Liquid-Crystalline Polymers - ACS Publications - American Chemical

Chapter 8

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Thermotropic Poly(ester-co-carbonate) 1,2,3

1

1

Yu-Chin Lai , Bruce T. DeBona , and Dusan C. Prevorsek 1

Corporate Research and Development, Allied Signal, Inc., Morristown, NJ 07960

A number of thermotropic polyester-carbonates were prepared through melt-polymerization of substituted hydroquinones and diphenyl tere phthalate and diphenyl carbonate to have high molecular weight, with reduced viscosity in the range of 2-3. The molecular weights of the polymers can be advanced further by s o l i d state heat-treatment, with the rate of postpolymerization depending on temperature and Concentra tion of catalyst. Samples of some compositions can be spun into high performance fibers and processed into self-reinforced p l a s t i c s . The properties of thermotropic polyester-carbonates and polyesters were compared as fibers and plastics.

Although studies c o n c e r n i n g main c h a i n l i q u i d c r y s t a l l i n e p o l y m e r s were o r i g i n a t e d by O n s a g e r ( l a ) a n d I s h i h a r a ( l b ) i n t h e l a t e 1 9 4 0 ' s , e x t e n s i v e work i n t h i s f i e l d d i d not r e a l l y begin u n t i l the e a r l y 1970*s. J a c k s o n and K u h f u s s (2.) r e p o r t e d t h e f i r s t t h e r m o t r o p i c p o l y e s t e r by m o d i f y i n g p o l y e t h y l e n e t e r e p h t h a l a t e w i t h v a r i o u s amounts o f p - h y d r o x y b e n z o i c a c i d ( H B A ) . They f o u n d t h a t t h e c o p o l y e s t e r w i t h HBA c o n t e n t o f a t l e a s t 35 m o l e % h a v e opaque m e l t s . S u b s e q u e n t s t u d i e s i n t h e a r e a o f a r o m a t i c p o l y e s t e r s by v a r i o u s a u t h o r s r e s u l t e d i n a l a r g e number o f p a t e n t s and p u b l i c a t i o n . ( 3 ) These p o l y m e r s were a l l d e r i v e d f r o m u n s u b s t i t u t e d and 2

Current address: Bausch and Lomb, Inc., Rochester, NY 14534 Address correspondence to this author.

3

0097-6156/90/0435-0102$06.00/0 © 1990 American Chemical Society

Weiss and Ober; Liquid-Crystalline Polymers ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

8. LAI ET AL.

Thermotropic Poly (ester-co-carbonate)

103

s u b s t i t u t e d a r o m a t i c d i o l s and d i a c i d s and h y d r o x y a c i d s w i t h and w i t h o u t f l e x i b l e s p a c e r s . ( 3 . ) T h e r e a s o n s f o r t h e b r o a d i n t e r e s t i n t h i s a r e a , among o t h e r s , a r e t o c r e a t e m e l t - p r o c e s s a b l e h i g h s t r e n g t h , h i g h modulus f i b e r s and s e l f - r e i n f o r c e d p l a s t i c s . T h e r m o t r o p i c p o l y e s t e r s d e r i v e d from unsubstituted a r o m a t i c d i o l s and d i a c i d s u s u a l l y h a v e m e l t i n g p o i n t s which approach or exceed the thermal decomposition point. T h u s i t i s r e a s o n a b l e t o e x p e c t t h a t some m o d i f i c a t i o n i n m o l e c u l a r s t r u c t u r e w o u l d be r e q u i r e d t o r e n d e r them m e l t - p r o c e s s a b l e , e v e n t h o u g h some a d v e r s e e f f e c t s on l i q u i d c r y s t a l l i n i t y and m e c h a n i c a l p r o p e r t i e s o f the polymers would r e s u l t . The p r e p a r a t i o n s o f t h e r m o t r o p i c p o l y e s t e r - a m i d e s f r o m c o m p a r a b l e monomers a s t h o s e o f t h e r m o t r o p i c p o l y e s t e r s were a l o g i c a l e x t e n s i o n o f a s e r i e s o f s t u d i e s i n t h e r m o t r o p i c p o l y e s t e r s and l y o t r o p i c p o l y a m i d e s . ( 4 ) However t h e i n c l u s i o n o f c a r b o n a t e s h a d r a r e l y been e x p l o r e d . ( 5 ) Because o f t h e f l e x i b i l i t y o f c a r b o n a t e compared t o s u b s t i t u t e d a r o m a t i c r i n g s , it s h o u l d be an e v e n more e f f e c t i v e a p p r o a c h i n l o w e r i n g the melting temperatures of the unmodified a l l aromatic p o l y e s t e r s i n t o the e a s i l y processable range. The s o l i d - s t a t e h e a t - t r e a t m e n t s o f t h e r m o t r o p i c polyester fibers to obtain fibers with high tenacity were r e p o r t e d b e f o r e . ( 6 ) However, t h e n a t u r e o f t h i s p r o c e s s was n o t c l e a r when we commenced t h i s s t u d y . The o b j e c t i v e s o f t h i s p a p e r a r e t o d i s c l o s e t h e l e s s e x p l o r e d t h e r m o t r o p i c p o l y e s t e r - c a r b o n a t e s and t o demonstrate the nature of heat-treatment of the thermotropic polymers u s i n g p o l y e s t e r - c a r b o n a t e s as examples. In a d d i t i o n , the p r o p e r t i e s o f t h e r m o t r o p i c p o l y e s t e r s a n d p o l y e s t e r - c a r b o n a t e s a s f i b e r s and p l a s t i c s a r e compared. Experimental Monomers and c a t a l y s t s . The monomers m e t h y l h y d r o q u i n o n e (MHQ), t - b u t y l - h y d r o q u i n o n e (BHQ), r e s o r c i n o l ( R 0 ) , h y d r o q u i n o n e (HQ), d i p h e n y l c a r b o n a t e and c a t a l y s t t e t r a b u t y l t i t a n a t e (TBT) were p u r c h a s e d ( A l d i r c h ) a n d used as r e c e i v e d . D i p h e n y l t e r e p h t h a l a t e (DPT) was p r e p a r e d by i n t e r f a c i a l r e a c t i o n o f s o d i u m p h e n o x i d e i n w a t e r and t e r e p h t h a l o y l c h l o r i d e (TPC) i n m e t h y l e n e c h l o r i d e , u s i n g b e n z y l t r i e t h y l a m m o n i u m c h l o r i d e as c a t a l y s t , f o l l o w e d b y w a s h i n g w i t h h o t w a t e r and r e c r y s t a l l i z a t i o n f r o m t o l u e n e . The y i e l d was u s u a l l y 90% o r h i g h e r . General Procedure f o r the preparation of p o l y e s t e r carbonates. A r e s i n k e t t l e was c h a r g e d w i t h t h e a r o m a t i c d i o l s , DPT and DPC o f a s e l e c t e d m o l a r r a t i o . TBT i n t h e amount o f 30-1000 ppm o f t h e c o m b i n e d w e i g h t s o f monomers was a l s o a d d e d . The c o n t e n t s were h e a t e d u n d e r c o n s t a n t n i t r o g e n f l o w and s t i r r e d m e c h a n i c a l l y


