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Ammonolysis, aminolysis and alkaline hydrolysis of phenyl acetate groups of elastomers in latex
AMMONOLYSIS, AMINOLYSIS AND ALKALINE HYDROLYSIS OF PHENYL ACETATE GROUPS OF ELASTOMERS IN LATEX* L. M. KOGA•, A. I. YEZRIELEV,N. B. MONASTYRSKAYAand A. V. LEBEDEV S. V. Lebedev All-Union Synthetic Rubber Research Institute
(Received 17 May 1971) IN A~ earlier r e p o r t [1] we showed t h a t the relative reactivities of the m o n o m e r s in t h e c o p o l y m e r i z a t i o n of b u t a d i e n e a n d p - i s o p r o p e n y l p h e n y l a c e t a t e ( I P P h A ) (rl-~ 1.17, r 2 : 0 . 1 1 5 ) m a k e it possible even in the case of high degrees of conversion to o b t a i n p o l y m e r s t h a t h a v e m a r k e d compositional h o m o g e n e i t y when the m o l a r c o n t e n t of b u t a d i e n e is >/0.8. The aminolysis of b u t a d i e n e - I P P h A c o p o l y m e r s in solution results in rubbers t h a t have s u b s t i t u t e d p h e n y l units in the p o l y m e r chain [2]. O n l y t h e emulsion p o l y m e r i z a t i o n of b u t a d i e n e a n d I P P h A [3] is of interest f r o m a practical s t a n d p o i n t for the synthesis of elastomers c o n t a i n i n g p h e n y l a c e t a t e groups b y radical p o l y m e r i z a t i o n , a n d in view of this our aim was to i n v e s t i g a t e reactions of nucleophilic s u b s t i t u t i o n of the p h e n y l a c e t a t e groups o f elastomers in latex. EXPERIMENTAL The butadiene phenol ester latex containing 25.665/0 isopropenylphenyl acetate groups on the weight of polymer (BPhE-25) was prepared by emulsion copolymerization at 5°, the mix formulation being as follows (parts by wt.): butadiene--75; IPPhA--25; sodium
Alkaline hydrolysis of phenyl acetate groups of elastomers in latex
639
The kinetics of the ammonolysis and aminolysis reactions of the latex a t 70 ° were investigated in sealed ampoules, b u t in all other eases the reactions took place in test tubes provided with ground stoppers. The t e m p e r a t u r e control was accurate to 0.1 °. The reactants were a d d e d to the latex in the form of aqueous solutions. The kinetic measurements were carried out as follows: after fixed periods of time had elapsed the reactions were stopped b y decanting the contents of the test tubes (or ampoules) into 0.1 ~ hydrochloric acid solution, the excess acid being b a c k - t i t r a t e d with alkali, tile indicator being methyl red (ammonolysis, aminolysis) or bromthymol blue (alkaline hydrolysis). I n the case of slow reactions, recourse was had to direct titration of the unconsumed nucleophile, using hydrochloric acid. The I R spectroscopy and the gas-liquid chromatography were carried out by the method described in [1, 5]. The coefficients of amine distribution between water and n-hexane were determined as follows: to an aqueous solution of an amine of fixed concentration was added a certain amount of water so t h a t the total volume amounted to 25 ml, and 25 ml of n-lmxane was added. The mixture was agitated in a shaker for 0.5 hr, and the layers were separated. The amount of amine in an aqueous layer was determined by titration with 0.1 or 1 N hydrochl,oric acid (depending on the amount of amine in the system), using methyl red ~s the indicator. DISCUSSION OF RESULTS
I t is s e e n f r o m F i g . l a t h a t i n r e s p e c t t o r e a c t i v i t y t h e n u c l e o p h i l e s m a y b e placed in the following order: n-butylamine> dimethylamine>diethylamine > fl-hydroxyethylamine>ammonia; for the n-butyl-, eyclohexyl- and diethylamines t h i s o r d e r is i d e n t i c a l t o t h e o r d e r o f r e a c t i v i t y o f t h e a m i n e s w i t h t h e I P P h A a n d t h e c o p o l y m e r s i n h e t e r o g e n e o u s m e d i a [1, 4] for w h i c h s t e r i e f a c t o r s w e r e responsible.
|
a /.--o 2
,1
~
b
,'1'
...~_ ~',
6
20
O
g
8
0
I
I
l
f
q
10
16
27.
