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The crosslinking of the fluorine rubber SKF-26 by phosphorus containing hydroquinone derivatives
0032-3950/79]1201-2991507.5010
]Polymer Science U.S.S.R. Vol. 21, pp. 2991-2996.
() Pergamon Press Ltd. 1980. Printed in Poland
THE CROSSLINKING OF THE FLUORINE RUBBER SKF-26 BY PHOSPHORUS CONTAINING HYDROQUINONE DERIVATIVES* L. P. KARASEV,V. 1). ]~UKALOV,A. I. VAn'D~AS, E. YE. NIFANT'EVa~d A. P . TUSEYEV All-Union Research and Engineering Technology Institute of the Rubber Industry (Received 18 October 1978) The fluorine rubber SKF-26 has been found to react with a bis-phosphorylatod hydroquinone derivative, giving vulcanizates with valuable properties. The crosslinking is the result of phosphito alkylations by the SKF-26 and the formation of P - - C bonds by the Arbuzov mechanism. The thermal-oxidative degradation of the crosslinked structures was studied by the continuous, high temperature chemical relaxation method.
THE available crosslinking methods for fluorine rubbers, SKF-26 amongst them, are still not good enough to satisfy the demand for rubbers capable of resisting high temperatures, strongly aggressive media, and other factors. The use of some phosphorous acid derivatives opens up further means of improving the properties of suck rubbers [1, 2]. The crosslinking of SKF-26 with nuclcophilic reagents, e.g. amines, diols and ditkiols [3], gives rise to a system which has the properties of alkyl halides with reactive F atoms on the tert. 0 atoms; these are linked with the electronegative CF 3 radicals while the bond present (C--F) is weakened by conjugation in the allyl fragments forming during the dehydrofluorination of the rubber. SKF-26 rubber is modified by reactions with phospkites, like the fluorinated. olefines [4]; pseudo-pkosphonium t~rpe units form "appendages", or fragments of alkylphosphinie acid derivatives. The use of compounds with two or more reactive centres will give rise to the crosslinked structure present in vulcanizates. We are examining the crosslinking properties of P containing amidates and esters of hydroquinone of the general formula
R,P--0--~/~O--PR~, in which I%=--N(C21-15)2 (I), --OCdI-I9 (II), --OCeI-I 5 (III)
in this study. The results showed these compounds to be crosslinking agents for SKF-26 and to yield rubbers with stable crosslin~ages and mechanical properties depending on the chemical composition of the agents used and on the curing conditions. * Vysokomol. soyed. A21: No. 12, 2708-2712, 1979. 2991
L. P. KARASEVet al.
2992
The SKF-26 crosslinked with amidophosphite I can be regarded as due to a n alkylation on the phosphorus and the formation of a pseudophosphonium complex which will react with water; an alkyl phosphonate is produced as a result of the reaction of metal oxides, liberated b y the dehydrofluorination of the rubber, with H F or by desorption from the additives when the diethylamine is cleaved off NEt2 NEt, {+ j = ~ {+ 2~,o 2 R u b b e r - { - I -+ { R u b b e r - - P |
--0
~__~--O--P|
--Rubber}
2F-
--2HF'HNEt,
l~Et, l~Et, O o II ~ II -~ Rubber --P--O ~ - ~ - - O - - P - Rubber
:NEt, NEt, The spectralresultsconfirmed the suggested reaction scheme. The IR spectrum of the rubber film heated during curing with product I was found to contain the following absorption lines: 1470 and 1505 (phenylene), 1200 (P--O--aryl), 1245 (P=O), 1225 (C--F), 3340 cm -I (NH). The change of the phosphorus to the pentavalent state was also established by analysis and by the N M R method in a model reaction of S}(F-26 with the bis-diethylamide of phenylphosphorous acid, CsHsOP[N(C2Hs)~]~ (IV), for which the ~qMR signal s1Pg~131 mag.div, is. typical [~]. The SKF-26+compound IV reaction product gave rise to a new signal, i.e. J--23.5 mag.div., for the pentacovalent phosphorus. TABLE 1. THE CROSSLINKING PROPERTIES OF P-CONTAINING HYDROQUINONE DERIVATIVES
Physico-cheraical properties Compound n~
I II
1.5115 1.4809
dl °
0.998 1.024
Mechanical properties of unfilled vulcanizates* curing under pressure (150°, 60 rain) 1/Q
O'f
0'19 0"17
9.5 8"5
Lrel
250 3"i0
heating (200°C/24 hr) 1/Q
[ Lresid.
af
0"45 14.5 O.3O 12.0
8 15
Lrel I lresta.