LIQUID-CRYSTALLINE POLYMERS

104

when m e l t e d . T h e p o l y m e r i - z a t i o n s t a r t e d t o o c c u r a t about 2 1 5 ° C as p h e n o l s t a r t e d t o d i s t i l l o u t . The t e m p e r a t u r e was s l o w l y r a i s e d as t h e r e a c t i o n p r o g r e s s e d and most o f t h e p h e n o l was d i s t i l l e d a t 2 6 0 - 2 7 0 ° C . Vacuum was t h e n a p p l i e d g r a d u a l l y t o r e a c h 0 . 2 - 0 . 5 t o r r i n a b o u t 5 m i n u t e s . The r e a c t i o n i n t e r - m e d i a t e , a f t e r h a l f an h o u r u n d e r vacuum, changed from f l u i d t o a v e r y v i s c o u s , g o l d e n , f i b r o u s m a t e r i a l . The r e a c t i o n was s t o p p e d when t h e t e m p e r a t u r e r e a c h e d 2 9 0 ° C and t h e p r o d u c t was removed f r o m t h e k e t t l e w h i l e s t i l l h o t . T h e p r o d u c t was f i r s t b r o k e n i n t o p i e c e s and t h e n c r u s h e d i n t o f i n e p i e c e s . I t was t h e n e x t r a c t e d w i t h h o t t o l u e n e and d r i e d i n v a c u o . The y i e l d was u s u a l l y o v e r 90%. When t h e p o l y m e r i z a t i o n was done on a l a r g e s c a l e , a t h e r m o c o u p l e was u s e d f o r d e t e c t i n g t h e t e m p e r a t u r e o f t h e c o n t e n t s a n d h e a t i n g medium s u c h a s T h e r m i n o l - 6 6 (Monsanto) was a d d e d i n t o t h e r e a c t i o n c o n t e n t s . Polymer c h a r a c t e r i z a t i o n . The t h e r m o t r o p i c b e h a v i o r s o f t h e p o l y e s t e r - c a r b o n a t e s p r e p a r e d were e x a m i n e d u n d e r a p o l a r i z e d hot stage microscope (Sybron C o . ) . Normally t h e s a m p l e became s o f t e r a t 1 2 0 - 1 5 0 ° C and m e l t e d w i t h b i r e f r i n g e n c e a f t e r w a r d s , d e p e n d i n g on t h e m o l e c u l a r w e i g h t a n d c o m p o s i t i o n o f t h e p o l y m e r . The s a m p l e s s t a y e d b i r e - f r i n g e n t u n t i l 350°c o r h i g h e r . Dilute solution v i s c o s i t i e s of most p o l y m e r s were m e a s u r e d a t room t e m p e r a t u r e i n p - c h l o r o p h e n o l / 1 , 2 d i c h l o r o e t h a n e ( 5 0 / 5 0 by w e i g h t ) , u s i n g an U b b e l h o d e v i s c o m e t e r . F o r s a m p l e s c o n t a i n i n g HQ/RO, t h e v i s c o s i t i e s were m e a s u r e d a t 5 0 ° C i n p e n t a f l u o r o p h e n o l . In any c a s e t h e m o l e c u l a r w e i g h t o r v i s c o s i t y o f e a c h s a m p l e was r e p o r t e d a s n p / c , o r r e d u c e d v i s c o s i t y , at 0.5 g / d l i n t h e u n i t s o f a l / g . The DSC s c a n s f o r a l l s a m p l e s were done u s i n g a DuPont 990 d i f f e r e n t i a l s c a n n i n g c a l o r i m e t e r a t a h e a t i n g r a t e o f 2 0 ° C / m i n u t e i n argon. In a l l c a s e s , the s a m p l e s were q u e n c h e d f r o m 3 5 0 ° C and r e h e a t e d t o c h e c k f o r changes i n t h e t r a n s i t i o n t e m p e r a t u r e s . S