Time, hr Fro. 1. Kinetics of the ammonolysis and aminolysis of BPhE-25 latex, concentrations 20, 15 (a) and 4"28yo (b) b y n-butylamine (1, 1'), dimethylamine (2, 2'), cyclohexylamine (3, 3'), diethylamine (4, 4'), fl-hydroxyethylamine (5, 5') and ammonia (6, 6'). The number of phenyl acetate groups in the polymer is 25.66 wt. ~ . The starting concentrations (mole/ /1.) of phenyl acetate groups were-" 0.267 (•); 0.262 (2); 0.263 (3, 5); 0.245 (4); 0.265 (6); 0-599 (1", 2', 5', 6'); 0.0592 (3'); 0.0602 (4'); the starting concentrations for the amines were: 0.112 (•); 0.150 (2); 0.086 (3); 0.129 (4); 0.147 (5); 0.135 (6); 0.0194 (•'); 0.0209 (2'); 0.0215 (3'); 0.0201 (4'); 0.0211 (3'); 0.0205 (6').
B40
L.M. KooAl,,l et
al.
The high reactivity of dimethylamine is probably likewise due to the small steric hindrance of the latter. The factors underlying the low reactivity of flhydroxyethylamine and ammonia will be discussed below. The shape of the kinetic curves in Fig. 1 shows that under the conditions of the experiment the reaction rate is high at first, but is then markedly lower after 40-500/o conversion of the amine (ammonia). An analysis of the ammonolysis and aminolysis of the phenyl acetate groups of BPhE-25 latex at different temperatures confirmed that in these cases also the shape of the kinetic curves remains qualitatively unaltered whether in respect to the effect of the structure of an amine on its reactivity, or in respect to the slowing down of the reaction after 40-50% conversion. A high initial reaction rate with marked slowing down later on was observed by Gordon and eoworkers during the hydrochlorination of polyisoprene latices. It was found b y those authors that the reaction started on the surface of latex globules, where it proceeded very rapidly. However, after the formation of a glasslike surface layer of polyisoprene hydrochloride the marked slowing down of the diffusion of HC1 into the globules resulted in a correponding reduction in the rate o f the reduction. I t is improbable that one could account the same w a y for the limit on the conversion-time curve (Fig. 1), as the products of aminolysis of phen y l acetate groups of the latex, being rubber-like polymers, have a glass transition temperature ( T g ~ - - 5 1 . 8 °) which differs little from that of the starting copolymer ( T g = - 53.3 °) and they are incapable of forming a surface film hindering diffusion of the reactants into the globules. The marked retardation of the aminolysis of phcnyl acetate groups in the latex after 40-50~/o conversion of the amine is probably due to the formation of phenol groups in the course of the reaction with only approximately one haft of the amine being used, the whole of the unreacted amine being bound b y phenol hydroxyl into a complex that has much weaker nucleophilic properties than free amine. This mechanism is similar to the one reported [4] in an investigation of the amino]ysis of I P P h A with no solvent [4]. I t should be noted that the acetamides that are formed in the course of the reaction and which, as was shown in the earlier investigation [4], accelerate the aminolysis reaction, have much higher solubility in water than in the polymeric phase of the latex, and are consequently removed from the reaction zone, which further adds to the retardation of the process. The removal of components from the reaction zone is a characteristic feature of the chemical changes in the latices. As the chemical reactions involving the water-insoluble polymer take place in polymeric globules, while the low-molecular reactants m a y dissolve either in the polymer, or in water, the rate of reactions in the latices will be determined b y the actual concentration of a reactant in the immediate vicinity of an active centre, i.e. in the polymeric phase. In view of this it is understandable, that the ammonolysis and aminolysis of the phenyl acetate groups in the latex are largely determined b y the distribution of the amine beCween the aqueous phase and the polymeric phase.
Alkaline hydrolysis of phenyl acetate groups of elastomers in latex
641
f l - H y d r o x y e t h y l a m i n e a n d ammonia, which a m o n g the amines i n v e s t i g a t e d have the m o s t strongly hydrophilic properties, are obviously only soluble with difficulty in the polymeric phase of the latex, and this accounts for the small c o n c e n t r a t i o n s of these amines in the latex globules, and for the low rate of the reactions (Fig. 1). H o w e v e r , even in the ease of olefinic amines the distribution o f the l a t t e r in a p o l y m e r - w a t e r s y s t e m will have a definite effect on the n a t u r e of the process. F o r instance, if the starting B P h E - 2 5 latex is diluted to a concentration of 4.28% , the smallest r e t a r d a t i o n of the reaction occurs during the interaction of the p h e n y l acetate groups with cyclohexylamine, while the r e t a r d a t i o n is most m a r k e d with d i m e t h y l a m i n e (Fig. lb). This relation is p r o b a b l y the result of a difference in the distribution of these amines in the p o l y m e r - w a t e r system. Of all the amines used in the e x p e r i m e n t s cyclohexylamine is certainly the most strongly oleophilic, while d i m e t h y l a m i n e , which in respect to r e a c t i v i t y is similar to cyclohexylamine, has m u c h stronger hydrophilic properties. This conclusion is borne out b o t h b y the d a t a published [6] on the coefficients o f amines distribution in the systems b e n z e n e - w a t e r a n d diethyl e t h e r - w a t e r , and b y our own findings in regard to the amines distribution in t h e s y s t e m n - h e x a n e - w a t e r (see Fig. 2).
