Cellulose Technology Research

5 Utilization of the Novel Reaction of Cellulose with Amic Acids to Produce Cellulose Derivatives Containing Carboxylic Acid Groups THOMAS C. A L L E N New

Products and Processes Research, American Enka Co., Enka, N.C. 28728

JOHN A. C U C U L O Department of Textile Chemistry, North Carolina State University, Raleigh, N.C. 27607 Introduction One of the main reasons f o r the widespread use of c e l l u l o s e has been the abundance of h y d r o x y l groups and t h e i r ability t o r e a c t with a v a r i e t y of compounds t o form c e l l u l o s e d e r i v a t i v e s . These d e r i v a t i v e s e x h i b i t s e l e c t e d d e s i r e d p r o p e r t i e s , depending on the new f u n c t i o n a l group added. Although the m o d i f i c a t i o n of c e l l u l o s e has been s t u d i e d and p r a c t i c e d commercially f o r s e v e r a l years, new r e a c t i o n s and new d e r i v a t i v e s with new p r o p e r t i e s are still being i n v e s t i g a t e d and much of the chemistry i n v o l v e d i s not completely understood. One of the most s t u d i e d f u n c t i o n a l groups is c a r b o x y l i c a c i d . In a recent review the methods of preparation and the p r o p e r t i e s of these c a r b o x y l i c a c i d containi n g d e r i v a t i v e s were discussed (1). Some of these p r o p e r t i e s , which are under a c t i v e i n v e s t i g a t i o n today are: s a l t formation solubility of alkali metal and amine s a l t s i n water f i b e r formation f i l m s , coatings, and b i n d e r s ion-exchange c a t i o n i c dye a t t r a c t i o n water absorbency soil release opening of s t r u c t u r e f o r subsequent r e a c t i o n s new s i t e f o r chemical r e a c t i o n s crosslinking monomeric grafting One c l a s s of such d e r i v a t i v e s , the c e l l u l o s e semi-esters, has achieved little commercial s i g n i f i c a n c e , even though it was first i n v e s t i g a t e d over thirty years ago. T h i s paper is concerned with the n o v e l r e a c t i o n of c e l l u l o s e w i t h amic acids prepared by the r e a c t i o n of poly c a r b o x y l i c a c i d anhydrides with ammonia e i t h e r beforehand or even in s i t u i n the

51

52

CELLULOSE TECHNOLOGY

RESEARCH

t r e a t i n g s o l u t i o n . T h i s r e a c t i o n , f i r s t reported by Cuculo (2,3 Λ ) and l a t e r s t u d i e d f o r g e n e r a l i t y (5 »6) o f f e r s the unique features of u s i n g r e l a t i v e l y inexpensive and r e a d i l y a v a i l a b l e m a t e r i a l s i n a simple aqueous pad-bake technique with short r e a c t i o n times. Furthermore, by choosing d i f f e r e n t amic a c i d s such as succinamic, maleamic, and phthalamic, a l i p h a t i c , un saturated, and aromatic d e r i v a t i v e s can be obtained. Three major products can be expected from the r e a c t i o n of c e l l u l o s e with amic a c i d s : (a) the c e l l u l o s e h a l f - a c i d ester,(b) the c r o s s l i n k e d c e l l u l o s e d i e s t e r , and (c) the c e l l u l o s e h a l f amide e s t e r . Cellulose-QH + lH C(o)RC0 H 2

(a) (b) (c)

~>

2

Cellulose-OC(0)RC0 H 2

Cellulose-OC(θ)RC(θ)0-Cellulose Cellulose-OC(0)RC(0)NH

2

The c e l l u l o s e h a l f - a c i d e s t e r was shown t o be present- i n r e l a t i v e l a r g e amounts as evidenced by t e s t s f o r the c a r b o x y l i c acid. Comparison of the f r e e c a r b o x y l value with the t o t a l carboxyl value showed t h a t one or both of the other products was present. The half-amide e s t e r was b e l i e v e d t o be a minor product due t o the copious e v o l u t i o n of ammonia during the r e a c t i o n and very low n i t r o g e n a n a l y s i s of the t r e a t e d f a b r i c (2,5)· The object of t h i s work i s t o explore the amic a c i d r e a c t i o n t o determine i f the many v a r i a b l e s i n the process can be c o n t r o l l e d t o maximize the formation of the c e l l u l o s e h a l f a c i d e s t e r and t o i n c r e a s e the extent of r e a c t i o n so t h a t the p r o p e r t i e s p e c u l i a r t o the c a r b o x y l i c a c i d group can be r e a l i z e d . Experimental Reactants. Succinamic a c i d was the p r i n c i p a l reactant i n t h i s study due t o i t s demonstrated r e a c t i v i t y and i t s r e l a t i v e l y high s o l u b i l i t y (2,5,). I t was prepared by d i s s o l v i n g as much as p o s s i b l e of 500 grams of commercial grade s u c c i n i c anhydride i n one l i t e r of acetone. The s o l u t i o n was then cooled t o 10-20°C, l e a v i n g the u n d i s s o l v e d anhydride as a p r e c i p i t a t e i n acetone. Then 300 ml. of a 29$ aqueous ammonia s o l u t i o n was added as f a s t as p o s s i b l e but slow enough so t h a t no b o i l i n g occured. The s o l u t i o n was cooled t o 0-10°C with constant s t i r r i n g u n t i l the amic a c i d had p r e c i p i t a t e d . A f t e r f i l t e r i n g under vacuum, the c r y s t a l s were washed with acetone i n the funnel with the vacuum o f f f o r f i v e minutes before sucking dry. T h i s wash procedure was repeated two times. The c r y s t a l s were spread on a t r a y and allowed t o dry. A 75$ y i e l d was obtained. P u r i t y was determin ed by melting p o i n t (15Î+-I56°c), n e u t r a l i z a t i o n equivalent, and

5.

ALLEN

AND CUCULO

Reaction of Cellulose with Amic Acids

53

n i t r o g e n a n a l y s i s . Maleamic a e i d was made by the same pro cedure. Other amic a c i d s were purchased and used as r e c e i v e d . The woven f a b r i c used i n most o f the experiments i n t h i s i n v e s t i g a t i o n was a 100 per cent v i s c o s e rayon s a t i n weave, 120 χ *4·0, 150 d e n i e r χ 75 d e n i e r w i t h a yarn weight of 2.75 ounces per square y a r d . I t was d e s i z e d , scoured, and d r i e d b e f o r e treatment. A c o t t o n f a b r i c of 78 χ 78, 3θ/ΐ χ ho/l 3-5 oz./yd. , s a t i n weave c o n s t r u c t i o n was used i n some experiments. The f a b r i c was t e n t e r e d t o 80 χ 80 standard p r i n t c o n s t r u c t i o n a f t e r d e s i z i n g , s c o u r i n g , and b l e a c h i n g . F i b e r s and wood pulp were formed i n t o nonwoven mats by d i s p e r s i n g i n water and f i l t e r i n g on a f i b e r g l a s s screen i n a Buchner f u n n e l under vacuum. About 2.5 grams of dry f i b e r s on a 25Ο mm. f u n n e l gave a mat t h i n and u n i f o r m enough f o r the t r e a t ment d e s i r e d . F i b e r s t r e a t e d by t h i s process were: 2

V i s c o s e Rayon- Beaunit F i b e r s , Code 212, b r i g h t r e g u l a r rayon s t a p l e , 1.5 d e n i e r , cut 1 9/l6 inch. V i s c o s e Rayon - Never D r i e d - ITT Rayonier Co., r e g u l a r rayon s t a p l e f i b e r never d r i e d , 1.5 d e n i e r , 3/8 i n c h s t a p l e l e n g t h , f i n i s h e d w i t h Arquad 2C75 as anti-mildew agent. C e l l u l o s e A c e t a t e - Celanese C o r p o r a t i o n , Lot kkB., Bale 2629^, b r i g h t s t a p l e , 3-0 denier, 1 9/l6 inch cut. Wood Pulp- Rayacord XF-ITT Rayonier Co., southern pine, s u l f i t e bleached, approximately 97$ alpha c e l l u l o s e , cuene i n t r i n s i c v i s c o s i t y o f 9 - 2 . Never D r i e d Cotton-Cotton b o l l s s t o r e d i n water were obtained from Cotton, Inc. and cut open under water t o remove f i b e r s from seeds w i t h a r a z o r bla.de. A l l water used i n the t r e a t i n g s o l u t i o n as w e l l as i n a l l p u r i f i c a t i o n and a n a l y t i c a l procedures was . d i s t i l l e d and then d e i o n i z ed by p a s s i n g through a Barnstead Type HN, M u l t i p l e Bed d e m i n e r a l i z e r . A l l c a t a l y s t s and s o l v e n t s were purchased and used as r e c e i v e d . T r e a t i n g S o l u t i o n . At a 2 t o 1 pick-up r a t i o , an 18$ (0.015k molar) s o l u t i o n o f succinamic a c i d i n water g i v e s a 0.5 t o 1 molar r a t i o of succinamic a c i d t o anhydroglucose u n i t . T h i s 18$ s o l u t i o n and h i g h e r c o n c e n t r a t i o n s must be kept warm, at l e a s t ^0°C, t o keep the succinamic a c i d i n s o l u t i o n . The only c o n c e n t r a t i o n s used lower than 18$ were 9$ or 0.25/1 molar r a t i o S A A / A H G U at 2 / l PUR. T h i s c o n c e n t r a t i o n d i d not r e q u i r e heat f o r s o l u t i o n or p r e c i p i t a t i o n but heat was u s e f u l t o reduce the time needed f o r complete s o l u t i o n . The g e n e r a l procedure f o l l o w e d i n a l l bath make-up was t o weigh the succinamic a c i d i n t o a beaker, add warm water t o about SO per cent t o t a l weight, s t i r u n t i l a l l the succinamic a c i d was d i s s o l v e d (on a. s t i r r i n g