Heat-treatments of thermotropic polyester-carbonates. The s o l i d - s t a t e h e a t - t r e a t m e n t s o f t h e r m o t r o p i c p o l y e s t e r - c a r b o n a t e s i n f i n e p i e c e s were c o n d u c t e d i n a B l u e M h i g h t e m p e r a t u r e i n e r t g a s o v e n (Model A G C 1 7 0 E M T I ) . T h e s e s a m p l e s were t r e a t e d a t d i f f e r e n t t e m p e r a t u r e s , f o r d i f f e r e n t p e r i o d o f t i m e . The t r e a t e d s a m p l e s were c h a r a c t e r i z e d f u r t h e r b y DSC and v i s c o s i t y m e a s u r e m e n t s . The t r e a t e d s a m p l e s were u s e d i n f i b e r s p i n i n g and p l a s t i c p r o c e s s i n g s t u d i e s . (2x8.) Results

and D i s c u s s i o n

Polymer S y n t h e s i s . Though s o l u t i o n p o l y m e r i z a t i o n i s a f e a s i b l e p r o c e s s i n m a k i n g p o l y c a r b o n a t e s and c o p o l y e s t e r - c a r b o n a t e s , (9) i t i s n o t a c c e p t a b l e f o r m a k i n g t h e r m o t r o p i c p o l y m e r s b e c a u s e t h e low s o l u b i l i t y


8. LAI ET AL.

105

Thermotropic Poly(ester-co-carbonate)

of thermotropic polyesters i n i n e r t solvent l i m i t s the growth o f m o l e c u l a r weight of product i n s o l u t i o n . (3a) T h u s m e l t - p o l y m e r i z a t i o n was a p p l i e d h e r e t o p r e p a r e p o l y e s t e r - c a r b o n a t e s w i t h m o l e c u l a r w e i g h t h i g h enough for processing studies. E q u a t i o n 1 shows t h e r e a c t i o n scheme w h i c h l e a d s t o t h e

+ DPT

(m+n)

HO-Ar-OH

DPC Tetrabuty1 titanate

4

- ^ © ^ - ^ ^ -

t

° "

A

r

" ° ^ + n - J - x

+ 2(m+n) @ - O H

(1)

formation of high molecular weight p o l y e s t e r - c a r b o n a t e s d e r i v e d from d i p h e n y l t e r e p h t h a l a t e (DPT), d i p h e n y l c a r b o n a t e (DPC), and a r o m a t i c d i o l s (Ar i n t h e e q u a t i o n ) s u c h a s t - b u t y l h y d r o i q u i n o n e (BHQ), m e t h y l - h y d r o q u i n o n e (MHQ), h y d r o q u i n o n e (HQ) and r e s o r c i n o l ( R O ) . For the polymerization to proceed at a reasonable r a t e , the use o f a t r a n s e s t e r i f i c a t i o n c a t a l y s t is needed. Compounds w h i c h a r e u s u a l l y u s e d a s a c a t a l y s t for the preparation of polyesters through t r a n s e s t e r i f i c a t i o n c a n be u s e d h e r e . T h e s e i n c l u d e l i t h i u m , s o d i u m , z i n c , magnesium, c a l c i u m , t i t a n i u m , maganese, c o b a l t , t i n , antimony, e t c . i n t h e form o f a h y d r i d e , hydroxide, oxide, h a l i d e , alcoholate, or phenolate or i n t h e form o f s a l t s o f o r g a n i c o r m i n e r a l a c i d s , complex s a l t s , o r mixed s a l t s . ( 1 0 ) In t h i s s t u d y , tetrabuty1 t i t a n a t e (TBT) i n t h e amount o f 1000 ppm was u s e d normally. I n o r d e r t o k e e p t h e c o n t e n t s more f l u i d - l i k e f o r p r o p e r h e a t e x c h a n g e a n d smooth s t i r r i n g d u r i n g t h e course of r e a c t i o n , a high temperature-stable heating medium s u c h a s T h e r m i n o l - 6 6 was u s e d . Polymer C o m p o s i t i o n - P r o p e r t y R e l a t i o n s h i p . Tables I summarized t h e r e p r e s e n t a t i v e t h e r m o t r o p i c p o l y e s t e r c a r b o n a t e s a m p l e s p r e p a r e d f r o m BHQ/MHQ/DPT/DPC. The f i r s t s e r i e s ( e n t r y 1-3) o f c o m p o s i t i o n s u n d e r i n v e s t i g a t i o n was t h o s e c o n t a i n i n g BHQ. H i g h e r DPT/DPC r a t i o gave polymer w i t h h i g h e r m e l t i n g t e m p e r a t u r e . T h e s e s a m p l e s showed b i r e f r i n g e n c e o n l y u n d e r s h e a r when melted. The i n c l u s i o n o f MHQ i n t o t h e p o l y e s t e r - c a r b o n a t e c o m p o s i t i o n s gave polymers w i t h s t r o n g b i r e f r i n g e n c e


106


Table I.