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F~c.. 2. Plots of the distribution coefficients of eyelohexylamine (1, 1'), n-butylamine (2) and diethylamine (3) at 25 (1-3) and 5° (1'). FIG. 3. Kinetics of saponification of phenyl acetate groups in the latex at 70° in the systems BPhE-25 latex-caustic soda (1), BPhE-17 latex-caustic soda (2) (amount of phenyl acetate groups in the polymer= 17.45 wt. ~), BPhE-17 latex-caustic soda-triethylamine (3) and BPhE-17 latex-caustic soda-triethylamine-aleohol (4). The starting concentrati()ns of phenyl acetate groups (mole/1.) were: 0.0630 (1), 0.0208 (2-4); OH groups 0-0802 (1), 0"0345 (2-4); (C2H5) groups: 0.0125 (3, 4); C2HsOH groups: 0.15 (4). I t is characteristic t h a t on changing to low amine concentrations the distribution of ambles b e t w e e n n - h e x a n e and w a t e r changes in the direction of b e t t e r solubility in water. W i t h o u t d o u b t this is due to a r e d u c t i o n in the amine concent r a t i o n being a c c o m p a n i e d b y a higher degree of dissociation of the amine in water, a n d the effect is to reduce f u r t h e r t h e rate of aminolysis of the p h e n y l a c e t a t e groups in the latices in the case of a n y considerable degree of conversion.
642
L.M. KooxN et
al.
.
I t was shown in an earlier investigation that the rate of alkaline hydrolysis of I P P h A is high (the rate constant is higher by 3-4 orders than that of I P P h A aminolysis by n-butylamine). On the other hand, the alkali is practically insoluble in polymer. As is seen from Fig. 2, the rate of alkaline hydrolysis of the phenyl acetate groups of the latex is quite low. Seeing that in alcohol-aqueous alkali there is a high rate of transesterification of I P P h A to ethyl acetate [7] taking place in addition to the hydrolysis of IPPhA, an attempt was made to accelerate the formation of phenol groups by using the system latex-alkyl alcohols-alkali. However, it was found that this reaction was inhibited in the latex owing to the fact that alkali, like the alcohols used in the experiment (ethyl alcohol, and even n-butyl alcohol) are difficultly soluble in a non-polar polymer. Another method of bringing about the transesterification of phenyl acetate groups is by using the transesterification of amines as catalysts [8]. As in addition to catalyzing transestcrification reactions primary and secondary amines likewise participate in the formation of substituted acetamides, it was not possible in this case to take the existence and identification of polymer containing phenol groups, in the reaction products, as definite proof of a transesterification reaction. The fact that this reaction takes place in the latex also was demonstrated by us by using tricthylaminc as the transestcrification catalyst. I t was certainly found that when the system latex-triethylamine-ethyl alcohol was subjected to prolonged heating (160 hr) at 70 ° a polymer was separated in the I R spectrum of which a band was found at 3615 cm -a, characteristic for the phenol group [1], and ethyl acetate was found in the products extracted from the later by means of isopcntane and gas-liquid chromatography. At the same time, if there is no alcohol in the system latcx-triethylamine-water, practicaUy no saponification of phenyl acetate groups takes place through the action of triethylaminc hydrate under the conditions referred to above. I n addition we investigated the system latcx-triethylamine-ethyl alcoholalkali, in which the following reactions m a y well take place: OCOCI-I,
o
~CH
--}-2NaOH --> ,--
OCOCHs
ONa + CHaCOONa
(1)
---C--CHs--
OH 12)
--~--CH2--
~H8
--C---CH2-~Hs
Alkaline hydrolysis of phenyl acetate groups of elastomers in latex OCOCH3
643
OH ~C~H60H
N(C~Hsh
+CHsCOOC2Hs
'~
(3)
--C--CH 2 -
J
]
CHa
CHa
OCOCHa
ONa +C~HsONa -->
--C--CH2--
i
-t-CH3COOC2H5
(4)
I
--C--CH~--
I
CI-I3 CH3 CHsCOOC2H5~-NaOH --->CH3COONa-~C2tt50H
(5)