°°13
180
7
* 1]Q--crosslinking density assessed as the inverse swelling value in acetone; at-fracturing stress, MPa; L,~, and L~--ralative and residual % elongation.
The results of I R spectral and GLC analysis show the SKF-26 crosslinking with phosphite I I to have the mechanism of the Arbuzov reaction: O--C]H8 O--CdH, +J / = \ I 2 Rubber--F+II
CRabber-- r - - O -
I
O--CdH~
Rubbor
OCdH,
O O H / ~ , U R u b b e r - - P - - O - - ~ / _ ~ O - - P - - Rubber -[-2C,H.--F /
O--C,H,
- -
|
O--C,H,
2F-
Crosslinlfing of fluorine rubber SKF-26
2993:
The I R spectrum of the crosslinked (SK'F-26q-phosphite II) film contained the following absorption lines: 1470 and 1505 (phenylene), 1035 ( P - - O - - a l k y l ) , 1205 (P-- O--aryl), 1225 and 1395 cm -1 (C--F and C - - H bonds of the rubber). The gases liberated b y the vulcanizate were found to contain butyl fluoride ( A K t t M r 8MD chromatograph with a 3 × 3 mm column, 5 A molecular sieves as adsorbent, helium as inert carrier gas and 50 1./rain flow rate, 50°C, 195 sec passage). The phosphite I I I which reacts with alkyl iodides at 130°C [6] will react with SKF-26 to a phosphonium type compound only after prolonged t~eating above 220°C. The use of compounds I and II (1.5 × 10 -a g-mole/100 g rubber) yielded r u b b e r s with fairly good mechanical properties after a two-stage curing (Table 1). The crosslinking density varied; it was best where diethylamine was liberated in t h e SK_F-26 reaction with the amidophosphite I because of the additional crosslinking b y the diethylamine. M
!
#F
0.8
#
3
4
2 -/11/ ,
0"6
20
Time, day~ "FZG. 1
#0"
I
i
i
I0
t
1
t
20 T/me, rain
I
30
I
I
qo
FzG. 2
TrG. 1. The steric network density changes in vulcanizates based on SKF-26 while swelling
in 57~o nitric acid: /--with product I; 2--product II; Q0-initial swelling of vulcanizate in acetone, ~o; Q~-after soaking in nitric acid, washing with water and drying, %. FIG. 2. The kinetic curves of the SKF-26 curing with phosphitc II (continuous lines) anti after an accelerator addition (dashes) at temperatures of (°C): 1--150; 2--160; 3--170; 4-- 180. M-- torsion moment. The chemical stability of the crosslinkages present in the rubber was t e s t e d b y exposing it to the action of concentrated nitric acid [7] which is known not t o affect the molecular chains of the polymer b u t the C - - N and C = N bonds present in amine type vulcanizates. The amount of fractured crosslinkages was f o u n d to vary (Fig. 1). The use of the phosphite II as crosslinking agent gave the bes~ chemical resistance to nitric acid, which equalled that of the peroxide vulcanizates [7]. The amidophosphite I gave less chemically stable vulcanizates. The deeom~ position factors correlated with those of the physico-mechanical properties.
