Introduction to Hindered Amine Stabilizers - American Chemical Society

1 Introduction to Hindered Amine Stabilizers

Downloaded by 203.64.11.45 on May 3, 2015 | http://pubs.acs.org Publication Date: June 14, 1985 | doi: 10.1021/bk-1985-0280.ch001

PETER P. K L E M C H U K CIBA-GEIGY Corporation, Ardsley, NY 10502

The hindered amine story is an interesting success story involving participation by scientists throughout the world. The success of hindered amines has partly been due to the free exchange of infor mation among scientists, so that the accomplishments of one group, studying stable free radicals, could be picked up by those in other groups, in other parts of the world, who were interested in stable free radicals as polymer stabilizers. The mechanisms of stabiliza tion by hindered amines were somewhat mysterious in the beginning since these compounds didn't f i t any of the known stabilizer types and known mechanisms. Since stable free radicals had been of inter est for their antioxidant activity as trappers of chain-propagating peroxy radicals the triacetoneamine-N-oxyl and derivatives thus were, at f i r s t , of interest as radical-trapping antioxidants. How ever, it wasn't long before the light stabilizing activity of that class of materials was recognized and not much longer before practi cal versions of hindered amine light stabilizers were synthesized, tested, and introduced for market development. Their high order of effectiveness as light stabilizers encouraged many scientists to investigate the mechanisms by which they functioned. We now know much about those mechanisms and can marvel at the effectiveness of hindered amines which apparently are dependent on what are very small concentrations of N-oxyls for their activity. There is much to learn and admire in the hindered amine story. Chemists can take pride in how effectively they have worked together across national boundaries to make hindered amine stabilizers an important product group for the stabilization of polymers. This introduction is a modest effort to review some of the early history of stable-free radicals including triacetoneamine-N-oxyl. This chapter was intended to serve primarily as an introduction to the hindered amine review which took place at the symposium and inten tionally avoids covering material which other participants were expected to present. It is a "light-touch" overview. 0097-6156/ 85/ 0280-0001 $06.00/ 0 © 1985 American Chemical Society In Polymer Stabilization and Degradation; Klemchuk, P.; ACS Symposium Series; American Chemical Society: Washington, DC, 1985.

2

POLYMER STABILIZATION AND DEGRADATION

E a r l y Free R a d i c a l Research


R a d i c a l p r o c e s s e s o c c u r i n many important c h e m i c a l r e a c t i o n s including: polymerization e l e c t r i c a l discharge reactions halogenation photochemical r e a c t i o n s combustion high e n e r g y - i n i t i a t e d reactions autooxidation heterogeneous c a t a l y s i s enzyme p r o c e s s e s The r a d i c a l n a t u r e o f t h e s e r e a c t i o n s was i d e n t i f i e d through mechani s t i c and k i n e t i c a n a l y s e s , but t h e l i f e t i m e s o f t h e f r e e r a d i c a l s i n v o l v e d a r e u s u a l l y t o o b r i e f t o p e r m i t them t o have been s t u d i e d directly. T h u s , s t a b l e f r e e r a d i c a l s o f f e r an o p p o r t u n i t y t o g a i n b a s i c i n f o r m a t i o n about f r e e r a d i c a l s and f r e e r a d i c a l r e a c t i o n s , in particular: 1.

2.

3.

e l u c i d a t i o n o f t h e n a t u r e o f the u n p a i r e d e l e c t r o n ; i t s b e h a v i o r ; p r o p e r t i e s o f i t s m o l e c u l a r o r b i t a l s ; reasons f o r i t s stabil ity; e l u c i d a t i o n o f t h e k i n e t i c s and mechanisms o f r a d i c a l r e a c t i o n s w i t h s t a b l e r a d i c a l s which can be observed and measured directly; e l u c i d a t i o n of s t r u c t u r e s o f l i q u i d s and s o l i d s c o n t a i n i n g s t a b l e f r e e r a d i c a l s by t h e use o f EPR and ESR t e c h n i q u e s .