It was found by experiment that reactions (2) and (4) take place extremely slowly, and have virtually no effect on the character of the process. Moreover, it m a y be assumed that reactions (1), (3) and (5) will take place at comparable rates. It is certainly seen from Fig. 3 that the rates of the processes of saponification of phenyl acetate groups in the systems latex-alkali and latex-triethylamincalkali are very similar, which confirms that the contribution of reaction (2) to the overall rate of the process is quite inconsiderable, and that the saponification of the phenyl acetate groups of the polymer takes place much more rapidly in the system latex-triethylamine-alkali-alcohol. This may be attributed to reaction (3), taking place along with reaction (1), the former reaction leading to the formation of ethyl acetate, which is much more soluble in water (8.08%) [9] than the polymer, and is therefore saponified more rapidly b y aqueous alkali (reaction (5)). I t should be noted that the actual conversion of phenyl acetate groups to phenol groups exceeds the value corresponding to the alkali consumption based on curve 4 (Fig. 3). This is due to the fact that reaction (3), which likewise leads to the formation of phenol groups, is unrelated to the consumption of alkali. CONCLUSIONS
(1) The amonolysis and aminolysis of phenyl acetate groups in latex are not described b y a second order equation, and the rate of the reactions is largely determined b y the distribution of amines between the aqueous and organic phases. (2) I t has been shown that the rate of alkaline hydrolysis of the phenyl acetate groups of the copolymer in latex is very low. The addition of alcohol and triethylamine to the latex increases the rate of transformation of phenyl acetate groups to phenol groups owing to the transesterification reaction catalyzed b y triethylamine. Translated by R. J. A. HENDRY
644
V.V.
PEBALK et al.
REFERENCES 1. L. M. KOG.~T, A. I. YEZRIELEV, A. B. PEIZNER and A. V. LEBEDEV, Vysokomol. soyed. 1O: 2028, 1968 (Translated in Polymer Sci. U.S.S.R. 10: 9, 2354, 1968) 2. L. M. KOGAN, A. I. YEZRIELEV and N. B. MONASTYRSKAYA, Vysokomol. soyed. B15: 108, 1973 (Not translated in Polymer Sci. U.S.S.R.) 3. A. I. Y E Z R I E L E V , L. M. KOGAN, N. B. MONARSTYRSKAYA and A. B. PEIZNER, U.S.S.R. Pat. No. 236004, 1970; Byull. izob., 33, 1970 4. A. M. KOGAN, A. I. YEZRIELEV, A. V. LEBEDEV and A. B. PE1ZNER, Zh. obshch. khim. 40: 2309, 1970 5. E. GRAMPSEY, M. GORDON and J. S. TAYLOR, J. Chem. Soe., 3925, 1953 6. Chemistry Handbook, vol. I I I . Izd. " K h i m i y a " , 474, 1964 7. L. M. KOGAN, A. I. YEZRIELEV and N. B. MONASTYRSKAYA, Zh. obshch, khim. 42: 2264, 1972 8. L. M. KOGAN and A. I. YEZRIELEV, Zh. obshch, khim. 40: 2314, 1970 9. A. WAISBERGER, E. PROSKAUER, D. RIDDICK and E. TUBBS, Organic solvents, 1958
CONTINUOUS COPOLYMERIZATION OF ETHYLENE AND PltOPYLENE BY THE HOMOGENEOUS COMPLEX CATALYTIC SYSTEM VANADIUM TRIACETYLACETONATEDHSOBUTYLALUMINIUM CHLORIDE* V. V. PEBALK, V. I . GERBICH, D . M. LISITSYN a n d N . M. CHIRKOV (dec.) Chemical Physics Institute, U.S.S.R. A c a d e m y of Sciences
(Received 17 May 1971) BY INVESTIGATINGthe copolymerization of ethylene with propylene in an open system it should be possible to obtain reliable experimental data verifying the reaction mechanism previously obtained for the copolymerization process on the basis of intermittent experiments. It has already been established that ethylenepropylene copolymerization catalyzed by the system vanadium triacetylacetohate (VTAA)-diisobutylaluminium chloride (DISC) involves a bimolecular mechanism of decay of the active centres, and the rate constants obtained for the homopolymerization of ethylene and propylene w e r e ~11 ~ 1.3 × 105 exp (--44,000/RT) and 0.29 1./mole.sec (--10 °) respectively, while the rate constants for the entry into the copolymerization of ethylene after propylene, and vice versa, were respectively k21--~14.5 1./mole-sec (-- 10°) and k 1 ~ 2 . 2 1./mole. sec (-- 10°); the two main types of chain limitation in the copolymerization are square termination, * Vysokomol. soyed. A15: No. 3. 570-574, 1973.