2994
L. P. KA~ASEV et al.
The crosslinking kinetics of SKF-26 were studied on product II with and without the addition of 2-methyl-5-ethylpyridinium methyl sulphate as curing accelerator (0.5 x 10 -5 g-mole/100g rubber). The processing of the kinetic curves reproduced in Fig. 2 on a "Monsanto" rheometer [8] showed the ascending branches o f the curves to be approximated by an exponential function, and that the curing is a reaction of pseudo-first order with an induction period which became shorter on raising the temperature. The activation parameters of crosslinking were got from the Arrhenius equation and the theory of absolute reaction rates. The true activation energy Eact=16.gkcal/mole, the pre-exponential factor 4og A =5.50 (sec-~), the entropy of activation A S # = - 35.4 energy units and the free activation energy AG#= 26.4 kcal/mole for mixtures not containing the accelerator. The respective values with an accelerator present were: 11.3 kcal/mole, 3.0 sec -1, --46.8 energy units, and 24-7 kcal/mole. These values show crosslinking to be easier in the presence of an accelerator, i.e. a quaternary ammonium compound. Its most probable effect is an acceleration of the dehydrofluorination and the consequent larger amount of allyl fluoride fragments which have better alkylating properties than the CF3--C--F chain unit. I T A B L E 2. T H E KINETICS AND ACTIVATION PARAMETERS OF THE CHEMICAL STRESS RELAXATION AFTER A 50~O STRETCHING OF TJNFILLED S K F - 2 6 BASED VULCAI~IZATES 210 °
Main process
I~+lk.lO,
230 °
250 °
270 °
vl~¢lklo,
~ la~l+.lO,
v;4+[+.1o,
Eaet
log~ - ~ s ¢ I Ag~
Vulcanizates with amidophosphite 1"
0.5 0.14i 141 0"12 I 13~ 0"32[ • 8.5 0.3o 50 0'28 0"08 32 0.32 96 0"28 0"01 65 0.24
17.6 I 0.2 0.15r 22.0 1.241 5"51°"331 2.45
0.110.15 I 30"2
I 7"21 0'37
1.510.34 l 5.55120 51 5.01
0"23;10 0"31[ 0'68 5"5 0"31[ 1"70 26'01 6"72 0"02 [ 23"5 0"21 0"03 15 0'21[ 0.07 30.5i 7.+4
58-8 I 24"1 37"7 31'1 30"0 34"3 28'1 38"3
Vulcanlzates with phosphite I I
1"3[ 0'14 [ 10.6 r o.oIolol 1~.1 0.3 0.17 18.6 0.210.18 I 23.4 16.01 0.1~ 10 10.24/ 0"37 t 12 [0'22[ 0"85 7"5 0"26 1 " 4 1 2'11 0"28] 3.03110.51 4.40 08 0.31 0-04 39 10,291 015 20 1020l 0.27 12 /026 0.7027.2 ~;8oO 110
0.31
0.01 65
0'33
0"02 27
0'31[
0"27 10 /0'29
0'22 31"2
•
59"8 I 24"1 40"4 30"9 29"4 2414
35"4 37"9
* v-relaxation time, hr, Aa-proportion of initial stress loss, k-reaction rate constant, sec-1; see text for the dlInension of the activation parameters.
One of the thermal stability indicators of fluoride rubbers is their resistance to thermal-oxidative degradation under conditions of high temperature chemical stress relaxation. The thermal-oxidative degradation in air is primarily due to t h e fracture of the crosslinking joints, and secondarily to the main chain decomposition in the dehydrofluorinated polymer [9]. The type of the crosslinkages present between SKF-26 and the various agents varied so that it was interesting to find out the type and rate of their degradation and to establish the temperatare range for the practical uses of the vuleanizates.
Crosslinking of fluorine rubber SKF-26
2995
The thermal-oxidative ageing parameters were tested in the 21()-270°C range a n d the results established on the basis of the continuous chemical stress relaxation during a 50~o elongation. These functions were non-exponential and the relaxation curves were therefore processed by the Bryukhanov-Tobolsky m e t h o d [10]. Each of the found elementary acts had the kinetic and activation parameters listed in Table 2. The degradation analysis showed 4 stages, ° f w h i c h the first is short and most rapid; it has a small Eact and the most suitable AS s and seems to be linked with the fractures of intermolecular ionic and hydrogen bonds. The Eact of the second stage is similar to t h a t of the thermal-oxidative degradation of unsaturated rubbers (~21 kcal/mole) [11]. This stage is most probably t h a t in which the grafts of carbon-chain systems to the fluorine rubber are destroyed. The third and fourth stages 1}ave differing rates and the largest Eact; here the network joints and the main chains of the polymer are evidently fractured. The Eact values were similar to those of the pyrolysis of fluorinated elastomers ( ~ 30 kcal/mole) [12]. The ziG* a n d the log A increase in the post-stage relaxation; there is a compensating linear correlation between Eact and log A. The isolated Eact level agreed well with those given by Kuz'minskii and co-workers [9]. One gathers from the examined parameters and the consideration of the post-stage rate and total chemical relaxation times t h a t the rubbers cured with phosphite I I have the best thermal stability. The use of the continuous chemical relaxation method thus permits an objective assessment of the thermal stability of steric structures consisting of various t y p e of crosslinkages and shows the possibility of making good practical use of the curing procedures developed with new curing agents.