54


RESEARCH

hot p l a t e ) , add c a t a l y s t i f any, and b r i n g t o t o t a l weight with water from a squeeze b o t t l e . F a b r i c Treatment. Most o f the f a b r i c treatments were done by d i p p i n g the weighed f a b r i c i n t o the s o l u t i o n , which was kept warm t o prevent p r e c i p i t a t i o n , f o r one minute and then removing the f a b r i c and squeezing i t by hand u n t i l t h e weight i n d i c a t i n g the d e s i r e d pick-up r a t i o was obtained. T h i s d i p procedure appears t o be q u i t e s a t i s f a c t o r y due t o the r e p r o d u c i b i l i t y o f v a r i o u s experiments and the u n i f o r m i t y o f treatment i n d i c a t e d by dyeing t h e t r e a t e d f a b r i c with i n d i c a t o r dye (Geigy F i b e r I n d i c a t o r Syn and I d e n t i f i c a t i o n S t a i n No. 1 New), and by d i p p i n g t h e f a b r i c i n water c o n t a i n i n g a s m a l l amount o f methy l e n e b l u e , squeezing t o a d e s i r e d pick-up r a t i o , and d r y i n g . Nonwoven f a b r i c s had t o be p l a c e d between a f i b e r g l a s s screen b e f o r e d i p p i n g t o prevent d i s p e r s i o n o f t h e f i b e r s . A f t e r d i p p i n g , most o f t h e excess t r e a t i n g s o l u t i o n was squeezed out. The f a b r i c was then removed from the screen and squeezed t o the d e s i r e d pick-up r a t i o . F a b r i c Heat Treatment. The t r e a t e d f a b r i c was e i t h e r a i r d r i e d by hanging on a l i n e a t room temperature, heat d r i e d by p l a c i n g i n an oven and observing the temperature with a thermo couple attached t o the f a b r i c , or cured immediately. Curing or baking was accomplished by suspending the sample v e r t i c a l l y i n a l a r g e f o r c e d a i r oven o f i n t e r n a l s i z e 36 χ 25 χ 19 i n c h e s . P u r i f i c a t i o n . As soon as p o s s i b l e a f t e r d r y i n g , the f a b r i c was p l a c e d i n water t o prevent f u r t h e r r e a c t i o n and t o remove unreacted m a t e r i a l . Successive 15 t o 30 minute washes a t room temperature o f water, acetone, water u n t i l c o l o r l e s s , IN H2SO4 t o convert a l l a c i d s a l t s t o the f r e e a c i d , and 1N Η ά0|ψ were given the f a b r i c . The cured f a b r i c was u s u a l l y c o l o r e d from l i g h t t o dark brown, depending on t h e time and temperature o f cure. Some, but not a l l , o f t h e c o l o r was removed by the water, acetone, and s u l f u r i c a c i d i n the above procedure. S e v e r a l f a s t (5 t o 15 minutes) washings with water then f o l l o w e d . The f a b r i c was then c u t with s c i s s o r s i n t o small pieces and put i n t o an automatic blender c o n t a i n i n g water. The blender was turned on h i g h speed f o r 15 t o 20 seconds or u n t i l the b i t s . o f f a b r i c were reduced t o f i b e r s . The f i b e r s were then f i l t e r e d under vacuum on a Buchner f u n n e l . The f i l t r a t e was d i s c a r d e d and the f i b e r s were washed with water u n t i l a c o l o r change from yellow t o blue occurred when two drops o f a 0.1$ s o l u t i o n o f bromc r e s o l purple i n d i c a t o r i n 95$ ethanol and then one drop o f a 0.1 Ν sodium hydroxide s o l u t i o n were added t o 100 ml. o f the f i l t r a t e . A f t e r a l l the unattached a c i d was out o f the f i b e r s , as evidenced by t h e i n d i c a t o r c o l o r change above, the water remaining i n the f i b e r s was exchanged with acetone. The f i b e r s were then d r i e d at 60 ± 5°C f o r one t o two hours under vacuum 2

5.

ALLEN

AND


CUCULO

55

i n a heated vacuum d e s s i c a t o r . Pendant Carboxyl. A m o d i f i c a t i o n o f the calcium acetate method described by Cuculo (2) was used t o determine the pendant c a r b o x y l i c a c i d groups attached t o the c e l l u l o s e . A blank was determined by t i t r a t i n g 50 ml o f the o r i g i n a l O.I33N calcium acetate s o l u t i o n i n t h e same manner. A f u r t h e r blank value was determined f o r untreated v i s c o s e rayon f a b r i c , which was washed and processed e x a c t l y the same as the t r e a t e d f a b r i c . Both blanks were subtracted from a l l t r e a t e d sample values i n the t a b l e s . The r e s u l t s expressed as m i l l i q u i v a l e n t s o f h a l f a c i d e s t e r p e r gram of sample were c a l c u l a t e d as follows : meq. NaOH used - meq. HC1 used - meq. calcium acetate blank -meq. untreated substrate blank = meq. NaOH consumed f o r pendant COOH = meq. COOH meq. COQH NaOH consumed f o r pendant COOH Ν NaOH 2 χ Ν NaOH (ml. NaOH consumed » ml. correction" f a c t o r ) = wt. o f sample a c t u a l meq. COQH per gram of sample I t was found about h a l f way through t h i s work that the t e s t method described was s a t i s f a c t o r y a.t low amounts of pendant c a r b o x y l content. However, as t h e amount o f c e l l u l o s e h a l f - a c i d e s t e r increased i n r e l a t i o n t o t h e constant calcium acetate concentration, the exchange of calcium i o n decreases, r e s u l t i n g i n a low determination f o r pendant carboxyl. F i n a l l y , a method suggested by Cramer i n v o l v i n g the t i t r a t i o n o f s e v e r a l sample s i z e s of v a r y i n g c a r b o x y l i c a c i d content (7)was a p p l i e d . A p l o t of sample s i z e vs carboxyl content and e x t r a p o l a t i o n t o zero sample s i z e gives the t r u e c a r b o x y l i c a c i d content. A f u r t h e r p l o t of the t r u e carboxyl content minus the found c a r b o x y l content f o r a standard sample s i z e (one gram i n t h i s work) versus the found carboxyl content f o r a v a r i e t y of d i f f e r e n t c a r b o x y l i c a c i d c o n t a i n i n g samples gives the c o r r e c t i o n f a c t o r i n m i l l i t e r s of NaOH used f o r any subsequent sample. =

m

l

e

T o t a l E s t e r . The t o t a l carboxyl t e s t method depends on s a p o n i f i c a t i o n which converts t h e c a r b o x y l i c e s t e r groups a t t a c h ed d i r e c t l y t o the c e l l u l o s e molecule t o c a r b o x y l i c a c i d groups, with back t i t r a t i o n determining the amount of t o t a l c a r b o x y l i c a c i d groups present, both those that came from the e s t e r l i n k a g e and those present as pendant carboxyl. The method chosen was the Eberstadt method as modified by Genung and Mallatt(8). A f u r t h e r m o d i f i c a t i o n used here was that 50 ml. each o f 75$ ethanol and 0.5 Ν NaOH was used i n s t e a d of the hO ml. used by Genung and M a l l a t t . In l a t e r experiments, the 75$ ethanol, which was deemed questionable i n value by Genung and M a l l a t t (8) was r e p l a c e d with water with no change of r e s u l t s . The water i s more l i k e l y t o s w e l l the e s t e r s studied here than ethanol. A l l f l a s k s c o n t a i n i n g the sample stood i n a t r a y of water f o r k8