S t a b l e f r e e r a d i c a l s a r e o f p a r t i c u l a r importance t o t h o s e who a r e engaged i n polymer s t a b i l i z a t i o n because t h e y p l a y a key r o l e i n t h e i n h i b i t i o n of autooxidation r e a c t i o n s . The mechanisms o f a u t o o x i d a t i o n r e a c t i o n s were e l u c i d a t e d t h r o u g h t h e landmark r e s e a r c h c a r r i e d out at the B r i t i s h Rubber P r o d u c e r s ' R e s e a r c h A s s o c i a t i o n , where t h e k i n e t i c s o f a u t o o x i d a t i o n o f o l e f i n s were s t u d i e d i n t h e 1940's and e a r l y 1 9 5 0 ' s . Some o f t h e key r e s e a r c h e r s engaged i n t h a t work were L . Bateman, J . L . B o l l a n d , G. G e e , A . L . M o r r i s , P. Ten Have, among o t h e r s . They c o n t r i b u t e d enormously t o our u n d e r s t a n d i n g o f a u t o o x i d a t i o n r e a c t i o n s o f organic m a t e r i a l s . R e - r e a d i n g t h e i r papers produces a p p r e c i a t i o n o f t h e i r important work and emphasizes t h e debt we, i n polymer s t a b i l i z a t i o n work, owe them. That work e s t a b l i s h e d t h e f o l l o w i n g : 1. 2. 3. 4. 5. 6.

mechanisms and k i n e t i c s o f a u t o o x i d a t i o n r e a c t i o n s o f o r g a n i c materials; f r e e r a d i c a l n a t u r e of a u t o o x i d a t i o n ; chain r e a c t i o n nature of a u t o o x i d a t i o n ; h y d r o p e r o x i d e s as the main o x i d a t i o n p r o d u c t s ; p r o d u c t i o n o f a u t o o x i d a t i o n i n i t i a t i o n r a d i c a l s from h o m o l y s i s of h y d r o p e r o x i d e s ; i n h i b i t i o n o f a u t o o x i d a t i o n by h y d r o q u i n o n e ; t h e s t a b i l i t y o f r e s u l t a n t semiquinone r a d i c a l s t e r m i n a t e d o x i d a t i o n c h a i n s w i t h no c h a i n t r a n s f e r .

The work at t h e B r i t i s h Rubber P r o d u c e r s ' A s s o c i a t i o n and s u b sequent work by B i c k e l and Kooyman, Thomas and Tolman, among o t h e r s , l e d t o t h e a p p r e c i a t i o n t h a t a key r e q u i r e m e n t o f o x i d a t i o n i n h i b i -

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

1. KLEMCHUK

Introduction to Hindered Amine Stabilizers

3

t o r s was t h e i r a b i l i t y t o form s t a b l e r a d i c a l i n t e r m e d i a t e s . These r a d i c a l i n t e r m e d i a t e s s h o u l d be s u f f i c i e n t l y s t a b l e so t h a t t h e y d o n ' t p a r t i c i p a t e i n hydrogen a b s t r a c t i o n from t h e s u b s t r a t e t h e y are s t a b i l i z i n g and t h e r e f o r e , not l e a d t o c h a i n t r a n s f e r . In Scheme I are shown the key s t e p s i n i n h i b i t i o n by t h e two main c l a s s e s o f o x i d a t i o n i n h i b i t o r s , h i n d e r e d phenols and s e c o n d a r y aromatic amines.


