Multiple chain termination by binuclear quinones in oxidized polypropylene containing hydroperoxide groups

1964

Yu. B. SmLov and YE. T. DeNisov

20. I. P. GRAGEROV, V. K. POGORELYI and N. F. FRANCHUK, Vodorodnaya svyaz' i bystry[~ protonnyi obmen, p. 134, Naukova dumka, Kiev, 1978 21. G. PIMENTEL, O. MacCLELLAN, Vodorodnaya svyaz', p. 200, Mir,-Moscow, 1964 22. A. GORDON and R. FORCE, Sputnik khimika, p. 130, Mir, Moscow, 1976

Polymer Science U.S.S.R. Vol. 26, ~lo. 8, pp. 1964-1971, 1984 Printed in Poland

0032-3950/84 $ 1 0 . 0 0 + . 0 0 © 1985 Pergamon Press Ltd~

MULTIPLE CHAIN TERMINATION BY BINUCLEAR QUINONES IN OXIDIZED POLYPROPYLENE CONTAINING HYDROPEROXIDE GROUPS* Yu. B. SHILOV and YE. T. DENISOV Branch of the Institute of Chemical Physics, U.S.S.R. Academy of Sciences (Received 20 March 1983)

A study was made of the inhibiting action of a number of binuclear quinones on oxidation of PP and PE in the solid phase under conditions of initiated oxidation at 366°K. Quinones terminate chains by reaction with alkyl and peroxide macroradicais. In previously oxidized PP the anti-oxidizing activity of quinones increases markedly and the effective stoichiometric coefficient of inhibition increases from 5 to 20. DUmNG oxidation o f PP inhibited with bisphenols hydroperoxide groups have a dual role. On the one hand, breaking down to free radicals, they accelerate the consumptior~ o f inhibitors, on the other, they increase the stoichiometric coefficient o f inhibition [l]. During the transformation of binuclear phenols corresponding quinones accumulate in the system, which also have an inhibiting effect [2-8]. In spite of the c o m p a r a lively large number of studies dealing with kinetics of oxidation, inhibited with quinones, some aspects of this problem remain unanswered. This paper deals with new results concerning the inhibition with binuclear quinone~ o f oxidation of PP and PE. It was established that preliminary oxidation of solid P P intensifies the antioxidizing activity of quinones and increases the stoichiometric grosscoefficient of inhibition. The structure of polymer hydroperoxide is of importance in effect. Isotactic PP with M=2.8 x 105, an ash content of 0-02 wt. ~, crystallinity of 0.65 and low density PE (LDPE) of m.p. "~ 378°K were used. Experiments were carried out under conditions of ini* Vysokomol. soyed. A26: No. 8, 1753-1758, 1984.

Multiple chain termination by binuclear quinones in oxidized PP

1965

tiated oxidation. Benzoyl peroxide (BP) and hydroperoxide groups (POOH) of oxidized PP and L D P E were the initiators of oxidation. Polymers containing P O O H groups were obtained by two methods: by oxidation of solid PP and L D P E at 365°K in the presence of [BP]o -~ 0"02 mole/kg and'by oxidation of PP in cumene solution (PP concentration 40 g/l.) with cumyl peroxide of concentration 0"02 mole/l, at 387°K. With the first method of oxidation in solid PP block P O O H groups, with the second m e t h o d - separate POOH groups were obtained [9]. BP initiator was removed by extraction with alcohol from the polymer. Single P O O H groups were formed during oxidation of LDPE. Hydroperoxide groups in PP and L D P E were determined iodometrically. Kinetics of oxygenabsorption were measured by a pressure gauge under constant pressure [10]. In oxidized polymers containing P O O H groups the rate of initiation vi was determined from the rate of 02 absorption measured experimentally using the ratio v~=v2/a2 for chain oxidation. C o efficient a (mole/kg.sec)* was determined from experiments of oxidation without an inhibitor with fixed vl values. For PP at 366°K a= 1"66 × 10 -2 (mole/kg.sec) ~. With mixed initiation using BP andi P O O H groups v=a (v~P+v~°°a)~'.For BP at 366°K ki =4.5 x 10 -5 sec -1. The following compounds were used as inhibitors: X

X

llt}--~--CtI2

X

--{}tl,

X"/--:

X

{)_ //:==~,-- (;I-t. . . . . . . .