(Received 17 May 1971) IN A~ earlier r e p o r t [1] we showed t h a t the relative reactivities of the m o n o m e r s in t h e c o p o l y m e r i z a t i o n of b u t a d i e n e a n d p - i s o p r o p e n y l p h e n y l a c e t a t e ( I P P h A ) (rl-~ 1.17, r 2 : 0 . 1 1 5 ) m a k e it possible even in the case of high degrees of conversion to o b t a i n p o l y m e r s t h a t h a v e m a r k e d compositional h o m o g e n e i t y when the m o l a r c o n t e n t of b u t a d i e n e is >/0.8. The aminolysis of b u t a d i e n e - I P P h A c o p o l y m e r s in solution results in rubbers t h a t have s u b s t i t u t e d p h e n y l units in the p o l y m e r chain [2]. O n l y t h e emulsion p o l y m e r i z a t i o n of b u t a d i e n e a n d I P P h A [3] is of interest f r o m a practical s t a n d p o i n t for the synthesis of elastomers c o n t a i n i n g p h e n y l a c e t a t e groups b y radical p o l y m e r i z a t i o n , a n d in view of this our aim was to i n v e s t i g a t e reactions of nucleophilic s u b s t i t u t i o n of the p h e n y l a c e t a t e groups o f elastomers in latex. EXPERIMENTAL The butadiene phenol ester latex containing 25.665/0 isopropenylphenyl acetate groups on the weight of polymer (BPhE-25) was prepared by emulsion copolymerization at 5°, the mix formulation being as follows (parts by wt.): butadiene--75; IPPhA--25; sodium
Alkaline hydrolysis of phenyl acetate groups of elastomers in latex
639
The kinetics of the ammonolysis and aminolysis reactions of the latex a t 70 ° were investigated in sealed ampoules, b u t in all other eases the reactions took place in test tubes provided with ground stoppers. The t e m p e r a t u r e control was accurate to 0.1 °. The reactants were a d d e d to the latex in the form of aqueous solutions. The kinetic measurements were carried out as follows: after fixed periods of time had elapsed the reactions were stopped b y decanting the contents of the test tubes (or ampoules) into 0.1 ~ hydrochloric acid solution, the excess acid being b a c k - t i t r a t e d with alkali, tile indicator being methyl red (ammonolysis, aminolysis) or bromthymol blue (alkaline hydrolysis). I n the case of slow reactions, recourse was had to direct titration of the unconsumed nucleophile, using hydrochloric acid. The I R spectroscopy and the gas-liquid chromatography were carried out by the method described in [1, 5]. The coefficients of amine distribution between water and n-hexane were determined as follows: to an aqueous solution of an amine of fixed concentration was added a certain amount of water so t h a t the total volume amounted to 25 ml, and 25 ml of n-lmxane was added. The mixture was agitated in a shaker for 0.5 hr, and the layers were separated. The amount of amine in an aqueous layer was determined by titration with 0.1 or 1 N hydrochl,oric acid (depending on the amount of amine in the system), using methyl red ~s the indicator. DISCUSSION OF RESULTS
I t is s e e n f r o m F i g . l a t h a t i n r e s p e c t t o r e a c t i v i t y t h e n u c l e o p h i l e s m a y b e placed in the following order: n-butylamine> dimethylamine>diethylamine > fl-hydroxyethylamine>ammonia; for the n-butyl-, eyclohexyl- and diethylamines t h i s o r d e r is i d e n t i c a l t o t h e o r d e r o f r e a c t i v i t y o f t h e a m i n e s w i t h t h e I P P h A a n d t h e c o p o l y m e r s i n h e t e r o g e n e o u s m e d i a [1, 4] for w h i c h s t e r i e f a c t o r s w e r e responsible.
|
a /.--o 2
,1
~
b
,'1'
...~_ ~',
6
20
O
g
8
0
I
I
l
f
q
10
16
27.
Time, hr Fro. 1. Kinetics of the ammonolysis and aminolysis of BPhE-25 latex, concentrations 20, 15 (a) and 4"28yo (b) b y n-butylamine (1, 1'), dimethylamine (2, 2'), cyclohexylamine (3, 3'), diethylamine (4, 4'), fl-hydroxyethylamine (5, 5') and ammonia (6, 6'). The number of phenyl acetate groups in the polymer is 25.66 wt. ~ . The starting concentrations (mole/ /1.) of phenyl acetate groups were-" 0.267 (•); 0.262 (2); 0.263 (3, 5); 0.245 (4); 0.265 (6); 0-599 (1", 2', 5', 6'); 0.0592 (3'); 0.0602 (4'); the starting concentrations for the amines were: 0.112 (•); 0.150 (2); 0.086 (3); 0.129 (4); 0.147 (5); 0.135 (6); 0.0194 (•'); 0.0209 (2'); 0.0215 (3'); 0.0201 (4'); 0.0211 (3'); 0.0205 (6').