Translated by K. A. ALr~E~ REFERENCES
1. Russian Authors' Certificate 438661, 1973; Byull. Izobrct., No. 29, 1974 2. Russian Authors' Certificate 537095, 1975; Byull. Izobret., lqo. 44, 1976 3. F. A. GALIL-OGLY,A. S. NOVIKOV and Z. N. NUDEL'MAN, Ftorkauchuki i reziny na ikh osnove (Fluorine Rubbers and Resins Based on Them). Izd. "Khimiya", 1966 4. I. L. KNUNYANTS, V. V. TYULENEVA, Ye. Ya. PERVOVA and R. N. STERLIN, Izv. Akad. Nauk SSSR, Seriya khim., 1797, 1964 5. Yu. Yu. SAMITOV and T. V. ZYKOVA, V. Sb.: Khimiya i primenenie fosfororganicheskikh soedinenii (In: The Chemistry and Uses of Organic Phosphates). p. 49, Izd. "Nauka", 1972 ~. N. A. MUKMENEVA, P. A. KIRPICHNIKOV and A, N. PUDOVIK, Zhur. Obsh. Khim. 33: 3192, 1963 7. N. S. GILINSKAYA,F. A. GALIL-OGLY,G. A. GUBAI and S. A. NOVIKOV, Kauehuk i Rezina, No. 12, 7, 1964 8. S. M. MARKOV, A. M. POLEKHIN, N. A. LOSHADKIN, G. A. KOSTENKO, et al.,
Zhur. Obsh. Khim. 36: 1098, 1966 9. F. A. MAKHLIS, L. Ya. NIKITIN, A. S. KUZ'MINSKII and A. B. KRYUKOVA, Vysokomol, soyed. A18: 101, 1976 (Translated in Polymer Sci. U.S.S.R. 18: l, 118, 1976)
10. G. M. BARTENEV, Relaksatsionnye yavleniya v polimerakh (Relaxation Phenomena in Polymers). p. 249, Izd. "Khimiya", 1972
T. M. TffSHAXOVAet aL
2996
11. A. S. KUZ'MINSKII, L. I. LYUBCHANSKAYA, L. G. ANGERT and G. K. MIKHAILOV, V sb.: Dostizheniya nauki i tekhnologii v oblasti reziny (In: The Scientific and Technical Achievements in the Field of Resins). p. 96, Izd. " K h i m i y a " , 1969 12. G. G. DEGTEYA and A. S. KUZ'MINSKII, V sb.: Khimicheskie svoistva i modifikatsiys, polimerov (In: The Chemical Properties and the Modification of Polymers). p. 110, Izd. " N a u k a " , 1964
Polymer
0032-3950/79/1201-2996507.50]@
Science U.S.S.R. Vol. 21, pp. 2996-3001. Pergamon Press Ltd. 1980. Printed in Poland
POLYALKYL ALUMOXANES AND THEIR USES AS VANADIUM CATALYST CARRIERS FOR OLEFIN POLYMERIZATIONS * T. M. USI-IAXOVA,I. L. DUBNIKOVA, I. l~. MESH:KOVA, L. N. BAsPoPov, YU. L. LELYUKITLNA, S. L. GERSHKOKHEIV, i~{.N. KORIVEYEV and F. S. D'YACHKOVSKII Chemical Physics Institute,U.S.S.R. Academy of Sciences (Received 21 September 1978) /
Carrier catalysts have been produced b y the reactions of v a n a d i u m oxytrichloride (VOC18) with polyalkyl alumoxanes (PAAO). The kinetics of the ethylene polymerization on the carrier catalysts have been compared with those over the system VOC18-A1Et~C1. The reactive form of v a n a d i u m is stabilized on the surface of the organic aluminium compound; a n y change of the carrier t y p e affects the properties of the[polymerization products.
ZI~,GLER catalysts with improved activities can be prcduced by increasing the efficiency of the transition metal deposition on the carrier smface. The polyalkyl alumoxanes (PAAO) having a 2-5 m~/g specific surface and reactive alkyI groups are used as carriers for the ethylene polymerization catalysts [1, 2]. This work is dedicated to the kinetics of the ethylene polymerization over vanadium carrier catalysts, the comparison of the process kinetics on these with those over the two component VOC13-A1Et~C1 catalytic system, and to the study of the part played by the organo-metallic carrier. EXPERIMENTAL
The characteristics of the reagents (VOC18, alkylaluminium chlorides, ethylene, n-heptane) are those described b y Meshkova and co-workers [3]. Those of the PAAO used a~ carriers are listed in Table 1. * Vysokomol. soyed. A21: :No. 12, 2713-2718, 1979.