56

CELLULOSE TECHNOLOGY RESEARCH

hours. The t r a y o f water was used when f l u c t u a t i o n s o f r e s u l t s appeared on repeat analyses o f the same sample and was a t t r i b u t ed t o temperature f l u c t u a t i o n s . Blanks containing a l c o h o l or water and NaOH were run with each s e t of samples. Calculations f o r percent t o t a l COOH a r e t h e same as f o r percent f r e e COOH except the f a c t o r o f two i s not needed here. Results were e x pressed as m i l l i e q u i v a l e n t s o f t o t a l e s t e r p e r gram o f sample by s u b t r a c t i n g the pendant from the t o t a l carboxyl value. C a l c u l a t i o n s . The r e s u l t s were expressed as m i l l i e q u i v a l e n t s per anhydroglucose u n i t (meq./AHGU), c a l c u l a t e d by the general method of A l l e n (9)· The s p e c i f i c procedure used was : H = m i l l i e q u i v a l e n t s o f h a l f - a c i d e s t e r p e r gram o f sample Τ = m i l l i e q u i v a l e n t s o f t o t a l e s t e r per gram o f sample A = m i l l i e q u i v a l e n t s o f half-amide e s t e r per gram o f sample C = m i l l i q u i v a l e n t s o f c e l l u l o s e per gram of sample and

f o r the r e a c t i o n o f succinamic a c i d

0.100 H + 0.08UT + 0.099A + 0.162C = 1.00 Η, Τ and A were obtained as p r e v i o u s l y be c a l c u l a t e d .

d e s c r i b e d so C can

then, m i l l i e q u i v a l e n t s o f h a l f - a c i d e s t e r per anhydroglucose u n i t TJ or pendant D.S. = -g and,

m i l l i e q u i v a l e n t s o f t o t a l e s t e r per anhydr ogluc ose or t o t a l D.S. = 1 C

and,

unit

m i l l i e q u i v a l e n t s o f half-amide ester per anhydroglucose u n i t or half-amide e s t e r D.S. = A ϋ Half-Amide E s t e r Determination. Nitrogen content was determined by the K j e l d a h l method (9) · The r e s u l t s were expressed as mi .11 i equivalent s o f amide per gram o f sample, as follows : meq. amide per gram of sample = Meq. HC1 used f o r sample - meq. HC1 f o r b l a n k weight o f sample

5.

ALLEN

AND

CUCULO


57

R e s u l t s and D i s c u s s i o n Reaction Method. A f i r s t step i n t h i s i n v e s t i g a t i o n was t o determine i f some other method o f r e a c t i o n other than the pad-bake method used by Cuculo (2) o f f e r e d more promise i n o b t a i n i n g the d e s i r e d o b j e c t i v e o f i n c r e a s i n g the D.S. and max i m i z i n g the formation of t h e c e l l u l o s e h a l f - a c i d e s t e r . One method i n v e s t i g a t e d was t h e h e a t i n g of a s o l u t i o n of succinamic a c i d with the c e l l u l o s e f o r a p e r i o d of time. This i s the method u s u a l l y used i n c e l l u l o s e e s t e r i f i c a t i o n where t h e anhy d r i d e or the a c i d i s the r e a c t a n t . The h i g h r a t i o of succinamic a c i d t o c e l l u l o s e was used i n a n t i c i p a t i o n t h a t the Mass A c t i o n Law would f a v o r t h e formation of the monoester. No c a t a l y s t was present i n t h i s or the other two methods. The other method chosen was the placement of the c e l l u l o s e i n molten succinamic a c i d h e l d j u s t above the m e l t i n g p o i n t a t approximately l60°C f o r t e n minutes. The r e s u l t s o f the t h r e e r e a c t i o n methods are shown i n Table I . Table I : E f f e c t of Reaction Method i n the Succinamic Acid-Rayon F a b r i c Reaction

Reaction Method

Moles Succinamic Acid/AHGU

Total Ester Meq./AHGU

Half-Acid Ester Meq/AHGU

Half-Amide Cross Ester links Meq/AHGU Me/AGO.

Pad-Bake

0.872

Ο.316

0.272

0.013

0.015

Melt

3k£

0.283

O.lhk

0.01+8

0.0^5

Reflux

16.2

Ο.195

0.077

0.028

0.01+5

Reaction C o n d i t i o n s : Pad-Bake : 18$ aqueous succinamic a c i d s o l u t i o n , 3 - 5 p i c k up r a t i o (PUR),cure 150°C 10 minutes. Melt: d i p f a b r i c i n molten succinamic a c i d (approx. l60°C) f o r 10 minutes. Reflux: 58.5$ succinamic a c i d i n N,N-Dimethylformamide ( D M F ) , r e f l u x 150-l60°C f o r 75 minutes. The f i r s t s u r p r i s i n g aspect o f the amic a c i d r e a c t i o n i s immediately seen from the t o t a l e s t e r r e s u l t s . Even though the pad-bake procedure has l e s s succinamic a c i d a v a i l a b l e t o the c e l l u l o s e , more e s t e r groups are formed than i n the other two methods. Furthermore, the d e s i r e d o b j e c t i v e of miximizing the formation o f the c e l l u l o s e h a l f - a c i d e s t e r i s s i g n i f i c a n t l y greater i n the pad-bake procedure where 81+$ of the e s t e r groups c o n t a i n f r e e c a r b o x y l on the other end compared t o 51$ and 39$ f o r the melt and r e f l u x methods, r e s p e c t i v e l y . A ready explan-


58

at i o n a t t h i s point i s t h a t t h e wa.ter used i n t h e pad-bake procedure allows a more complete p e n e t r a t i o n and opening o f t h e f i b e r s t r u c t u r e . Further examination o f t h e r e s u l t s show that the pad-bake procedure gives only about kfo of t h e t o t a l e s t e r groups c o n t a i n i n g the amide group on t h e other end, while the melt and r e f l u x procedures c o n t a i n r e s p e c t i v e l y about 17$ and 14$ amide groups i n r e l a t i o n t o e s t e r l i n k s . F i n a l l y , only about 7$ o f the c a r b o x y l i c a c i d group formed reacted f u r t h e r t o form e s t e r c r o s s l i n k s i n the pad-bake method while i n t h e melt and r e f l u x methods, the extent o f f u r t h e r r e a c t i o n was 2k$ and 37$ r e s p e c t i v e l y . Somewhat s u r p r i s i n g low extent o f r e a c t i o n and high percent age o f c r o s s l i n k i n g i n t h e r e f l u x procedure l e d t o a f a r t h e r e x p l o r a t i o n o f t h i s r e a c t i o n method f o r succinamic a c i d i n r e gard t o solvent type. I n Table I I a number o f solvents t h a t are Table I I :

Solvent

E f f e c t o f Solvent Type i n Reflux Reaction o f Succinamic A c i d with Rayon F a b r i c Crosslinks

Total Ester Meq/AHGU


Half-Amide Ester Meq/AHGU

DMF

0.195

0.077

0.028

Formamide

0.109

O.Okl

0.05k

Sulfoxide

0.116

0.070

0.023

Water

0.067

Ο.Ο51

0.008

Meq/AHGU 0.01+5

Dimethyl

Pyridine Succinic Aohydrife

0.230 0.6V? i n Pyridine

O.lBl Ο.38Ο

O.OO3

0.023 O.I32

Reaction C o n d i t i o n s : 0.5 molar succinamic a c i d i n each solvent, heat with f a b r i c 150-l60°C (or r e f l u x i f b o i l i n g point o f solvent i s l e s s than 150°c) f o r 75 minutes except 2 l/2 hours w i t h H 0 2

4

g e n e r a l l y regarded t o have some s w e l l i n g e f f e c t on c e l l u l o s e a r e compared. Some d i f f e r e n c e i n r e a c t i o n temperature was present due t o b o i l i n g p o i n t d i f f e r e n c e s . Formamide and dimethly s u l f o x i d e gave somewhat l e s s r e a c t i o n than DMF but DMS0 d i d g i v e a higher percentage o f c a r b o x y l i c a c i d groups (60$ compared t o 39$) Another q u i t e s u r p r i s i n g r e s u l t occurs with water as the s o l v e n t . Although the extent o f r e a c t i o n i s only about 1/3 t h a t of DMF and l / 2 t h a t o f formamide and DMS0, such s i g n i f i c a n t

5.