~ ~'X

X~

0CII3

I

~X. II

X

X

\

Oil

X

ocn~ /

X

\

/

o <%=,:-,::S>=o, X/

0CH8 III

~ X

.X /

X

x)

7 :J

~ r II tl IV

"--%"X

X

v

-\x

where X = C (CH3)3. Compounds I I - V were synthesized by methods described previously [11-13]. Quinone IV was subjected to quantitative analysis spectrophotometrically using SF-26 after being extracted from polymer samples using an ethanol solution in CC14 (A=442 nm, ~= 74,000 l./mole.cm [12]). f Values were determined by two m e t h o d s - f r o m 02 absorption and from the rate of quinone consumption. If kinetic curves of 02 absorption had clear induction periods ~ and vl was unchanged during z time, f w a s determined from the formula

f= - [InH]o

(1)

If during the experiment the rate of 02 absorption during t period of time was unchanged, the lower value of f was determined from the formula

f~,v,t(l-V~--~o)

[InH]o 1

(2}

1966

Yti. B. SHILOV and YE. T. DENISOV

The value of f was calculated from experiments using the rate of quinone consumption Vi f=--, /3x

(3)

where v= is the rate of quinone consumption.

~

6

~4

4 0'2 z

4O

80 120 Time, min

0

FIG. 1

I

2 4 [Q] , 1~ rnole/kg

I

6

FIG. 2

Fro. 1. Kinetics of oxidation of solid PP, initiated with BP(vl=2.8 x 10 -6 mole/kg, sec) and POOH groups (v1=2"5 x 10 -6 mole/kg.sec) at 366°K without an inhibitor (1) and in the presence of 4 x x 10-* (2), 5.1 x 10 -3 (3), 1"3 x 10 -3 mole/kg quinone IV (4) and kinetics of consumption of quinone IV in solid PP at 366°K in the presence of BP (v,=2.8 x 10 -6 mole/kg.sec) and POOH groups (vt = 1"3 x 10 -6 mole/kg.sec). Light points show reactions in the presence of BP, dark ones - in the presence of POOH groups. FIG. 2. Dependence of F on the concentration of quinone IV using formula (4). Initiation with BP (1) (v1=2"8 x 10 -6 mole/kg.sec), POOH groups (2) (vl= 1.26 x 10 -6 mole/kg.sec and v1=2-5 x 10-a mole/kg.sec) and joint initiation with BP and POOH groups (3) (vi =4"1 x 10 -6 mole/kg.sec) of solid PP. C o m p a r e d with bisphenols, q u i n o n e s I I I - V are less active inhibitors, b u t o x i d a t i o n is i n h i b i t e d f r o m the very start. I t is n o t e w o r t h y t h a t the r a t e o f 0 2 a b s o r p t i o n r e m a i n s c o n s t a n t f o r a long p e r i o d a l t h o u g h q u i n o n e c o n c e n t r a t i o n n o t i c e a b l y decreases d u r i n g this p e r i o d o f time (Fig. 1). This is evidence o f the fact t h a t b o t h q u i n o n e s a n d their p r o d u c t s o f t r a n s f o r m a t i o n have an inhibiting effect. A c c o r d i n g to results in the literature, chain t e r m i n a t i o n over q u i n o n e s takes place by r e a c t i o n with alkyl radicals [14, 15]. Cases are k n o w n , when p e r o x i d e radicals also react with q u i n o n e s [16]. I n the general case the system o f o x i d a t i o n inhibited with q u i n o n e s takes the form: BP

or

P O O H L~ p"

P ' + 0 2 ~ PO~ P 0 2 + P H -~ P O O H + P"

