" i s due to the o v e r l a p p i n g c a r b o x y l i c a c i d and e s t e r c a r b o n y l a b s o r p t i o n s . The a c i d - e s t e r combination peak i s r e s o l v e d i n spectrum C 1

1


S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E


154

œ

l

»

1900

'

I

I

I

1400

I

L_ll

I

1900 FREQUENCY, CM"

Figure 1.

I

1

1400

1

1

I

1900

1

FIBERS

1

1

1400

1

Carbonyl absorption region for (A) unmodified cellulose, (B) cellulose hemisuccinate, and (C) cellulose hemisuccinate, sodium salt


11.

BOWMAN AND

cucuLO

155

Reactions of Cellulose

when the c e l l u l o s e h e m i s u c c i n a t e i s n e u t r a l i z e d w i t h sodium b i c a r b o n a t e . The peak a t 1730 cm" d e c r e a s e s i n i n t e n s i t y and i n c r e a s e s i n s h a r p n e s s as a new peak due t o c a r b o x y l a t e appears a t 1570 cm" . These assignments are c o n s i s t e n t with the l i t e r a t u r e (6, 2 ) · The r e a c t i o n between the a, β-amic a c i d s and c e l l u l o s e i s s i g n i f i c a n t because the d e r i v a t i v e , the c e l l u l o s e h a l f - a c i d e s t e r , can be r a p i d l y formed u s i n g r e l a t i v e l y i n e x p e n s i v e s t a r t i n g m a t e r i a l s and aqueous systems. T h i s i s not g e n e r a l l y t r u e f o r t h e other methods o f p r e p a r a t i o n o f c e l l u l o s e h a l f - a c i d e s t e r s which have been r e p o r t e d (8). 1


1

II.

D i s c u s s i o n o f t h e P r o b a b l e Mechanisms o f the R e a c t i o n Between C e l l u l o s e and α , β-Amie A c i d s

The r e a c t i o n o f c e l l u l o s e w i t h a , 3 - a m i c a c i d s r e p r e s e n t s an apparent d e p a r t u r e from the t r a d i t i o n a l o b s e r v a t i o n s o f amide c h e m i s t r y . The r e a c t i o n i s e s s e n t i a l l y an a l c o h o l y s i s o f the amide group as the o v e r a l l s t o i c h i o m e t r y i n d i c a t e s ( E q u a t i o n 1 ) . The amide group i s a r e l a t i v e l y s e l e c t i v e a c y l moiety and r e q u i r e s a s t r o n g n u c l e o p h i l e f o r a t t a c k a t the t r i g o n a l carbon atom o f the group. The a t t a c k o f an a l c o h o l , a weak n u c l e o p h i l e , on the amide group w i t h subsequent l o s s o f ammonia i s not a v e r y f a v o r a b l e reaction. Indeed, March s t a t e s i n Advanced O r g a n i c Chemistry: R e a c t i o n s , Mechanisms and S t r u c t u r e t h a t " A l c o h o l y s i s o f amides i s p o s s i b l e but i s seldom performed . . ." ( £ ) . The reason f o r t h e i n e r t n e s s o f amides i s the high b a s i c i t y o f the amide i o n which i s the l e a v i n g group expected i n the u n c a t a l y z e d a l c o h o l y s i s (Equation 4 ) .

e ο +

ROH

—>-

ο

R

0

C R

I \

'

+ NH.3

(4)

L

T h i s i s the same r e a s o n i n g used t o e x p l a i n the r e l a t i v e i n e r t n e s s o f amides toward n e u t r a l h y d r o l y s i s ( 9 ) .


S O L V E N T SPUN R A Y O N , MODIFIED

156

CELLULOSE

FIBERS


The p r o b a b l e mechanism by which α,β-amic a c i d s r e a c t w i t h c e l l u l o s e can be d i v i d e d i n t o two g e n e r a l classes: 1. D i r e c t a l c o h o l y s i s by a t t a c k o f the c e l l u l o s i c h y d r o x y l s at the amide c a r b o n y l ; and 2. A l c o h o l y s i s o f a r e a c t i v e i n t e r m e d i a t e formed by the i n i t i a l d e c o m p o s i t i o n o f the amic a c i d .

The d i r e c t a l c o h o l y s i s may be e i t h e r c a t a l y z e d by a c i d or u n c a t a l y z e d . The u n c a t a l y z e d r e a c t i o n mechanism i s shown i n E q u a t i o n 4 . The mechanism proposed by Johnson and C u c u l o i n v o l v e s i n t e r m o l e c u l a r a c i d c a t a l y s i s ( E q u a t i o n 5) (2^). A t t a c k by a c e l l u l o s i c h y d r o x y l on the amide i s a s s i s t e d by the i n i t i a l p r o t o n a t i o n o f the amide and by the f o r m a t i o n o f

Φ

Ο

ÇOH

C

s

fl

N

C -

H

f

i

+

· _ ^

CH,

NH

f 2

+

CH,

t

\

C '

O. Ί1

2

\

C

e

l

l

0

H

OH C

/

H

ο

0

H

2

N

CH-

HO — C CellO

0

Θ

s

^ 2

— ^

1

CellO

c

-

C -

CH CH C0 H 2

2

2

+ H

>»

OH

Ο

CellOCCB^CB^COH

+ NH

(5) 2

a hydrogen bond between the a l c o h o l i c p r o t o n and the c a r b o x y l c a r b o n y l . The j u s t i f i c a t i o n s g i v e n f o r t h i s r e a c t i o n mechanism were the apparent s p e c i f i c i t y o f the r e a c t i o n f o r a, β-amic a c i d s d e r i v e d from d i c a r b o x y l i c



11. B O W M A N A N D CUCULO


157

a c i d s which form i n t e r n a l p e n t a c y c l i c a n h y d r i d e s and the c a t a l y t i c e f f e c t of a c i d s . Another source of c a t a l y z i n g a c i d i s the a d j a c e n t c a r b o x y l group. This l e a d s to the p o s s i b i l i t y of i n t r a m o l e c u l a r a c i d c a t a l y s i s as shown i n E q u a t i o n 6. The second c l a s s i f i c a t i o n of mechanisms i n v o l v e s the f o r m a t i o n o f r e a c t i v e i n t e r m e d i a t e s which can more e a s i l y undergo a l c o h o l y s i s . S i n c e α , β-amic-acids are c h a r a c t e r i s t i c a l l y easy to h y d r o l y z e (10^ 11_, 12, 13, 14, 15, 1J6, Γ7, 18) t h e r e i s good reason to s u s p e c t t K a t i n an aqueous pad-bath, the amic a c i d c o u l d be hydrolyzed. T h i s h y d r o l y s i s r e a c t i o n would y i e l d both the d i a c i d and ammonia which c o u l d s u b s e q u e n t l y be d e p o s i t e d as the p a r t i a l

ammonium s a l t when the water i s removed. E s t e r i f i c a t i o n of c e l l u l o s e by ammonium s a l t s has been r e p o r t e d ( E q u a t i o n 7) (19, 20, 21).


S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FIBERS


158

r

'OR

+

NH

3

+

(7)

H 0 2

,OH

While t h i s r e a c t i o n c o u l d c o n t r i b u t e to the f o r m a t i o n of the c e l l u l o s e h a l f - a c i d e s t e r , the e x p e r i m e n t a l r e s u l t s of Cuculo and Johnson (2^) have i n d i c a t e d t h a t the ammonium s a l t r e a c t i o n i s not the major c o n t r i b u t o r i n r e a c t i o n s of s u c c i n a m i c a c i d w i t h v i s c o s e rayon. An a l t e r n a t i v e r e a c t i v e i n t e r m e d i a t e i s the a n h y d r i d e which has been proposed as the intermediate i n the h y d r o l y s i s (10, 11, 12, 13, 14, 1£, 16, Γ7, _18) and a m i n o l y s i s (22) r e a c t i o n s oT^ a,~T-amic a c i d s . A n h y d r i d e might "Form i n the r e s i d u e l e f t on the f a b r i c a f t e r the pad-bath s o l v e n t i s removed and s u b s e q u e n t l y r e a c t w i t h the c e l l u l o s e ( E q u a t i o n 8 ) . T h i s mechanism is

attractive 1.

2.

f o r the

following

reasons:

Formation o f a n h y d r i d e from a, 3-amic a c i d s has been d i r e c t l y d e t e c t e d i n s e v e r a l cases (18, 23, 24, 25) and Tïïe anhycfride i n much l e s s s e l e c t i v e than the amide i n s o l v o l y s i s r e a c t i o n s and e a s i l y under goes a l c o h o l y s i s at room tempeature (^6).

T h i s paper d e s c r i b e s a study undertaken to determine the c h e m i c a l changes which occur i n s u c c i n a m i c and p h t h a l a m i c a c i d s d u r i n g the p r e p a r a t i o n of the pad-bath and the pad-bake r e a c t i o n . The



11.

B O W M A N A N D CUCULO


159

pad-bake procedure was s i m u l a t e d under c o n d i t i o n s which a l l o w e d complete r e c o v e r y o f the r e s i d u e o f r e a c t i o n . The r e a c t i o n s were performed i n the absence o f c e l l u l o s i c s u b s t r a t e i n the hope t h a t any s t a b l e i n t e r m e d i a t e which might be the p r e c u r s o r t o the c e l l u l o s e h a l f - a c i d e s t e r might be d i r e c t l y d e t e c t e d . A l s o sought were the p r o d u c t s o f r e a c t i o n s i n c o m p e t i t i o n w i t h the e s t e r i f i c a t i o n . The c o m p o s i t i o n of the r e s i d u e was s t u d i e d as a f u n c t i o n o f bake time and temperature, i n i t i a l c o n c e n t r a t i o n o f the b a t h , presence o f c a t a l y s t , s o l v e n t , and d r y i n g c o n d i t i o n s (removal o f s o l v e n t ) . Experimental P r e p a r a t i o n o f Amic A c i d S o l u t i o n s . Phthalamic a c i d or s u c c i n a m i c a c i d was p r e p a r e d by the methods g i v e n i n r e f e r e n c e s (4^) and (21) . The amic a c i d s o l u t i o n was p r e p a r e d i n a 10 ml v o l u m e t r i c f l a s k m a i n t a i n e d a t 60±3°C i n a water b a t h . The d i s t i l l e d water used t o p r e p a r e the amic a c i d s o l u t i o n was i n c u b a t e d i n the water b a t h . When c a t a l y s t was used i t was added a f t e r the amic a c i d . P e r f o r m i n g the R e a c t i o n . An a l i q u o t o f amic a c i d s o l u t i o n was removed from the f l a s k w i t h a p r e h e a t e d c o n s t a n t d e l i v e r y s y r i n g e and i n j e c t e d through a rubber septum i n t o a p r e h e a t e d 25 ml r e a c t i o n f l a s k . The f l a s k was heated by a l a r g e volume o i l bath h e l d at the r e a c t i o n temperature ±1°C. The i n i t i a l amount o f amic a c i d was determined from the s o l u t i o n c o n c e n t r a t i o n and a l i q u o t volume. The r e a c t i o n f l a s k was f i t t e d w i t h a n i t r o g e n i n l e t and condenser. N i t r o g e n at a s l i g h t p o s i t i v e p r e s s u r e flowed through the r e a c t i o n f l a s k and out through the condenser i n t o a f l a s k c o n t a i n i n g s t a n d a r d a c i d t o t r a p any v o l a t i l e ammonia. In some cases the a c i d t r a p was preceded by a c h l o r o f o r m t r a p . The d u r a t i o n o f the r e a c t i o n was taken as the time from i n j e c t i o n o f the s o l u t i o n u n t i l the removal o f the r e a c t i o n f l a s k from the o i l bath f o r quenching i n a stream o f acetone. The f l a s k was then c l e a n e d , and d r i e d under vacuum at 40°C f o r one hour, and i t s mass determined. R e a c t i o n s from Ν, N-dimethylformamide and formamide r e q u i r e d l o n g e r p e r i o d s o f d r y i n g . The r e s i d u e mass was determined by d i f f e r e n c e . The c o n d i t i o n s under which the r e a c t i o n s were performed are summarized i n T a b l e I . A n a l y s i s o f the P r o d u c t s . The r e a c t i o n p r o d u c t s were a n a l y z e d q u a l i t a t i v e l y by i n f r a r e d s p e c t r o s c o p y . The s p e c t r a were determined as KBr p e l l e t s u s i n g a


In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. 175 200

Ν

" w

tl

M

II

tt tt M M fl tt

175

5 15 10 Ν Ν ft It fl

10 η

Ν

1.5 4.0 1.5 2.5 Μ Ν

ft

s

8

Ρ

8

8

Ρ

14*

15*

16

17

18

tt

Ρ

Μ

2.5

tt

η

M

tt

15

formamide

DMF

formamide

η

tl

II

"

tt

M

η

175 η

8

5

II

M

175 200

Ν

m

It

Ρ

150

η

η

m

η

water

150

10

2.5 M

Bath Solvent

Conditions Reaction Temperature °C

Reaction

I

Duration of Reaction, min.