ALLEN

AND

CUCULO


59

e s t e r i f i c a t i o n i s not g e n e r a l l y expected i n the presence of water. A l s o , the r e a c t i o n temperature was only 100°C. The percentage o f f r e e a c i d groups, compared t o t o t a l ester groups, i s ah out the same as i n the pad-bake procedure. l y r i d i n e i s regarded as a c l a s s i c a l e s t e r i f i c a t i o n solvent, being e x t e n s i v e l y used i n studies o f the r e a c t i o n o f various a c i d s , a c i d c h l o r i d e s , and a c i d anhydrides w i t h c e l l u l o s e . Although the extent o f r e a c t i o n i s s i g n i f i c a n t l y greater than w i t h the other solvents studied, i t i s s t i l l somewhat lower than i n the aqueous pad-bake method from Table I, and about l / 3 as much as that with s u c c i n i c anhydride i n p y r i d i n e . The l a t t e r comparison i n d i c a t e s a s i g n i f i c a n t l y lower r a t e o f r e a c t i o n o f succinamic a c i d compared t o s u c c i n i c anhydride. However, with the amic a c i d , only 12$ o f the f r e e a c i d groups reacted f u r t h e r t o give c r o s s l i n k s compared t o 26$ with the anhydride. On the other hand, 76$ o f the t o t a l e s t e r groups are i n the form o f the h a l f - a c i d ester i n the amic a c i d r e a c t i o n , compared t o 59$ i n the anhydride r e a c t i o n . The lower extent o f c r o s s l i n k i n g with anhydride i n p y r i d i n e solvent i s g e n e r a l l y explained by the formation o f the pyridinium s a l t o f the f r e e a c i d group. However, the use o f succinamic a c i d f u r t h e r reduces c r o s s l i n k i n g , p o s s i b l y due t o the formation o f the ammonium s a l t and again p o s s i b l y due t o a unique mechanism o f r e a c t i o n . Since solvent seems t o have some e f f e c t on the extent o f h a l f - a c i d e s t e r formation i n the r e f l u x r e a c t i o n , the pad-bake procedure was examined f o r the e f f e c t o f applying the amic a c i d from m a t e r i a l s other than water. Table I I I shows a number o f s u r p r i s i n g r e s u l t s . F i r s t , the e f f e c t o f p y r i d i n e i n g i v i n g a h i g h amount o f f r e e a c i d i n the r e f l u x r e a c t i o n i s e s s e n t i a l l y nonexistent i n the pad-bake r e a c t i o n . Second, the r e l a t i o n o f formamide and DMF i s reversed. Formamide gives an extent o f r e a c t i o n only somewhat l e s s than t h a t of water while DMF gives very l i t t l e r e a c t i o n i n the pad-bake process compared t o the 0.2 D.S. f o r the r e f l u x method. An e f f e c t of the amide proton i s suggested by the f a c t t h a t N-methyl formamide gives about t h e same r e s u l t as formamide. The r e l a t i o n s h i p i s seen with the p a i r o f N-methyl p y r r o l i d o n e and 2-pyrrolidone, except 2-pyrr o l i d o n e does give l e s s r e a c t i o n than N-methyl formamide. The extent o f r e a c t i o n with DMSO compared t o formamide i s a l s o lower than expected from the r e f l u x r e a c t i o n . Yet even l e s s r e a c t i o n i s obtained on going t o the sulfone group and a c y l i c s t r u c t u r e i n the form o f tetramethylene sulfone. In Table IV, v a r i a t i o n s on the use o f forma.mide and d i ~ methylformamide are explored. Increasing the amount o f s u c c i n amic a c i d i n DMF by four times increases the extent o f r e a c t i o n more than four times but s t i l l not t o the extent o f that o b t a i n ed i n water. A d d i t i o n o f a c a t a l y s t t o the lower concentration of succinamic a c i d i n DMF a l s o increases the extent o f r e a c t i o n . Furthermore, the combination of water and DMF as solvent i n creases the extent o f r e a c t i o n almost t o that obtained with


60

RESEARCH

Table I I I : E f f e c t of Solvent i n the Pad-Bake Reaction o f Succinamic A c i d with Rayon F a b r i c

Solvent




Crosslinks Meq/AHGU

Water

0.161

0.113

0.024

DMF

0.020

0.024

0.000

Formamide

0.179

0.120

O.O3O

N-Methyl Formamide

0.131*

0.114

0.010

2-Çyrrolidinone

O.O5O

N-Methyl Çyrrolidinone

0.022

pyridine*

Ο.Ο38

Dimethyl Sulfoxide Tetramethylene Sulfone

0.101

0.075

0.001

0.013

0.019

Reaction C o n d i t i o n s : 9% succinamic a c i d , 2.0 PUR, cure 150°C 8 minutes. *

Small amount of water added f o r s o l u b i l i t y .

water alone. However, the mixture o f water and formamide o f f e r s no improvement over formamide alone. The obvious c o n c l u s i o n from these r e s u l t s i s t h a t water serves some unique f u n c t i o n i n the pad-bake r e a c t i o n o f succinamic a c i d with c e l l u l o s e , d u p l i c a t e d by only formamide and p o s s i b l y sulfamic a c i d . T h i s f u n c t i o n i s not as pronounced i n r e f l u x r e a c t i o n s . One could argue t h a t the optimum solvent, time, temperature or c a t a l y s t has not been used i n the few r e f l u x experiments per formed here and t h a t more experimental work could produce b e t t e r r e s u l t s . The same arguments could a l s o be a p p l i e d t o the melt method, p a r t i c u l a r l y with regard t o t h e a c c e s s i b i l i t y o f t h e r e a c t a n t s t o each other. I n a d d i t i o n , a pre-swollen c e l l u l o s e may be more r e a c t i v e . Thus, a woven v i s c o s e rayon f a b r i c wet with an 18$ s o l u t i o n o f succinamic a c i d ( t o a 4.0 pick-up r a t i o ) was placed i n t h e molten succinamic a c i d a t l60 t o 170°C f o r 10 minutes. S u r p r i s i n g l y , t h i s procedure gave l e s s r e a c t i o n than

5.

ALLEN

AND

CUCULO


61

Ta.ble IV. Continued I n v e s t i g a t i o n o f Solvent E f f e c t i n t h e PadBake Reaction o f Succinamic A c i d with Rayon F a b r i c

Solvent DMF/Water

Total Half-Acid Ester Ester Meq/AHGU Meq/AHGU


Crosslinks Meq/AHGU

0.015

0.155

0.125

0.137

0.101

0.002

0.018

0.152

0.101

0.002

0.026

0.192

0.155

0.002

0.018

0.326

0.282

50/50 Formamide /Water

50/50 DMF + Sulfamic Acid Catalyst (6$ on wt. o f succinamic a c i d ) DMF but 36$ succinamic a c i d Water b u t 36$ succinamic a c i d

Reaction C o n d i t i o n s :

0.022

9$ succinamic a c i d except where noted, 2.0 PUR, cure 150°C 8 minutes.

that o f j u s t p u t t i n g t h e d r y f a b r i c i n the melt. The water i n the f a b r i c should have aided i n the d i f f u s i o n o f the succinamic a c i d i n t o the f a b r i c and i t should not have i n t e r f e r r e d with the r e a c t i o n s i n c e i t was evaporated away very r a p i d l y . Decomposition o f amic a c i d s by water i s v e r y common (lO)and c o u l d have occurred i n t h i s case. Other experiments, such as the use of a non-aqueous s w e l l i n g solvent or t h e use o f solvent-exchanged f a b r i c , may i n c r e a s e the D.S. However, i t was concluded t h a t an i n v e s t i g a t i o n o f the v a r i a b l e s i n e i t h e r o f these two processes o f f e r e d no more promise o f o b t a i n i n g the d e s i r e d o b j e c t i v e s than the study o f the many v a r i a b l e s i n the pad-bake process, which as a l r e a d y seen was much more promising i n the i n i t i a l screens. The next step was t o then i n v e s t i g a t e the v a r i a b l e s i n the aqueous pad-bake process t o determine those t h a t had the g r e a t e s t e f f e c t on both the extent of e s t e r i f i c a t i o n and the subsequent c r o s s l i n k i n g . The unusual e f f e c t of the presence of water was seen again when the d r y i n g c o n d i t i o n s were i n v e s t i g a t e d . I t was reasoned t h a t a i r d r y i n g a f t e r impregnation o f the f a b r i c could give a b e t t e r d i s t r i b u t i o n o f t h e r e a c t a n t , l e a d i n g p o s s i b l e t o more extensive and uniform r e a c t i o n . As seen i n Table V, both the t o t a l e s t e r and c a r b o x y l content decrease s i g n i f i c a n t l y a f t e r even one hour o f a i r d r y i n g before the heat treatment. The D.S. decreases even more a f t e r 3 hours a t ambient temperature b e f o r e