Multiple chain termination by binuclear quinones in oxidized PP

1967

PO2 + P O 2 -~ products PO2 + Q -~ products

k'7

P" + Q ~ products It follows from the scheme that

F= vi (1 v2 v

(4)

-- 7 ) = (G + D) [ Q ] ,

where G = k2 [PH---~ '

D = kl ?Po2

v = v0

when

[Q] = 0"

y is the proportionality factor between oxygen pressure in the gaseous phase (Po=) and its concentration in the solid polymer. In Figs• 2 and 3 coordinates of equation (4) show dependences of the rate of oxidation v of solid PP, initiated with BP and POOH groups, on the concentration of quinone 1V and V. It can be seen that F shows a linear dependence on quinone concentration F

F

0.8

-

-2

F

- ~ I0 3

/+

-1.

COJ.~o 4

14

3

/ 10

2

0"I

0

FIG. 3

8

2

q

6

(Vpo ), lo' (k

-'

FIG. 4

FIG. 3. Dependence of F on the concentration of quinone V according to formula (4) for solid PP at 366°K. Initiation with BP (1), (vl=2"8x 10 -6 mole/kg.sec), P O O H groups (2) ( v i = 3 " 9 x l 0 -6 mole/kg.sec) and joint initiation with BP and P O O H groups (3) (vl = 3'5 x 10-6 mole/kg.sec). H y d r o peroxide groups were previously broken down, initiation took place with BP (4) (v~=2.8 x 10 -6` mole/kg-sec). FiG. 4. Dependence of F/[Q] on l/Po, using formula (4) for solid PP. Light points show initiation~ with BP (v1=2"8 x 10 -6 mole/kg-sec) in the presence of 1.3 x 10 -3 mole/kg quinone IV (1) and 5-3 x x 10 -3 mole/kg quinone V (2), dark points show initiation with hydroperoxide groups of oxidized ]PP (v1=2.5 x 10 -6 mole/kg.sec) in the presence of 2'4 x 10 -4 mole/kg quinone IV (3)and (v~= 3.9 x x 10 -6 mole/kg'sec) in the presence of 1"1 x 10 -a mole/kg quinone V (4).

1968

Yu. B. SHILOV and YE. T. DEmSov

therefore, quinones inhibit oxidation causing chain termination. It is very interesting that the inhibiting action of quinones increases sharply in oxidized PP which contains hydroperoxide groups. A study of the dependence of v on Po2 shows that chain termination takes place both by reaction with alkyl and peroxide macroradicals, whereby in oxidized PP containing POOH groups both reactions are intensified (Fig. 4). For a process initiated with POOH groups the ratio of constantsfk'~/kiy is 22,500 kg.kPa/mole for quinone IV and of constants fkT/k2 [PH]=200 kg/mole, while for quinone V it is 6500 kg.kPa/mole and 40 kg/mole, respectively. For a process initiated by BP, for quinone IV fk'7/kl 7 = 3100 kg. kPa/mole, fkT/k2 [PH] ~-20 kg/mole, for quJnone V it is 600 kg. kPa/mole and ~- 15 kg/mole, respectively. To explain, whether this increase in the effectiveness of quinones is only due to hydroperoxide groups or to the presence of other groups accumulated in PP during oxidation, hydroperoxide groups of oxidized PP (0"33 mole/kg) were broken down by treatment with an alcoholic solution of KI and experiments carried out of oxidation of this PP with a BP initiator and quinone V. Experiments show that oxidation of such a PP sample is inhibited with quinone V even slightly less strongly than that of unoxidized PP. Therefore, an increase in the inhibiting effect of quinones is due to hydroperoxide groups. Stoichiometry of chain termination was studied using quinone IV, the consumption of which was observed spectrophotometrically. Without initiating additives (BP and POOH groups) this quinone introduced into PP in a concentration of 1.4 x 10 - 3 mole/kg, in 8 hr at 366 K in inert atmosphere is not used up in practice. In the presence of BP or POOH groups the rate of consumption of quinone IV shows a linear increase with an increase of its concentration in the polymer. The equation of the rate of consumption of quinone IV takes the form