Stable

Free

Radicals

The e f f e c t i v e n e s s o f compounds y i e l d i n g s t a b l e r a d i c a l i n t e r mediates i n the s t a b i l i z a t i o n of o r g a n i c m a t e r i a l s l e d to i n t e r e s t in stable free r a d i c a l s i n general. A r e v i e w o f the l i t e r a t u r e on s t a b l e f r e e r a d i c a l s i n d i c a t e s t h a t n i t r i c o x i d e and n i t r o g e n d i o x i d e have been known t o be s t a b l e f r e e r a d i c a l s f o r a v e r y l o n g time. In 1 8 4 5 , Fremy f i r s t d e s c r i b e d h i s s a l t which i s an i n o r g a n i c N-oxyl d e r i v a t i v e . The f i r s t r e p o r t o f an o r g a n i c N - o x y l was by W i e l a n d and O f f e n b a c h e r i n 1 9 1 4 when t h e y d e s c r i b e d the s y n t h e s i s and p r o p e r t i e s o f d i p h e n y l - N - o x y l . D i p h e n y l p i c r y l h y d r a z y l was r e c o g n i z e d as a s t a b l e f r e e r a d i c a l i n 1 9 2 2 by G o l d s c h m i d t and Benn. S t r u c t u r e s o f o t h e r e a r l y s t a b l e f r e e r a d i c a l s may be seen i n F i g u r e 1. Those i n c l u d e s e v e r a l N - o x y l d e r i v a t i v e s as w e l l as g a l v i n o x y l , a s t a b l e - f r e e r a d i c a l d e r i v e d from a h i n d e r e d p h e n o l . These are o n l y a few o f the s t a b l e f r e e r a d i c a l s , e s p e c i a l l y N - o x y l r a d i c a l s , which have been d i s c o v e r e d . D r . Murayama o f the Sanyko Company i n c l u d e d many such s t r u c t u r e s i n a paper p u b l i s h e d i n t h e early 1970's ( J . ) . The f i r s t s y n t h e s i s of 2 , 2 , 6 , 6 - t e t r a m e t h y l - 4 - o x y p i p e r i d i n e - N o x y l was d e s c r i b e d i n a paper by M. B . Neiman, E . G. R o z a n t s e v , and Y . G . Mamedova 0 2 ) . The s y n t h e s i s was a c h i e v e d by t h e o x i d a t i o n o f t r i a c e t o n e a m i n e w i t h hydrogen p e r o x i d e i n the p r e s e n c e o f sodium tungstate. The key p r o p e r t i e s o f t h e t e t r a m e t h y l o x y p i p e r i d i n e - N o x y l , which s u b s e q u e n t l y l e d t o the whole f a m i l y o f h i n d e r e d amine s t a b i l i z e r s , were o u t s t a n d i n g t h e r m a l and c h e m i c a l s t a b i l i t y . D e t a i l s o f i t s p r o p e r t i e s are summarized i n F i g u r e 2 . The compound m e l t e d at 3 6 ° C It was s t a b l e t o m e l t i n g , r e c r y s t a l l i z a t i o n , and distillation. IJ^underwent r e a c t i o n s o f t h e c a r b o n y l f u n c t i o n a l i t y and had 6 . 1 x 1 0 spins/mole. The N - o x y l was reduced w i t h h y drogen on p a l l a d i u m c a t a l y s t t o the c o r r e s p o n d i n g h y d r o x y l a m i n e . The N - o x y l remained i n t a c t a f t e r r e a c t i o n s w i t h 1 ) h y d r o x y l a m i n e t o form t h e o x i m e , 2 ) s e m i c a r b a z i d e t o form the semicarbazone and 3) 2 , 4 - d i n i t r o p h e n y l h y d r a z i n e t o form the 2 , 4 - d i n i t r o p h e n y l h y d r a z o n e . The d i s c o v e r y o f the 2 , 2 , 6 , 6 - t e t r a m e t h y l - 4 - o x y l p i p e r i d i n e - N o x y l was an i m p o r t a n t m i l e s t o n e i n s t a b i l i z a t i o n t e c h n o l o g y but the t r i a c e t o n e a m i n e - N - o x y l was not u s e f u l by i t s e l f as a polymer s t a b i l i z e r because i t i s orange and would impart o b j e c t i o n a b l e c o l o r t o polymers and because i t has a r e l a t i v e l y low m o l e c u l a r weight and too h i g h a v a p o r p r e s s u r e f o r p r a c t i c a l u s e s . In o r d e r t o commerc i a l i z e a p r a c t i c a l s t a b i l i z e r based on t r i a c e t o n e a m i n e - N - o x y l , the f o l l o w i n g had t o be a c h i e v e d :


4


INH—^R0 H

+ IN*

2

IN* =

REQUISITES: 1 ) I N . MUST BE STABLE 2)

I N . MUST NOT P A R T I C I P A T E IN H-ABSTRACTION;


(IN.

+ RH

NO CHAIN

TRANSFER.

INH + R.)

B I C K E L AND KOOYMAN, J . CHEM. S O C , 3 2 1 1 ( 1 9 5 3 ) , "

, ",

"

2215 (1956) "

, 2217 (1957)

THOMAS AND TOLMAN, J . AM. CHEM. S O C , 8 4 ' 2 9 3 0

(1962)

Scheme 1. Key requirement o f o x i d a t i o n i n h i b i t o r s : r a d i c a l intermediates. • N0

NO.

stable

O

FREMY ANN. CHIM. PHYS. 15, 108 (1845)

N0 ( C

H

)

6 5 2

N 0

WlELAND AND OFFENBACHER BER.,

2

*

0 N--O-N-N(C H ) * Ktr\ N0 2

6

5

2

N

47,2111 (1911)

2

DPPH GOLDSCMIDT BER.,

CH,

CH, -NO

H,CO

AND BENN,

5 5 , 628 (1322)

C.H?N^-C H 6

5

OCH MEYER AND REPPE

BANFIELD,KENYON

BER.,

J.