]Polymer Science U.S.S.R. Vol. 21, pp. 2991-2996.
() Pergamon Press Ltd. 1980. Printed in Poland
THE CROSSLINKING OF THE FLUORINE RUBBER SKF-26 BY PHOSPHORUS CONTAINING HYDROQUINONE DERIVATIVES* L. P. KARASEV,V. 1). ]~UKALOV,A. I. VAn'D~AS, E. YE. NIFANT'EVa~d A. P . TUSEYEV All-Union Research and Engineering Technology Institute of the Rubber Industry (Received 18 October 1978) The fluorine rubber SKF-26 has been found to react with a bis-phosphorylatod hydroquinone derivative, giving vulcanizates with valuable properties. The crosslinking is the result of phosphito alkylations by the SKF-26 and the formation of P - - C bonds by the Arbuzov mechanism. The thermal-oxidative degradation of the crosslinked structures was studied by the continuous, high temperature chemical relaxation method.
THE available crosslinking methods for fluorine rubbers, SKF-26 amongst them, are still not good enough to satisfy the demand for rubbers capable of resisting high temperatures, strongly aggressive media, and other factors. The use of some phosphorous acid derivatives opens up further means of improving the properties of suck rubbers [1, 2]. The crosslinking of SKF-26 with nuclcophilic reagents, e.g. amines, diols and ditkiols [3], gives rise to a system which has the properties of alkyl halides with reactive F atoms on the tert. 0 atoms; these are linked with the electronegative CF 3 radicals while the bond present (C--F) is weakened by conjugation in the allyl fragments forming during the dehydrofluorination of the rubber. SKF-26 rubber is modified by reactions with phospkites, like the fluorinated. olefines [4]; pseudo-pkosphonium t~rpe units form "appendages", or fragments of alkylphosphinie acid derivatives. The use of compounds with two or more reactive centres will give rise to the crosslinked structure present in vulcanizates. We are examining the crosslinking properties of P containing amidates and esters of hydroquinone of the general formula
R,P--0--~/~O--PR~, in which I%=--N(C21-15)2 (I), --OCdI-I9 (II), --OCeI-I 5 (III)
in this study. The results showed these compounds to be crosslinking agents for SKF-26 and to yield rubbers with stable crosslin~ages and mechanical properties depending on the chemical composition of the agents used and on the curing conditions. * Vysokomol. soyed. A21: No. 12, 2708-2712, 1979. 2991
L. P. KARASEVet al.
2992
The SKF-26 crosslinked with amidophosphite I can be regarded as due to a n alkylation on the phosphorus and the formation of a pseudophosphonium complex which will react with water; an alkyl phosphonate is produced as a result of the reaction of metal oxides, liberated b y the dehydrofluorination of the rubber, with H F or by desorption from the additives when the diethylamine is cleaved off NEt2 NEt, {+ j = ~ {+ 2~,o 2 R u b b e r - { - I -+ { R u b b e r - - P |
--0
~__~--O--P|
--Rubber}
2F-
--2HF'HNEt,
l~Et, l~Et, O o II ~ II -~ Rubber --P--O ~ - ~ - - O - - P - Rubber
:NEt, NEt, The spectralresultsconfirmed the suggested reaction scheme. The IR spectrum of the rubber film heated during curing with product I was found to contain the following absorption lines: 1470 and 1505 (phenylene), 1200 (P--O--aryl), 1245 (P=O), 1225 (C--F), 3340 cm -I (NH). The change of the phosphorus to the pentavalent state was also established by analysis and by the N M R method in a model reaction of S}(F-26 with the bis-diethylamide of phenylphosphorous acid, CsHsOP[N(C2Hs)~]~ (IV), for which the ~qMR signal s1Pg~131 mag.div, is. typical [~]. The SKF-26+compound IV reaction product gave rise to a new signal, i.e. J--23.5 mag.div., for the pentacovalent phosphorus. TABLE 1. THE CROSSLINKING PROPERTIES OF P-CONTAINING HYDROQUINONE DERIVATIVES
Physico-cheraical properties Compound n~
I II
1.5115 1.4809
dl °
0.998 1.024
Mechanical properties of unfilled vulcanizates* curing under pressure (150°, 60 rain) 1/Q
O'f
0'19 0"17
9.5 8"5
Lrel
250 3"i0
heating (200°C/24 hr) 1/Q
[ Lresid.
af
0"45 14.5 O.3O 12.0
8 15
Lrel I lresta.
