Kinetics and mechanism of cyclic trimerization of isocyanates using a tertiary amine-alkylene oxide catalytic system

494

~a. P. T~aB ~ at. REFERENCES

1. Patent of the German Federal Republic 1166474, 1166475, 1964; 1174955, 11174986, 1965 2. G. E. KESSLER, V. Ya. RO(rHEV, R. A. STUKAN and L. M. ROMANOV, Vysokomo! soyed. B18: 159, 1971 (Not translated in Polymer Sei. U.S.S.R.) 3. L. M. ROMANOV, L. M. PUSHCHAYEVA and A. •. GRUZNOV, Vysokomol. soyed. A1O~ 2495, 1968 (Translated in Polymer Sci. U.S.S.R. 10: 11, 2898, 1968) 4. J. D. DONALDSON, W. MOSER and W. B. SIMPSON, J. Chem. Soe., 5942, 1964 5. U.S.A. Pat. 2475994, 1949 6. L. M. ROMANOV, A. G. GRUZNOV and L. M. P U S H ~ Y E V A , Auth. Cert. 259859, 1969; Buyll. izobr., No. 3, 1970 7. V. I. GOL'DANSKII, V. V. ](HRAPOV, V. Ya. ROCHEV, T. N. SUMAROKOVA and D. E. SURPINA, Dokl. AN SSSR 183: 364, 1968

KINETICS AND MECHANISM OF CYCLIC TRIMERIZATION OF ISOCYANATES USING A TERTIARY AMINE-ALKYLENE OXIDE CATALYTIC SYSTEM* R. P. TIGER, I. G. BADAYEVA, S. P. BONDARENKO

and S. G. ENTELIS Institute of Chemical Physics, U.S.S.R. Academy of Sciences (Received 20 Selvtember 1976) A study was made of kinetic relations of cyclic trimerization of NCO groups, trimerization of m-chlorophenylisocyanate in the presence of a triethylenediamlnepropylene oxide catalytic system and kinetics of formation of active centres in the system. It is assumed that a new, highly effective catalyst of matrix type is formed during the process, in which a trimer containing three active centres capable of simultaneous coordination of three monomer molecules functions as matrix. CYCLIC trimerization o f isocyanates was discovered b y H o f m a n n over 100 y e a r s ago, b u t u p t o r e c e n t l y it has n o t been used in practice e v e n in p r e p a r a t o r y organic chemistry. I n view o f the a p p e a r a n c e o f several new effective c a t a l y s t s interest in cyclic t r i m e r i z a t i o n has increased cohsiderably [1]. The use o f specific c a t a l y t i c systems enabled s e c o n d a r y processes a c c o m p a n y i n g t r i m e r i z a t i o n t o h e e l i m i n a t e d in m a n y cases; cyclic dimerization o f NCO groups is the m a i n process o f this kind. I t b e c a m e possible to use cyclotrimerization, in order t o effect steric crosslinking o f oligomers ~rith NCO e n d groups a n d m o d i f y u r e t h a n e materials b y adding fairly h e a t resistant (up to 300 °) i s o c y a n u r a t e rings to t h e * Vysokomol. s0yed. AIg: No. 2, 419-427, 1977.

Kinetics and mechanism of cyclic trimerization of isocyanates

485

polymer network. Several procedures, very promising from a technical aspect ~2, 3] are now known, but limited information about ~inetic relations of trimerization and the lack of information about the catalytic mechanism using various catalytic systems impede the control of trimerization by rational methods. Of the numerous catalysts used in trimerization (reviews [1, 4]) catalytic systems based on tertiary amines and co-catalysts such as alkylene oxides, aldehydes and imines should be mentioned. Trimerization using these catalytic systems takes place at moderate temperatures with 100% conversion of NCO groups and is comparatively easy to control. From a technical point of view the S-shaped form of kinetic curves of trimerization using these catalytic systems is significant, which enables agitation and filling of the mould to be carried ou~ with comparatively low viscosity of the initial composition. C mole/l.

0.4 -

0.2

-

1

~1212 ztO

80

120

~g

!

#B

8O

120

Time, rain :FIG. 1. Typical kinetic curves of trimerization: /--monomer consumption, 2--trimer formation.

There are only two studies [5, 6] concerned with a quantitative investigation of trimerization of isocyanates using a tertiary amine cpoxide catalytic system and the information available is insufficient for forming any idea about the reaction mechanism and type of catalysis. Using trimerization of m-chlorophenylisocyanate (CPIC) in the presence of a triethylene diamine (TEDA)-propylene oxide (PO) catalytic system a study was made of main kinetic regularities of cyclic trimerization of NCO groups, kinetics of interaction between catalyst components and conclusions drawn concernin/g the mechanism of catalysis.