vx=v° +kx [Q] EP-I,

(5)

where P is BP or POOH, v° corresponds to the rate of consumption of quinone IV by reaction with free radicals. The rate constant kx= 1.1 × 10 -4 kg/mole.sec for POOH groups and 1.7x 10-s kglmole.sec for BP. Inhibition with stilbenequinone of the formation of active peroxides during autooxidation of oct-2-ene has been noted previously [17]. In oxidized PP with [POOH]o = 0"127 mole/kg (vi = 1.3 x 10-6 mole[kg, sec) v0x = 6 x 10 -s mole/kg.sec and f=vilv°=20. In the presence of BP (0.062 mole/kg, vi =2.8 x 10 -6 mole/kg-sec) Vx=°5 × 10 -7 mole/kg.sec andf'-~5. It follows from a comparison of the results that in oxidized PP one molecule of quinone IV introduced terminates up to 20 chains, whereas without POOH groups it terminates ~-5 chains. We evaluate f by experiments of oxidation of PP. When introducing 4 x 10 -4 mole/kg quinone IV into oxidized PP (vi =2.5 x 10 - 6 mole/kg.sec) oxidation is inhibited for ~ 80 min (Fig. 1, straight line 2), while the rate of O2 absorption during this time does not show any signs of increasing. The proportion of linear chain termination on the inhibitor is ---0.8. Evaluation o f f from formula (2) gives f'~24, which is in agreement with f = 2 0 , calculated from the rate of consumption of quinone IV.

Multiple chain termination by binuclear quinones in oxidized PP INHIBITION WITH PHENOLS AND QUINONES OF INITIATED OXIDATION O]F L D P E

1969

AND P P IN T H E

SOLID PHASEAT 366°K ANt) WITH Po,= 100 kPa (kl (BP in LDPE)= 5"4 x 10- s sec- l, k, (BP in PP) = 4"5 x 10- 5 sec- '. In LDPE [POOH] ---0"053 mole/ ,/ks, in PP [POOHI=0"31 mole/kg, concentration of cumyl hydroperoxide being 0-057 mole/ks) Vl X 106,

Polymer

Initiator

mole/kg"

Inhibitor

"see

LDPE

PP

BP BP BP POOH BP + POOH BP + POOH BP BP BP BP BP BP + POOH POOH POOH POOH* POOH* BP + C H t BP + CH

2-8 2"8 2-8 2.8 3"0 3"0 2"8 2"8 2"8 3'2 3"2 3"4 3-1 3-1 3"1 3.1 2"8 2.8

[InH]o x x 10a, mole/kg"

v , × l 0 s,

r x 10 -3 mole/kg.

-

I I

2"7 5"6

2"5 4"8

I

5"4 3"8 3"7

III

5"6 5"6 2"7+2"9 5"6

IV IV

1'3 1"3

II II II

0"23

II

2.6

II I+II

0-23

f

V/v°

2'6 2'4

0"61 0.23

2.9 1-8 1"3

0-43 0.53 0"34 1-0

"see

"sec

F

1"3 0'8 0-3 0"3 1"6 0"7 0.7 0'45 1.30 1 "30

I-

2'4 2"7 2"1

1.1 1"0 2"8 1.3 2'0 0.8 1.8 1.35

-

0.85 0.77 33

0"46

36

0"40

2.2

7.75

* p o t = 33 kPa. t Cumyl hydroperoxide. : v in the p r ~ n c ¢ o f phenols I and II is shown after an induction period ~.

