Polymer Stabilization and Degradation - ACS Publications - American

18 Bis- and Trisphosphites Having Dioxaphosphepin and Dioxaphosphocin Rings as Polyolefin-Processing Stabilizers

Downloaded by CORNELL UNIV on August 29, 2016 | http://pubs.acs.org Publication Date: June 14, 1985 | doi: 10.1021/bk-1985-0280.ch018

J O H N D. SPIVACK, S T E P H E N D. PASTOR, A M B E L A L PATEL, and L E A N D E R P. STEINHUEBEL CIBA-GEIGY Corporation, Ardsley, NY 10502

In a previous paper, the effectiveness of certain hindered mono phosphites and phosphonites as processing stabilizers for polyolefins(1) was discussed. The present paper describes several new classes of hindered phenyl bis- and tris-phosphites having dibenzo[d,f][1,3,2]dioxaphosphepin and dibenzo[d,g][1,3,2]dioxaphosphocin rings. The latter compounds exhibit superior effectiveness as processing stabilizers together with greater resistance to discoloration and hydrolysis. The di- and tri-alkanolamine esters are of particular interest because of their even greater resistance to hydrolysis at 50°C for extended time periods previously achievable only in the case of certain di-hindered phenyl phosphonites. Processing stabilizers are a special class of antioxidants used to inhibit polymer degradation during the processing steps subsequent to polymerization such as extrusion, injection molding, spinning, etc. These steps are carried out at relatively high temperatures (220-320°C) in the presence of some entrapped oxygen and the resulting radical species. Attempts to counteract degradation by the use of 2,6-di-tertbutyl-4-methylphenol (BHT) and various organophosphorus compounds such as tris-nonylphenyl phosphite (_1) , 3 ,9-dioctadecyloxy-2 ,4,8,10tetraoxa-3,9-diphospha[5.5]-spiroundecane (2) and the 3,9 bis(2,4di-tert-butylphenyl) analog (3) have only been partially successful. BHT is volatile at high temperatures and contributes to discoloration during processing. 1, J2, and can undergo hydrolysis and loss of processing stabilizer effectiveness i f stored improperly. Products of hydrolysis can lead to problems with extrusion and spinning as well as contamination of extrudates with hydrolysis products. 0097-6156/85/0280-0247$06.00/0 © 1985 American Chemical Society

Klemchuk; Polymer Stabilization and Degradation ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

POLYMER STABILIZATION AND DEGRADATION

248

O-CHo C H 9

1 9

•-0--P

CHo-0

RO-P

P-OR

3

2a


2

R = n-C

1 8

H

2 7

A g e n e r a l l y a c c e p t e d mechanism f o r t h e o x i d a t i o n o f p o l y o l e f i n s , RH, i n t h e p r e s e n c e o f a n t i o x i d a n t s o f t h e hydrogen-atom donor t y p e , AH, i n v o l v e s i n i t i a t i o n , p r o p a g a t i o n and t e r m i n a t i o n s t e p s (2). In t h e i n i t i a t i o n s t e p , t h e p o l y o l e f i n , RH, i s c o n v e r t e d t o the p o l y m e r i c r a d i c a l , R», w h i l e t h e p o l y m e r i c peroxy r a d i c a l , ROO*, i s formed i n t h e p r o p a g a t i o n s t e p b y r a p i d r e a c t i o n w i t h oxygen. I n t h e absence o f an e f f i c i e n t a n t i o x i d a n t , t h e peroxy r a d i c a l i s c o n v e r t e d t o t h e h y d r o p e r o x i d e , ROOH, b y hydrogenatom a b s t r a c t i o n from t h e polymer c h a i n g i v i n g r i s e t o another p o l y m e r i c r a d i c a l , R» , and peroxy r a d i c a l ROO*. P r o p a g a t i o n v i a c h a i n t r a n s f e r i s a l s o promoted b y h o m o l y s i s o f ROOH t o R0» and »0H i n t h e absence o r d e p l e t i o n o f t h e a n t i o x i d a n t AH. C h a i n t r a n s f e r w i l l take p l a c e t o an i n s i g n i f i c a n t degree i f A* i s a s t a b l e f r e e r a d i c a l such as i s p r o v i d e d b y a h i n d e r e d phenol as i s shown i n F i g u r e 1. A s i m p l i f i e d v e r s i o n o f t h e r e a c t i o n sequence i n t h e p r e s e n c e o f h i n d e r e d phenols (AH) and a t e r t i a r y phosphorus ( i l l ) compound i s shown i n F i g u r e 1.