62


RESEARCH

Table V. E f f e c t o f Drying C o n d i t i o n s on Succinamic A c i d Rayon F a b r i c Reaction Drying Conditions


Half-Acid Ester Meq./AHGU

Crosslinks Meq./AHGU

None- Cure Wet

O.I5I+

O.I33

0.011

A i r Dry 1 Hour

0.121

0.102

0.010

A i r Dry 3 Hours

Ο.Ο65

0.06*7

0.000


9$ aqueous succinamic a c i d s o l u t i o n 2.0 PUR, Cure 150°C 12 minutes.

c u r i n g . The decrease i n D.S. continues and l e v e l s o f f a t around 2k hours o f a i r d r y i n g . I n f a c t , a f t e r 2k hours a t ambient temperature between treatment and c u r i n g , i t takes 15 minutes a t 150°C t o o b t a i n the same extent o f r e a c t i o n w i t h a 9$ by weight succinamic a c i d s o l u t i o n as obtained i n 6 minutes at 150°C with no time between t r e a t i n g and c u r i n g . As the amount o f succinamic a c i d i n the bath i n c r e a s e s , the time d i f f e r e n t i a l i n c r e a s e s f u r t h e r . Yet s i g n i f i c a n t r e a c t i o n i s obtained a t low temperatures i n long p e r i o d s o f time such as : 125°C t o t a l D.S. i n 1 hour = 0.19; 125°C t o t a l D.S. i n l6 hours = Ο.36; 100°C t o t a l D.S. i n 2k hours = 0.18; ambient temperature t o t a l D.S. i n 3 months = 0.05. The extent of r e a c t i o n d i f f e r e n t i a l i s not observed i f the f a b r i c i s d r i e d a t an elevated temperature (l20°C or g r e a t e r ) and then p l a c e d a t ambient temperature f o r extended p e r i o d s o f time b e f o r e c u r i n g . I t i s p o s s i b l e that the presence o f water during the heat t r e a t ment allows some s o r t of s t e r e o s p e c i f i c hydrogen bonded complex of the amic a c i d and c e l l u l o s e t o be set up i n preference t o the l o s s o f water t o form an imide. The r o l e o f water as a t r a n s p o r t agent i s a l s o a p o s s i b i l i t y . H y d r o l y i s o f amic a c i d s t o the d i a c i d i s a d i s t i n c t p o s s i b i l i t y , so the s t a b i l i t y o f the t r e a t i n g s o l u t i o n was i n v e s t i g a t e d . Using a 18$ succinamic a c i d s o l u t i o n no change was seen i n extent o f r e a c t i o n on f a b r i c t r e a t e d i n a f r e s h s o l u t i o n compared t o a s o l u t i o n maintained a t 60 t o JO°C f o r two hours. Furthermore, f a b r i c was maintained i n the s o l u t i o n f o r one or f i f t y minutes, with or without sulfamic a c i d c a t a l y s t (Table V l ) . However, an i n t e r e s t i n g e f f e c t i s seen i n t h i s t a b l e i n comparison o f the amount o f t o t a l e s t e r obtained w i t h c a t a l y s t present compared t o no c a t a l y s t . The use o f c a t a l y s t a c t u a l l y reduces the t o t a l e s t e r content while main t a i n i n g the h a l f - a c i d e s t e r content, thus reducing the amount o f crosslinking. With t h i s l e a d i n hand, a number o f v a r i o u s compounds were i n v e s t i g a t e d f o r p o s s i b l e c a t a l y s t a c t i v i t y , beginning w i t h

5.

ALLEN

A N D CUCULO


63

Table V I : E f f e c t of Time i n T r e a t i n g S o l u t i o n i n Reaction o f Rayon F a b r i c with Succinamic A c i d



Apparent Crosslinks Meq./AHGU

1

0.225

0.194

0.016

50

0.227

0.200

0.013

1

0.195

0.208

0.000

50

0.202

0.209

0.000

F a b r i c Time i n Bath (Min.) No C a t a l y s t

Catalyst

Reaction Conditions :

% aqueous succinamic a c i d , c a t a l y s t i s 6$ sulfamic a c i d on weight of succinamic a c i d , maintain t r e a t i n g s o l u t i o n at 50-60°C, 2.0 PUR, cure 150°C 6 minutes.

acids and extending t o bases, s a l t s , and amides. As seen i n Table V I I some compounds o f each c l a s s gave a s l i g h t i n c r e a s e i n the extent o f r e a c t i o n , but the only s i g n i f i c a n t c a t a l y s t e f f e c t was the c o n f i r m a t i o n of the r e d u c t i o n o f c r o s s l i n k i n g by s u l famic a c i d . Ammonium sulfamate behaved s i m i l a r l y while sodium sulfamate was l e s s e f f e c t i v e . I n t e r e s t i n g comparisons are the i n c r e a s e i n r e a c t i o n with maleic a c i d while fumarie, s u c c i n i c , c i t r i c , and t a r t a r i c a c i d s were the same as the c o n t r o l . Ammonium s u l f a t e gave no i n c r e a s e i n r e a c t i o n or decrease i n c r o s s l i n k i n g . At the same c o n c e n t r a t i o n , urea, t h i o u r e a form amide, and b i u r e t showed no a c t i v i t y , compared with the 10$ i n c r e a s e i n t o t a l e s t e r by guanidine h y d r o c h l o r i d e . The unique e f f e c t s o f ammonia as an a d d i t i v e , undoubtedly r e s u l t i n g i n the formation of ammonium succinamate, and ammonium sulfamate i n Table VII l e d t o the e x p l o r a t i o n o f other s a l t s of succinamic a c i d . This concept i s i n t e r e s t i n g from the p o s s i b i l i t y of reducing c r o s s l i n k i n g s i m i l a r t o t h a t with t e r t i a r y organ i c bases as solvent and c a t a l y s t i n the anhydride r e f l u x r e a c t i o n ( l l ) , or the p o s s i b i l i t y o f i n c r e a s i n g the extent o f r e a c t i o n i n the same manner as t h a t of u s i n g the sodium and triethylammonium s a l t s o f p o l y c a r b o x y l i c a c i d s ί]£>]3?1^) · Al though i n Table V I I I the extent o f r e a c t i o n was a c t u a l l y decreas ed by the metal and primary amine s a l t s and t h e extent o f c r o s s l i n k i n g was not reduced by the t e r t i a r y amine s a l t s , a very s i g n i f i c a n t i n c r e a s e i n both t o t a l e s t e r and pendant c a r b o x y l was found with the triethylammonium s a l t . Although no reason f o r


64

RESEARCH

Table V I I : E f f e c t of C a t a l y s t i n Succinamic Acid-Rayon F a b r i c Reaction Total Ester Meq./AHGU



None

0.245

0.196

0.024

Maleic A c i d

0.272

0.236

0.018

Phosphoric A c i d

0.264

0.232

0.016

Sulfamic A c i d

0.208

0.208

0.000

Ammonia*

0.259

0.220

0.020

Monoammonium Phosphate

0.245

0.216

0.014

Ammonium Sulfamate

0.235

0.231

0.002

Sodium Sulfamate

0.251

0.222

0.015

Sodium Hypophosphite

0.245

0.228

0.008

Urea**

0.264

0.226

0.019

Guanidine HC1

0.299

0.184

0.057

Catalyst


18$ aqueous succinamic a c i d , 2.0 PUR, cure 150°C 6 minutes, add succinamic a c i d , 90$ o f water, heat t o 90°C, add c a t a l y s t and then remaining water, c a t a l y s t concentration i s 1.08$ except where noted. *Coneentrâtion i s 23.3$ on weight o f s o l u t i o n . **Concentration i s 5$ on weight o f s o l u t i o n . the increased r e a c t i o n o f the triethylammonium s a l t s o f p o l y c a r b o x y l i c a c i d s was given i n the previous work (12)· The r e s u l t s here i n d i c a t e t h a t a t l e a s t some r e a c t i o n i s t a k i n g place through t h e c a r b o x y l i c a c i d group of the amic a c i d . Table IX shows a very important d i s c o v e r y i n meeting the s t a t e d o b j e c t i v e of i n c r e a s i n g the extent of r e a c t i o n - the b a l a n c i n g of cure time and temperature with r a t i o of amic a c i d and water t o c e l l u l o s e . As the cure time i s increased with i n c r e a s i n g succinamic a c i d concentration, t h e t o t a l e s t e r D.S. increases t o over 1.0, q u i t e a h i g h value f o r a pad-bake r e a c t i o n . A l s o , the h a l f - a c i d e s t e r content i s lower at a value of around Ο.65, i n d i c a t i n g increased c r o s s l i n k i n g .

5.