Concen tration, molar

Ρ η

M

s

Acid

Ρ

Amic

13

12

11

10

9

8

7

6

5

4

3

2

1

Reaction Number

Summary o f

Table


In Solvent Spun Rayon, Modified Cellulose Fibers and Derivatives; Turbak, A.; ACS Symposium Series; American Chemical Society: Washington, DC, 1977. p,

6% ammonium s u l f a m a t e

s o l u t i o n evaporated

**

succinaroic a c i d

*

8,

in a

stream

of

based on the

phthalamic

-

"

of

air

moles of

for

the

-

"

before

acid 12 h r s .

amic

DMF, N , N - d i m e t h y l f o r m a m i d e

compressed

no.

acid

ρ

23

"

melt

8

22

n

"

"

"

e

being

Reaction Temperature C

" -

.

"

—

Duration of Reaction, min.

s

.

Concentration. molar

ρ

ρ

Amic A c i d

1 continued

19 20** 21**

Reaction Number

Table


heated

none

Η

water

DMF

Bath Solvent

r

a

Ο

^

S

»

g

a

Β



igure 2. Infrared spectra of (A) succinamic acid and (B) phthalamic acid in the region 4000-1200 cm' 1



11.

BOWMAN AND

cucuLO

163


P e r k i n - E l m e r I n f r a c o r d 337 R e c o r d i n g Spectrophotometer. The p o s i t i o n o f a b s o r p t i o n maxima r e p o r t e d here were measured from p o l y s t y r e n e r e f e r e n c e f i l m . The p r o d u c t s were a n a l y z e d f o r ammonium i o n by N e s s l e r i z a t i o n (2*8) u s i n g s t a n d a r d s prepared from ammonium s u l f a t e . The n e u t r a l i z a t i o n e q u i v a l e n t o f the r e a c t i o n p r o d u c t was determined by p o t e n t i o m e t r i c t i t r a t i o n w i t h s t a n d a r d ammonium h y d r o x i d e . The e n d p o i n t s were determined a n a l y t i c a l l y from v a l u e s o f the second d e r i v a t i v e curve i n the r e g i o n o f the e n d p o i n t . The a n a l y s i s with the weak base was n e c e s s a r y because a p o r t i o n o f the r e s i d u e was an ammonium s a l t . The d e t e r m i n a t i o n o f f r e e a c i d i t y i n the presence o f a s a l t of the a c i d w i t h a weak base i s d i s c u s s e d i n r e f e r e n c e (29). The amount o f c h l o r o f o r m s o l u b l e m a t e r i a l i n the r e a c t i o n p r o d u c t was determined by e x t r a c t i o n o f a powdered sample o f p r o d u c t w i t h an a l i q u o t o f c h l o r o f o r m . The e x t r a c t i o n was performed i n a f r i t t e d funnel. The e x t r a c t i o n was c o n s i d e r e d complete when the d e c r e a s e i n mass o f the r e s i d u e on s u c c e s s i v e e x t r a c t i o n s was l e s s than 0.1% o f the i n i t i a l mass. The c h l o r o f o r m e x t r a c t s were r e c o v e r e d by e v a p o r a t i o n and t h e i r i n f r a r e d s p e c t r a and m e l t i n g ranges were determined. T o t a l n i t r o g e n i n the samples was determined by the m i c r o - K j e l d a h l t e c h n i q u e ( 3 0 ) . D e t e r m i n a t i o n o f the S t a b i l i t y o f the Amic A c i d Solutions. The s t a b i l i t y of the s o l u t i o n s prepared as above was determined by f o l l o w i n g the appearance o f ammonium i o n w i t h time and by e x a m i n a t i o n o f the i n f r a r e d spectrum o f the m a t e r i a l i n the s o l u t i o n . In both a n a l y s e s an a l i q u o t o f s o l u t i o n was withdrawn and N e s s l e r i z e d f o r ammonium c o n t e n t or evaporated to d r y n e s s under vacuum f o r e v a l u a t i o n o f the i n f r a r e d spectrum as d e s c r i b e d above. R e s u l t s o f the

Experiments

The i n f r a r e d s p e c t r a o f s u c c i n a m i c and p h t h a l a m i c a c i d s are g i v e n i n F i g u r e 2. The d i s t i n c t i v e f e a t u r e s of the amic a c i d s p e c t r a are the c a r b o n y l d o u b l e t near 1700 cm" and the d o u b l e t i n the r e g i o n 3000 cm" to 3500 cm" due t o the n i t r o g e n - h y d r o g e n s t r e t c h i n g vibrations. The c a r b o n y l peaks i n s u c c i n a m i c a c i d are at 1710 cm" and 1650 cm" . In p h t h a l a m i c a c i d the c a r b o n y l peaks occur a t 1695 cm"^ and 1645 cm' . The h i g h energy peak i s due t o the c a r b o x y l i c a c i d c a r b o n y l s t r e t c h i n g v i b r a t i o n and the low energy peak due t o the 1

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amide c a r b o n y l s t r e t c h i n g v i b r a t i o n . The n i t r o g e n hydrogen s t r e t c h i n g v i b r a t i o n peaks occur a t 3375 cmand 3215 cmi n s u c c i n a m i c a c i d and a t 3355 cm" and 3155 c m i n phthalamic a c i d . This doublet corresponds to t h e asymmetric and symmetric N-H s t r e t c h i n g vibrations. These assignments a r e c o n s i s t e n t with the l i t e r a t u r e (31, 2, 3 2 ) . The s p e c t r a o f t h e p r o d u c t s o f the r e a c t i o n o f s u c c i n a m i c a c i d f o r t e n minutes a t 1 5 0 ° C 175°C, and 200°C ( r e a c t i o n s 1,2, and 3, T a b l e I ) a r e shown i n F i g u r e 3. Comparison o f these s p e c t r a w i t h t h a t o f s u c c i n a m i c a c i d i n F i g u r e 2 shows t h a t s i g n i f i c a n t changes have o c c u r r e d i n the n i t r o g e n - h y d r o g e n and carbonyl s t r e t c h i n g regions. In spectrum A, the N-H s t r e t c h i n g peaks a r e o f almost e q u a l i n t e n s i t y , whereas i n the pure amic a c i d t h e h i g h energy peak i s by f a r the most i n t e n s e . In s p e c t r a Β and C (175°C and 200°C, r e s p e c t i v e l y ) t h e i n t e n s i t y o f the low energy N-H s t r e t c h i n g v i b r a t i o n i s the g r e a t e s t . The amide c a r b o n y l a b s o r p t i o n which has begun t o d e c r e a s e i n spectrum A has become a s h o u l d e r i n s p e c t r a Β and C. T h i s i n d i c a t e s a p r o g r e s s i v e d e c r e a s e i n the amount o f amide i n the r e s i d u e as the temperature o f r e a c t i o n increases. In a d d i t i o n the peak which appears near 1575 cm" i n t h e pure amic a c i d ( p r o b a b l y the amide II band (£, p.94,95) has broadened and the p o s i t i o n o f the maximum has s h i f t e d t o 1550 cm' i n s p e c t r a Β and C. T h i s i s an i n d i c a t i o n o f the f o r m a t i o n o f an ammonium s a l t i n the r e s i d u e s i n c e the c a r b o n y l s t r e t c h i n g a b s o r p t i o n o f t h e c a r b o x y l a t e anion o c c u r s near 1550 cm" (j>). T h i s c o n c l u s i o n i s supported by the appearance o f two broad peaks o f medium i n t e n s i t y near 2500 cm" and 2000 cmwhich would be expected i n the s p e c t r a o f ammonium s a l t s ( j 6 , p.94). A f u r t h e r change which o c c u r s i n the c a r b o n y l r e g i o n i s the appearance o f a shoulder a t 1760 cm" i n spectrum Β which i s s h a r p l y r e s o l v e d i n spectrum C. The appearance o f the peak a t 1760 cm' can b e s t be e x p l a i n e d by the presence o f succinimide i n the product. The spectrum o f the pure imide i s shown i n F i g u r e 4 (spectrum A) along w i t h t h a t of s u c c i n a m i c a c i d c o n t a i n i n g 20% s u c c i n i m i d e by weight prepared from t h e pure compounds (spectrum B ) . The s p e c t r a c l e a r l y show t h a t the a b s o r p t i o n peak a t 1760 cm" can be e x p l a i n e d by the presence o f s u c c i n i m i d e . Thus i t can be concluded on the b a s i s o f the i n f r a r e d s p e c t r a t h a t t h e r e l a t i o n p r o d u c t s i n c l u d e unreacted s u c c i n a m i c a c i d , ammonium s a l t which c o u l d be a mixture of ammonium succinamate, monoammonium s u c c i n a t e , and diammonium s u c c i n a t e , and s u c c i n i m i d e . The q u a l i t a t i v e a n a l y s i s o f the r e a c t i o n p r o d u c t s 1

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MODIFIED C E L L U L O S E

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by i n f r a r e d s p e c t r o s c o p y i s supported by the q u a n t i t a t i v e a n a l y t i c a l data presented i n Table I I ( R e a c t i o n s 1,2,3). The presence o f ammonium i o n as determined by N e s s l e r ' s reagent i n d i c a t e s t h a t a s u b s t a n t i a l amount o f h y d r o l y s i s has o c c u r r e d e i t h e r i n the p r e p a r a t i o n o f the s o l u t i o n or i n the bake s t e p . The amount o f ammonium i o n i s markedly lower a t the h i g h e s t temperature, 200°C. The d e c r e a s e i n the amount o f ammonium i o n with temperature i s accompanied by an i n c r e a s e i n the amount of c h l o r o f o r m s o l u b l e m a t e r i a l and n e u t r a l i z a t i o n equivalent. T h i s r e f l e c t s an i n c r e a s i n g amount o f succinimide i n the r e s i d u e . The imide i s c h l o r o f o r m s o l u b l e and i s t o o weak an a c i d t o be determined by the n e u t r a l i z a t i o n equivalent determination. When imide i s removed from t h e r e s i d u e by e x t r a c t i o n the r e s i d u e c o n t a i n s the a c i d s and s a l t s . The t o t a l amount o f n i t r o g e n (as ammonia) p r e s e n t i n t h i s r e s i d u e was determined by m i c r o - K j e l d a h l a n a l y s i s . T h i s v a l u e r e p r e s e n t s the t o t a l amide and ammonium n i t r o g e n on an i m i d e - f r e e b a s i s . When based on the t o t a l mass o f t h e r e s i d u e t h i s v a l u e can be used t o determine the % amide ammonia i n t h e m i x t u r e . These d e r i v e d v a l u e s f o r % amid ammonia a r e g i v e n i n T a b l e I I . The amount o f amide ammonia d e c r e a s e s from 9.19% a t 150°C t o 7.62% a t 200° C. By u s i n g the v a l u e s f o r % c h l o r o f o r m s o l u b l e m a t e r i a l , i t i s p o s s i b l e to c a l c u l a t e the % y i e l d o f imide i n the r e a c t i o n . I t i s a l s o p o s s i b l e t o c a l c u l a t e t h e y i e l d s o f ammonium s a l t (as monoammonium s u c c i n a t e ) and amic a c i d from the % i o n i c ammonia and % amide ammonia v a l u e s r e s p e c t i v e l y . I t i s a l s o p o s s i b l e to c a l c u l a t e the y i e l d o f d i a c i d from t h e v a l u e s o f the n e u t r a l i z a t i o n e q u i v a l e n t and the y i e l d s o f monoammonium s a l t and amic a c i d . T h i s l a s t c a l c u l a t i o n i s based on the assumption t h a t the a c i d s p r e s e n t i n the m i x t u r e a r e the amic a c i d , t h e monoammonium s a l t and t h e d i a c i d . The r e s u l t s o f such c a l c u l a t i o n s are shown i n T a b l e III. The d a t a f o r r e a c t i o n s 1, 2 and 3 show t h a t the amide content d e c r e a s e s w h i l e the y i e l d s o f imide and d i a c i d i n c r e a s e (as the temperature i s i n c r e a s e d ) . The ammonium s a l t c o n t e n t d e c r e a s e s . These d a t a a r e c o n s i s t e n t with the c o n c l u s i o n t h a t h y d r o l y s i s o c c u r s i n the p r e p a r a t i o n o f the amic a c i d s o l u t i o n and d u r i n g the v o l a t i l i z a t i o n o f the s o l v e n t . The d e h y d r o c y c l i z a t i o n r e a c t i o n which y i e l d s imide i s a competing r e a c t i o n which y i e l d s an i n e r t product (_3) · The s p e c t r a o f the p r o d u c t s o f the pad-bake r e a c t i o n o f p h t h a l a m i c a c i d f o r 10 minutes a t 150 ( A ) , 175 ( B ) , and 200°C (C) ( r e a c t i o n 4 , 5, and 6, T a b l e I)