F o r c o m p a r i s o n , similar experirrkents were c a r r i e d o u t with o x i d i z e d L D P E c o n l a i n i n g h y d r o p e r o x i d e g r o u p s ( [ P O O H ] = 0 - 0 5 3 moletkg). Results are t a b u l a t e d . I t c a n b e seen t h a t the presence o f the P O O H g r o u p in o x i d i z e d L D P E has p r a c t i c a l l y n o ,effect either on t h e ' i n c r e a s e o f coefficient f f o r p h e n o l s I a n d II, o r on the intensification o f a n t i o x i d i z i n g activity o f q u i n o n e s I I I a n d IV. I n this o x i d a t i o n L D P E differs f r o m o x i d a t i o n o f PP. D u r i n g o x i d a t i o n o f L D P E s e p a r a t e h y d r o p e r o x i d e g r o u p s a r e f o r m e d , while in PP they are m a i n l y f o r m e d as blocks. T o e x p l a i n the role o f b l o c k h y d r o p e r o x i d e g r o u p s in increasing f for quinones, similar e x p e r i m e n t s were c a r r i e d o u t with PP, which was o x i d i z e d in c u m e n e a n d c o n t a i n e d s e p a r a t e h y d r o p e r o x i d e g r o u p s . A t 366°K the rate o f o x i d a t i o n o f P P c o n t a i n i n g 0.206 m o l e / k g s e p a r a t e h y d r o p e r o x i d e g r o u p s is 4 . 0 × 10 - 6 m o l e / k g . s e c . The v i v a l u e c a l c u l a t e d f r o m the r a t e o f o x i d a t i o n is 6 . 0 x 10 - 8 m o l e / k g . s e c . W i t h a given c o n c e n t r a t i o n o f h y d r o p e r o x i d e g r o u p s the initial rate o f c o n s u m p t i o n o f q u i n o n e IV is v~= 5 x 10 - s m o l e / k g . s e c ( F i g . 5). T h e r a t e o f c o n s u m p t i o n o f q u i n o n e IV b y the r e a c t i o n with r a d i c a l s vox w a s e v a l u a t e d f r o m the difference between the overall r a t e o f c o n s u m p t i o n o f q u i n o n e I V

Yu. B. SHILOVand YE. T. DENIsov

1970

0 and the rate of its consumption by the reaction with hydroperoxide groups: v~=v,~ - k ~ [Q] [POOH]. When [Q]= 1.6× 10 -3 mole/kg and [POOH]=0.206 mole/kg v~~ - 1 - 4 × 10 - s mole/kg.sec, which corresponds to f - - 4 . Experiments of oxidation of P P

[02], Io~,nole/kg

5!

a

I [Ql"lO~m°le/k~b

8

I

20

60

I00

T/me,rain

8O0

500

FiG. 5. Kinetics of 02 absorption by PP in the presence of BP (vj=2"8 × 10-6 mole/kg'sec) and separate POOH groups (0-206 mole/kg) without quinone (1) and in the presence of 5-1 x 10-3 mole/kg. quinone IV (2) (a) and kinetics of consumption of quinone IV in PP containing 0-206 mole/kg separate POOH groups, without BP initiator (b). with [POOH]=0.206 mole/kg were also carried out in the presence of a BP initiator with vi = 2 . 8 x 10 -6 mole/kg.sec. As shown by Fig. 5, quinone IV in a concentration of 5.1 x 10-a mole/kg restrains initiated oxidation of PP for ~ 30 rain, which corresponds to f = 1; the rate of 02 absorption then increases to a value which is typical of" uninhibited oxidation. Therefore, it is precisely the structure of polymeric hydroperoxide groups which determines the inhibiting effect of quinones; binuclear quinones~ in the presence of block hydroperoxide groups acquire the ability to undergo repeated chain termination, this procoss taking place more vigorously. This is probably caused by the ability of fl-hydroperoxide radicals to undergo a recurrent cycle of reactions. with binuclear quinones and phenoxyl radicals formed from them, which results in repeated chain termination. This mechanism is, evidently, responsible for repeated: chain termination in PP oxidized when introducing binuclear quinones.