ALLEN

AND

CUCULO

Table V I I I :


65

E f f e c t of Amine and Metal S a l t s on the Reaction of Succinamic A c i d with C e l l u l o s e Total Ester Meq./AHGU



None

0.624

0.488

0.608

Ethanolamine

0.065

0.059

0.003

Ethylenediamine

-

0.022

pyridine

Ο.636

0.472

0.082

Sodium

0.101

0.110

0.000

Calcium

0.106

0.092

0.007

None*

0.336

0.302

0.017

Tr i ethylamine*

0.489

Ο.363

Ο.Ο63

Cation


*2.0

PUR,

36$ succinamic a c i d plus one e q u i v a l e n t of c a t i o n p l u s 3$ sulfamic a c i d on weight of succinamic a c i d , 4.0 PUR, cure 150°C 18 minutes. cure 150°C 18 minutes.

The amount of c a r b o x y l i c a c i d groups formed t h a t r e a c t e d f u r t h e r t o form c r o s s l i n k s i n c r e a s e d with cure time from a 5$ t o a 10> f i g u r e at the 6 and 9 minute cures t o a 14, 18, 22, and 29$ f i g u r e f o r the 18, 22, 33, and 170°C 22 minute cures r e s p e c t i v e l y f o r the 54$ succinamic a c i d s o l u t i o n . Table I I showed t h a t the amount o f amide formation i n the pad-bake r e a c t i o n i s s m a l l but the amount a t a higher t o t a l e s t e r content was of i n t e r e s t . I t was found t h a t the r a t i o of amide t o c r o s s l i n k a c t u a l l y de creased with extent of r e a c t i o n . For example, the 5^$ s u c c i n amic a c i d s o l u t i o n , 150°C 22 minute cure sample had an amide D. S. of only O.O3 out of the 0.131 c r o s s l i n k f i g u r e or a r a t i o of about 4 t o 1 compared t o the approximately 1 t o 1 r a t i o at lower amic a c i d c o n c e n t r a t i o n and cure time i n Table I I . In Table X, i t i s seen t h a t the l e v e l o f f and a c t u a l de crease of D.S. with i n c r e a s i n g succinamic a c i d concentrations does take p l a c e when wood pulp i s used as the s u b s t r a t e , even at longer cure times. T h i s r e s u l t could be due t o the l e s s open s t r u c t u r e of wood pulp, a concept t h a t w i l l be explored i n greater d e t a i l l a t e r . Another way t o i n c r e a s e the r a t i o of amic a c i d t o c e l l u l o s e and the cure time i s the use of r e p e t i t i v e treatments. Table XI

66


Table IX:

Moles Succinamic Acid/AHGU

E f f e c t o f C u r i n g C o n d i t i o n s at Higher R a t i o s o f Succinamic A c i d t o C e l l u l o s e i n Amic A c i d Rayon F a b r i c R e a c t i o n Cure Time (min.)

Amic Acid Conc.$

PUR


Half-Acid Ester Meq/AHGU 0.227

Apparent Crosslinks Meq/AHGU 0.020

0.997

6

18

4.0

0.267

0.997

12

18

4.0

0.303

0.274

0.014

0.997

6

36

2.0

0.209

0.201

0.004

0.997

9

36

2.0

Ο.336

0.302

0.017

1.231

6

36

4.0

O.IB3

0.157

0.013

1.231

9

36

4.0

0.469

0.395

0.037

1.231

18

36

k.O

0.624

0.488

0.068

2.991

IS

54

k.O

0.719

O.500

O.O82

2.991

22

54

k.O

0.866

Ο.594

0.131

2.991

33

54

k.O

0.996

Ο.638

0.179

2.991

22*

54

k.O

1.177

0.653

0.262

R e a c t i o n C o n d i t i o n s : V i s c o s e rayon f a b r i c , cure 150°C *170°C Table X: E f f e c t o f Succinamic A c i d - C e l l u l o s e R a t i o i n Amic Acid-Wood Palp Reaction Moles Succinamic Acid/AHGU

Reactant Cone. $

PUR



Crosslinks Meq/AHGU

7.0

0.l6l

0.122

0.020

5.23

7.0

0.202

0.151

0.025

3.51

h.7

0.249

0.201

0.024

7.0

0.244

0.185

0.029

6.98

3Λ9

72

36


Aqueous s o l u t i o n , 3$ ammonium sulfamate on weight o f succinamic a c i d , wet formed wood pulp mat, cure 150°C 22 minutes.

5.

ALLEN

AND

cucuLO


67

shows t h a t the extent o f r e a c t i o n i s doubled with two treatments when the f a b r i c i s washed t o remove unreacted m a t e r i a l between treatments. I f the f a b r i c i s not washed between treatments, t h e extent o f r e a c t i o n i s t r i p l e d , i n d i c a t i n g that some o f the r e actant from the f i r s t treatment i s s t i l l i n i t s r e a c t i v e form and has not decomposed t o some i n a c t i v e species such as succinimide. In t h i s case 70$ of the amic a c i d a v a i l a b l e t o the c e l l u l o s e has reacted. Table X I : E f f e c t o f Repeat Treatments on I n c r e a s i n g Reaction i n Succinamic A c i d - Rayon F a b r i c Reaction Number of Treatments



Crosslinks Meq/AHGU

9

1

0.140

0.102

0.019

9/9

2*

0.268

0.227

0.020

9/9

2

0.432

0.352

0.040

18

1

0.157

0.123

0.018

18/18

2

Ο.366

0.332

0.017

1S/18/18

3

0.486

0.429

0.028

Cone, o f Succinamic A c i d i n Bath - $

PUR, cure 150°C 6 minutes, 1.08$ sulfamic a c i d c a t a l y s t on weight o f bath. * A f t e r f i r s t treatment r i n s e i n water u n t i l c o l o r i s gone, then r i n s e i n acetone, r i n s e i n 5-10$ a c e t i c a c i d , r i n s e i n water 3 times, r i n s e i n acetone and a i r d r y from acetone. Each r i n s e i s approximately 5 minutes. I f the c o n c e n t r a t i o n o f succinamic a c i d i n the t r e a t i n g s o l u t i o n i s increased, t h e amount o f r e a c t i o n i s increased, but the e f f i c i e n c y of r e a c t i o n i s g r e a t l y reduced. I n two treatments the extent o f r e a c t i o n i s the same as with the lower amic a c i d concentration, although the cure time i s the same. I f t h e succinamic a c i d c o n c e n t r a t i o n and cure time are i n creased g r e a t l y , D.S. values o f 1.5 f o r t o t a l e s t e r and 1.0 f o r h a l f - a c i d e s t e r a r e obtained (Table X I I . ) . These values a r e q u i t e h i g h f o r a heterogeneous pad-bake system. With the achievement o f these r e l a t i v e l y h i g h D.S. v a l u e s , i t was o f i n t e r e s t t o see i f other substrates would behave s i m i l a r l y . Cotton has been shown t o g i v e l e s s r e a c t i o n than rayon (2). I n Table X I I I i t i s seen t h a t s t r u c t u r e apparently l i m i t s the extent of r e a c t i o n with c o t t o n more than with rayon. A t t h e time i t was thought t h a t s t r u c t u r e l i m i t a t i o n s could be overcome by u s i n g never d r i e d c o t t o n but recent s t u d i e s on the s t r u c t u r e o f never Reaction C o n d i t i o n s :

2.0

CELLULOSE

68 Table X I I :

TECHNOLOGY

Repeat Treatments with Higher Concentration o f Succinamic A c i d i n Cellulose-Amic A c i d Reaction Total Ester Meq./AHGU