102.3 100.8 92.4 107.5 104.9 94.9 99.6 97.6 110.7 103.8 96.7 99.3 99.3 99.1 99.5 71.5 84.1 80.1 83.2 98.9 97.6 90.4 88.1

% Mass Recovered

4.09 5.27 0.99 8.36 8.08 5.16 3.63 2.78 8.25 7.58 2.92 3.69 7.87 5.04 7.97 1.32 0.07 0.74 0.13 3.41 6.57 1.65 1.02

0.43 5.84 41.11 6.95 12.41 45.70 0.62 21.42 2.05 11.27 14.88 11.27 3.16 6.36 6.71 1.27 33.87 90.05 100.00 14.73 18.64 24.40 87.20

Ionic NH 3

%

% CHCI3 Extracts

13.31 9.35 13.96 9.41

129.52 223.36 140.51 183.20***

•*

9.19 7.35 7.62 0.31 0.00 0.00 9.61 6.35 0.95 0.00 7.55 7.65 0.83 7.44 1.08 15.80 9.,26 0.51 0.00 7.84 1.06 8.48 0.23 13.33 13.38 14.63 9.32 9.34 9.32 13.33 11.63 9.40 9.39 12.30 12.79 8.98 13.33 9.70 17.34 14.08 12.51

115.40 123.13 173.11 196.67 204.41 331.85 117.53 134.67 185.62 205.14 124.93 122.72 165.55 122.98 202.69 121.92 171.10

* *

% Amide NH-

% NH 3 1n Extract Residue

Study

Neutral 1zation Equivalent

Data f o r R e a c t i o n S t o l c h l o m e t r y

II

* not determined * * no r e s i d u e *** neutralization equivalent of the extraction residue

12 13 14 15 16 17 18 19 20 21 22 23

11

2 3 4 5 6 7 8 9 10

1

Reaction Number

Analytical

Table


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168

SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

are shown i n F i g u r e 5. Comparison of these s p e c t r a with t h a t of p h t h a l a m i c a c i d (B i n F i g u r e 2) show t h a t a v e r y s i g n i f i c a n t change has o c c u r r e d d u r i n g the r e a c t i o n . A f t e r r e a t i o n at 150°C (spectrum A ) , the N-H s t r e t c h i n g d o u b l e t has been r e p l a c e d by a s t r o n g a b s o r p t i o n , a t 3125 cm"" and a weak a b s o r p t i o n at 3480 cm' . The c a r b o x y l s t r e t c h i n g r e g i o n has a l s o changed. The amide and c a r b o x y l absorbances at 1695 cm" and 1645 cm" have been r e p l a c e d by two peaks at 1675 cnr^and 1550 cm" . The l a t t e r peak i s q u i t e i n t e n s e . A d d i t i o n a l l y , two broad, m o d e r a t e l y i n t e n s e peaks have appeared at 2450 crif and 1950 cm" . The absorbances are c o n s i s t e n t with those o f an ammonium s a l t c o n t a i n i n g some d i c a r b o x y l i c a c i d as noted b e f o r e i n the d i s c u s s i o n o f the r e a c t i o n o f s u c c i n a m i c a c i d . In t h i s c a s e however, the spectrum i n d i c a t e s the h y d r o l y s i s r e a c t i o n i s v i r t u a l l y complete. With i n c r e a s i n g temperature, the s p e c t r a change, p a r t i c u l a r l y i n the c a r b o n y l a b s o r p t i o n r e g i o n ( s p e c t r a B, C ) . The peak which appears at 1675 cnr in spectrum A has s h i f t e d to 1705 cm*" i n spectrum Β and has i n c r e a s e d i n i n t e n s i t y r e l a t i v e to the maximum at 1550 cm" . In a d d i t i o n a s m a l l shoulder has appeared at 1780 c m ' i n spectrum B. In spectrum C, the h i g h energy maximum now i s the most i n t e n s e and i s l o c a t e d at 1745 cm" . The s h o u l d e r at 1780 cm" i n Β i s now a sharp peak at 1780 cm' . In a d d i t i o n the broad peaks at 2450 cm' and 1950 cm' noted i n A have s u b s t a n t i a l l y d i s a p p e a r e d i n C. The N-H s t r e t c h i n g r e g i o n i s v i r t u a l l y the same i n each spectrum but, as noted b e f o r e , d i f f e r s r a d i c a l l y from t h a t o f p h t h a l a m i c acid. These s p e c t r a are c o n s i s t e n t with the c o n c l u s i o n t h a t p h t h a l a m i c a c i d i s almost c o m p l e t e l y h y d r o l y z e d i n the pad-bake r e a c t i o n or d u r i n g the p r e p a r a t i o n o f the pad s o l u t i o n . The m a t e r i a l d e p o s i t e d i s e s s e n t i a l l y the monoammonium s a l t o f p h t h a l i c a c i d . T h i s s a l t i s i n c r e a s i n g l y c o n v e r t e d to the i n a c t i v e p r o d u c t , p h t h a l i m i d e as the temperature i s i n c r e a s e d . These c o n c l u s i o n s are supported by the a n a l y t i c a l d a t a i n T a b l e I I . The % amide ammonia i s o n l y 0.31% i n the p r o d u c t s o f r e a c t i o n 4 and zero i n r e a c t i o n s 5 and 6. The i o n i c ammonia v a l u e s are r e l a t i v e l y high but d e c r e a s e from 8.36% a t 150°C ( r e a c t i o n 4) t o 5.16% a t 200°C ( r e a c t i o n 6 ) . The n e u t r a l i z a t i o n e q u i v a l e n t and % c h l o r o f o r m s o l u b l e m a t e r i a l i n c r e a s e from 196.67 g r a m s / e q u i v a l e n t and 6.95% a t 150°C ( r e a c t i o n 4) t o 331.85 g r a m s / e q u i v a l e n t and 45.70% a t 200°C ( r e a c t i o n 6). These o b s e r v a t i o n s can be e x p l a i n e d by the p r o g r e s s i v e c o n v e r s i o n o f the monoammonium s a l t i n t o phthalimide. By u s i n g the methods d i s c u s s e d p r e v i o u s l y 1

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B O W M A N AND CUCULO

Figure 5. Infrared spectra of the products of the reaction of phthalamic acid for 10 min at 150°C (A), 175°C (B), and 200°C (C)




170

CELLULOSE

FIBERS

the y i e l d s o f the v a r i o u s p r o d u c t s pan be c a l c u l a t e d . The r e s u l t s o f t h e c a l c u l a t i o n s a r e shown i n T a b l e I I I . The y i e l d o f ammonium s a l t d e c r e a s e s with i n c r e a s i n g temperature from an i n i t i a l v a l u e o f 87.5% a t 150°C. The amic a c i d was almost e n t i r e l y h y d r o l y z e d i n these r e a c t i o n s and the h y d r o l y z a t e , monoammonium p h t h a l a t e , i s c o n v e r t e d t o p h t h a l i m i d e . The y i e l d o f the imide i n c r e a s e s r a p i d l y w i t h temperature from 8.4% a f t e r 10 minutes a t 150°C t o 48.7% a f t e r 10 minutes a t 200°C. Small amounts o f the amic a c i d and d i a c i d were a l s o indicated. The s p e c t r a o f the p r o d u c t s o f the r e a c t i o n o f s u c c i n a m i c a c i d a t 175°C f o r 5, 10, and 15 minutes ( r e a c t i o n s 7, 2, and 8, r e s p e c t i v e l y ) a r e shown i n F i g u r e 6. With i n c r e a s i n g bake time t h e changes noted i n the s p e c t r a a r e v e r y n e a r l y the same as the changes caused by i n c r e a s i n g temperature ( F i g u r e 3 ) . The amide c a r b o n y l s t r e t c h i n g a b s o r p t i o n which appears a t l 6 5 0 cm" i n t h e p a r e n t compound, s u c c i n a m i c a c i d (spectrum A, F i g u r e 2) d e c r e a s e s i n i n t e n s i t y w i t h time as the peak at 1575 cm- broadens and a s h o u l d e r appears a t 1760 cm" . A g a i n the n i t r o g e n - h y d r o g e n s t r e t c h i n g v i b r a t i o n s have r e v e r s e d i n r e l a t i v e i n t e n s i t y . These changes i n the s p e c t r a o f the p r o d u c t s o f the bake r e a c t i o n are c o n s i s t e n t w i t h the c o n c l u s i o n t h a t the succinamic acid i s deposited during v o l a t i l i z a t i o n of the s o l v e n t as a mixture o f s u c c i n a m i c a c i d and monoammonium s u c c i n a t e . T h i s m a t e r i a l i s p r o g r e s s i v e l y c o n v e r t e d i n t o s u c c i n i m i d e as the h e a t i n g i s c o n t i n u e d . A g a i n t h e a n a l y t i c a l d a t a support this conclusion. F i v e minutes i n t o the r e a c t i o n ( r e a c t i o n 7) t h e r e a c t i o n p r o d u c t s c o n t a i n 3.63% ammonia as ammonium i o n . The % amide ammonia i s 9.61% which c o r r e s p o n d s t o a y i e l d o f 65.9% s u c c i n a m i c a c i d . Thus, a f t e r f i v e minutes, t h e amount o f amic a c i d has d e c r e a s e d 34.1%. The y i e l d v a l u e s a r e g i v e n i n T a b l e III. The y i e l d o f s u c c i n a m i c a c i d d e c r e a s e s w i t h time from 65.9% a f t e r 5 minutes t o 39.8% a f t e r 15 minutes as the amic a c i d i s p r o g r e s s i v e l y c o n v e r t e d i n t o s u c c i n i m i d e and ammonium s a l t . The y i e l d o f imide i n c r e a s e s from 0.6% a t 5 minutes t o 23.1% a t 15 minutes. The y i e l d o f ammonium s a l t i s maximum a t 10 minutes a t 34.0% and d e c r e a s e s a f t e r 15 minutes t o 23.1% i n d i c a t i n g the p o s s i b i l i t y o f i t s c o n v e r s i o n t o d i a c i d or i m i d e . The y i e l d o f d i a c i d i n c r e a s e d from 4% a f t e r 5 minutes t o 13% a t 15 minutes. The s p e c t r a o f t h e p r o d u c t s o f the r e a c t i o n o f p h t h a l a m i c a c i d a t 175°C f o r 5 10, and 15 minutes ( r e a c t i o n s 9, 5, and 10 r e s p e c t i v e l y ) a r e shown i n F i g u r e 7. The s p e c t r a a g a i n d i f f e r g r e a t l y from the

:

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f



11.