Thermotropic Polyester-carbonates From BHQ/MHQ/DPT/DPC

Feed molar r a t i o BHQ/MHQ/DPT/DPC 100/0/50/50 100/0/40/60 100/0/30/70 50/50/50/50 50/50/52.5/47.5 50/50/55/45 50/50/57.5/42.5 50/50/60/40 * ** *** ****

n

sp/

c

0, ,58 0. .76 0, .80 2, .98 2,.07 1. .79 1,.98 2, .88

Derived

Tg (°C)*

Tm (°C)**

Thermotropic Behavior

119 142 149 135 130 133 126 135

270 170 160 180 210 240 260 290

*** *** *** **** **** **** **** ****

By DSC. By v i s u a l o b s e r v a t i o n u n d e r p o l a r i z e d m i c r o s c o p e . B i r e f r i n g e n c e under shear o n l y . B i r e f r i n g e n c e without shear.

w i t h o u t s h e a r when m e l t e d . I n t h i s s e r i e s o f s t u d y , t h e f e e d m o l a r r a t i o o f DPT/PTC was c h a n g e d f r o m 5 0 / 5 0 t o 6 0 / 4 0 w h i l e t h e m o l a r r a t i o o f BHQ/MHQ was k e p t a t 5 0 / 5 0 . The m e l t i n g t e m p e r a t u r e o f t h e p o l y m e r was c h a n g e d f r o m 1 8 0 ° C t o 2 9 0 ° C when t h e m o l a r r a t i o o f DPT/DPC o f s a m p l e s was c h a n g e d f r o m 5 0 / 5 0 t o 6 0 / 4 0 . I t must be s t r e s s e d h e r e t h a t t h e m o l a r r a t i o s mentioned i n t h i s a r t i c l e always r e f e r r e d t o the feed m o l a r r a t i o . T h e t r u e m o l a r r a t i o s o f BHQ/MHQ a n d DPT/DPC o f p r o d u c t s m i g h t be d i f f e r e n t from t h e f e e d r a t i o s . The t r u e m o l a r r a t i o s o f DPT/DPC i n two p o l y e s t e r - c a r b o n a t e s a m p l e s d e r i v e d from BHQ/MHQ/DPT/DPC i n f e e d m o l a r r a t i o s o f 5 0 / 5 0 / 5 0 / 5 0 and 5 0 / 5 0 / 6 0 / 4 0 were checked by A t t e n u a t e d t o t a l r e f l e c t i o n F o u r i e r t r a n s f e r infrared spectroscopy. They were f o u n d t o be 4 2 / 5 8 and 5 0 / 5 0 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 DPC i s more r e a c t i v e . T h i s was e x p e c t e d i n v i e w o f t h e f l e x i b i l i t y o f DPC r e l a t i v e t o DPT. T h i s i d e n t i - f i c a t i o n was made p o s s i b l e by c o m p a r i n g t h e IR a b s o r p t i o n o f t h e p o l y e s t e r - c a r b o n a t e p r o d u c t a t 1777.5 cm" ( f o r the c a r b o n y l g r o u p s o f c a r b o n a t e ) and a t 1738.8 c m " (for t h e c a r b o n y l g r o u p s o f e s t e r ) , u s i n g t h e IR a b s o r p t i o n s o f DPT and DPC a s c o n t r o l s ( t o c a l c u l a t e t h e r e s p e c t i v e e x t i n c t i o n c o e f f i c i e n t s o f c a r b o n y l g r o u p s ) . However, t h e same IR method c o u l d n o t g i v e t h e r a t i o o f BHQ/MHQ, b e c a u s e o f t h e o v e r l a p o f a b s o r p t i o n b a n d s a t 2925-2975 cm" a t t r i b u t e d t o m e t h y l and t - b u t y l g r o u p s o f t h e p r o d u c t . B e c a u s e o f s o l u b i l i t y p r o b l e m i n common o r g a n i c s o l v e n t , no NMR s p e c t r u m o f t h e p r o d u c t was t a k e n . T h e r a t i o o f BHQ/MHQ c a n be o b t a i n e d b y s o l i d s t a t e NMR i f a v a i l a b l e . I n v i e w o f t h e s t r u c t u r e s o f BHQ and MHQ, no d i f f e r e n c e i n r e a c t i v i t y was e x p e c t e d . 1

1

1


8. LAI ET AL.


107

Thermotropic polyester-carbonates containing only HQ and RO h a v e m e l t i n g p o i n t s near thermal decomposition. However when MHQ and BHQ were i n c l u d e d i n t h e c o m p o s i - t i o n s , t h e m e l t i n g t e m p e r a t u r e s were d e p r e s s e d somewhat c l o s e t o 3 0 0 ° C as shown i n T a b l e I I .

Table I I .

T h e r m o t r o p i c P o l y e s t e r - c a r b o n a t e s D e r i v e d from HQ/RO/BHQ/MHQ a n d DPT/DPC ( m o l a r r a t i o 5 0 / 5 0 )

Feed molar r a t i o HQ/RO/BHQ/MHQ 40/35/15/10 40/30/20/10** 35/35/15/15** 35/30/25/10 35/30/20/15 30/30/25/15 * **

As n

s

1. 0. 1. 1. 1. 0.

18 92 49 65 61 87

is Tg

("C)

118 119 122 135 122 112

A f t e r annealed* Tm Tg ( C) U

n

sp/

c

1 .11 insol insol 1 .52 1 .55 0 .92

115 127 130 128 119 112

U

( C)

288 327 330 285 290 285

A t 2 4 0 ° C f o r 30 m i n u t e s . Annealed at 250°C f o r 6 hours.