5 4 , 327 ( 1 9 2 1 )

CHEM.

1612

Soc.

(1926)

'NO-

HOFFMAN AND HENDERSON

GALVINOXYL COPPINGER, 77,

J . AM. CHEM. SOC

501 (1957)

Figure

1.

J.

AM. CHEM.

Soc,

83, 4671 (1961)

E a r l y si a b l e f r e e

redicals.



1. KLEMCHUK

5


1.

a suitable derivative a. high s t a b i l i z i n g b. low c o l o r and low c. s t a b l e to polymer d. low v o l a t i l i t y ;

w i t h d e s i r e d p r o p e r t i e s had to be activity t e n d e n c y to d i s c o l o r i n polymers processing conditions

2.

an e c o n o m i c a l m a n u f a c t u r i n g p r o c e s s

had t o be

found

developed.

A l l t h e s e o b j e c t i v e s have now been a c h i e v e d and we a r e a b l e t o e n j o y t h e a v a i l a b i l i t y o f h i n d e r e d amine s t a b i l i z e r s w i t h o u t s t a n d i n g l i g h t s t a b i l i z i n g a n d , i n many i n s t a n c e s , t h e r m o s t a b i l i z i n g properties. The d i s c o v e r y by D r . Murayama and h i s c o - w o r k e r s at the Sankyo Company i n Japan t h a t the N - o x y l f u n c t i o n a l i t y was not c r i t i c a l t o the e f f e c t i v e n e s s o f t h e t r i a c e t o n e a m i n e - N - o x y l as a l i g h t s t a b i l i z e r but t h a t the N-H compounds o f t h a t c l a s s a l s o p o s s e s s e d i m p r e s s i v e l i g h t s t a b i l i z i n g a c t i v i t y , was a key f i n d i n g which l e d to the subsequent development o f polymer s t a b i l i z e r s which were c o l o r l e s s and had low d i s c o l o r a t i o n t e n d e n c i e s . S t a b l e F r e e R a d i c a l s i n Polymer S t a b i l i z a t i o n The e f f e c t i v e n e s s o f f r e e r a d i c a l s , such as N - o x y l s , h y d r a z y l s , and p h e n a z y l s , as s t a b i l i z e r s f o r polymers was d e s c r i b e d i n a p a t e n t i s s u e d i n 1952 ( 3 ) . V a r i o u s compounds o f t h e s e c l a s s e s were found t o be e f f e c t i v e as t h e r m a l and l i g h t s t a b i l i z e r s i n n y l o n f a b r i c , n y l o n f i l m , p o l y c h l o r o p r e n e , p o l y e t h y l e n e , and p o l y ( m e t h y l m e t h a c r y late). Some o f the s t r u c t u r e s d e s c r i b e d i n t h a t p a t e n t are shown i n F i g u r e 3. B r o w n l i e and I n g o l d (4) were among the f i r s t t o show the e f f e c t i v e n e s s o f N - o x y l s and h y d r o x y l a m i n e a n a l o g s i n s t a b i l i z i n g organic substances against a u t o o x i d a t i o n . The e f f e c t i v e n e s s o f N - o x y l s i n t r a p p i n g c a r b o n - f r e e r a d i c a l s and p e r o x y - f r e e r a d i c a l s was c l e a r l y demonstrated i n t h a t work. The N - o x y l s o f t h a t work, shown i n F i g u r e 4, were a l s o e f f e c t i v e i n i n h i b i t i n g the A I B N i n i t i a t e d p o l y m e r i z a t i o n of s t y r e n e . As shown i n F i g u r e 5, h i n d e r e d h y d r o x y l a m i n e s can f u n c t i o n as polymer s t a b i l i z e r s by the d o n a t i o n o f a hydrogen atom t o a peroxy r a d i c a l t o y i e l d an N - o x y l . The N - o x y l i s i n t u r n a b l e t o t r a p c a r b o n - f r e e r a d i c a l s and i n t h a t way t e r m i n a t e the o x i d a t i o n c y c l e at the f i r s t s t a g e , which i s the i d e a l p o i n t at which t o t e r m i n a t e c h a i n p r o p a g a t i n g f r e e r a d i c a l s - b e f o r e t h e y have an o p p o r t u n i t y t o r e a c t w i t h oxygen t o form peroxy r a d i c a l s . Non-hindered h y d r o x y l amine s , w i t h H-atoms on (X-carbon atoms, u s u a l l y g i v e r i s e t o n i t r o n e s as a r e s u l t o f hydrogen atom d o n a t i o n and do not t r a p c a r bon f r e e r a d i c a l s t o y i e l d alkoxyamino p r o d u c t s . The t h e r m a l s t a b i l i t y a s s o c i a t e d w i t h h y d r o x y l a m i n e s and the c o s t o f c o n v e r t i n g a t r i a c e t o n e a m i n e d e r i v a t i v e to a h y d r o x y l a m i n e d e r i v a t i v e a r e d i s advantages f o r the development o f h y d r o x y l a m i n e s as p r a c t i c a l comm e r c i a l polymer s t a b i l i z e r s . The e f f e c t i v e n e s s o f d i b e n z y l h y d r o x y l a m i n e as a i n h i b i t o r o f A I B N - i n i t i a t e d t e t r a l i n o x i d a t i o n can be seen from the d a t a i n F i g u r e 6. A comparison between d i b e n z y l h y d r o x y l a m i n e and b u t y l a t e d h y d r o x y t o l u e n e (BHT) can be made from t h o s e d a t a . The lower r a t e o f oxygen consumption i n the s o l u t i o n c o n t a i n i n g d i b e n z y l h y d r o x y l -