B O W M A N AND

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Figure 6. Infrared spectra of the products of the reaction of succinamic acid at 175°C for 5 min (A), 10 min (B), and 15min(C)



CELLULOSE

Table I I I Product Y i e l d Data, Time, Temp., Cone, and C a t a l y s t


% Yield

Reaction Number

Unreacted Amic Acid

Monoammonium «ait

Imide

Diacid

1 2

64.6

28.6

0.5

6.

53.2

34.0

5.7

6.

3

41.5

7.7

41.1

11

4

3.3

87.5

8.4

0

5

0

81.5

14.9

1

6

0

47.6

48.7

1

24.7

0.6

4

7

65.9

8

39.8

23.1

23.1

9

10.2

88.6

2.5

0

10

1.4

82.1

17.2

0

11

50.2

19.3

17.0

8

12

52.1

25.0

13.1

9

13

7.8

74.6

3.6

10

14

51.3

34.6

7.6

7

15

10.9

80.3

6.7

1

13


FD3ERS

11.

B O W M A N A N D cucuLO

173


spectrum o f p h t h a l a m i c a c i d ( F i g u r e 2, spectrum B) and i n d i c a t e by the absence o f any s i g n i f i c a n t a b s o r p t i o n at 1645 cm"" due t o t h e amide c a r b o n y l s t r e t c h i n g a b s o r p t i o n and by the p r e s e n c e o f the s t r o n g a b s o r p t i o n at 1550 cm" and 3200 cm" t h a t t h e p h t h a l a m i c a c i d i s extensively hydrolyzed. Dehydrocyclization to y i e l d imide a l s o o c c u r s as i n d i c a t e d by the appearance o f the s h o u l d e r a t 1780 cm"i i n s p e c t r a Β ( r e a c t i o n 5) and C ( r e a c t i o n 10). These o b s e r v a t i o n s i n d i c a t e t h a t the p h t h a l a m i c a c i d i s almost c o m p l e t e l y h y d r o l y z e d a t the o u t s e t o f the bake s t e p and i s d e p o s i t e d d u r i n g t h e v o l a t i l i z a t i o n o f t h e s o l v e n t as the p a r t i a l ammonium salt. The a n a l y t i c a l d a t a i n T a b l e I I support t h i s c o n c l u s i o n with the % i o n i c ammonia q u i t e h i g h a t 8.25% a f t e r 5 minutes ( r e a c t i o n 9) and d e c r e a s i n g t o 7.58% a f t e r 15 minutes ( r e a c t i o n 10). T h i s decrease i s accompanied by an i n c r e a s e i n the % c h l o r o f o r m e x t r a c t a b l e s from 2.05% t o 11.27% and the n e u t r a l i z a t i o n e q u i v a l e n t from 185.62 g r a m / e q u i v a l e n t to 205.14 g r a m / e q u i v a l e n t i n t h e same r e a c t i o n s . These d a t a were used t o c a l c u l a t e the % y i e l d v a l u e s shown i n T a b l e I I I . Here the y i e l d o f ammonium s a l t i s q u i t e high a t 88.6% a f t e r f i v e minutes and d e c r e a s e s t o a n e a r l y c o n s t a n t v a l u e o f 81.5% a f t e r 10 m i n u t e s . The y i e l d o f p h t h a l i m i d e i n c r e a s e s c o n t i n u o u s l y throughout the r e a c t i o n from a v a l u e o f 2.5% a f t e r 5 minutes t o 17.2% a f t e r 15 m i n u t e s . The r e s i d u a l p h t h a l a m i c a c i d y i e l d which i s 10.2% a f t e r 5 minutes has d e c r e a s e d t o 1.4% a f t e r 15 m i n u t e s . P h t h a l i c a c i d was d e t e c t e d a t 10 minutes i n a 1% y i e l d . These d a t a i n d i c a t e t h a t the ammonium s a l t i s formed i n h i g h y i e l d d u r i n g t h e p r e p a r a t i o n o f the amic a c i d s o l u t i o n and d u r i n g the v o l a t i l i z a t i o n o f the s o l v e n t by the h y d r o l y s i s o f a s u b s t a n t i a l amount (88.6% a t 5 minutes) o f the i n i t i a l phthalamic a c i d . The r e s i d u a l p h t h a l a m i c a c i d d i s appears g r a d u a l l y as does the ammonium s a l t . This d i s a p p e a r a n c e i s accompanied by t h e appearance o f p h t h a l i m i d e which c o u l d r e s u l t from the d e c o m p o s i t i o n of the p h t h a l a m i c a c i d and the p a r t i a l ammonium s a l t . 1


1

1

I t i s o f i n t e r e s t t o determine the e f f e c t o f the pad bath c o n c e n t r a t i o n on the r e s i d u e c o m p o s i t i o n . The s p e c t r a o f the p r o d u c t s o f the r e a c t i o n o f s u c c i n a m i c a c i d a t 175°C f o r 10 minutes a t i n i t i a l c o n c e n t r a t i o n s of 4.00, 2.50, and 1.50 molar ( r e a c t i o n s 12, 2, and 11, r e s p e c t i v e l y ) a r e shown i n F i g u r e 8. In comparison w i t h t h e spectrum o f s u c c i n a m i c a c i d (spectrum A i n F i g u r e 2) a l l t h e s p e c t r a show a d e c r e a s e i n the amide c a r b o n y l s t r e t c h i n g a b s o r p t i o n a t 1650 cm" accompanied by broadening and i n c r e a s e i n absorbance a t 1575 cm" , the c a r b o x y l a t e c a r b o n y l s t r e t c h i n g a b s o r p t i o n , a 1

1


S O L V E N T S P U N R A Y O N , MODIFIED C E L L U L O S E FD3ERS


OOi

.50

IJO •

ool

' 3500

• 3000

' 2500

FREQUENCY, CM*

' 2000

1500 1

1

Figure 8. Infrared spectra of the products of the reaction of succinamic acid at 175°C for 10 min at an initial solution con centration of 4.00M (A), 2.5M (B), and 1.50M (C)

3500

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FREQUENCY, CM"'

Figure 9. Infrared spectra of the products of the reaction of phthalamic acid at 175°C for 10 min at an initial solution concen tration of 1.50M (A) and 2.50M (B)


11.


175


change i n the r e l a t i v e i n t e n s i t y of the d o u b l e t i n the n i t r o g e n - h y d r o g e n s t r e t c h i n g r e g i o n (3000 cm" to 3500 c m " ) , and the appearance of a shoulder at 1760 cm"" . These changes i n d i c a t e t h a t the amic a c i d has undergone both h y d r o l y s i s and d e h y d r o c y c l i z a t i o n . From the s p e c t r a i t can be seen t h a t the e x t e n t o f r e a c t i o n i s g r e a t e s t f o r r e a c t i o n 2 (spectrum B) s i n c e the spectrum o f the r e s i d u e of t h i s r e a c t i o n shows the g r e a t e s t change. The a n a l y t i c a l d a t a i n T a b l e I I show q u a n t i t a t i v e l y the changes which occur i n the s u c c i n amic a c i d d u r i n g the pad-bake r e a c t i o n . The amount of h y d r o l y s i s which has o c c u r r e d i s the g r e a t e s t at the i n t e r m e d i a t e c o n c e n t r a t i o n as i n d i c a t e d by the % i o n i c ammonia v a l u e s . In r e a c t i o n s 11 and 12, the v a l u e s for the % i o n i c ammonia are 2.92% and 3.69% r e s p e c t i v e l y w h i l e i n r e a c t i o n 2, the v a l u e i s 5.27%. The % c h l o r o f o r m e x t r a c t a b l e s i s lower at the i n t e r m e d i a t e c o n c e n t r a t i o n s where the v a l u e i s 5.84% for an i n i t i a l c o n c e n t r a t i o n of 2.50 molar ( r e a c t i o n 2) and 14.88% and 11.27% a t i n i t i a l c o n c e n t r a t i o n s o f 1.50 ( r e a c t i o n 11) and 4.00 molar ( r e a c t i o n 12), respectively. These r e s u l t s i n d i c a t e t h a t the e x t e n t of d e h y d r o c y c l i z a t i o n r e a c t i o n i s l e s s than t h a t at the other c o n c e n t r a t i o n s . The n e u t r a l i z a t i o n e q u i v a l e n t s of the r e s i d u e s are n e a r l y the same as are the % amide ammonia v a l u e s f o r a l l the i n i t i a l c o n c e n t r a t i o n s . The y i e l d d a t a c a l c u l a t e d as b e f o r e are shown i n T a b l e I I I . The d a t a show l i t t l e e f f e c t of the i n i t i a l c o n c e n t r a t r a t i o n on the y i e l d o f s u c c i n a m i c a c i d i n the range o f 1.50 t o 4.00 molar a f t e r 10 minutes bake time at 175°C. The y i e l d o f imide g e n e r a l l y d e c r e a s e s with the s o l u t i o n c o n c e n t r a t i o n w h i l e the y i e l d o f ammonium s a l t increases. The y i e l d o f s u c c i n i c a c i d v a r i e s between 6% and 9%. The s p e c t r a of the p r o d u c t s of the r e a c t i o n o f p h t h a l a m i c a c i d at 175°C f o r 10 minutes at an i n i t i a l c o n c e n t r a t i o n o f 1.50 molar ( r e a c t i o n 13) and 2.50 molar ( r e a c t i o n 5) are shown i n F i g u r e 9. (Solutions of p h t h a l a m i c a c i d o f a c o n c e n t r a t i o n o f 4.00 molar c o u l d not be p r e p a r e d ) . The s p e c t r a show t h a t the p h t h a l a m i c a c i d has been e x t e n s i v e l y h y d r o l y z e d and t h a t d e h y d r o c y c l i z a t i o n has taken p l a c e to a s l i g h t e x t e n t as might be expected from the p r e v i o u s r e s u l t s . In T a b l e I I the d a t a show t h a t the % i o n i c ammonia v a l u e s f o r r e a c t i o n s 5 and 13 are 8.08% and 7.87% r e s p e c t i v e l y i n d i c a t i n g the e x t e n t o f h y d r o l y s i s i s about the same i n each c a s e . At the lower i n i t i a l (1.50 molar) c o n c e n t r a t i o n the % c h l o r o f o r m e x t r a c t a b l e s i s 3.16% compared w i t h 12.41% a t an i n i t i a l c o n c e n t r a t i o n o f 2.50 m o l a r . The n e u t r a l i 1

1


1



S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E

3500

3000

2500

2000

FREQUENCY, CM"

FIBERS

1500

1

Figure 10. Infrared spectra of the products of the reaction of succinamic ana phthahmic acids at 175°C for 10 min at an initial concentration of 2.50M and 0.171M ammonium sulfamate as catalyst

col

1

,

•

3500

3000

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,

2000

FREQUENCY, CM"

•

1500

1

Figure 11. Infrared spectra of the products of the reaction of succinamic acid at 175°C for 10 min at an initial concentration of 2.50M in N,N-dimethylformamide (A), formamide (B), and water (C)



11.