B e c a u s e o f t h e v e r y amorphous n a t u r e o f t h e s e p o l y m e r s due t o t h e s y n t h e t i c p r o c e d u r e e m p l o y e d ( m e l t - p o l y m e r i z a t i o n a n d q u e n c h i n g o f p r o d u c t s ) and t h e c o m p o s i t i o n s s t u d i e d , t r u e m e l t i n g t e m p e r a t u r e s c a n be o b t a i n e d f r o m the DSC s c a n s o n l y a f t e r t h e a s - p r e p a r e d s a m p l e s were a n n e a l e d a t t e m p e r a t u r e below m e l t i n g f o r a s h o r t p e r i o d of t i m e . Almost a l l p o l y e s t e r - c a r b o n a t e samples d e r i v e d f r o m HQ/RO/BHQ/MHQ and l i s t e d i n T a b l e I I were a n n e a l e d at 240°C (more t h a n 4 0 ° C b e l o w Tm) f o r 30 m i n u t e s t o g i v e s a m p l e s w i t h more c r y s t a l l i n i t y , y e t t h e y were n o t o v e r t r e a t e d t o cause changes i n m o l e c u l a r weight as d e m o n s t r a t e d b y c o n s t a n t v i s c o s i t i e s and T g * s b e f o r e and a f t e r a n n e a l i n g . M e l t i n g t e m p e r a t u r e s were t h e n m e a s u r e d by DSC. Two s a m p l e s were t r e a t e d a t h i g h e r t e m p e r a t u r e ( 2 5 0 ° C ) f o r l o n g e r p e r i o d o f t i m e (6 h o u r s ) t o g e t t h e u l t i m a t e m e l t i n g t e m p e r a t u r e f o r samples w i t h e x t r e m e l y h i g h m o l e c u l a r w e i g h t s ( s a m p l e s i n s o l u b l e i n t h e same s o l v e n t u s e d f o r m e a s u r i n g v i s c o s i t y o f low v i s c o s i t y s a m p l e s ) . B o t h o f them were c l o s e t o 3 3 0 ° C . I n g e n e r a l , h i g h m o l e c u l a r w e i g h t p o l y m e r s c a n be o b t a i n e d r o u t i n e l y w i t h t h e s y n t h e t i c p r o c e d u r e as d e s c r i b e d e a r l i e r u n l e s s when t h e s t i r r i n g o f r e a c t i o n c o n t e n t s were n o t e f f i c i e n t d u r i n g t h e vacuum d i s t i l l a t i o n stage. N o r m a l l y samples o f r e d u c e d v i s c o s i t y o f 2-3 c a n be o b t a i n e d as l o n g a s t h e m e l t i n g t e m p e r a t u r e o f t h e p o l y m e r was 2 9 0 ° C o r b e l o w . The m o l e c u l a r w e i g h t o f t h e r m o t r o p i c p o l y m e r s p r e p a r e d by m e l t - p o l y m e r i z a t i o n i s much h i g h e r t h a n t h o s e p r e p a r e d by s o l u t i o n p o l y m e r i z a t i o n . ( 3 a ) I n t h o s e c a s e s t h e i n h e r e n t v i s c o s i t y were n o r m a l l y i n t h e r a n g e o f 0.3 t o 1.0.


108


The E f f e c t o f S o l i d - S t a t e H e a t - T r e a t m e n t on M o l e c u l a r w e i g h t and C r y s t a l l i n i t y . Solid-state heat-treatment had b e e n done b e f o r e on t h e r m o t r o p i c p o l y e s t e r f i b e r t o o b t a i n advancement i n t e n a c i t y (6) a n d on p o l y e s t e r c a r b o n a t e s a m p l e s t o g e t advancement i n m o l e c u l a r w e i g h t . ( 1 1 ) I t was u n d e r s t o o d t h a t p o s t p o l y m e r i z a t i o n and t h e r m a l a n n e a l i n g o c c u r r e d on t h e r m o t r o p i c p o l y m e r s a t s o l i d s t a t e , as t h e term p o s t - p o l y m e r i z a t i o n has been used i n t e r c h a n g e a b l y f o r s o l i d - s t a t e heat-treatment. The o b j e c t i v e s o f c a r r y i n g o u t s o l i d - s t a t e h e a t t r e a t m e n t s o f t h e r m o t r o p i c p o l y e s t e r - c a r b o n a t e s were twofold. O n e , t o s t u d y t h e h e a t - t r e a t m e n t phenomena. Two, t o p r e p a r e s a m p l e s o f h i g h e r m o l e c u l a r w e i g h t f o r p r o c e s s i n g s t u d i e s i n t o h i g h p e r f o r m a n c e f i b e r s and p l a s t i c s i f h e a t - t r e a t m e n t d i d cause advances i n molecular weight. S e l e c t e d samples ( i n f i n e - p i e c e s ) o f t h e r m o t r o p i c p o l y e s t e r - c a r b o n a t e s d e r i v e d from BHQ/MHQ/DPT/DPC, ( c o n t a i n e d 1000 ppm o f TBT) and a l s o t h o s e c o n t a i n i n g HQ/RO a s d e s c r i b e d i n t h e p r o c e d i n g s e c t i o n , were h e a t t r e a t e d i n t h e s o l i d s t a t e a t t e m p e r a t u r e s between 4 0 ° b e l o w Tm and Tm f o r d i f f e r e n t p e r i o d s o f t i m e . I t was f o u n d t h a t t h e c r y s t a l l i n i t y was i n c r e a s e d i n a l l s a m p l e s , a s s u g g e s t e d by t h e DSC s c a n s a f t e r t h e s a m p l e was h e a t - t r e a t e d . I t was a l s o f o u n d t h a t t h e m o l e c u l a r w e i g h t s o f a l l samples i n c r e a s e d w i t h the advances d e p e n d i n g on t h e t i m e and t e m p e r a t u r e o f h e a t - t r e a t m e n t . T a b l e I I I s u m m a r i z e d some t y p i c a l e x a m p l e s i n t h i s s t u d y . A s e x p e c t e d from t h e g e n e r a l c h e m i c a l r e a t i o n k i n e t i c s , the higher the heat-treatment temperature, the f a s t e r the advances i n m o l e c u l a r weight. Because h i g h m o l e c u l a r weight t h e r m o t r o p i c p o l y e s t e r - c a r b o n a t e p r o d u c t s c a n be o b t a i n e d b y t h i s process, the d i f f i c u l t y i n obtaining high molecular w e i g h t m a t e r i a l s d i r e c t l y from m e l t - p o l y m e r i z a t i o n i s circumvented. I t was o b s e r v e d t h a t t h e e f f i c i e n c y i n h e a t t r e a t m e n t i s i r r e v e l e n t t o t h e powder s i z e i n o u r experiments. However i t was f o u n d t h a t s a m p l e s o f t h e same m o l e c u l a r w e i g h t c a n be t r e a t e d more e f f i c i e n t l y i n t h e f i b e r form ( p a r t i c u l a r l y i n f i n e d e n i e r f i b e r ) t h a n i n powder f o r m Because o f d i f f e r e n c e s i n s u r f a c e a r e a . F o r e x a m p l e , a s a m p l e i n powder form d e r i v e d f r o m BHQ/MHQ/DPT/DPC ( 5 0 / 5 0 / 5 5 / 4 5 ) w i t h r e d u c e d v i s c o s i t y o f 1 . 9 7 , c a n be t r e a t e d t o g i v e a p r o d u c t w i t h r e d u c e d v i s c o s i t y o f 4 . 1 9 a t 240"C f o r 6 h o u r s , w h i l e a s a m p l e i n f i b e r f o r m , s p u n from a sample o f t h e same v i s c o s i t y , became i n s o l u b l e i n t h e same s o l v e n t a f t e r i t was t r e a t e d u n d e r t h e same c o n d i t i o n s . The E f f e c t o f C a t a l y s t C o n c e n t r a t i o n on M e l t p o l v m e r i z a t i o n and S o l i d - s t a t e H e a t - t r e a t m e n t . In preparation of polyester-carbonates of d i f f e r e n t