B40
L.M. KooAl,,l et
al.
The high reactivity of dimethylamine is probably likewise due to the small steric hindrance of the latter. The factors underlying the low reactivity of flhydroxyethylamine and ammonia will be discussed below. The shape of the kinetic curves in Fig. 1 shows that under the conditions of the experiment the reaction rate is high at first, but is then markedly lower after 40-500/o conversion of the amine (ammonia). An analysis of the ammonolysis and aminolysis of the phenyl acetate groups of BPhE-25 latex at different temperatures confirmed that in these cases also the shape of the kinetic curves remains qualitatively unaltered whether in respect to the effect of the structure of an amine on its reactivity, or in respect to the slowing down of the reaction after 40-50% conversion. A high initial reaction rate with marked slowing down later on was observed by Gordon and eoworkers during the hydrochlorination of polyisoprene latices. It was found b y those authors that the reaction started on the surface of latex globules, where it proceeded very rapidly. However, after the formation of a glasslike surface layer of polyisoprene hydrochloride the marked slowing down of the diffusion of HC1 into the globules resulted in a correponding reduction in the rate o f the reduction. I t is improbable that one could account the same w a y for the limit on the conversion-time curve (Fig. 1), as the products of aminolysis of phen y l acetate groups of the latex, being rubber-like polymers, have a glass transition temperature ( T g ~ - - 5 1 . 8 °) which differs little from that of the starting copolymer ( T g = - 53.3 °) and they are incapable of forming a surface film hindering diffusion of the reactants into the globules. The marked retardation of the aminolysis of phcnyl acetate groups in the latex after 40-50~/o conversion of the amine is probably due to the formation of phenol groups in the course of the reaction with only approximately one haft of the amine being used, the whole of the unreacted amine being bound b y phenol hydroxyl into a complex that has much weaker nucleophilic properties than free amine. This mechanism is similar to the one reported [4] in an investigation of the amino]ysis of I P P h A with no solvent [4]. I t should be noted that the acetamides that are formed in the course of the reaction and which, as was shown in the earlier investigation [4], accelerate the aminolysis reaction, have much higher solubility in water than in the polymeric phase of the latex, and are consequently removed from the reaction zone, which further adds to the retardation of the process. The removal of components from the reaction zone is a characteristic feature of the chemical changes in the latices. As the chemical reactions involving the water-insoluble polymer take place in polymeric globules, while the low-molecular reactants m a y dissolve either in the polymer, or in water, the rate of reactions in the latices will be determined b y the actual concentration of a reactant in the immediate vicinity of an active centre, i.e. in the polymeric phase. In view of this it is understandable, that the ammonolysis and aminolysis of the phenyl acetate groups in the latex are largely determined b y the distribution of the amine beCween the aqueous phase and the polymeric phase.
Alkaline hydrolysis of phenyl acetate groups of elastomers in latex
641
f l - H y d r o x y e t h y l a m i n e a n d ammonia, which a m o n g the amines i n v e s t i g a t e d have the m o s t strongly hydrophilic properties, are obviously only soluble with difficulty in the polymeric phase of the latex, and this accounts for the small c o n c e n t r a t i o n s of these amines in the latex globules, and for the low rate of the reactions (Fig. 1). H o w e v e r , even in the ease of olefinic amines the distribution o f the l a t t e r in a p o l y m e r - w a t e r s y s t e m will have a definite effect on the n a t u r e of the process. F o r instance, if the starting B P h E - 2 5 latex is diluted to a concentration of 4.28% , the smallest r e t a r d a t i o n of the reaction occurs during the interaction of the p h e n y l acetate groups with cyclohexylamine, while the r e t a r d a t i o n is most m a r k e d with d i m e t h y l a m i n e (Fig. lb). This relation is p r o b a b l y the result of a difference in the distribution of these amines in the p o l y m e r - w a t e r system. Of all the amines used in the e x p e r i m e n t s cyclohexylamine is certainly the most strongly oleophilic, while d i m e t h y l a m i n e , which in respect to r e a c t i v i t y is similar to cyclohexylamine, has m u c h stronger hydrophilic properties. This conclusion is borne out b o t h b y the d a t a published [6] on the coefficients o f amines distribution in the systems b e n z e n e - w a t e r a n d diethyl e t h e r - w a t e r , and b y our own findings in regard to the amines distribution in t h e s y s t e m n - h e x a n e - w a t e r (see Fig. 2).