6


O

M.P.

O

36°C.;

MELTING/ ZATION,

DISTILLATION,

REACTIONS SPIN

KEY

PROPERTY

- OUTSTANDING

S T A B L E TO

RECRYSTALLIOF C A R B O N Y U

PER MOLE:

6.1

>23

x 10'

STABILITY.


REACTIONS 1.

PD/H

2.

N-OXYL

2

REDUCTION INTACT

TO H Y D R O X Y L A M I N E

AFTER

REACTIONS

A.

HYDROXYLAMINE—>OXIME

B.

SEMICARBAZIDE—>

C.

2,4-DlNITROPHENYLHYDRAZINE

WITH:

(ALSO

BECKMANN

REARRANGEMENT)

SEMICARBAZONE ^ 2,4~DlNITROPHENYL" HYDRAZONE

M. B. NEIMAN, E. G. ROZANTSEV, Y. G. MAMEDOVA, NATURE, 196,

472 ( 1 9 6 2 ) .

Figure 2 . F i r s t synthesis of 2 , 2 , 6 , 6 - t e t r a m e t h y l - 4 - o x o piperidine-N-oxyl.

COMPOUNDS EVALUATED:

POLYMERS TESTED

(THERMAL AND LIGHT S T A B I L I T Y ) :

NYLON FABRIC, NYLON F I L M ,

POLYCHLOROPRENE,

POLYETHYLENE, PMMA D. Me QUEEN, U . S . 2 , 6 1 9 , 4 7 9 ; APPLIED 1 2 / 2 8 / 5 0 ; ISSUED 1 1 / 2 5 / 5 2

F i g u r e 3. S t a b i l i z a t i o n o f polymers w i t h N - o x y l s , and p h e n a z y l s .

hydrazyls,


1.

KLEMCHUK


o

in

II


I,

II,

III,

AND C O R R E S P O N D I N G

AUTOOXIDATION

OF

R.

AND R 0 . .

ALIPHATIC

R.

+

0 —L->R0 .

R.

+

IN.^—>N0R

I,

II,

2

2

STYRENE.

HYDROXYLAMINES

AROMATIC

N-OXYL

N-OXYLS

REACTED

INHIBITED.THE REACTED

ONLY

WITH

WITH

R..

2

AND

III

BROWNLIE AND

— K

INHIBITED

INGOLD

10

AIBN-INITIATED

CAN.

J.

OF

FOR

I

2

STYRENE

CHEM.,

45,

POLYMERIZATION

2427

(1967).

F i g u r e 4. I n h i b i t i o n of a u t o x i d a t i o n of s t y r e n e by N - o x y l s and h y d r o x y l a m i n e s .

ADVANTAGES: GENERATE

N-OXYL

^NOH

+ R0 -

^NO.

+ R.

ON H Y D R O G E N > >N0.