I t i s thus apparent t h a t s e l e c t e d a n t i o x i d a n t s , AH, i n t h e p r e s e n t case h i n d e r e d p h e n o l i c s , and h y d r o p e r o x i d e decomposers, such as PR ^, a c t s y n e r g i s t i c a l l y t o i n h i b i t r a d i c a l i n i t i a t e d polymerchain oxidations. The two c l a s s e s o f h i n d e r e d s u b s t i t u t e d b i s - and t r i s - phosp h i t e s having e i t h e r (a) dibenzo[d,f][1,3,2]dioxaphosphepin or (b) d i b e n z o [ d , g ] [ 1 , 2 , 3 ] d i o x a p h o s p h o c i n r i n g s were s e l e c t e d f o r s t u d y as p r o c e s s i n g s t a b i l i z e r s because t h e i r b i c y c l i c s t r u c t u r e s p r o mised s t a b i l i z e r s o f i n c r e a s e d thermal and h y d r o l y t i c s t a b i l i t y compared t o t h e a c y c l i c h i n d e r e d p h e n y l p h o s p h o n i t e s p r e v i o u s l y studied ( 1 ) . 11

The s p e c i f i c compounds s u b m i t t e d shown i n F i g u r e 2.

f o r comparative

studies are

Experimental Section E v a l u a t i o n o f E x p e r i m e n t a l Organophosphorus E s t e r s i n P o l y o l e f i n s . The compounds were t e s t e d i n t h e f o l l o w i n g p o l y o l e f i n s as l i s t e d below, t h e r e s u l t s b e i n g shown i n t h e T a b l e s i n p a r e n t h e s i s : P o l y p r o p y l e n e ( T a b l e I , compounds 4^ t o ^9 i n c l u s i v e ) . High M o l e c u l e r Weight High D e n s i t y P o l y e t h y l e n e .


18.

SPIVACK ET AL.

Bis- and Trisphosphites

249

Initiation


Initiation

> R* l i g h t , heat metal c a t a l y s t s , e t c .

RH

->

ROO*

fast

RH ROO-

->

ROOH + R-

Chain T r a n s f e r

ROOH

->

RO» + -OH

Propagation

ROO-

->

Molecular Products

. . Termination

ROOH

R

1

QOR (Chain ITransfer

RO*

+

0=PR" .

ROH

+

0=PR" ..Termination

3

However: RO \ ROOH

+

PR"

3

/

PR"
P-OH g r o u p . Thus, the IR a b s o r p t i o n bands s e r v e t o i d e n t i f y the type o f r e a c t i o n s r e s p o n s i b l e f o r the d i s a p p e a r a n c e o f the p r o c e s s i n g s t a b i l i z e r t e s t e d . The i n f r a r e d spectrum o f the samp l e was o b t a i n e d on 1% s o l u t i o n s o f the sample i n methylene c h l o r i d e i f the sample was c o m p l e t e l y s o l u b l e . I f t h i s was not the c a s e , the IR spectrum was o b t a i n e d on a KBr p e l l e t . Time i n days t o complete h y d r o l y s i s can be r e a d i l y d e t e r m i n e d by TLC. H y d r o l y s i s T e s t s at 50°C/80%^Relative H u m i d i t y . One gram o f sample was weighed i n t o an open v i a l measuring 1" diam. x 2 1/4" h i g h and p l a c e d on a bed o f g l a s s beads j u s t immersed i n s a t u r a t e d KC1 s o l u t i o n t o a l e v e l o f 1 i n c h i n a 1 p i n t Mason j a r . The Mason j a r was s e a l e d w i t h a screw cap and p l a c e d i n an oven t h e r m o s t a t i c a l l y c o n t r o l l e d at 50°C. The i n c r e a s e i n weight o f t h i s v i a l was m o n i t o r e d and the h y d r o l y s i s o f the t e s t sample measured as d e s c r i b e d above. D i s c u s s i o n and

Results

Comparative E f f e c t i v e n e s s o f E x p e r i m e n t a l Stabilizers in Polyolefins