B O W M A N AND cucuLO


177

z a t i o n e q u i v a l e n t o f the r e s i d u e i n r e a c t i o n 5 i s 204.41 g r a m s / e q u i v a l e n t w h i l e t h a t o f the r e s i d u e i n r e a c t i o n 13 i s 165.55 g r a m s / e q u i v a l e n t . The % amide ammonia v a l u e s a r e 0.00 and 0.83% f o r r e a c t i o n s 5 and 13 r e s p e c t i v e l y . These d a t a were used t o c a l c u l a t e the y i e l d v a l u e s g i v e n i n T a b l e I I I which show by the y i e l d of ammonium p h t h a l a t e t h a t the amount o f h y d r o l y s i s i s about the same i n each r e a c t i o n . The y i e l d o f d i a c i d d e c r e a s e s with i n i t i a l c o n c e n t r a t i o n w h i l e the y i e l d o f imide i n c r e a s e s . The y i e l d o f r e s i d u a l p h t h a l a m i c a c i d remains about the same. The s p e c t r a o f the p r o d u c t s o f the r e a c t i o n s o f s u c c i n a m i c a c i d (spectrum A, r e a c t i o n 14) and p h t h a l a m i c a c i d (spectrum B, r e a c t i o n 15) a t 175°C f o r 10 minutes a t an i n i t i a l c o n c e n t r a t i o n o f 2.50 molar i n amic a c i d and 0.171 molar i n ammonium s u l f a m a t e c a t a l y s t are shown i n F i g u r e 10. The s p e c t r a d i f f e r i n the same manner from the s p e c t r a o f the p a r e n t compounds, s u c c i n a m i c a c i d ( F i g u r e 2, spectrum A) and p h t h a l a m i c a c i d ( F i g u r e 2, spectrum B) as do the p r o d u c t s o f r e a c t i o n 2 ( F i g u r e 3, Spectrum B) and r e a c t i o n 5 ( F i g u r e 6, spectrum B) which were performed under i d e n t i c a l c o n d i t i o n s as r e a c t i o n s 14 and 15 except f o r the p r e s e n c e o f the c a t a l y s t . The a n a l y t i c a l d a t a i n T a l e I I r e f l e c t the s i m i l a r i t i e s . The % i o n i c ammonia i n r e a c t i o n 2 i s 5.27% compared with 5.04% i n r e a c t i o n 14. In r e a c t i o n 5 t h e % i o n i c ammonia i s 8.08% whereas i n r e a c t i o n 15 the v a l u e i s 7.97%. In r e a c t i o n 2 the" v a l u e s f o r % c h l o r o f o r m e x t r a c t a b l e s , n e u t r a l i z a t i o n e q u i v a l e n t , and % amide ammonia were 5.84%, 123.13 g r a m s / e q u i v a l e n t , and 7.35%, r e s p e c t i v e l y , w h i l e i n r e a c t i o n 14 w i t h c a t a l y s t p r e s e n t the v a l u e s were 6.36%, 122.98 g r a m s / e q u i v a l e n t , and 7.44%, r e s p e c t i v e l y . In r e a c t i o n 5 the v a l u e s f o r % chloroform extractables, n e u t r a l i z a t i o n equivalent, and % amide ammonia were 12.41%, 204.41 g r a m s / e q u i v a l e n t , and 0.00% r e s p e c t i v e l y w h i l e i n r e a c t i o n 15 the v a l u e s were 6.71%, 202.69 g r a m s / e q u i v a l e n t , and 1.08%. The a n a l y t i c a l d a t a are t r a n s l a t e d i n t o product y i e l d s i n Table I I I . Clearly the presence o f ammonium s u l f a m a t e c a t a l y s t has no g r e a t e f f e c t on t h e y i e l d s o f the p r o d u c t s i n the residue. The s p e c t r a o f the p r o d u c t s o f r e a c t i o n o f s u c c i n a m i c a c i d i n v a r i o u s s o l v e n t s are shown i n F i g u r e 11. The s o l u t i o n s were 2.50 molar i n Ν,Ν-dimethylformamide ( r e a c t i o n 17, spectrum A ) , formamide ( r e a c t i o n 16, spectrum B ) , and water ( r e a c t i o n 2, spectrum C ) . Comparison o f the s p e c t r a i n F i g u r e 11 w i t h t h a t o f the pure s u c c i n a m i c a c i d i n



178

S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FD3ERS

F i g u r e 2 (spectrum A) r e v e a l s a g r e a t e r d i f f e r e n c e i n r e a c t i o n 2 w i t h water as s o l v e n t than i n r e a c t i o n s 16 and 17 w i t h nonaqueous s o l v e n t s . The spectrum o f the p r o d u c t s of r e a c t i o n 16 (B) i s v e r y s i m i l a r to t h a t o f the pure s u c c i n a m i c a c i d w i t h o n l y a s l i g h t d e c r e a s e i n the amide c a r b o n y l a b s o r p t i o n . In spectrum A t h i s d i f f e r e n c e i s more pronounced. A p p a r e n t l y , the changes t a k i n g p l a c e i n DMF and formamide are q u i t e d i f f e r e n t from those o c c u r r i n g i n water. The a n a l y t i c a l d a t a i n T a b l e I I r e f l e c t t h e s e d i f f e r e n c e s . The % i o n i c ammonia v a l u e s f o r the p r o d u c t s from formamide ( r e a c t i o n 16) and DMF ( r e a c t i o n 17) are 1.32% and 0.07%, r e s p e c t i v e l y , whereas the v a l u e i s 5.27% f o r water ( r e a c t i o n 2 ) . T h i s i n d i c a t e s t h a t a much g r e a t e r amount o f h y d r o l y s i s t a k e s p l a c e i n water than i n the other s o l v e n t s , as e x p e c t e d . The % c h l o r o f o r m e x t r a c t a b l e s i s 5.84% f o r r e a c t i o n 2 (water), 1.27% for r e a c t i o n 16 (formamide), and 33.87% f o r r e a c t i o n 17 (DMF). T h i s i n d i c a t e s t h a t imide i s formed more e a s i l y i n the a p r o t i c s o l v e n t , DMF, than i n the p r o t i c s o l v e n t s , water and formamide. The n e u t r a l i z a t i o n e q u i v a l e n t and the % amide ammonia v a l u e s o f the p r o d u c t s of the r e a c t i o n s are 123.13 g r a m s / e q u i v a l e n t , 7.35%; 121.92 grams e q u i v a l e n t , 15.80% and 171.10 g r a m s / e q u i v a l e n t , 9.26% f o r r e a c t i o n s 2, 16, and 17, respectively. The d a t a were used to c a l c u l a t e the p r o d u c t y i e l d s i n T a b l e IV. The amount o f the o r i g i n a l s u c c i n a m i c a c i d s t i l l p r e s e n t a f t e r the pad-bake p r o c e d u r e i s much g r e a t e r f o r formamide (76.6%) than f o r DMF (59.3%) and water (53.2%). The h y d r o l y s i s r e a c t i o n t a k e s p l a c e to a much g r e a t e r e x t e n t i n water than i n DMF or formamide as i n d i c a t e d by the y i e l d s o f monoammonium s u c c i n a t e . These y i e l d v a l u e s are 34.0%, 7.4% and 0.4% f o r water, formamide, and DMF, respectively. The d e h y d r o c y c l i z a t i o n r e a c t i o n t o y i e l d s u c c i n i m i d e o c c u r r e d to a much g r e a t e r e x t e n t i n DMF (37.3% y i e l d ) than i n water (5.7%) or i n formamide (1.0%). S u c c i n i c a c i d was d e t e c t e d i n low y i e l d i n r e a c t i o n s 2 and 17. The y i e l d o f s u c c i n i c a c i d was 6%, 0%, and 2% f o r r e a c t i o n s 2, 16, and 17, r e s p e c t i v e l y . The s p e c t r a of the p r o d u c t s of the r e a c t i o n o f p h t h a l a m i c a c i d i n DMF ( r e a c t i o n 19), formamide ( r e a c t i o n 18), and water ( r e a c t i o n 5) are shown i n F i g u r e 12. The r e a c t i o n c o n d i t i o n s employed were 10 minutes bake time at 175°C and a s o l u t i o n c o n c e n t r a t i o n o f 2.50 m o l a r . The s p e c t r a o f the r e a c t i o n p r o d u c t s d i f f e r g r e a t l y from t h a t of the pure p h t h a l a m i c a c i d ( F i g u r e 2, spectrum B ) . The s p e c t r a i n d i c a t e t h a t with formamide ( r e a c t i o n 18, spectrum B) and DMF (reaction 19, spectrum A) the r e s i d u e s p e c t r a are q u i t e s i m i l a r




B O W M A N AND cucuLO

°°

3500

3000

2500 FREQUENCY, C M

2000

1500

H

Figure 12. Infrared spectra of the products of the reaction of phthafomic acid at 175°C for 10 min at an initial concentration of 2.50M in N,N-dimethylformamide (A), formamide (B), and water (C)



180


and i n d i c a t e t h a t the major p r o d u c t i s p h t h a l i m i d e . In water (spectrum C) the major p r o d u c t i s the ammonium salt. The d a t a i n T a b l e I I show t h a t the % i o n i c ammonia v l u e s f o r the p r o d u c t s of r e a c t i o n s 18 and 19 are o n l y 0.74% and 0.13%, r e s p e c t i v e l y , w h i l e t h a t o f r e a c t i o n 5 i s 8·08%. The % c h l o r o f o r m e x t r a c t a b l e s i s q u i t e high at 90.05% i n r e a c t i o n 18 and 100.00% i n r e a c t i o n 19. The v a l u e s would be expected to be l a r g e due to the l a r g e amount o f imide i n the r e s i d u e . The % amide v a l u e s are 0.51% f o r r e a c t i o n 18 and zero f o r r e a c t i o n 19. The p r o d u c t y i e l d v a l u e s are g i v e n i n T a b l e IV. The d a t a show t h a t i n a l l t h r e e s o l v e n t s the i n i t i a l p h t h a l a m i c a c i d i s almost c o m p l e t e l y c o n v e r t e d to one major p r o d u c t . In water ( r e a c t i o n 5) t h i s p r o d u c t i s the monoammonium s a l t of p h t h a l i c a c i d (81.5% y i e l d ) w h i l e i n formamide ( r e a c t i o n 18) and DMF ( r e a c t i o n 19) t h i s p r o d u c t i s p h t h a l i m i d e (74.7% and 92.5% y i e l d , r e s p e c t i v e l y ) . A l l e n has shown t h a t the manner i n which the s o l v e n t i s removed i n the pad-bake r e a c t i o n of aqueous s u c c i n a m i c a c i d s o l u t i o n s w i t h v i s c o s e rayon g r e a t l y a f f e c t s the e x t e n t of the e s t e r i f i c a t i o n r e a c t i o n (4^). F a b r i c which was padded, d r i e d at room temperature and baked was e s t e r i f i e d to a much l e s s e r e x t e n t than f a b r i c which was d r i e d and baked at an e l e v a t e d temperature i n the same s t e p . A l l e n a l s o found t h a t l i t t l e r e a c t i o n o c c u r r e d between molten s u c c i n a m i c a c i d and v i s c o s e rayon f a b r i c , i n e s s e n c e , a r e a c t i o n i n which the amic a c i d i s the s o l v e n t . To determine the e f f e c t of the s o l v e n t removal c o n d i t i o n s on the c o m p o s i t i o n of the r e s i d u e - d e p o s i t e d on the f a b r i c , amic a c i d was r e a c t e d under t h r e e s e t s of c o n d i t i o n s : normal pad-bake, pad, p r e d r y at room temperature f o r 24 hours under a stream of a i r and bake, and f u s i o n w i t h o u t added s o l v e n t . The s p e c t r a of the p r o d u c t s of the r e a c t i o n of s u c c i n a m i c a c i d under normal ( r e a c t i o n 2) p r e d r y ( r e a c t i o n 20) and f u s i o n c o n d i t i o n s ( r e a c t i o n 22) are shown i n F i g u r e 13. In each r e a c t i o n , the spectrum of the p r o d u c t d i f f e r s s i g n i f i c a n t l y from t h a t o f the pure s u c c i n a m i c a c i d ( F i g u r e 2, spectrum A ) . In a l l the s p e c t r a the amide c a r b o n y l s t r e t c h i n g a b s o r p t i o n has decreased s i g n i f i c a n t l y , i n d i c a t i n g p a r t i a l conversion of the o r i g i n a l s u c c i n a m i c a c i d i n t o s u c c i n i m i d e and monoammonium s u c c i n a t e . The a n a l y t i c a l d a t a i n T a b l e I I r e v e a l t h a t the % i o n i c ammonia i s 5.27%, 3.41%, and 1.65% i n r e a c t i o n s 2, 20, and 22, r e s p e c t i v e l y . The amount o f h y d r o l y s i s which has taken p l a c e i s g r e a t e s t i n the pad-bake p r o c e d u r e and l e a s t i n the f u s i o n p r o c e d u r e . The % c h l o r o f o r m e x t r a c t a b l e v a l u e s f o r


B O W M A N AND

cucuLO

Reactions of Cellulose Table

Product


Reaction Number

Unreacted Amic Acid

Yield

IV

Data,

Solvents

Monoammonium salt

Imide

Diacid

16

76.7

7.4

1.0

0

17

59.3

0.4

37.3

2

18

3.9

5.7

74,7

0

19

0

1.1

92.5

0

20

53.1

23.1

17.3

9

21

10.0

56.3

28.2

0

22

52,7

13.6

30.8

2

23

2.0

8.7

85.8

0

3500

3000

2500

2000

1500

FREQUENCY, CM*'

Figure 13. Infrared spectra of the products of the reaction of succinamic acid at 175°C for 10 min under normal (A), predry (B), and fusion (C) conditions


SOLVENT SPUN RAYON, MODIFIED CELLULOSE FIBERS

Γ


αο

°°

3500

3000

2500

2000

FREQUENCY, CM"

1500

1

Figure 14. Infrared spectra of the products of the reaction of phthalamic acid at 175°C for 10 rain under normal (A), predry (B), and fusion (C) condition



11.