2

>

EFFECTIVE

IN THERMAL

EFFECTIVE

IN

ABSTRACTION +

R0 H 2

>N0R OXIDATION

PHOTOOXIDATION

INHIBITION

INHIBITION

DISADVANTAGES: THERMAL COSTLY

Figure 5 .

STABILITY TO M A K E

N-HYDROXY-TRIACETONEAMINE

Hydroxylamines

as polymer

stabilizers.


7

8



amine o v e r t h a t f o r BHT can be seen c l e a r l y from t h e d a t a p l o t t e d i n F i g u r e 6. C a l c u l a t i o n s o f o x i d a t i v e c h a i n l e n g t h - t h e number o f m o l e c u l e s o f oxygen consumed p e r f r e e r a d i c a l g e n e r a t e d - shows t h e h i g h e r e f f i c i e n c y o f d i b e n z y l h y d r o x y l a m i n e o v e r BHT as a r a d i c a l trapping i n h i b i t o r . Both d i b e n z y l h y d r o x y l a m i n e and BHT were found t o t r a p about two r a d i c a l s p e r i n h i b i t o r m o l e c u l e t o t h e end o f the induction period. Beyond t h e i n d u c t i o n p e r i o d both a d d i t i v e s were e s s e n t i a l l y w i t h o u t e f f e c t and t h e o x i d a t i o n proceeded as i f u n i n hibited . And s o , t h e work on mechanisms o f a u t o o x i d a t i o n at t h e B r i t i s h Rubber P r o d u c e r s ' A s s o c i a t i o n , t h e e a r l y work on t h e s y n t h e s i s and r e a c t i o n o f s t a b l e f r e e r a d i c a l s , the r e c o g n i t i o n o f t h e r j l e o f s t a b l e f r e e r a d i c a l s i n polymer s t a b i l i z a t i o n , t h e d i s c o v e r y o f s t a b l e t r i a c e t o n a m i n e - N - o x y l , and t h e s e a r c h f o r p r a c t i c a l c a n d i d a t e s f o r c o m m e r c i a l i z a t i o n , have l e d t o the development o f h i n d e r e d amine s t a b i l i z e r s , a new c l a s s o f polymer s t a b i l i z e r s . They a r e e f f e c t i v e i n many polymers a g a i n s t p h o t o d e g r a d a t i o n and a l s o a r e e f f e c t i v e a g a i n s t t h e r m o o x i d a t i o n i n some p o l y m e r s . The s t r u c t u r e s o f t h e c u r r e n t c o m m e r c i a l l y a v a i l a b l e p r o d u c t s f o r polymer s t a b i l i z a t i o n may be seen i n F i g u r e 7. These compounds a r e e f f e c t i v e i n meeting the s t a b i l i z e r r e q u i r e m e n t s i n many commercial p o l y m e r s ; however, o t h e r s a r e under development t o s a t i s f y r e q u i r e m e n t s not b e i n g met by them.

TETRALIM,

2.50 M

INHIBITOR, AIBN,

2.0

CHLOROBENZENE

x 10'*

M

OXYGEN,

3.0 x 10~^ M

SOLUTION

1 ATM.

60°C

OXIDATIVE

CHAIN

RADICALS

LENGTH

INH.

INITIAL

END

TRAPPED IND. PER.

PER. I N H . M O L .

0.20

1.8

0.79

1.8

2.2

(

1

22.00

44.00

1

1

66.00

r

1

1

88.00

TIME

1

UO.00

1

C

6

H

1

132.00

5

C

1

H

2

)

2

N

0

T

154.00

H

BHT

/

1

1

176.00

1

1

198-00

1 ~

220-00

(MINUTES)

Figure 6 . I n h i b i t i o n of t e t r a l i n o x i d a t i o n by d i b e n z y l h y d r o x y l amine, A I B N - i n h i b i t e d .


KLEMCHUK


1.


Chimassorb 944LD

Figure 7 .

Commercially a v a i l a b l e h i n d e r e d amine s t a b i l i z e r s .


9

10


Literature Cited (1) (2) (3) (4)

K. Murayama, Yuki Gosei Kagaku Kyoka Shi, 29, 366 (1971). M. B. Neiman, E. G. Rozantsev, Y. G. Mamedova, Nature, 196, 472 (1962). D. McQueen, U. S. Patent 2,619,479. I. T. Brownlie and K. U. Ingold, Can., J . of Chem., 45, 2427 (1967).


RECEIVED December 7, 1984


Introduction to Hindered Amine Stabilizers - American Chemical Society

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