Processing

Polypropylene. The s i x organophosphorus compounds ( F i g u r e 1, 0.05 weight %) were each f o r m u l a t e d t o g e t h e r w i t h AO-1 (0.10%) i n H e r c u l e s g e n e r a l purpose P r o f a x 6501 p o l y p r o p y l e n e and were s u b j e c t e d t o m u l t i p l e e x t r u s i o n i n two s e r i e s , one at 500°F (260°C) and another at 550°F ( 2 8 8 ° C ) . Comparison o f t h e t e s t compounds i n the p r e s e n c e o f AO-1 were made at each temperature by m e a s u r i n g the melt f l o w r a t e and c o l o r development a f t e r the f i r s t , t h i r d and f i f t h e x t r u s i o n s ( 6 , 7 ) . The r e s u l t s a f t e r the f i f t h e x t r u s i o n a r e shown i n T a b l e I . TABLE I PROCESSING STABILITY OF GENERAL PURPOSE POLYPROPYLENE 500 Temp. °F. 5 00,^ 550,^ 500 ^ 550 550 °(3) MFR MFR Color ' Color g/10 min. g/10 min. Y . I . Y.I. (

}

(

5 5

}

^

V J ;

Series Compound 4

I

II

I

2.8 To.l 4.1 3.7 5.3 10.9 3.4 5.8 9.8 3.7 10.6 6.4 2 3.6 5.0 10.1 3.6 6.0 10.6 4.8 6.7 12.0 6.4 13.2 7.4 Base R e s i n A. * 20.6 78.5 8.1 Base R e s i n B 6.6 15.6 13.6 Notes: TT5 P r o f a x 6501 + 0.1% Ca S t e a r a t e . (2) Base R e s i n A + 0.1% AO-1. (3) M e l t f l o w r a t e (MFR) a f t e r 5 t h e x t r u s i o n .

II 12.3 10.3 10.8 10.0 9.6 10.1 11.8 7.7 8.6 12.5



254 Conclusions

A l l the p r o c e s s i n g s t a b i l i z e r s , b o t h e x p e r i m e n t a l (compounds 4^ t o 9) as w e l l as commercial (_1 and 2), p r o v i d e d improved m e l t s t a b i l i t y over base r e s i n A at b o t h 500°F (260°C) and 550°F (288°C) . E x p e r i m e n t a l compounds 4^ and 9_ commercial compounds _1 showed improved melt s t a b i l i t y over base r e s i n B at 500°F w h i l e commercial compound _2 p r o v i d e d no improvement at t h i s same tempe r a t u r e . At 550°F e x p e r i m e n t a l compounds 4^ t o 9_ and commercial compound _1 showed marked improvement over base r e s i n B, w h i l e compound _2 p r o v i d e d o n l y comparable performance and f a i l e d t o i n h i b i t the r a p i d r i s e i n m e l t f l o w . D e s p i t e i t s d e f i c i e n c y as a m e l t s t a b i l i z e r , commerical compound _2 p r o v i d e d the b e s t c o l o r s t a b i l i t y b e i n g e q u i v a l e n t i n t h i s r e g a r d t o base r e s i n A c o n t a i n i n g no AO-1. E x p e r i m e n t a l compound j$ i s the next b e s t p r o v i d i n g marked c o l o r improvement over base r e s i n B. The p h e n y l p h o s p h o n i t e d e r i v a t i v e , 4, p r o v i d e d the b e s t melt s t a b i l i z a t i o n at 500°F and 550°F, but p r o v i d e d no improvement i n c o l o r over t h a t o b t a i n e d w i t h base r e s i n B. Compound 8 i s comparable i n melt s t a b i l i t y t o b o t h at 500°F and 550°F p r o v i d i n g a d d i t i o n a l l y an improvement o f c o l o r o f about 3 YI u n i t s over base r e s i n B.


a

n

d

Polyethylene High D e n s i t y P o l y e t h y l e n e (HDPE). The p r e f e r r e d method o f e v a l u a t i n g HDPE was found t o be t h e time t o c r o s s l i n k at 220°C u s i n g the Brabender a p p a r a t u s , as i s made e v i d e n t by the r a p i d i n c r e a s e i n t o r q u e . D e t e r m i n i n g melt v i s c o s i t y by m u l t i p l e e x t r u s i o n showed o n l y s m a l l d i f f e r e n c e s compared t o the base polymer. The r e s u l t s are p r e s e n t e d i n T a b l e IV.