Translated by E. SEMERE REFERENCES

1. Yu. B. SI-I~OV and Ye. T. DENISOV, Vysokomol. soyed. A24: 837, 1982 (Translated in, Polymer Sci. U.S.S.R. 24: 4, 938, 1982) 2. I. I. LEVANTOVSKAYA, V. Y. GUR'YANOVA, B. M. KOVARSKAYA and I. Ya. SLONIM~ Vysokomol. soyed. All: 1043, 1969 (Translated in Polymer Sci. U.S.S.R. 11: 5, 1180, 1969), 3. K.I. IVANOV, T. N. KULIKOVSKAYA, V. K. SAVINOVA, Ye. S. PANFILOVA, V. P. SHAKHOVSKAYA and M. G. SEMENOV, Dokl. AN SSSR 205: 851, 1972

Generalized dependences of viscosity of dilute polymer solutions

197t

4. L. T A I M R , H. P I V C O V A and J. P O S P I S I L , Collect. Czechosl. Chem. Communs 3 7 : 1 9 1 2 1972 5. L B U B E N a n d J. P O S P I S I L , Collect. Czechosl. Chem. Communs 40: 987, 1975 6. L. P. Z A I C H E N K O , L. V. N O V O S E D O V A , V. G. BABEL' and V. A. P R O S K U R Y A K O V , Zh. prikl, khimii 18: 261, 1971 7. C. D. COOK, J. Organ. Chem. 18: 261, 1953 8. L. L. YASINA, B. A. G R O M O V , V. B. M I L L E R and Yu. A. SI-ILYAPNIKOV, Vysokomol. soyed. A8:141 l, 1966 (Translated in Polymer Sci. U.S.S.R. 8: 8, 1553, 1966) 9. N. V. Z O L O T O V A and E. T. D E N I S O V , J. Polymer Sci. A-l, 9: 3311, 1971 10. V. F. T S E P A L O V and V. Ya. S H L Y A P I N T O K H , Dokl. A N SSSR 124: 883, 1959 11. G. M. C O P P I N G E R , J. Amer. Chem. Soc. 20: 501, 1957 12. M. S. K H A R A S C H a n d B. S. J O S H I , J. Organ. Chem. 22: 1435, 1957 13. C. D. COOK, N. G. N A S H a n d H. R. FLANAGAN, J. Amer. Chem. Soc. 77: 1783, 1955 14. N. M. E M A N U E L ' , Ye. T. D E N I S O V a n d Z. K. M A I Z U S , Tsepnyye reaktsii okisleniya uglevodorodov v zhidkoi raze, Nauka, Moscow, 1965 15. Yu. B. S I - I ~ O V and Ye. T. D E N I S O V , Vysokomol. soyed. A16: 1736, 1974 (Translated in Polymer Sci. U.S.S.R. 16: 8, 2009, 1974) 16. Ye. T. D E N I S O V , Izv. A N SSSR, Ser. khim., 2, 328, 1969 17. S. A. S U B B O T I N , S. K. Z Y K O V A and B. V. STOLYAROV, Zh. prikl, khimii 36: 875, 1963

Polymer Science U.S.S.R. Vol. 26, 3No.8, pp. 1971-1979, 1984 Printed in Poland

0032-3950/84 $10.00+ .00 1985 Pergamon l~'ess Ltd.

ANALYSIS OF GENERALIZED D E P E N D E N C E S OF THE VISCOSITY OF DILUTE POLYMER SOLUTIONS*

T. A . ROVEN'KOVA, M . P. BABUSHKINA, A . I. KORETSKAYA, I. A . GORCHAKOVA a n d G . I. KUDRYAVTSEV Scientific Industrial Association " K h i m v o l o k n o "

(Received 21 March 1983)

Methods and a set of computer programs were developed, in order to identify and discriminate between models describing the concentration dependence of viscosity. The difference was established between competing models for specific systems: poly-p-phenylene terephthalamide-sulphuric acid (96.3 a n d 99-3~). Most reliable results of predictions were obtained using the Martin formula and the Budtov model. Constants of these models were evaluated. These formulae may be mutually transformed by functional expansion, correct up to high orders of magnitude. * Vysokomol. soyed. A26: No. 8, 1759-1765, 1984.