the

8. LAI ET AL.

Table I I I .


109

E f f e c t o f H e a t - t r e a t m e n t on M o l e c u l a r W e i g h t ( n / c ) f o r Thermotropic Polymers D e r i v e d froftt BHQ/MHQ/DPT/DPC (BHQ/MHQ 5 0 / 5 0 ) S D

Heat Treatment T (°C) t (hours) Original 240

250

260

3 6 12 18 24 3 6 9 12 24 1 3

DPT/DPC 55/45

Molar Ratio 57.5/42.5 60/40

1.97

2.07

2.88

3.66 4.19 5.86 9.45 12.7

— — — — 3 .— 67

— — — — 6 .— 01

6.63 10.9 16.3 insol

8.76

— — — — — — —

— —

— 5 .— 28

insol

insol

c o m p o s i t i o n s a s d e s c r i b e d i n t h e p r e v i o u s s e c t i o n s , TBT i n t h e amount o f 1000 ppm was u s e d u n i v e r s a l l y . T h i s m e l t - p o l y m e r i z a t i o n d i d need c a t a l y s t . I n some c a s e s , t h e a d d i t i o n o f TBT was w i t h h e l d i n t e n t i o n a l l y , the r e a c t i o n c o n t e n t s s t a y e d f l u i d a t 2 5 0 - 2 7 0 ° C , w i t h no p h e n o l d i s t i l l e d . However, o n c e a few d r o p s o f TBT was added, phenol s t a r t e d t o d i s t i l l over. To s t u d y t h e e f f e c t o f TBT on p o l y m e r i z a t i o n k i n e t i c s , t h e m e l t - p o l y m e r i z a t i o n o f BHQ/MHQ/DPT/DPC ( 5 0 / 5 0 / 5 7 . 5 / 4 2 . 5 ) was c a r r i e d o u t w i t h TBT i n t h e amount o f 1000, 300, 100 and 30 ppm's r e s p e c t i v e l y . Attempts were made t o c a r r y t h e s e p o l y m e r i z a t i o n s u n d e r t h e same r e a c t i o n c o n d i t i o n s , p a r t i c u l a r l y t h e same d i s t i l l a t i o n t i m e u n d e r t h e same vacuum and t h e same r e a c t i o n temperature. However some v a r i a t i o n s i n r e a c t i o n c o n d i t i o n s were s t i l l p o s s i b l e due t o t h e e q u i p m e n t l i m i t a t i o n s . T a b l e I V s u m m a r i z e d some r e p r e s e n t a t i v e d a t a i n t h i s s t u d y . A s c a n be s e e n , t h e m o l e c u l a r w e i g h t o f t h e p r o d u c t a c h i e v e d was a b o u t t h e same (2.07 v s 1.81) when t h e amount o f TBT u s e d was 1000 ppm o r 300 ppm. However, when t h e amount o f TBT was d r o p p e d down t o 100 ppm o r 30 ppm, t h e m o l e c u l a r w e i g h t o f t h e p r o d u c t ( r e d u c e d v i s c o s i t y was 1.11 and 0.87 respectively) a c h i e v e d was o n l y h a l f o f t h o s e o b t a i n e d w i t h a h i g h amount o f T B T . The e f f e c t o f TBT c o n c e n t r a t i o n on s o l i d - s t a t e h e a t - t r e a t m e n t was a l s o s t u d i e d . I t was assumed h e r e t h a t t h e l o s s o f TBT d u r i n g p u r i f i c a t i o n was i n


110


T a b l e I V . E f f e c t o f TBT C o n c e n t r a t i o n on M e l t p o l y m e r i z a t i o n and S o l i d S t a t e H e a t - t r e a t m e n t f o r BHQ/MHQ/DPT/DPC ( 5 0 / 5 0 / 5 7 . 5 / 4 2 . 5 ) Reaction Condition

Melt-polymerization D i s t i l l a t i o n t i m e (hr) under n i t r o g e n under vacuo n /c s p