°°13
180
7
* 1]Q--crosslinking density assessed as the inverse swelling value in acetone; at-fracturing stress, MPa; L,~, and L~--ralative and residual % elongation.
The results of I R spectral and GLC analysis show the SKF-26 crosslinking with phosphite I I to have the mechanism of the Arbuzov reaction: O--C]H8 O--CdH, +J / = \ I 2 Rubber--F+II
CRabber-- r - - O -
I
O--CdH~
Rubbor
OCdH,
O O H / ~ , U R u b b e r - - P - - O - - ~ / _ ~ O - - P - - Rubber -[-2C,H.--F /
O--C,H,
- -
|
O--C,H,
2F-
Crosslinlfing of fluorine rubber SKF-26
2993:
The I R spectrum of the crosslinked (SK'F-26q-phosphite II) film contained the following absorption lines: 1470 and 1505 (phenylene), 1035 ( P - - O - - a l k y l ) , 1205 (P-- O--aryl), 1225 and 1395 cm -1 (C--F and C - - H bonds of the rubber). The gases liberated b y the vulcanizate were found to contain butyl fluoride ( A K t t M r 8MD chromatograph with a 3 × 3 mm column, 5 A molecular sieves as adsorbent, helium as inert carrier gas and 50 1./rain flow rate, 50°C, 195 sec passage). The phosphite I I I which reacts with alkyl iodides at 130°C [6] will react with SKF-26 to a phosphonium type compound only after prolonged t~eating above 220°C. The use of compounds I and II (1.5 × 10 -a g-mole/100 g rubber) yielded r u b b e r s with fairly good mechanical properties after a two-stage curing (Table 1). The crosslinking density varied; it was best where diethylamine was liberated in t h e SK_F-26 reaction with the amidophosphite I because of the additional crosslinking b y the diethylamine. M
!
#F
0.8
#
3
4
2 -/11/ ,
0"6
20
Time, day~ "FZG. 1
#0"
I
i
i
I0
t
1
t
20 T/me, rain
I
30
I
I
qo
FzG. 2
TrG. 1. The steric network density changes in vulcanizates based on SKF-26 while swelling
in 57~o nitric acid: /--with product I; 2--product II; Q0-initial swelling of vulcanizate in acetone, ~o; Q~-after soaking in nitric acid, washing with water and drying, %. FIG. 2. The kinetic curves of the SKF-26 curing with phosphitc II (continuous lines) anti after an accelerator addition (dashes) at temperatures of (°C): 1--150; 2--160; 3--170; 4-- 180. M-- torsion moment. The chemical stability of the crosslinkages present in the rubber was t e s t e d b y exposing it to the action of concentrated nitric acid [7] which is known not t o affect the molecular chains of the polymer b u t the C - - N and C = N bonds present in amine type vulcanizates. The amount of fractured crosslinkages was f o u n d to vary (Fig. 1). The use of the phosphite II as crosslinking agent gave the bes~ chemical resistance to nitric acid, which equalled that of the peroxide vulcanizates [7]. The amidophosphite I gave less chemically stable vulcanizates. The deeom~ position factors correlated with those of the physico-mechanical properties.