486

R.P. Tmn

e~ a/.

Kin~ o] ~rimerization were exa.miued in a d i o x a n e s o l u t i o n at, 25 °. T h e c o n e e n t r a •tions of CPIC, T E D A and PO varied in the ranges of 0.2-0.6, 2 × 1 0 - ' - 1 × 10 -I and 0.08-2.() mole]l, respectively. I R spectroscopy was used to s t u d y kinetics. Samples were t a k e n from a thermostatically controlled reactor a t given moments o f time, these samples were placed into CaFa cells 0.02 Inm in thickness and I R spectra obtained in a UR-20 device in the range of 1550-2500 cm -1. The existence of intense bond-stretchlng v i b r a t i o n bands of a C----O bond in the dimer (1790 cm -~) and trimer (1710 cm -~) rings a n d b o n d stretching vibration bands of the N = C = O group (2260 cm -~) after special ealibratio~ (optical density-concentration ) made it possible to measure the concentrations of the reagenb a n d products over a period of time. Deviations of the monomer a n d trimer solution from t h e L a m b e r t - B e e r law, due to auto-association, were observed from an approximate concexlt r a t i o n of N 0-25 mole/l. Kinetics of interaction between components of the T E D A and PO catalytic mjstem were studied b y UV spectroscopy (Specord UV-VIS) according to t h e optical density reduction of T E D A in dilute dioxane with 2 = 230 n m and a PO excess. W i t h T E D A concentrations of ,~ (3-6) × 10 -5 mole/1, the L a m b e r t - B e e r law is observed and kinetic curves in coordinates showing optical density D vs. time are described b y a first order equation. The reaction was carried out in a hermetically closed quartz cell 1 cm thick placed in a thermostatically controlled cell-holder of the spectrophotometer. Before use the raw materials and solvent were specially purified and dried. Chemically" pure CPIC was distilled in vacuo at 47°/1-2 torr and stored under argon in sealed ampoules. P O distilled in the column was dried over CaHi and chilled in ampoules under argon before use. While heating slightly T E D A volatilized on the surface cooled with liquid nitrogen. Pure dioxane was freed from peroxides b y boiling with ferrous sulphate, dried a n d distillecl over sodium; water content according to Fischer was 0.02-0-04%. The presence of trace8 o f water in dioxane after conventional drying was easily recorded b y I R spectra after a d d i n g T E D A and CPIC: as a result of r a p i d hydrolysis* bands of substituted area appeared in t h e I R spectrum of the solution a t 1740 and 1550 cm - t and COs a t 2360 cm -1. F o r more satisfactory drying this dioxane was boiled with CP]:C a n d then repeatedly distilled under argon. The contents of unreacted isocyanato were controlled after every distillation using UV a b sorption spectra. Kinetic relations of trimerization. T y p i c a l k i n e t i c c u r v e s s h o w i n g m o n o m e r loss and increased trimer concentration in the catalytic system studied, are S-shaped. On conversion to the degree of transformation a both kinetic curves s h o w a g r e e m e n t u p t o 1 0 0 % t r a n s f o r m a t i o n ( F i g . 1). T h i s a n d t h e f a c t t h a t during trimerization in the presence of TEDA and PO no dimer formation takes p l a c e i n a p r o p o r t i o n r e c o r d e d b y I R s p e c t r o s c o p y is e v i d e n c e o f t h e c o m p l e t e transformation of the monomer to a cyclic trimer under experimental conditions. A s t u d y o f r e l a t i o n s b e t w e e n t h e m a x i m u m r a t e Wmax o f t h e r e a c t i o n , ¢ t h e i n d u c t i o n p e r i o d T~nd a n d c o n c e n t r a t i o n s o f c o m p o n e n t s o f t h e c a t a l y t i c s y s t e m * Catalytic hydrolysis of CPIC in the presence of T E D A has been studied previously t wmax (molefl.min) was derived b y graphic aldifferentiation of the kinetic curve ~-$ a n d assigning the gradient (rain -1) at the point of inflection to the initial concentration o f t h e monomer. The time value intersected on the abscissa of the tangent to curve ~-t in p o i n t ~max was accepted as ~ina.