1

0.590

0.1*68

0.061

2

0.927

0.702

0.112

3

1.29k

0.833

Ο.23Ο

k

1.571

Ο.986

0.298

Number of Treatments

RESEARCH

36$ aqueous s o l u t i o n o f succinamic a c i d plus 1.08$ sulfamic a c i d , k.O PUR, cure ll+0°C 28 minutes, v i s c o s e rayon f a b r i c , no wash between treatments, d r i e d cotton f i b e r s i n d i c a t e t h a t the s m a l l i n c r e a s e i n r e a c t i o n over d r i e d cotton f i b e r s i s not so unexpected (15, 16,17)· The r e a c t i o n with wood pulp f a l l s between cotton and rayon i n a manner s i m i l a r t o the openess o f s t r u c t u r e or the average d i s ordered f r a c t i o n measured by v a r i o u s techniques (l8). The r e s u l t of t h e s a p o n i f i e d c e l l u l o s e acetate f i b e r s i s somewhat c o n s i s t e n t with the s t r u c t u r e comparison although D.S. values i n the range o f those with rayon c o u l d be expected. The low r e a c t i o n w i t h p o l y v i n y l a l c o h o l f i b e r s , together with data on r e a c t i o n o f amic a c i d s w i t h simple a l c o h o l s (19), i n d i c a t e t h a t r e a c t i o n with secondary a l c o h o l s i s somewhat slower. In Table XIV, never d r i e d rayon, which i s more a c c e s s i b l e than d r i e d rayon, does give more r e a c t i o n than d r i e d rayon. The s t r u c t u r e concept i s explored f u r t h e r i n Table XV where c o t t o n i s decry st a l i i zed. When water i s used t o remove the dec r y s t a l l i z i n g agent the extent of r e a c t i o n i s increased g r e a t l y . Some r e e r y s t a l i i z a t i o n o f the c e l l u l o s e chains does take p l a c e i n the presence o f water ( 2 0 ) , p o s s i b l y decreasing the amount of r e a c t i o n . I f s o l v e n t s o f lower hydrogen bonding c a p a c i t y , l e s s p o l a r i t y and more b u l k a r e used t o remove the sodium hydroxide, l e s s r e c r y s t a l l i z a t i o n and more r e a c t i o n should take p l a c e , as i s the case with dimethylf ormamide and i s o p r o p y l a l c o h o l ( 20^2 3 ) . However, s t r u c t u r e does not appear t o be the only l i m i t i n g f a c t o r s i n c e the amount o f r e a c t i o n with v i s c o s e rayon i s not i n c r e a s e d by the sodium hydroxide treatment. Male amic and phthalamic a c i d s were shown t o be c l o s e s t i n r e a c t i v i t y t o succinamic a c i d i n e a r l i e r s t u d i e s (5). I n Table XVI the a p p l i c a t i o n o f the high r a t i o o f amic a c i d t o c e l l u l o s e , longer cure time, and repeat treatment procedures were a p p l i e d t o these a c i d s with the unexpected r e s u l t t h a t t h e D.S. values d i d not i n c r e a s e i n the same manner as with succinamic a c i d . The Reaction C o n d i t i o n s :

5.

ALLEN

AND

cucuLO

Table X I I I :


69

E f f e c t of Substrate i n C e l l u l o s e - Amic A c i d Reaction

Substrate




Woven Viscose Rayon F a b r i c

0.855

0.594

O.13I

O.I78

Ο.165

0.006

0.176

0.212

0.000

0.249

0.201

0.024

0.401

0.000

0.054

0.015

Woven Cotton Fabric Never D r i e d Cotton F i b e r s Wet Formed Mat Wood Pulp Wet Formed Mat

Saponified C e l l u l o s e Acetate Ο.387 F i b e r s Kept Wet Wet Formed Mat C r o s s l i n k e d Poly v i n y l Alcohol 0.085 Fibers Wet Formed Mat Reaction Conditions :

Jhfo aqueous succinamic a c i d s o l u t i o n plus 1.62$ ammonium sulfamate, 4 . 0 PUR, cure 150°C 22 minutes.

i n c r e a s e i n c r o s s l i n k i n g w i t h no increase i n h a l f - a c i d e s t e r content i n the repeat treatment with male amic a c i d i s i n d e f i n i t e contrast t o the r e s u l t s i n Table X I . No s a t i s f a c t o r y explanation of these r e s u l t s can be made u n t i l the mechanism of r e a c t i o n i s known. Studies i n t h i s area are i n progress ( 19) · In a f u r t h e r e f f o r t t o understand the r e a c t i o n involved, various s p e c i a l i z e d amic acids were looked at (Table XVII). The amine group i n asparagine suppresses the r e a c t i o n , i n d i c a t i n g t h a t the a c i d part of the molecule takes part i n the r e a c t i o n . Parti c i p a t i o n o f the amide group i s a l s o i n d i c a t e d by the r e s u l t s of hydantoic a c i d , where again no r e a c t i o n took p l a c e . An attempt was made t o t i e up the amine group i n asparagine with other a c i d s . A c e t i c a c i d gave no increase i n r e a c t i o n . Phosphoric a c i d i n equimolar q u a n t i t i e s with asparagine gave some r e a c t i o n but d i r e c t e s t e r i f i c a t i o n by the phosphoric a c i d was a c o n t r i b u t i n g f a c t o r . I f the amide part o f the molecule i s r e a c t i n g , then sub s t i t u t e d amides should g i v e l e s s r e a c t i o n , depending on the

70


Table XIV:

E f f e c t o f Never D r i e d Rayon i n Amic A c i d C e l l u l o s e Reaction

Type o f Rayon



Apparent X - l i n k s Meq/AHGU

Woven F a b r i c

0.297

0.264

0.016

Never D r i e d F i b e r s Wet Formed Mat

Ο.355

Ο.3Ο3

0.026

D r i e d Never D r i e d Fibers

0.291

Ο.25Ο

0.020

1 8 $ aqueous succinamic plus 1 . 0 8 $ sulfamic a c i d , 4 . 0 PUR, cure 150°C 9 minutes. Table XV: E f f e c t o f D e c r y s t a l l i z a . t i o n o f Substrate on Succinamic A c i d - C e l l u l o s e Reaction Half-Acid Apparent D e c r y s t a l l i z a t i o n Rinse Total Ester Ester Crosslinks Treatment Solvent Meq/AHGU Meq/AHGU Meq/AHGU Reaction

Conditions:

A. Cotton F a b r i c None 17.5$

None

O.I78

0.164

0.006

Water

Ο.349

0.291

0.029

DMF Isopropyl Alcohol

Ο.382

Ο.33Ο

0.026

0.502

0.426

Ο.Ο38

NaOH,

-7.5°C 3 hrs. 1 7 . 5 $ NaOH, -7.5°C 3 hrs. 1 7 . 5 $ NaOH, -7.5°C 3 hrs.

B. Viscose Rayon F a b r i c None

None

0.855

0.594

0.131

1 7 . 5 $ NaOH, -7.5°C 3 hrs.

Isopropyl Alcohol

0.861

0.610

0.125

5 ^ $ succinamic a c i d , 1 . 6 $ ammonium sulfamate, 4 . 0 PUR, cure 150°C 22 minutes, substituent. I f t h e a c i d groups i s r e a c t i n g , then a l l t h e e s t e r should be half-amide e s t e r . The l a s t three r e s u l t s i n Table XVII show again t h a t there i s no c l e a r d i s t i n c t i o n , and that both groups can be c o n t r i b u t i n g . The theme o f t h i s paper has been the unique and s u r p r i s i n g aspects o f t h e amic a c i d - c e l l u l o s e r e a c t i o n . S e v e r a l o f t h e Reaction C o n d i t i o n s :

5.

ALLEN

AND

Table XVI:


CUCULO

71

E f f e c t o f Reactant Type i n C e l l u l o s e - Amic A c i d Reaction and Phthalamic A c i d s a t High Concentrations Apparent Crosslinks Meq/AHGU

Number of Treatments



Succinamic

1

0.590

0.1*68

0.06l

Succinamic

2

0.927

0.702

0.112

Maleamic

1

0.21+5

0.21+2

0.002

Maleamic

2

0.J26

0.21*0

0.01*3

Phthalamic

1

0.129

0.127

0.001

Amic Acid

Reaction C o n d i t i o n s : 0.1*6 molar aqueous amic a c i d except f o r phthalamic a c i d l i m i t e d t o 0.31 molar f o r s o l u b i l i t y reasons, plus 6$ on weight o f amic a c i d ammonium sulfamate, v i s c o s e rayon f a b r i c , k.O PUR, cure 150°C 22 minutes. Table XVII: E f f e c t o f Reactant Type i n Cellulose-Amic A c i d Reaction Total Ester Meq/AHGU

Amic A c i d

L- Asparagine 0.000 HOC ( θ) CH(NH ) CH C ( θ) NH 2

Amide Ester Meq/AHGU

0.195

0.231

Succinamic A c i d

2


Crosslinks Meq/AHGU

0.018

0.000 2

0.000

0.000

0.121

0.066

0.050

0.025

0.002

0.012

S u c c i n i c Anhydride 0.0l6 plus Ethylenediamine

0.000

0.001+

0.006

Hydantoic A c i d HOC(O)CH NHC(O)NH 2

2

S u c c i n i c Anhydride plus Ethanolamine S u c c i n i c Anhydride plus G l y c i n e


O.15I+

0.055

molar s o l u t i o n o f amic a c i d ,

2.0 PUR,

v i s c o s e rayon f a b r i c , cure 150°C 6 minutes ,

72 Table XVIII:


E f f e c t o f Reactant Type i n Amic A c i d - C e l l u l o s e Reaction E x p l o r a t i o n o f S u c c i n i c A c i d Reaction