TABLE I I PROCESSING STABILIZERS f o r HMW-HDPE PROCESSING STABILITY Lupolene 5260Z (BASF) P r o c e s s i n g S t a b i l i t y - 220°C Additive Brabender ( M i n u t e s t o C r o s s l i n k ? "

2 8 (1) (2)

0.05% 8.5 9 9 9 11

( 2 )

0.1% 13.5 15 16 15 16.5

(

1

)

( 2 )

Data p r o v i d e d by CIBA-GEIGY C o r p o r a t i o n , B a s l e , S w i t z e r l a n d . +0.05% AO-1

The d a t a o f T a b l e I I demonstrates t h a t i n HMW HDPE compound j* i n c o m b i n a t i o n w i t h AO-1 i s the most e f f e c t i v e c o m b i n a t i o n . _5> 6. and _9 a r e about e q u a l l y e f f e c t i v e when t e s t e d s i m i l a r l y w i t h AO-1.


SPIVACK ET AL.

255



L i n e a r - L o w D e n s i t y P o l y e t h y l e n e (LLDPE) and E t h y l e n e P r o p y l e n e Diene (EPDM) S t a b i l i z a t i o n . Prevention of d i s c o l o r a t ion o f LLDPE and EPDM are prime o b j e c t i v e s i n a d d i t i o n t o t h e r m a l stabilization. While t h e r m a l s t a b i l i z a t i o n i s r e a d i l y a c h i e v e d by the use o f p h e n o l i c a n t i o x i d a n t s , p r e v e n t i o n o f d i s c o l o r a t i o n r e q u i r e s a c o - a d d i t i v e such as a p h o s p h i t e . TABLE I I I PREVENTION OF DISCOLORATION L-LDPE at 90"C 0.02% AO-1 + Lba 0.02% C o - A d d i t i v e Initial AO-1 a l o n e 0.60 2 -2.70 £ -2.80 £ -3.70 Note:

(a) (b)

OF Lba A f t e r 6 Weeks 4.50 0.70 0.60 0.00

Dow grade 2552 Lba C o l o r .

I t i s apparent from the d a t a o f T a b l e I I I t h a t w h i l e a l l t h r e e compounds ^2* * J$> are e f f e c t i v e i n p r e v e n t i n g d i s c o l o r a t i o n i n i t i a l l y , the most e f f e c t i v e i n c o u n t e r a c t i n g the c o l o r c o n t r i b u t e d by AO-1 i s compound J3. S i m i l a r l y , compounds 2, and are most p r o f i c i e n t i n p r e v e n t i n g y e l l o w i n g o f EPDM plaques c o n t a i n i n g AO-2 kept at 90°C at 100% R.H. f o r 20 days ( T a b l e I V ) . a n c

TABLE IV PREVENTION OF DISCOLORATION OF EPDM AT 9 0 C and 100% R.H. Gardner C o l o r Antioxidant phr Initial 13 Days Blank 3 4 AO-2 0.05 3 5 AO-2 + J. 0.05 + 0.05 3 5 AO-2 + 2 0.05 + 0.05 3 3 AO-2 + £ 0.05 + 0.05 3 5 AO-2 + 8 0.05 + 0.05 3 4 Note: (1) v e r y y e l l o w W

Hydrolytic

S t a b i l i t y of Experimental

Processing

20

Days 4

5 5 4, 6 4 K

n

'

Stabilizers

Compounds j4 and J>, two o f the e x p e r i m e n t a l p r o c e s s i n g s t a b i l i z e r s l i s t e d i n F i g u r e 2, remained e s s e n t i a l l y unchanged when exposed neat t o an a i r atmosphere o f 80% r e l a t i v e h u m i d i t y at room tempera t u r e f o r 50 d a y s . T h i s i s i n c o n t r a s t t o some o f the commercial compounds such as 1, 2, and 3 which h y d r o l y z e r a p i d l y under the same c o n d i t i o n s ( T a b l e V ) . H y d r o l y s i s t e s t s at 50°C/80% r e l a t i v e h u m i d i t y show t h a t compounds 4 t o 9 i n c l u s i v e a r e much more r e s i s t a n t t o h y d r o l y s i s t h a n _3 ( T a b l e V I ) . Of p a r t i c u l a r i n t e r e s t i n t h i s r e s p e c t i s the d r a m a t i c i n c r e a s e i n h y d r o l y t i c s t a b i l i t y o f compounds ^6 and _9 a l l o f which have t e r t i a r y amino f u n c t i o n s i n t h e i r phosphite s t r u c t u r e s capable of p r e f e r e n t i a l l y n e u t r a l i z i n g