Heat-treatment at 250°C, N for 2

2 3 4 6 9 12 24 48 60 72

TBT C o n c e n t r a t i o n 1000 300 100

1.8 2.0 2.07

(hr)

—

2.2 2.0 1.11

3.0 2.0 0.87

—

—

—

— —

1.41

—

1.79

—

— — —

4.80 5.63 insol

— — —

1.0 1.8 1.81

n

(ppm) 30

s p

/c

2.71

3.67

—

6.63 10.9 16.3 insol

— — —

3.03

—

p r o p o r t i o n t o t h e amount o f TBT u s e d . The l o s s o f TBT f o r a s a m p l e p r e - p a r e d w i t h 300 ppm o f TBT was a n a l y z e d by I C P a n a l y s i s . I t was f o u n d t h a t t h e p u r i f i e d p r o d u c t c o n t a i n e d 272 ppm o f T B T , r e p r e s e n t i n g a 50% l o s s o f TBT, a f t e r a d j u s t i n g f o r the l o s s o f p h e n o l . T h i s s e r i e s o f h e a t - t r e a t m e n t s t u d i e s were c a r r i e d o u t a t 2 5 0 ° C f o r d i f f e r e n t p e r i o d s o f time w i t h t h e r e s u l t s summarized i n T a b l e I V . As e x p e c t e d , the m o l e c u l a r weight o f the s a m p l e a d v a n c e d f a s t e r when more TBT was u s e d . When t h e TBT c o n c e n t r a - t i o n u s e d was v e r y low ( s u c h a s 100 ppm o r 30 ppm), t h e h e a t - t r e a t m e n t p r o c e s s became v e r y i n e f f i c i e n t i n g a i n i n g an advancement i n m o l e c u l a r weight.

C o r r e l a t i o n of T r a n s i t i o n Temperatures with M o l e c u l a r Weight. T a b l e V shows t h e T m ' s and T g ' s o f t h e r m o t r o p i c polyester-carbonates of higher molecular weight a f t e r heat-treatments. I n a l l t h r e e s e r i e s , t h e Tm a d v a n c e d a s the molecular weight increased, but i t reached a a s y m p t o t i c f i g u r e . The T g ' s s t a y e d r e l a t i v e l y c o n s t a n t . The Tm v s r e d u c e d v i s c o s i t y were p l o t t e d i n F i g u r e 1. 1

T h e r m o t r o p i c P o l y e s t e r - c a r b o n a t e s as F i b e r s and S e l f reinforced Plastics. The m a j o r o b j e c t i v e o f o u r s t u d y i n t h e r m o t r o p i c p o l y e s t e r - c a r b o n a t e s was t o e v a l u a t e


8. LAI ET AL.


111

320

220' 0

1

2

1

4

1

1

1

1

1

6 8 10 12 14 R E D U C E D VISCOSITY

1

'

1

16

18

Figure 1. Melting temperature versus reduced v i s c o s i t y for polyester-carbonates. (•) DPT/DPC 55:45; (+) DPT/DPC 57.5:42.5; (*) DPT/DPC 60:40


20

112


T a b l e V . Tm a n d T g v s M o l e c u l a r W e i g h t ( i n n / c ) f o r T h e r m o t r o p i c P o l y e s t e r - c a r b o n a t e s D e r i v e d from BHQ/MHQ/DPT/DPC ( w i t h BHQ/MHQ a t 5 0 / 5 0 ) s p

Composition DPT/DPC 55/45

n

l

c

sp/ '

Tm

and

Tg

2.88 275 129

3.38 278 130

4.15 282 131

6.95 294 134

9.45 299 134

12.7 303 137

Tg

2.07 260* 128

3.29 288 132

4.27 288 133

6.63 297 133

10.9 304 137

Insol 307 138

_IS_

2.97 290* 136

3.10 289 137

4.77 300 138

6.52 303 138

8.76 306 137

Insol 308 140

S D

/c

Tfi Tg

1.9 240 128

57.5/42.5

60/40

* By v i s u a l

observation

on a p o l a r i z e d

microscope.

t h e s e p o l y m e r s a s f i b e r s and p l a s t i c s , i n hope t h a t h i g h t e n a c i t y f i b e r and s e l f - r e i n f o r c e d e n g i n e e r i n g p l a s t i c s c a n be o b t a i n e d . The f i b e r - s p i n n i n g and p l a s t i c p r o c e s s i n g s t u d i e s were d e s c r i b e d s e p a r a t e l y . ( 7 . 8 ) D u r i n g t h e c o u r s e o f o u r s t u d y , we h a d t h e o p p o r t u n i t y to evaluate the only a v a i l a b l e a l l aromatic, thermo t r o p i c p o l y e s t e r , LCP2000 from C e l a n e s e . P r e s u m a b l y i t was a c o p o l y m e r c o n t a i n i n g h y d r o x y b e n z o i c (HBA) and h y d r o x y n a p h t h o l i c a c i d (HNA) m o i e t i e s . T h e s a m p l e was s u b j e c t e d t o f i b e r s p i n n i n g s and p l a s t i c m o l d i n g s a s were t h e t h e r m o t r o p i c p o l y e s t e r - c a r b o n a t e s , u s i n g t h e same e q u i p m e n t a n d u n d e r c o m p a r a b l e c o n d i t i o n s . T a b l e V I c o m p a r e s t h e k e y p r o p e r t i e s o f t h e s e two t y p e s o f t h e r m o t r o p i c p o l y m e r s c a t e g o r y by c a t e g o r y . The s a m p l e s c o m p a r e d h a d t h e same m e l t i n g r a n g e s , b u t were v e r y d i f f e r e n t i n r e d u c e d v i s c o s i t i e s and s o l u b i l i t y c h a r a c t e r i s t i c s . The d a t a compared were t h o s e p r o c e s s e d u n d e r t h e most f a v o r a b l e c o n d i t i o n s . Interestingly e n o u g h , t h e a s - s p u n f i b e r s from t h e p o l y e s t e r - c a r b o n a t e c a n be h e a t - t r e a t e d more e f f i c i e n t l y t h a n t h o s e f i b e r s ( o f same t e n a c i t y ) s p u n from t h e p o l y e s t e r . B o t h o f them gave f i b e r p r o p e r t i e s f a r s u p e r i o r t o t h o s e o f n y l o n s and p o l y e t h y l e n e t e r e p h t h a l a t e . T h e s e two c l a s s e s o f polymers a l s o had c o m p a r a t i v e p r o p e r t i e s (such as t e n s i l e s t r e n g t h , t e n s i l e modulus, f l e x modulus, notched I z o d i m p a c t s t r e n g t h ) a s p l a s t i c s ; and t h e i r p r o p e r t i e s were f a r s u p e r i o r t o most p l a s t i c s w i t h o u t any reinforcement.