50F
I' . . . .
F
I
1
I
I
3 Fro. 2
I
I
5
7"
/
-
i
0
1
7
"~
F
I
I
gO
I
Time, hp
I
i ..
#~
Fro. 3
F~c.. 2. Plots of the distribution coefficients of eyelohexylamine (1, 1'), n-butylamine (2) and diethylamine (3) at 25 (1-3) and 5° (1'). FIG. 3. Kinetics of saponification of phenyl acetate groups in the latex at 70° in the systems BPhE-25 latex-caustic soda (1), BPhE-17 latex-caustic soda (2) (amount of phenyl acetate groups in the polymer= 17.45 wt. ~), BPhE-17 latex-caustic soda-triethylamine (3) and BPhE-17 latex-caustic soda-triethylamine-aleohol (4). The starting concentrati()ns of phenyl acetate groups (mole/1.) were: 0.0630 (1), 0.0208 (2-4); OH groups 0-0802 (1), 0"0345 (2-4); (C2H5) groups: 0.0125 (3, 4); C2HsOH groups: 0.15 (4). I t is characteristic t h a t on changing to low amine concentrations the distribution of ambles b e t w e e n n - h e x a n e and w a t e r changes in the direction of b e t t e r solubility in water. W i t h o u t d o u b t this is due to a r e d u c t i o n in the amine concent r a t i o n being a c c o m p a n i e d b y a higher degree of dissociation of the amine in water, a n d the effect is to reduce f u r t h e r t h e rate of aminolysis of the p h e n y l a c e t a t e groups in the latices in the case of a n y considerable degree of conversion.
642
L.M. KooxN et
al.
.
I t was shown in an earlier investigation that the rate of alkaline hydrolysis of I P P h A is high (the rate constant is higher by 3-4 orders than that of I P P h A aminolysis by n-butylamine). On the other hand, the alkali is practically insoluble in polymer. As is seen from Fig. 2, the rate of alkaline hydrolysis of the phenyl acetate groups of the latex is quite low. Seeing that in alcohol-aqueous alkali there is a high rate of transesterification of I P P h A to ethyl acetate [7] taking place in addition to the hydrolysis of IPPhA, an attempt was made to accelerate the formation of phenol groups by using the system latex-alkyl alcohols-alkali. However, it was found that this reaction was inhibited in the latex owing to the fact that alkali, like the alcohols used in the experiment (ethyl alcohol, and even n-butyl alcohol) are difficultly soluble in a non-polar polymer. Another method of bringing about the transesterification of phenyl acetate groups is by using the transesterification of amines as catalysts [8]. As in addition to catalyzing transestcrification reactions primary and secondary amines likewise participate in the formation of substituted acetamides, it was not possible in this case to take the existence and identification of polymer containing phenol groups, in the reaction products, as definite proof of a transesterification reaction. The fact that this reaction takes place in the latex also was demonstrated by us by using tricthylaminc as the transestcrification catalyst. I t was certainly found that when the system latex-triethylamine-ethyl alcohol was subjected to prolonged heating (160 hr) at 70 ° a polymer was separated in the I R spectrum of which a band was found at 3615 cm -a, characteristic for the phenol group [1], and ethyl acetate was found in the products extracted from the later by means of isopcntane and gas-liquid chromatography. At the same time, if there is no alcohol in the system latcx-triethylamine-water, practicaUy no saponification of phenyl acetate groups takes place through the action of triethylaminc hydrate under the conditions referred to above. I n addition we investigated the system latcx-triethylamine-ethyl alcoholalkali, in which the following reactions m a y well take place: OCOCI-I,
o
~CH
--}-2NaOH --> ,--
OCOCHs
ONa + CHaCOONa
(1)
---C--CHs--
OH 12)
--~--CH2--
~H8
--C---CH2-~Hs
Alkaline hydrolysis of phenyl acetate groups of elastomers in latex OCOCH3
643
OH ~C~H60H
N(C~Hsh
+CHsCOOC2Hs
'~
(3)
--C--CH 2 -
J
]
CHa
CHa
OCOCHa
ONa +C~HsONa -->
--C--CH2--
i
-t-CH3COOC2H5
(4)
I
--C--CH~--
I
CI-I3 CH3 CHsCOOC2H5~-NaOH --->CH3COONa-~C2tt50H
(5)