256


p r o t o n s from a c i d i c m o i e t i e s . The p r o t o n a t i o n o f t r i v a l e n t phosphorous e s t e r s , which i s a p r e c u r s o r t o h y d r o l y s i s , i s a v o i d e d . Such p r o t o n a t i o n has been i m p l i c a t e d i n t h e c l e a v a g e o f t r i a l k y l p h o s p h i t e s ( 8 ) , m o n o c y c l i c p h o s p h i t e e s t e r s (9) as w e l l as phosphonite esters ( 1 0 ) .

TABLE V HYDROLYTIC STABILITY AT ROOM TEMPERATURE ( c a 25°C) - 80% RELATIVE HUMIDITY HYDROLYSIS TIME % DAYS 100 4r

1 8 2 Note: General

u

>62 >62 (1) S l i g h t i n c i p i e n t h y d r o l y s i s

Conclusions

I t i s apparent t h a t o f t h e compounds s t u d i e d h e r e i n t h e h i n d e r e d s u b s t i t u t e d b i s - and t r i s - p h o s p h i t e s h a v i n g d i b e n z o [ d , f ] [ 1 , 3 , 2 ] d i o x a p h o s p h e p i n r i n g s , a r e t h e most e f f e c t i v e compounds i n t h e s p e c i f i c p o l y o l e f i n substrates tested. Of p a r t i c u l a r i n t e r e s t i n t h i s r e g a r d i s t h e t r i e t h a n o l a m i n e t r i s - p h o s p h i t e compound J5. Acknowledgment s The a s s i s t a n c e o f M e s s r s . Thomas M. C h u c t a and P e t e r W. Stewart i s g r a t e f u l l y acknowledged f o r t h e i r h e l p i n p r o v i d i n g some o f the e v a l u a t i o n d a t a p r e s e n t e d h e r e i n . The a u t h o r s w i s h t o thank V i c t o r i a R i v e r a and T e r e s a S c h a e f f e r f o r p r e p a r a t i o n o f t h e manuscript.


18. SPIVACK ET AL.


257

Literature Cited


1.

Previous Paper, Spivack, J. D.; Patel, A.; and Steinhuebel, L. P."Phosphorus Chemistry" - ACS Symposium 171 1981, pp. 351-354. 2. For Example, Chapter 12, Howard, J. A., in "Free Radicals Vol. II", Kochi, Jay K.; Ed. John Wiley, N.Y. 1973 3. Spivack, J. D., U.S. 4,233,207, 1980; Chem. Abstr., 94, 6670y. 4. (a) Spivack, J. D., U.S. 4,288,391, 1981; Chem. Abstr., 96, 7586m. (b) U.S. 4,351,759, 1982; Chem. Abstr. 97, 199111t. (c) Odorisio, P. A.; Pastor, S. D.; Spivack, J.D.; Bini, D.; Rodebaugh, R. K. Phosphorus and Sulfur, 1984, 19, 285 5. (a) Spivack, J. D.; Dexter, M.; Pastor, S. D., U.S. 4,318,845 1982; Chem. Abstr., 96, 182292 (b) Odorisio, P. A.; Pastor, S. D.; Spivack, J.D., Phosphorus and Sulfur 1984, 19, 1. 6. ASTM METHOD 1238 Condition L 7. ASTM METHOD D1925-70T 8. Hudson, H. R.; Roberts, J.C., J. Chem. Soc. Perkin II, 1974, 1575-1580. 9. Weiss, R.; Vande Griend, L.J.;Verkade, J.G, J. Org. Chem. 1979, 44, 1860-1863. 10. Hudson, H.R.; Kow, A.; and Roberts, J.C. Phosphorus and Sulfur 1984, 19, 375-378. RECEIVED January 31, 1985


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