2994
L. P. KA~ASEV et al.
The crosslinking kinetics of SKF-26 were studied on product II with and without the addition of 2-methyl-5-ethylpyridinium methyl sulphate as curing accelerator (0.5 x 10 -5 g-mole/100g rubber). The processing of the kinetic curves reproduced in Fig. 2 on a "Monsanto" rheometer [8] showed the ascending branches o f the curves to be approximated by an exponential function, and that the curing is a reaction of pseudo-first order with an induction period which became shorter on raising the temperature. The activation parameters of crosslinking were got from the Arrhenius equation and the theory of absolute reaction rates. The true activation energy Eact=16.gkcal/mole, the pre-exponential factor 4og A =5.50 (sec-~), the entropy of activation A S # = - 35.4 energy units and the free activation energy AG#= 26.4 kcal/mole for mixtures not containing the accelerator. The respective values with an accelerator present were: 11.3 kcal/mole, 3.0 sec -1, --46.8 energy units, and 24-7 kcal/mole. These values show crosslinking to be easier in the presence of an accelerator, i.e. a quaternary ammonium compound. Its most probable effect is an acceleration of the dehydrofluorination and the consequent larger amount of allyl fluoride fragments which have better alkylating properties than the CF3--C--F chain unit. I T A B L E 2. T H E KINETICS AND ACTIVATION PARAMETERS OF THE CHEMICAL STRESS RELAXATION AFTER A 50~O STRETCHING OF TJNFILLED S K F - 2 6 BASED VULCAI~IZATES 210 °
Main process
I~+lk.lO,
230 °
250 °
270 °
vl~¢lklo,
~ la~l+.lO,
v;4+[+.1o,
Eaet
log~ - ~ s ¢ I Ag~
Vulcanizates with amidophosphite 1"
0.5 0.14i 141 0"12 I 13~ 0"32[ • 8.5 0.3o 50 0'28 0"08 32 0.32 96 0"28 0"01 65 0.24
17.6 I 0.2 0.15r 22.0 1.241 5"51°"331 2.45
0.110.15 I 30"2
I 7"21 0'37
1.510.34 l 5.55120 51 5.01
0"23;10 0"31[ 0'68 5"5 0"31[ 1"70 26'01 6"72 0"02 [ 23"5 0"21 0"03 15 0'21[ 0.07 30.5i 7.+4
58-8 I 24"1 37"7 31'1 30"0 34"3 28'1 38"3
Vulcanlzates with phosphite I I
1"3[ 0'14 [ 10.6 r o.oIolol 1~.1 0.3 0.17 18.6 0.210.18 I 23.4 16.01 0.1~ 10 10.24/ 0"37 t 12 [0'22[ 0"85 7"5 0"26 1 " 4 1 2'11 0"28] 3.03110.51 4.40 08 0.31 0-04 39 10,291 015 20 1020l 0.27 12 /026 0.7027.2 ~;8oO 110
0.31
0.01 65
0'33
0"02 27
0'31[
0"27 10 /0'29
0'22 31"2
•
59"8 I 24"1 40"4 30"9 29"4 2414
35"4 37"9
* v-relaxation time, hr, Aa-proportion of initial stress loss, k-reaction rate constant, sec-1; see text for the dlInension of the activation parameters.
One of the thermal stability indicators of fluoride rubbers is their resistance to thermal-oxidative degradation under conditions of high temperature chemical stress relaxation. The thermal-oxidative degradation in air is primarily due to t h e fracture of the crosslinking joints, and secondarily to the main chain decomposition in the dehydrofluorinated polymer [9]. The type of the crosslinkages present between SKF-26 and the various agents varied so that it was interesting to find out the type and rate of their degradation and to establish the temperatare range for the practical uses of the vuleanizates.
Crosslinking of fluorine rubber SKF-26
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The thermal-oxidative ageing parameters were tested in the 21()-270°C range a n d the results established on the basis of the continuous chemical stress relaxation during a 50~o elongation. These functions were non-exponential and the relaxation curves were therefore processed by the Bryukhanov-Tobolsky m e t h o d [10]. Each of the found elementary acts had the kinetic and activation parameters listed in Table 2. The degradation analysis showed 4 stages, ° f w h i c h the first is short and most rapid; it has a small Eact and the most suitable AS s and seems to be linked with the fractures of intermolecular ionic and hydrogen bonds. The Eact of the second stage is similar to t h a t of the thermal-oxidative degradation of unsaturated rubbers (~21 kcal/mole) [11]. This stage is most probably t h a t in which the grafts of carbon-chain systems to the fluorine rubber are destroyed. The third and fourth stages 1}ave differing rates and the largest Eact; here the network joints and the main chains of the polymer are evidently fractured. The Eact values were similar to those of the pyrolysis of fluorinated elastomers ( ~ 30 kcal/mole) [12]. The ziG* a n d the log A increase in the post-stage relaxation; there is a compensating linear correlation between Eact and log A. The isolated Eact level agreed well with those given by Kuz'minskii and co-workers [9]. One gathers from the examined parameters and the consideration of the post-stage rate and total chemical relaxation times t h a t the rubbers cured with phosphite I I have the best thermal stability. The use of the continuous chemical relaxation method thus permits an objective assessment of the thermal stability of steric structures consisting of various t y p e of crosslinkages and shows the possibility of making good practical use of the curing procedures developed with new curing agents.