It was found by experiment that reactions (2) and (4) take place extremely slowly, and have virtually no effect on the character of the process. Moreover, it m a y be assumed that reactions (1), (3) and (5) will take place at comparable rates. It is certainly seen from Fig. 3 that the rates of the processes of saponification of phenyl acetate groups in the systems latex-alkali and latex-triethylamincalkali are very similar, which confirms that the contribution of reaction (2) to the overall rate of the process is quite inconsiderable, and that the saponification of the phenyl acetate groups of the polymer takes place much more rapidly in the system latex-triethylamine-alkali-alcohol. This may be attributed to reaction (3), taking place along with reaction (1), the former reaction leading to the formation of ethyl acetate, which is much more soluble in water (8.08%) [9] than the polymer, and is therefore saponified more rapidly b y aqueous alkali (reaction (5)). I t should be noted that the actual conversion of phenyl acetate groups to phenol groups exceeds the value corresponding to the alkali consumption based on curve 4 (Fig. 3). This is due to the fact that reaction (3), which likewise leads to the formation of phenol groups, is unrelated to the consumption of alkali. CONCLUSIONS
(1) The amonolysis and aminolysis of phenyl acetate groups in latex are not described b y a second order equation, and the rate of the reactions is largely determined b y the distribution of amines between the aqueous and organic phases. (2) I t has been shown that the rate of alkaline hydrolysis of the phenyl acetate groups of the copolymer in latex is very low. The addition of alcohol and triethylamine to the latex increases the rate of transformation of phenyl acetate groups to phenol groups owing to the transesterification reaction catalyzed b y triethylamine. Translated by R. J. A. HENDRY
644
V.V.
PEBALK et al.
REFERENCES 1. L. M. KOG.~T, A. I. YEZRIELEV, A. B. PEIZNER and A. V. LEBEDEV, Vysokomol. soyed. 1O: 2028, 1968 (Translated in Polymer Sci. U.S.S.R. 10: 9, 2354, 1968) 2. L. M. KOGAN, A. I. YEZRIELEV and N. B. MONASTYRSKAYA, Vysokomol. soyed. B15: 108, 1973 (Not translated in Polymer Sci. U.S.S.R.) 3. A. I. Y E Z R I E L E V , L. M. KOGAN, N. B. MONARSTYRSKAYA and A. B. PEIZNER, U.S.S.R. Pat. No. 236004, 1970; Byull. izob., 33, 1970 4. A. M. KOGAN, A. I. YEZRIELEV, A. V. LEBEDEV and A. B. PE1ZNER, Zh. obshch. khim. 40: 2309, 1970 5. E. GRAMPSEY, M. GORDON and J. S. TAYLOR, J. Chem. Soe., 3925, 1953 6. Chemistry Handbook, vol. I I I . Izd. " K h i m i y a " , 474, 1964 7. L. M. KOGAN, A. I. YEZRIELEV and N. B. MONASTYRSKAYA, Zh. obshch, khim. 42: 2264, 1972 8. L. M. KOGAN and A. I. YEZRIELEV, Zh. obshch, khim. 40: 2314, 1970 9. A. WAISBERGER, E. PROSKAUER, D. RIDDICK and E. TUBBS, Organic solvents, 1958
CONTINUOUS COPOLYMERIZATION OF ETHYLENE AND PltOPYLENE BY THE HOMOGENEOUS COMPLEX CATALYTIC SYSTEM VANADIUM TRIACETYLACETONATEDHSOBUTYLALUMINIUM CHLORIDE* V. V. PEBALK, V. I . GERBICH, D . M. LISITSYN a n d N . M. CHIRKOV (dec.) Chemical Physics Institute, U.S.S.R. A c a d e m y of Sciences
(Received 17 May 1971) BY INVESTIGATINGthe copolymerization of ethylene with propylene in an open system it should be possible to obtain reliable experimental data verifying the reaction mechanism previously obtained for the copolymerization process on the basis of intermittent experiments. It has already been established that ethylenepropylene copolymerization catalyzed by the system vanadium triacetylacetohate (VTAA)-diisobutylaluminium chloride (DISC) involves a bimolecular mechanism of decay of the active centres, and the rate constants obtained for the homopolymerization of ethylene and propylene w e r e ~11 ~ 1.3 × 105 exp (--44,000/RT) and 0.29 1./mole.sec (--10 °) respectively, while the rate constants for the entry into the copolymerization of ethylene after propylene, and vice versa, were respectively k21--~14.5 1./mole-sec (-- 10°) and k 1 ~ 2 . 2 1./mole. sec (-- 10°); the two main types of chain limitation in the copolymerization are square termination, * Vysokomol. soyed. A15: No. 3. 570-574, 1973.