FhAn~ies and mechanLam of cyclic trimerization of i s o c y a n a ~

487

shows that with an increase of [TEDA] and [PO] the value of z~d decreases a n d

wm~x increases. Table 1 shows results concerning the effect of [TEDA] and [ P O ] concentrations on Wmax, Zmd, ~t and Tmax (~max being the time during which maximum rate is obtained) with [CPIC]0- const. On varying isocyanate concentration both Tind and Wmax change, w h e r e b y on reducing monomer concentration, the S-shaped form of kinetic curves becomes less clear. Figure 2 shows results concerning the dependence of Wmax on initial monomer concentration with constant concentrations of components of the catalytic system. I t can be seen that with an increas e of [CPIC]0 the v a l u e of Wmax increases. The reaction order of RNCO derived diagrammatically f r o m these'results in coordinates log wmax-log[RNCO]0 is ~-2.6. •~

¢, mole/l.

0"2

0,6

[CHC~o,mole/I. FIG. 2

80

I60

Time, rnin

2#O

FIG. 3

FIG. 2. Relation between Wmaxand the initial concentration of CPIC ([TEDA]~2.3X 10-8;: [PO] - 2.0 mole/L). FIG. 3. Kinetics of decomposition of a dimer in the presence of TEDA (1.6× 10-a mole]l.) and PO (1.95 mole/L): 1---dimer, 2--monomer and 3--trimer. It should be noted that without PO trimerization of T E D A in dioxane t a k e s place at a very low rate (above 50 hr) with the catalyst concentrations used in the s t u d y without an induction period for the monomer. Kinetic curves of trimer formation, however, are slightly S-shaped. Cyclic dimer is-not an intermediate product of trimerization with this catalytic system. Special experiments show that the addition of a dimer to a system containing a monomer and catalyst (TEDA-PO) has no effect on the shape o f kinetic curves of trimerization, or values of ~ind and Wmax. Furthermore, as shown b y Fig. 3, the dimer of CPIC breaks down slowly in the presence of T E D A - P O , being converted to a trimer; a monomer is first formed during the reaction, o f which the concentration passes through the maximum over a period of time. Without T E D A and PO trimer additives do not catalyse the reaction; the simple mechanism of auto-catalysis b y the end product which m a y formally explain the S-shaped form of kinetic curves, m a y therefore be ignored. The problem concerning the role of trimer, which is specific in this reaction, will be examined_ in detail when discussing results.

488

R . P . Tm~,la ~ a/,

The S-shaped form of ]dnetic curves observed experimentally cannot merely :be explained b y the slow formation of active eentres from TEDA and PO. Thus, -keeping the amine-oxide catalytic system without a monomer for 2 hr with concentrations of catalyst components used in the s t u d y does not remove the in,T~

1. Evv~.cT o~ co~o~r~rrs o~ TKZ C A T ~ O SYSTZMO~ ~ . ~ o

P~oP~.~Tms ov

TRIMERIZATION

'WmaxX

[CPIC] [TEDA] ,

x

10'

[PO]

"rind

Tmax

mole/1. 0"49 0"58 0"50 '0"53 "0"50 0"56 °0"57 ~)'52 0"60 0"56 0-52

1"04 0"99 0"99 1"01 0"97 1"10 1"06 0"20 0"20 0"20 0.23

r#

rain 57 0.127 40 0.440~ 25 0"530 23 0.990 19 1"260 13 1"760 10 0"450 106 1.050 74 1.540 70 1.950 50

80 63 40 38 30 23 17 145 103 93 73

0.080!