Translated by K. A. ALr~E~ REFERENCES
1. Russian Authors' Certificate 438661, 1973; Byull. Izobrct., No. 29, 1974 2. Russian Authors' Certificate 537095, 1975; Byull. Izobret., lqo. 44, 1976 3. F. A. GALIL-OGLY,A. S. NOVIKOV and Z. N. NUDEL'MAN, Ftorkauchuki i reziny na ikh osnove (Fluorine Rubbers and Resins Based on Them). Izd. "Khimiya", 1966 4. I. L. KNUNYANTS, V. V. TYULENEVA, Ye. Ya. PERVOVA and R. N. STERLIN, Izv. Akad. Nauk SSSR, Seriya khim., 1797, 1964 5. Yu. Yu. SAMITOV and T. V. ZYKOVA, V. Sb.: Khimiya i primenenie fosfororganicheskikh soedinenii (In: The Chemistry and Uses of Organic Phosphates). p. 49, Izd. "Nauka", 1972 ~. N. A. MUKMENEVA, P. A. KIRPICHNIKOV and A, N. PUDOVIK, Zhur. Obsh. Khim. 33: 3192, 1963 7. N. S. GILINSKAYA,F. A. GALIL-OGLY,G. A. GUBAI and S. A. NOVIKOV, Kauehuk i Rezina, No. 12, 7, 1964 8. S. M. MARKOV, A. M. POLEKHIN, N. A. LOSHADKIN, G. A. KOSTENKO, et al.,
Zhur. Obsh. Khim. 36: 1098, 1966 9. F. A. MAKHLIS, L. Ya. NIKITIN, A. S. KUZ'MINSKII and A. B. KRYUKOVA, Vysokomol, soyed. A18: 101, 1976 (Translated in Polymer Sci. U.S.S.R. 18: l, 118, 1976)
10. G. M. BARTENEV, Relaksatsionnye yavleniya v polimerakh (Relaxation Phenomena in Polymers). p. 249, Izd. "Khimiya", 1972
T. M. TffSHAXOVAet aL
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11. A. S. KUZ'MINSKII, L. I. LYUBCHANSKAYA, L. G. ANGERT and G. K. MIKHAILOV, V sb.: Dostizheniya nauki i tekhnologii v oblasti reziny (In: The Scientific and Technical Achievements in the Field of Resins). p. 96, Izd. " K h i m i y a " , 1969 12. G. G. DEGTEYA and A. S. KUZ'MINSKII, V sb.: Khimicheskie svoistva i modifikatsiys, polimerov (In: The Chemical Properties and the Modification of Polymers). p. 110, Izd. " N a u k a " , 1964
Polymer
0032-3950/79/1201-2996507.50]@
Science U.S.S.R. Vol. 21, pp. 2996-3001. Pergamon Press Ltd. 1980. Printed in Poland
POLYALKYL ALUMOXANES AND THEIR USES AS VANADIUM CATALYST CARRIERS FOR OLEFIN POLYMERIZATIONS * T. M. USI-IAXOVA,I. L. DUBNIKOVA, I. l~. MESH:KOVA, L. N. BAsPoPov, YU. L. LELYUKITLNA, S. L. GERSHKOKHEIV, i~{.N. KORIVEYEV and F. S. D'YACHKOVSKII Chemical Physics Institute,U.S.S.R. Academy of Sciences (Received 21 September 1978) /
Carrier catalysts have been produced b y the reactions of v a n a d i u m oxytrichloride (VOC18) with polyalkyl alumoxanes (PAAO). The kinetics of the ethylene polymerization on the carrier catalysts have been compared with those over the system VOC18-A1Et~C1. The reactive form of v a n a d i u m is stabilized on the surface of the organic aluminium compound; a n y change of the carrier t y p e affects the properties of the[polymerization products.
ZI~,GLER catalysts with improved activities can be prcduced by increasing the efficiency of the transition metal deposition on the carrier smface. The polyalkyl alumoxanes (PAAO) having a 2-5 m~/g specific surface and reactive alkyI groups are used as carriers for the ethylene polymerization catalysts [1, 2]. This work is dedicated to the kinetics of the ethylene polymerization over vanadium carrier catalysts, the comparison of the process kinetics on these with those over the two component VOC13-A1Et~C1 catalytic system, and to the study of the part played by the organo-metallic carrier. EXPERIMENTAL
The characteristics of the reagents (VOC18, alkylaluminium chlorides, ethylene, n-heptane) are those described b y Meshkova and co-workers [3]. Those of the PAAO used a~ carriers are listed in Table 1. * Vysokomol. soyed. A21: :No. 12, 2713-2718, 1979.