183


r e a c t i o n s 2, 20, and 22 a r e 5.84%, 14.73% and 24.40%, r e s p e c t i v e l y , i n d i c a t i n g t h a t imide f o r m a t i o n i s the most important i n t h e f u s i o n r e a c t i o n (22). This i s a l s o r e f l e c t e d i n the v a l u e s o f the n e u t r a l i z a t i o n e q u i v a l e n t s , 123.1, 129.5, and 140.5 g r a m s / e q u i v a l e n t f o r r e a c t i o n s 2, 20, and 22, r e s p e c t i v e l y . The a n a l y t i c a l d a t a were used t o c a l c u l a t e the % y i e l d v a l u e s i n T a b l e IV. The % y i e l d o f s u c c i n a m i c a c i d i s about the same i n each experiment. The y i e l d o f monoammonium s a l t i s g r e a t e s t i n the normal pad-bake procedure (34.0%) a t l e a s t i n the f u s i o n procedure (13.6%). T h i s r e l a t i o n s h i p i s r e v e r s e d i n the % y i e l d of s u c c i n i m i d e w i t h t h e normal p r o c e d u r e y i e l d 5.7% and the f u s i o n procedure y i e l d 30.8%. With the p r e d r y c o n d i t i o n s the y i e l d s o f monoammonium s a l t and s u c c i n i m i d e a r e i n t e r m e d i a t e i n v a l u e a t 23.1% and 17.3%, r e s p e c t i v e l y . These r e s u l t s i n d i c a t e t h a t h y d r o l y s i s o f t h e amic a c i d i s most complete i n t h e r e a c t i o n with water as s o l v e n t and t h a t the h i g h e r the temperature o f removal o f the water the g r e a t e r the hydrolysis. Dehydrocyclization t o form imide i s most f a v o r e d i n the absence o f water as the r e s u l t s o f the fusion reaction indicate. The y i e l d o f s u c c i n i c a c i d was 6%, 9%, and 2% i n t h e normal, p r e d r y , and f u s i o n reactions respectively. The t r e n d s noted i n the s u c c i n a m i c a c i d r e a c t i o n above were even more apparent i n the r e a c t i o n s o f p h t h a l a m i c a c i d under normal, p r e d r y , and f u s i o n conditions. The s p e c t r a o f the p r o d u c t s o f the r e a c t i o n s o f p h t h a l a m i c a c i d under normal ( r e a c t i o n 5), p r e d r y ( r e a c t i o n 21), and f u s i o n c o n d i t i o n s ( r e a c t i o n 23) a r e g i v e n i n F i g u r e 14 ( s p e c t r a A, B, and C, r e s p e c t i v e l y ) . S p e c t r a A and Β show t h a t h y d r o l y s i s i s the predominant r e a c t i o n by the absence o f the amide c a r b o n y l s t r e t c h a t 1645 cm"" and t h e presence o f the s t r o n g c a r b o x y l a t e c a r b o n y l s t r e t c h a t 1550 cm" . Spectrum C i n d i c a t e s t h a t the predominant p r o d u c t i n the f u s i o n r e a c t i o n i s p h t h a l i m i d e . These c o n l u s i o n s are r e f l e c t e d i n the a n a l y t i c a l d a t a i n T a b l e I I . In r e a c t i o n s 5 and 21 t h e % i o n i c ammonia i n the p r o d u c t i s 8.08% and 6.57%, r e s p e c t i v e l y , w h i l e i n r e a c t i o n 23 the v a l u e i s 1.02%. The % c h l o r o f o r m e x t r a c t a b l e v a l u e s a r e 12.41% and 18.64% i n r e a c t i o n s 5 and 21, r e s p e c t i v e l y , and 87.20% i n r e a c t i o n 22. The n e u t r a l i z a t i o n e q u i v a l e n t v a l u e s f o r r e a c t i o n s 5 and 21 were 204.4 and 223.4 g r a m s / e q u i v a l e n t , r e s p e c t i v e l y . The n e u t r a l i z a t i o n e q u i v a l e n t o f the p r o d u c t s o f r e a c t i o n 23 was not d i r e c t l y d e t e r m i n e d . The r e s i d u e of the c h l o r o f o r m e x t r a c t i o n was found t o have a n e u t r a l i z a t i o n e q u i v a l e n t o f 183.2 g r a m s / e q u i v a l e n t . 1

1


184

SOLVENT SPUN R A Y O N , MODIFIED C E L L U L O S E

FIBERS

Table Y Mass B a l a n c e and V o l a t i l e P r o d u c t Y i e l d D a t a


Reaction Number

% Yield of A d d Derivatives

% Yield of Nitrogen C o n t . Cmpds.

% Yield of V o l a t i l e Ammonia

1

99.7

93.7

0.0

2

98.9

92.9

0.8 4.1

3

97.1

87.1

4

99.2

99.2

0.2

5

98.0

97.0

0.2

% Yield of Sublimate

6

97.3

96.3

0.3

7

95.2

91.0

0.0

8

99.0

86.0

0.6

0.8*

9

100.5

100.5

0.1

0.5**

10

100.8

97.0

0.0

0.8**

11

94.5

86.5

4.0

12

99.4

90.4

2.3

13

96.0

86.0

0.8

14

100.4

94.4

1.7

15

100.0

99.0

0.0 0.6

16

86.1

85.1

17

99.0

97.0

1.7

18

84.4

84.4

3.9

19

93.6

93.6

5.9

20

98.0

89.0

2.2

21

92.7

93.3

0.0

22

98.6

94.6

0.6

23

96.5

96.5

0.1

0.2

* As s u c c i n a m i c a c i d * * As p h t h a l i m i d e



11.



185

The % amide ammonia was g r e a t e s t i n r e a c t i o n 21 at 1.06% and l e a s t i n r e a c t i o n 5 at 0.10%. The product y i e l d v a l u e s are g i v e n i n T a b l e IV. The p h t h a l a m i c a c i d i s almost t o t a l l y c o n v e r t e d i n t o p r o d u c t s under a l l t h r e e s e t s o f c o n d i t i o n s . The r e a c t i o n s under normal and p r e d r y c o n d i t i o n s g i v e the most h y d r o l y s i s as i n d i c a t e d by the % y i e l d o f monoammonium s a l t , 81.5% and 56.3%, r e s p e c t i v e l y . In the f u s i o n r e a c t i o n , 23, the imide y i e l d i s 85.8% w h i l e i n the normal ( r e a c t i o n 5) and p r e d r y r e a c t i o n s the y i e l d s are 14.9% and 28.2%, respectively. L i t t l e p h t h a l i c a c i d was d e t e c t e d . Volatile

Products

During the pad-bake procedure v o l a t i l e p r o d u c t s other than the s o l v e n t are e v o l v e d . T h i s becomes apparent when the m a t e r i a l b a l a n c e f o r the r e a c t i o n s i s computed. The m a t e r i a l b a l a n c e on the a c i d d e r i v a t i v e s and n i t r o g e n c o n t a i n i n g p r o d u c t s i s g i v e n i n T a b l e V along w i t h the e x p e r i m e n t a l l y determined v a l u e s of the y i e l d s of v o l a t i l e p r o d u c t s . The m a t e r i a l b a l a n c e v a l u e s vary from 100.5% i n r e a c t i o n 9 t o 84.4% i n r e a c t i o n 18. In the r e a c t i o n s i n formamide (16 and 18) the s o l v e n t was not c o m p l e t e l y removed i n the bake s t e p due t o the low v o l a t i l i t y of the s o l v e n t . The s o l v e n t was removed by e v a p o r a t i o n at room temperature under h i g h vacuum f o r s e v e r a l h o u r s . It i s p o s s i b l e that under these c o n d i t i o n s a p o r t i o n of the p r o d u c t s sublimed from the mixture and was l o s t . In both r e a c t i o n s 16 and 18 the m a t e r i a l balance v a l u e s are c o m p a r a t i v e l y low at 86.1% and 84.4%, r e s p e c t i v e l y , f o r the a c i d d e r i v a t i v e s , and 85.1% and 84.4% f o r the nitrogen containing products. The mass b a l a n c e v a l u e s d e c r e a s e with both the d u r a t i o n and temperature of reaction. The % y i e l d o f s u c c i n i c a c i d d e r i v a t i v e s and n i t r o g e n c o n t a i n i n g compounds i s 99.7% and 93.7%, r e s p e c t i v e l y i n r e a c t i o n 1 (150°C bake temperature) w h i l e i n r e a c t i o n 3 (200°C bake temperature) the v a l u e s are 97.1% and 87.1%, r e s p e c t i v e l y . The y i e l d o f p h t h a l a m i c a c i d d e r i v a t i v e s and n i t r o g e n c o n t a i n i n g compounds was 99.2%, and 99.2%, r e s p e c t i v e l y , i n r e a c t i o n 4 (150°C bake t e m p e r a t u r e ) , and 97.3% and 96.3%, r e s p e c t i v e l y , i n r e a c t i o n 6 (200° C bake temperaure). The e x p e r i m e n t a l l y determined y i e l d s o f s u b l i m a t e and v o l a t i l e ammonia are a l s o g i v e n i n T a b l e V. The s u b l i m a t e was o b t a i n e d by e v a p o r a t i o n of the t r a p of c h l o r o f o r m i n r e a c t i o n s 8, 9, and 10. On e v a p o r a t i o n of the c h l o r o f o r m a s m a l l amount of r e s i d u e was obtained. The i n f r a r e d s p e c t r a o f the r e s i d u e s are



S O L V E N T SPUN R A Y O N , MODIFIED C E L L U L O S E FD3ERS

FREQUENCY, CM"

1

Figure 15. Infrared spectra of the volitile products in reactions 8 (A) and 9(B)

60

80

100

120

140

MO

MO

TIME, MMUTES

Figure 16. Variation of the percent yield of ammonium ion in the padbath with time for 2.50M solutions of succinamic and phthafomic acid at 65° ± 1°C



11.