Reaction Conditions

Reactant



Crosslinks Meq/AHGU

Succinic Acid

A

Ο.Ο38

0.014

0.012

Succinamic A c i d

A

0.184

0.165

0.009

Succinamide

Β

0.042

0.011

0.016

S u c c i n i c A c i d plus Succinamide

D

0.115

0.061

0.027

Succinamic A c i d plus Succinamide

D

0.165

0.119

0.023

S u c c i n i c A c i d plus Fhthalamide

D

0.074

0.077

0.002

Succinic Acid Acetamide

D

0.054

0.051

0.000

Succinic Acid

C

—

0.079

—

Succinamic A c i d

C

—

0.120

—

Succinic Acid

Ε

0.541

0.439

0.051

Succinamic A c i d

Ε

0.725

0.536

0.095

plus

Reaction Conditions : A - 0.154 molar aqueous s o l u t i o n , 2.0 PUR, cure 150°C 6 minutes Β - 0.072 molar aqueous s o l u t i o n , 2.0 PUR, cure I50°C 6 minutes C - 0.072 molar formamide s o l u t i o n , 2.0 PUR, cure 150°C 8 minutes D - 0.072 molar aqueous s o l u t i o n o f each reactant, 1.08$ ammonium sulfamate, cure 150°C 6 minutes Ε - 0.46 molar aqueous s o l u t i o n plus 7.8 $ NH with s u c c i n i c a c i d , 1.62$ ammonium sulfamate, cure 150°C 22 minutes. 3

t a b l e s presented here have given r e s u l t s i n d i c a t i n g that the a c i d and amide groups may a c t together t o give r e a c t i o n with c e l l u l o s e that i s not r e a l i z e d by s u c c i n i c a c i d and succinamide, molecules containing e i t h e r the a c i d or the amide groups alone (Table XVIII, 5)· The r e s u l t s i n Table XVIII show the l a s t s u r p r i s i n g aspect o f

5.

A L L E N AND CUCULO


73

the amic a c i d r e a c t i o n - the formation of c e l l u l o s e h a l f - a c i d a c i d e s t e r s by combination of a c i d and amide groups not on the same molecule. Although the extent of r e a c t i o n i s not as great as with succinamic a c i d , the combination of s u c c i n i c a c i d w i t h such d i v e r s e ami des as succinamide, acetamide, or phthalamide g i v e s i g n i f i c a n t l y more r e a c t i o n than with s u c c i n i c a c i d alone. T h i s same t r e n d i s seen when formamide i s used as s o l v e n t . F i n a l l y , by use of the i n c r e a s e d r a t i o of reactant t o c e l l u l o s e w i t h sulfamic a c i d as c a t a l y s t , a r e l a t i v e l y h i g h amount of r e a c t i o n i s obtained with the ammonium s a l t of s u c c i n i c a c i d . The f a b r i c was n o t i c a b l y tendered, however. Such t e n d e r i n g does not occur with the amic a c i d s (j5). Conclusions By a c a r e f u l balance of amic a c i d type, a c c e s s i b i l i t y of the c e l l u l o s e s u b s t r a t e , amic a c i d - c e l l u l o s e r a t i o , and cure time and temperature, i t was found t h a t the amic a c i d - c e l l u l o s e r e a c t i o n can be u t i l i z e d t o produce e s s e n t i a l l y a l l c e l l u l o s e h a l f - a c i d e s t e r at a D.S. v a l u e below about 0.3. S u b s t i t u t i o n values s i g n i f i c a n t l y above 0.3 can be r e a l i z e d , but some c r o s s l i n k i n g occurs, the amount depending on the s e v e r i t y of the r e a c t i o n c o n d i t i o n s . S e v e r a l unexplained r e s u l t s were obtained i n t h i s study, i n d i c a t i n g t h a t some aspects of the amic a c i d r e a c t i o n are unique. A l though the object of t h i s work was not t o d e f i n e the mechanism of r e a c t i o n , s e v e r a l r e s u l t s l e d t o a b e l i e f t h a t the a c i d and the amide groups e x h i b i t a s y n e r g e s t i c e f f e c t , probably i n a s t e r e o s p e c i f i c manner. A working model has been developed t o e x p l a i n the unusual r e s u l t s obtained here. H0C(0)RC(0)m

2

-

The e m p i r i c a l i n f o r m a t i o n obtained i n t h i s study was then used t o prepare c e l l u l o s e semi-esters of v a r y i n g D.S. and c r o s s l i n k i n g values f o r e v a l u a t i o n o f s e l e c t e d p r o p e r t i e s l i s t e d e a r l i e r . D e t a i l e d r e s u l t s of these s t u d i e s w i l l be r e p o r t e d later. Acknowledgements We wish t o thank Cotton, Inc. and American Enka Co. f o r t h e i r support of p a r t s of t h i s work. We are a l s o t h a n k f u l t o Dr. Frank Cramer f o r h i s h e l p f u l advice on the pendant c a r b o x y l t e s t method,

p a r t i c u l a r l y i n regard t o the c o r r e c t i o n CELLULOSE f a c t o r . TECHNOLOGY S p e c i a l thanks 74 RESEARCH a l s o go t o the many i n d i v i d u a l s who c o n t r i b u t e d t o t h i s e f f o r t . Literature Cited 1.

2. 3. 4. 5. 6.

7. 8.

A l l e n , Thomas C. and Cuculo, John A, J. Polymer Sci.: Macromolecular Reviews, (1973),7, 189-262. Cuculo, J. Α., T e x t i l e Res. J . , ( 1 9 7 1 ) , 41 (4),321-326. Cuculo, J. Α., U.S. Patent 3,555,585 (1971)· Cuculo, J.Α., T e x t i l e Res. J . , ( 1 9 7 1 ) , 4 1 (5), 375-378. Johnson, Emmitt H. and Cuculo, John Α., T e x t i l e Res. J.(1973)

43 (5), 283-293. Johnson, Emmitt H., T h e s i s f o r Master o f Science Degree(1972) Department o f T e x t i l e Chemistry, North C a r o l i n a State Univ e r s i t y , R a l e i g h , N. C. Cramer, Frank Β., E . I . DuPont de Nemours and Co., P r i v a t e Communication, (1972). Genung, L. B. and M a l l a t t , R. C., Ind. Eng. Chem., ( 1 9 4 1 ) ,

13, 369-374. 9.

A l l e n , T. C . , T e x t i l e Res. J . , (1964), 34, 331-336. 10. Bender, M. L., Chloupek, F., and Neveu, M. C ., J. Amer. Chem.

S o c ., (1958), 80, 5384-5387.

11. Malm, C. J. and Fordyce, C. R., Ind. Eng. Chem., (1940),

(3), 405-408.

12. 13. 14.

32,

Rowland, S.P., Welch, C. M., Brannan, M. A. F., and Gallagher, D. M., T e x t i l e Res. J . , (1967), 37, 933-941. Rowland, S.P., Welch, C . M., and Brannan, M. A. F., U. S. Patent 3,526,048 (1970). B u l l o c k , A. L., Vail, S. L., and Mack, C. H., U. S. Patent

3,294,779 (1966).

15.

Ingram, P., Wood, D. Κ., P e t e r l i n , Α., and W i l l i a m s , J. L., T e x t i l e Res. J . , (1974), 44 (2), 96-106. 16. W i l l i a m s , J. L., Ingram, P., P e t e r l i n , Α., and Woods, D. K., T e x t i l e Res. J . , (1974), 44 (5), 370-377· 17. Morosoff, N., J. Appl. Polymer S c i . , (1974), 18 (6),1837-1854. 18. T r i p p , V. W. in Ν. M. B i k a l e s and L. Segal, Eds., " C e l l u l o s e D e r i v a t i v e s " , V o l . V in High Polymers, Part 5, p.307, WileyI n t e rscience, New York. 19. Bowman, B. G., Unpublished Work (1974). 20. Jeffries, R. and Warwicker, J. O., T e x t i l e Res. J . , (1969),

39 (6), 548-559.

21. Warwicker, J. O., Jeffries, R., Colbran, R. L., and Robinson, R. N., "A Review o f the L i t e r a t u r e on the E f f e c t o f C a u s t i c Soda and Other S w e l l i n g Agents on the F i n e S t r u c t u r e o f Cotton", p. 133 Shirley I n s t i t u t e Pamphlet No. 93, The Cotton Silk and Man-Made F i b r e s Research A s s o c i a t i o n , S h i r l e y I n s t i t u t e , Didsbury, Manchester, England, (1966). Work performed i n F i b e r and Polymer Science Program, School o f T e x t i l e s , North C a r o l i n a State U n i v e r s i t y ,

Cellulose Technology Research

Recommend Documents