8. LAI ET AL.

Thermotropic Poly(ester-co-carbonate)

113

Table V I . Comparative P r o p e r t i e s of Thermotropic P o l y e s t e r and P o l y e s t e r - c a r b o n a t e s C l a s s of polymer Composition n

spA

Polyester HBA/HNAcontaining > 17 i n pentafluorophenol at 50°C

Tm ( ° C )

272

Properties

as

& 292

fiber

Spun a t ( ° C ) 299 Properties: tenacity/modulus/denier (in grams/denier) as-spun 8.0/405/6 heat-treated for 6 hours at 250°C 14.3/445/8 Properties

as

Polyester-carbonate BHQ/MHQ/ D P T / DPC (50/50/57.5/42.5) 2.07 in p-chlorophenol/ 1,2-dichloroethane a t RT 250

260

5.7/360/7 240°C 18.2/410/6

plastics same 304

1.81 260

4.1

3.0

4

2.07

1.98

5

5.21

6.86

7.50

8.11

Sample v i s c o s i t y Molded a t ( ° C ) Notched Izod ft-lb/in Tensile strength (10 psi) T e n s i l e modulus (10 psi) F l e x modulus (105 p s i )

Conclusion High molecular weight thermotropic polyester-carbonates c a n be p r e p a r e d t h r o u g h t r a n s e s t e r i f i c a t i o n o f monomers i n t h e m e l t , u s i n g t e t r a m e t h y l t i t a n a t e a s c a t a l y s t . The p r o d u c t s c a n be h e a t - t r e a t e d i n t h e s o l i d - s t a t e t o g a i n a d v a n c e s i n m o l e c u l a r w e i g h t and c r y s t a l l i n i t y , w i t h t h e r a t e o f p o s t - p o l y m e r i z a t i o n d e p e n d i n g on t e m p e r a t u r e . T h e r m o t r o p i c p o l y e s t e r - c a r b o n a t e s c a n be s p u n a n d h e a t t r e a t e d i n t o h i g h performance f i b e r s and p r o c e s s e d into s e l f - r e i n f o r c e d p l a s t i c s , with mechanical p r o p e r t i e s e q u i v a l e n t t o t h o s e o f some a l l a r o m a t i c t h e r m o t r o p i c polyesters.



114

Literature Cited 1. a) Onsager, L. New York Acad. Sci. 1949. 51, 627. b) Isihara, A. J. Chem. Phys. 1951, 19, 1142. 2. a) Kuhfuss, H . F . ; Jackson, J r . , W. J. U.S. Patent 3 778 410, 1974. b) Jackson, J r . , W. J.; Kuhfuss, H . F. J. Polym. Sci. -Chem. 1976, 14, 2043. 3. Too much to be cited completely. Some examples are: a) Jin, J. I . ; Antoun, S.; Ober, C.; Lenz, R. W. Brit. Polym. J. 1980, 12, 132. b) Jackson, J r . , W. J. ibid. 1980, 12, 154. 4. a) Jackson, W. J.; Kuhfuss, H . F. J. Polym. Sci. Chem. 1980, 18, 1685. b) Calundann, G. W.; Charbonneau, L. F . ; Ease, A. J. U.S. Patents 4 339 375, 4 341 688, 4 351 917, 4 351 918, 4 355 132. 1982 c) McIntyre, J. E . ; Milburn, A. H . Brit. Polym. J. 1981, 13, 5. 5. a) Inata, H . ; Morinaga, T. U.S. Patent 4 107 143, 1978. b) Fayelle, B. EPO 15 856, 1980. U.S. Patent 4 284 757, 1981. 6. Luise, R. R. U.S. Patent 4 183 895, 1980. 7. Lai, Y. C . ; DeBona, B. T . ; Prevorsek, D. C. J. Appl. Polym. Sci. 1980, 36, 805. 8. Lai, Y. C . ; DeBona, B. T.; Prevorsek, D. C. ibid. 1988, 36, 819. 9. Prevorsek, D. C . ; DeBona. B. T . ; Kesten, Y. J. Polym. Sci. -Chem, 1980, 18, 75. 10. Mark, H . F . ; Gaylord, N. G.; Bikales, N. M. Ency. Polym. Sci. Tech. 1969, 10, 722. 11. Akkapeddi, M. K.; DeBona, B. T . ; Lai, Y. C.; Prevorsek, D. C. U.S. Patent 4 398 018, 1983. RECEIVED

March 26, 1990


Liquid-Crystalline Polymers - ACS Publications - American Chemical

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