187


g i v e n i n F i g u r e 15. Spectrum A, t h a t o f the s u b l i m a t e from r e a c t i o n 8, when compared w i t h t h a t o f the pure compound i n F i g u r e 2 (spectrum A) appears t o be the spectrum o f a p a r t i a l l y h y d r o l y z e d or n e u t r a l i z e d sample o f s u c c i n a m i c a c i d . Spectrum B, o b t a i n e d from the p r o d u c t o f r e a c t i o n 9 i s i d e n t i c a l t o the spectrum of p h t h a l i m i d e . The same i s t r u e f o r the spectrum o f the v o l a t i l e p r o d u c t o f r e a c t i o n 10 (not shown). Thus, the m a t e r i a l which s u b l i m e s from the r e a c t i o n i s s u c c i n a m i c a c i d i n the r e a c t i o n s o f s u c c i n a m i c a c i d and p h t h a l i m i d e i n the r e a c t i o n o f p h t h a l a m i c a c i d . The % y i e l d o f v o l a t i l e ammonia i n the r e a c t i o n s of s u c c i n a m i c a c i d i s p r o b a b l y too low s i n c e the s u c c i n a m i c a c i d i t s e l f i s a l s o passed i n t o the t r a p o f s t a n d a r d a c i d as i t s u b l i m e s . In the r e a c t i o n s o f p h t h a l a m i c a c i d i n water the y i e l d o f v o l a t i l e ammonia i s g e n e r a l l y lower than the y i e l d o f v o l a t i l e ammonia i n the c o r r e s p o n d i n g s u c c i n a m i c a c i d r e a c t i o n . The e x c e p t i o n t o t h i s i s i n the r e a c t i o n s i n formamide and DMF. Succinamic a c i d i n formamide ( r e a c t i o n 16) and DMF ( r e a c t i o n 17) y i e l d s 0.6% and 1.7% respectively, of v o l a t i l e ammonia, and p h t h a l a m i c a c i d i n formamide ( r e a c t i o n 18) and DMF ( r e a c t i o n 19) y i e l d s 3.9% and 5.9% i o n i c ammonia, r e s p e c t i v e l y . f

Pad

Bath

Stability

I t i s o f i n t e r e s t t o determine the changes which occur i n the pad-bath b e f o r e the bake s t e p . The main change expected i n the pad bath i s h y d r o l y s i s o f the amic a c i d . T h i s r e a c t i o n was f o l l o w e d by d e t e r m i n a t i o n of the i o n i c ammonia c o n t e n t o f a 2.50 molar aqueous pad-bath h e l d a t 65°C and by f o l l o w i n g the changes i n the c a r b o n y l s t r e t c h i n g r e g i o n o f the i n f r a r e d spectrum of the m a t e r i a l i n the b a t h . The % y i e l d o f the ammonium i o n p r e s e n t i n the pad bath i s shown as a f u n c t i o n o f time i n F i g u r e 16. The time o f i n t r o d u c t i o n o f the amic a c i d i n t o the water was the b e g i n n i n g o f the r e a c t i o n . Complete d i s s o l u t i o n o f the amic a c i d o c c u r r e d w i t h i n f i v e minutes i n the procedure. P h t h a l a m i c a c i d i s almost e n t i r e l y h y d r o l y z e d d u r i n g the d i s s o l u t i o n p e r i o d as h y d r o l y s i s rapidly occurs. Pad-bake r e a c t i o n s with aqueous s o l u t i o n s o f p h t h a l a m i c a c i d c e r t a i n l y i n v o l v e the monoammonium s a l t . S u c c i n a m i c a c i d i s more r e s i s t a n t to h y d r o l y s i s w i t h a y i e l d o f monoammonium s u c c i n a t e o f o n l y 34.0% a f t e r 3 h o u r s . These changes a r e a l s o r e f l e c t e d i n the changes which occur i n the c a r b o n y l s t r e t c h i n g r e g i o n o f the s p e c t r a o f the m a t e r i a l i n the bath which a r e shown i n F i g u r e 17. The s p e c t r a show


188

SOLVENT

SPUN R A Y O N ,


FIBERS

t h a t the amide c a r b o n y l s t r e t c h i n g . a b s o r p t i o n at 1650 cm*" g r a d u a l l y d i s a p p e a r s as the c a r b o x y l a t e c a r b o n y l s t r e t c h i n g a b s o r p t i o n g r a d u a l l y appears at 1550 cm" The changes i n the s p e c t r a of the p h t h a l a m i c a c i d r e s i d u e s are more d r a m a t i c than those i n the succinamic a c i d experiment. The amide c a r b o n y l a b s o r p t i o n a t 1645 cm^ i s c o m p l e t e l y absent at 15 minutes w h i l e the c a r b o x y l a t e c a r b o n y l s t r e t c h i n g a b s o r p t i o n i s f u l l y developed i n 15 minutes. There i s l i t t l e f u r t h e r change i n the s p e c t r a with time. 1

1


1

Conclusions During the pad-bake p r o c e s s the amic a c i d i s d i s s o l v e d i n the s o l v e n t at an e l e v a t e d temperature. The r e s u l t i n g s o l u t i o n i s a p p l i e d to the s u b s t r a t e , the s o l v e n t i s r a p i d l y v o l a t i l i z e d , and a r e s i d u e i s d e p o s i t e d on the s u b s t r a t e . The r e s i d u e i s then f u r t h e r heated i n the c o m p l e t i o n of the bake s t e p . The p r o c e s s can f o r the sake o f d i s c u s s i o n be d i v i d e d i n t o three steps: s o l u t i o n p r e p a r a t i o n and padding, v o l a t i l i z a t i o n of s o l v e n t , and bake of the r e a c t a n t s . During the p r e p a r a t i o n of the s o l u t i o n the predominant c h e m i c a l change which o c c u r s i n the amic a c i d i s h y d r o l y s i s . T h i s was g r a p h i c a l l y i l l u s t r a t e d i n the experiments t o determine the pad-bath s t a b i l i t y . P h t h a l a m i c a c i d i s almost e n t i r e l y h y d r o l y z e d d u r i n g the p r e p a r a t i o n of the s o l u t i o n w h i l e s u c c i n a m i c a c i d i s h y d r o l y z e d a t a somewhat slower r a t e . T h i s r e s u l t i s not s u r p r i s i n g i n l i g h t of the s t u d i e s o f the h y d r o l y s i s of ,α 3-amic a c i d s which have been r e p o r t e d (1^), 11,12,12,L4,JU5,lj>r_17,jj*). α, 3 -amic a c i d s which are derîvecPfrom d i c a r b o x y l i c a c i d s forming i n t e r n a l p e n t a c y c l i c a n h y d r i d e s are h y d r o l y z e d at r a t e s which are u n c h a r a c t e r i s t i c a l l y h i g h f o r amides. The mechanism f i r s t proposed t o e x p l a i n t h i s unusual b e h a v i o r i n v o l v e s the f o r m a t i o n of the i n t e r n a l anhydride i n a r a t e d e t e r m i n i n g s t e p f o l l o w e d by r a p i d hydrolysis (10,LI). T h i s mechanism was i n f e r r e d from the r e s u l t s 0 7 an i s o t o p i c l a b e l i n g experiment ( 1 1 ) . The f a c i l e h y d r o l y s i s o f many a , 3 - a m i c a c i d s has s i n c e been r e p o r t e d (1^,12,14^,15,1^,17,1^8), and the a n h y d r i d e was d i r e c t l y d e t e c t e c P a s tïïê r e a c t i v e i n t e r m e d i a t e i n the r e a c t i o n i n one r e c e n t study ( 1 8 ) . The r a t e c o n s t a n t s f o r the pseudo f i r s t order h y d r o l y s i s of s u c c i n a m i c and p h t h a l a m i c a c i d s at 65°C are 3.3 χ 1 0 " sec" and 1.3 χ 1 0 ~ sec" , r e s p e c t i v e l y (12^). By use of these f i r s t order r a t e c o n s t a n t s , the c o n c e n t r a t i o n of amic a c i d i n the pad bath at v a r i o u s times can be e s t i m a t e d . These v a l u e s 5

1

3

1



189

Reactions of Cellulose T a b l e VI

Comparison o f t h e o r e t i c a l and experimental v a l u e s o f % y i e l d o f ammonium s a l t d u r i n g h y d r o y l s i s o f t h e amic a c i d s i n t h e pad bath

% Y i e l d o f Ammonium S a l t i n Pad Bath

Age o f the Pad Bath (minutes a t 65 C)

Succinamic A c i d Calculated


Ρhtha1amic A c i d Calculated Pound

Found

e

15

1.5

3.0

92,2

87.8

20

3.0

3.9

95.0

94.0

30

6.5

5.8

97.5

98.5

45

12.6

8.6 98.5

99.9

99.0

100.0

11.3

60 120

23.2

21.3

180

33.8

30.2 51.3

360

* Ρ Γ Ο Π Ι t h e f i r s t order r a t e c o n s t a n t i n r e f e r e n c e (12).

1900

1600 1900 16001900

16001900

16001900

16001900 1600

FREQUENCY, CM"*

Figure 17. Variation in the carbonyl stretching absorption re gion of the infrared spectra of the pad-bath residues with time for 2.50M solutions of succinamic and phthalamic acid at 65° ± 1°C


190

SOLVENT

SPUN R A Y O N ,


are shown i n T a l e VI a l o n g w i t h e x p e r i m e n t a l v a l u e s from the d e t e r m i n a t i o n o f the pad-bath s t a b i l i t y . The d a t a from t h i s study p a r a l l e l c l o s e l y the c a l c u l a t e d data. A l s o , the r a t e c o n s t a n t f o r the pseudo f i r s t o r d e r h y d r o l y s i s o f s u c c i n a m i c a c i d was c a l c u l a t e d t o be 2.6 χ 10"" s e c - which i s i n good agreement with the v a l u e of Kezdy and B r u y l a n t s (12^) g i v e n above. The v a l u e o f the r a t e c o n s t a n t f o r the p h t h a l a m i c a c i d c o u l d not be e s t i m a t e d from the e x p e r i m e n t a l d a t a . The c l o s e p a r l l e l between the d a t a o b t a i n e d i n t h i s study to t h a t p r e d i c t e d by the l i t e r a t u r e i n d i c a t e a s i m i l a r i t y i n the paths by which the amic a c i d i s hydrolyzed. N o t a b l y , the two amic a c i d s d i f f e r g r e a t l y i n t h e i r s t a b i l i t i e s as t h i s study i n d i c a t e s . The d i f f e r e n c e i n the r e a c i v i t y o f the two amic a c i d s can be r e a d i l y e x p l a i n e d i n terms o f t h e i r s t r u c t u r e s . The c o n f o r m a t i o n a l l y mobile s u c c i n a m i c a c i d can e x i s t as extended c h a i n conformers which do not f a v o r the carboxyl-amide i n t e r a c t i o n demanded by the Bender mechanism f o r f a c i l e h y d r o l y s i s ( 1 1 ) . The p h t h a l a m i c a c i d molecule i s s t u c t u r a l l y r i g i c P a n d the c a r b o x y l and amide groups are c o n s t r a i n e d to i n t e r a c t . The r e l a t i v e r a t e s o f h y d r o l y s i s of the two compounds at 65°C i s g i v e n by the r a t i o of the above r a t e c o n s t a n t s ( 1 1 ) , thus p h t h a l a m i c a c i d i s h y d r o l y z e d 39 times f a s t e r than s u c c i n a m i c a c i d . Other s t r u c t u r a l l y r i g i d α , β -amic a c i d such as maleamic a c i d would be expected to behave i n the same manner as p h t h a l a m i c a c i d and be s u b s t a n t i a l l y h y d r o l y z e d d u r i n g the p r e p a r a t i o n o f the pad-bath at 65°C. The r a t e c o n s t a n t f o r the h y d r o l y s i s of maleamic a c i d at 65°C i s 2.4 χ 10 " s e c " or r o u g h l y t w i c e t h a t of p h t h a l a m i c a c i d (1_1 ). C a l c u l a t i o n s using t h i s c o n s t a n t p r e d i c t t h a t maleamic a c i d would be 88% h y d r o l y z e d i n 15 minutes i n an aqueous pad-bath at 65°C In the second s t e p i n the pad-bake procedure the solvent i s v o l a t i l i z e d . In the experiments with water, the v o l a t i l i z a t i o n of the bulk of the s o l v e n t o c c u r r e d i n a p p r o x i m a t e l y two minutes f o r the 2.50 molar solutions. Formamide and DMF, l e s s v o l a t i l e s o l v e n t s than water were p r e s e n t throughout the r e a c t i o n . Bake temperature made l i t t l e apparent d i f f e r e n c e i n the time r e q u i r e d f o r the removal o f the bulk o f the water. The r e s u l t s o f the experiments with a bake time of 5 minutes at 175°C , r e a c t i o n 7 f o r s u c c i n a m i c a c i d and r e a c t i o n 9 f o r p h t h a l a m i c a c i d , g i v e some i n s i g h t i n t o the changes which occur i n the amic a c i d d u r i n g v o l a t i l i z a t i o n o f the s o l v e n t . In r e a c t i o n 7 o n l y 65.9% o f the i n i t i a l l y p r e s e n t amide was accounted f o r by the amide ammonia a n a l y s i s . 1


FIBERS

3

1



11.

BOWMAN AND

cucuLO


191

S i n c e s u c c i n a m i c a c i d i s r e l a t i v e l y unchanged i n the bath a f t e r 10 m i n u t e s , the maximum bath age at the time of withdrawal o f the a l i q u o t of s o l u t i o n f o r r e a c t i o n , the extent of h y d r o l y s i s of s u c c i n a m i c a c i d would be r e l a t i v e l y s m a l l as p r e d i c t e d by the d a t a i n T a b l e IV and F i g u r e 16. C o n s e q u e n t l y , a s u b s t a n t i a l amount o f h y d r o l y s i s must occur d u r i n g the v o l a t i l i z a t i o n s t e p . By using the a c t i v a t i o n parameters r e p o r t e d i n r e f erence 12 the r a t e c o n s t a n t f o r the h y d r o l y s i s of s u c c i n a m i c a c i d i n water at 100°C can be shown to be 6.9 χ 10 * sec ~ . I f h y d r o l y s i s proceeds f o r two minutes at t h i s r a t e the y i e l d o f i o n i c ammonia expected would be at most about 8-10%, depending on the amount o f h y d r o l y s i s o c c u r r i n g i n the s o l u t i o n p r e p a r a t i o n s t e p . The y i e l d o f i o n i c ammonia i n r e a c t i o n 7 was found to be 24.7%, more than t w i c e the maximum amount p r e d i c t e d by the f i r s t order h y d r o l y s i s c o n s t a n t . This d i s c r e p a n c y c o u l d a r i s e f o r a number o f r e a s o n s . The temperature i n the r e a c t i o n mass p r o b a b l y d e v i a t e s c o n s i d e r a b l y from t h a t o f b o i l i n g water, p a r t i c u l a r l y d u r i n g the l a t t e r s t a g e s of the v o l a t i l i z a t i o n when the s o l u t i o n i s concentrated. A l s o , as water i s removed the r e a c t i o n medium undergoes a d r a s t i c change from aqueous s o l u t i o n to a s o l u t i o n of the p r o d u c t s of the r e a c t i o n s i n l i q u i d s u c c i n a m i c a c i d . Under these c o n d i t i o n s the pseudo f i r s t order r a t e c o n s t a n t s p r o b a b l y are not v a l i d . I n f r a r e d s t u d i e s of s o l u t i o n s of N - s u b s t i t u t e d s u c c i n a m i c a c i d s i n non-polar or a p r o t i c s o l v e n t s and i n the s o l i d s t a t e i n d i c a t e the f o r m a t i o n of hydrogen bonded dimers (33,32^). In one study the d i m e r i c form o f the amic a c i d was postulated to be more r e a c t i v e i n s o l v o l y s i s r e a c t i o n s {22). The r e a c t i o n r a t e i n c r e a s e d w i t h an i n c r e a s e i n the c o n c e n t r a t i o n o f s u c c i n a m i c a c i d or on the a d d i t i o n o f acetic acid. Sauers, e t . a l . (25), a l s o noted an e f f e c t of added a c i d i n the attempted d e h y d r o c y c l i z a t i o n s of N - s u b s t i t u t e d p h t h a l a m i c a c i d s in a c e t i c anhydride. In t h e i r study the competition between d e h y d r o c y c l i z a t i o n to form imides or i s o i m i d e s and the i n t e r n a l t r a n s a c y l a t i o n to form p h t h a l i c a n h y d r i d e f a v o r e d a n h y d r i d e f o r m a t i o n i n the presence of added a c i d or l a r g e i n i t i a l c o n c e n t r a t i o n s o f amic acid. The mechanism proposed to e x p l a i n these o b s e r v a t i o n s i n v o l v e d i n t e r m e d i a t e f o r m a t i o n of a mixed p h t h a l i c a c i d - a c e t i c a c i d a n h y d r i d e or d i r e c t f o r m a t i o n of p h t h a l i c a n h y d r i d e by a pathway s i m i l a r to the Bender mechanism (11). Thus, the o b s e r v a t i o n s noted i n the l i t e r a t u r e l e n d support to the c o n c l u s i o n t h a t the r a t e of h y d r o l y s i s of s u c c i n a m i c a c i d c o u l d be enhanced d u r i n g v o l a t i l i z a t i o n of the water due to the change el

l



192

S O L V E N T SPUN R A Y O N ,


FD3ERS

i n r e a c t i o n medium. With p h t h a l a m i c a c i d , l i t t l e change o c c u r s d u r i n g the v o l a t i l i z a t i o n o f the s o l v e n t s i n c e the compound i s s u b s t a n t i a l l y h y d r o l y z e d d u r i n g the p r e p a r a t i o n o f the pad-bath. In r e a c t i o n 9, the y i e l d o f i o n i c ammonia was 88.6%, w h i l e i n the pad bath a f t e r 15 minutes the y i e l d o f i o n i c ammonia was 92.2%. The r e s i d u e d e p o s i t e d by v o l a t i l i z a t i o n o f the s o l v e n t i s s o l i d and c o n s i s t s p r i n c i p a l l y o f monoammonium p h t h a l a t e . R e a c t i o n s o f aqueous s o l u t i o n s o f p h t h a l a m i c a c i d w i t h v i s c o s e rayon g e n e r a l l y l e a d t o lower D.S. v a l u e s than does the same r e a c t i o n w i t h s u c c i n a m i c a c i d ( 3 2 ) . Our r e s u l t s i n d i c a t e t h a t such r e a c t i o n s proceed tïïrough the p a r t i a l ammonium s a l t which i s d e p o s i t e d as a s o l i d and c o n s e q u e n t l y has low m o b i l i t y i n any f u r t h e r reaction. T h i s p r o b a b l y a c c o u n t s i n p a r t f o r the low r e a c t i v i t y o f p h t h a l a m i c a c i d i n i t s r e a c t i o n s with c e l l u l o s i c substrates. In t h e bake s t e p the r e s i d u e d e p o s i t e d by v o l a t i l i z a t i o n o f the s o l v e n t undergoes f u r t h e r c h e m i c a l change. The predominant r e a c t i o n d u r i n g t h i s phase o f the r e a c t i o n with both s u c c i n a m i c and p h t h a l a m i c a c i d i s d e h y d r o c y c l i z a t i o n t o y i e l d imide. S i n c e n e i t h e r s u c c i n i m i d e nor p h t h a l i m i d e (_3) undergoes any s i g n i f i c a n t r e a c t i o n with c e l l u l o s i c s u b s t r a t e s i n pad-bake r e a c t i o n s , the d e h y d r o c y c l i z a t i o n r e a c t i o n r e p r e s e n t s a s e r i o u s c o m p e t i t i o n i n the f o r m a t i o n o f c e l l u l o s e e s t e r s by r e a c t i o n w i t h a β -amic a c i d s . A f t e r 5 minutes a t 175°C ( r e a c t i o n 7) o n l y 65.9% of the o r i g i n a l s u c c i n a m i c a c i d remained i n the r e s i d u e as measured by the amide ammonia d e t e r m i n a t i o n . The m a j o r i t y o f the s u c c i n a m i c a c i d which has r e a c t e d has undergone h y d r o l y s i s as i n d i c a t e d by the h i g h y i e l d o f i o n i c ammonia (24.7%) i n the r e s i d u e . At t e n minutes bake time ( r e a c t i o n 2) t h e s u c c i n a m i c a c i d c o n t e n t has f u r t h e r d e c r e a s e d t o 53.2% w h i l e the y i e l d o f both imide and i o n i c ammonia have i n c r e a s e d t o 5.7% and 34.0%, r e s p e c t i v e l y . T h i s i n d i c a t e s t h a t s u c c i n a m i c a c i d i s f u r t h e r h y d r o l y z e d i n the melt d e p o s i t e d even a f t e r t h e m a j o r i t y o f the water has been v o l a t i l i z e d . Water i s produced by the d e h y d r o c y c l i z a t i o n r e a c t i o n and c o n s e q u e n t l y i s always p r e s e n t t o some e x t e n t i n the m e l t . The imide which has formed by t h i s time i s p r o b a b l y the r e s u l t o f d e h y d r o c y c l i z a t i o n o f the s u c c i n a m i c a c i d and the s a l t formed by the h y d r o l y s i s reaction. A f t e r 15 minutes at 175°C ( r e a c t i o n 8) o n l y 39.5% o f the i n i t i a l l y p r e s e n t s u c c i n a m i c a c i d i s accounted f o r i n the r e s i d u e w h i l e the y i e l d o f the d e h y d r o c y c l i z a t i o n p r o d u c t , s u c c i n i m i d e , i s 23.1%. The y i e l d o f i o n i c ammonia has d e c r e a s e d t o 23.1%. Thus, f



11.



193

at l o n g e r bake times both the r e s i d u a l s u c c i n a m i c a c i d and the h y d r o l y s i s p r o d u c t are c o n v e r t e d t o the i m i d e . In r e a c t i o n s o f s u c c i n a m i c a c i d the d e h y d r o c y c l i z a t i o n r e a c t i o n i s much f a s t e r a t h i g h e r temperatures. The y i e l d o f imide i n r e a c t i o n 3 a t 200° C i s over s i x times g r e a t e r than the y i e l d o f imide i n reaction 6 a t 175°C. The g r e a t e r c o m p e t i t i o n o f the d e h y d r o c y c l i z a t i o n r e a c t i o n a t h i g h e r tempertures accounts q u i t e w e l l f o r the o b s e r v a t i o n s o f both Johnson and C u c u l o t h a t the f r e e a c i d D.S. o f rayon f a b r i c m o d i f i e d i n t h e pad-bake r e a c t i o n with s u c c i n a m i c a c i d d e c r e a s e d a t bake temperatures h i g h e r than 170°C. The f o r m a t i o n o f s u c c i n i m i d e i s f a v o r e d by the e x c l u s i o n o f water from t h e bake s t e p . Succinamic a c i d which i s heated i n the absence o f water ( r e a c t i o n 22, melt r e a c t i o n ) y i e l d s over f i v e times the s u c c i n i m i d e as does the r e a c t i o n under normal pad-bake r e a c t i o n c o n d i t i o n s ( r e a c t i o n 2 ) . The ease o f f o r m a t i o n o f s u c c i n i m i d e i n molten s u c c i n a m i c c o u l d account f o r the low y i e l d s i n the r e a c t i o n s o f s u c c i n a m i c a c i d melts with c e l l u l o s i c s u b s t r a t e s ( 4 ) . Succinamic a c i d under the p r e d r y c o n d i t i o n s ( r e a c t i o n 20) a l s o gave a g r e a t e r y i e l d o f imide than d i d the r e a c t i o n under normal pad-bake c o n d i t i o n s ( r e a c t i o n 2 ) . Acknowledgements We wish t o thank The Sherwin W i l l i a m s Co., Tennessee Eastman Co., and N o r t h C a r o l i n a S t a t e u n i v e r s i t y f o r t h e i r support o f p a r t s o f t h i s work. List 1. 2. 3. 4. 5. 6.

7.

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