155 140 44 42 38 25 17 158 103 94 72

108, mole[l." .mill X

3.7 5.8 11.5 13.2 15.5 18.5 22.8

4.9 t0.0 12.3 12.0

~max

t~o.[Ox]o X l0 t,

min-1 ~ 0.25 N0.25 ,,,0.37 ~0.38 ,,,0.38

~0.40 ~O.38 N0.35 ~0.35 ~0'40 ,-,0.40

0.96 1.5 5-3 6.4 12.0 15.0 21.0 5.4 13.0 18.0 23.0

X

10*

X

sO*

molo/l. 0.520 0.594 1.290 1-510 2.230 2.200 2.220 1.120 1.800 2-480 2.400

0.730 0.891 2.080 2.420 3.380p 3.540 3.710 1"500 2.360 3.140 3"610

duction period. Even on keeping the amine-oxide system for 24 hr, there is an i n d u c t i o n period of trimerization, the value of z,, d increasing and Wmaxdecreasing somewhat, compared with standard experiments, in which TEDA, P 0 a n d '~PIC were added simultaneously. Interaction between componen~ of the catalytic system. I t is natural to assume t h a t active centres which initiate cyclotrimerization of isocaynate, are formed b y the interaction of TEDA and PO. I t is well known in particular [8, 9] t h a t terti,ary amines are catalysts in the reaction of opening the epoxide ring of oxides and polymerization. I t is established in this study t h a t with the concentration of TEDA and PO used in cyclotrimerization of RNCO in dioxane, the oxide is polymerized at a very low rate to form low molecular weight polyoxypropylene glycol. A typical feature of the polymer formed is the presence in the I R spectrum of bond-stretching vibration bands of the C = C bond in the 1640-1690 cm -1 range and deformation vibration bands of C - - H at the C = C bond at 1410-1420 e m -1, as well as bond stretching vibration bands of OH groups. Descriptions are given in the literature [9], according to which zwitterions o f the type R s N + - - C H ~ - - C H - - O - are the primary active centres of Chain

I O .extension in polymerization of epoxides on tertiary ,amines, although unfor"tunately there is so far no direct evidence of the formation of these ions. Since macromolecules containing hydroxyl are formed as a result of chain transfer

"K'inetlcs and mecha~;am of cyclic trimerization of isocyanat~

48g

(separation of the proton from the CHs group of PO, interaction with traces of moisture, etc.), the possibility of the formation of ionic pairs of the type of +

quaternary ammonium alcoholates R3NHO- in the system should not be excluded. We assume that zwitterions or ionic pairs taking part in polymerization of propylene oxide are also active centres in cyclotrimerization of isocyanate in the presence of the TEDA-PO catalytic system. The chemicalnature of active centres is of no fundamental significance from the point of view of formal-ldnetic analysis of trimerization. Importance is only attached to the fact that their formation takes place over a period of time during the interaction of amine with oxide. A relation between the rate of trimerization and the concentration of active centres may be established knowing the rate constant of formation in the system. The use of primary active centres for chain extension of polyoxypropylene glycol should either be excluded, or considered quantitatively. Chain rupture at the stage of formation of primary zwitterions may take place in particular by carrying out the reaction in the presence of proton-donor additives, e.g. wa~ter. It is assumed in many studies [10-12] concerning reaction kinetics of amines with epoxides that the stage of opening of the epoxide ring to form a zwitterion is the limiting stage in proton-donor media; conversion to amino-alcohol takes place rapidly by proton transfer from the solvent molecule. Assuming t h a t zwitterion (C)* formation is preceded by the equilibrium stage of complex formation between the reagents, the following reaction system between amine and oxide in the presence of water may be proposed:

CHs R.N+CH,__~ [ k, R~6+CH._C]H ~. • R~T--CH,,-----CH---O + CH+

\

A

/

~-,+

Ox

X

C*

-H,O R~+__CHI__CH__O H

rapidly

I

CHs When stationary in r~lation to [X] concentration in solution [X]=kl[A][Ox]/ /(/c1~ks) and when k_ 1>>k2 (equilibrium established rapidly) the formula of reaction rate takes the form: w = k , Ix]= ~

[g] [Ox]=Kk, [A] [Ox]=k,, [A] [Ox],

where K is the equilibrium constant of the formation of X, kefr=Kk 2 (1./mole. sec). In an excess of oxide, compared with amine, the pseudo-first order rate constant measured according to the concentration loss of amine in the system, takes the form:/~obs-~k~t [Ox] sec -1. Figure 4 shows the type of variation over a period of time of the UV spect~lm

R . P . T x a ~ a e# aL

~90

of T E D A in dilute dioxane in propylene oxide excess. The same Figure shows typical kinetic curves of D - t i m e and their semi-logarithmic transformations in coordinates of a first order equation. Results are given below con/)

a

210

b

/)

230

250 ;t,nm

IO

-Io9(D-D.o)

30

50

I0

c

gO

50

Time, rain

FIG. 4. U V spectra of T E D A in a dilute solution o f dioxane in t h e presence of PO: 1 - - 1 , 2 m 2 , 3 - - 5 , 4 - - 1 5 , 5 - - 3 0 rain (a), t y p i c a l kinetic c u r v e s of t h e r e a c t i o n (b) a n d t h e i r semil o g a r i t h m i c t r a n s f o r m a t i o n s (c); b, c: [ P O ] = 0 . 9 7 (1), 0.85 (2) a n d 1.0 m o l e ] l . (3)i [H=O]=5.@ (1}, 17.5 (2) a n d 27.9 mole/1. (3).

cerning the dependence of bobs on the concentration of T E D A and PO in water a t 25 °, which prove a first order reaction in relation to each reagent* [ T E D A ] × l0 s, mole/l. [PO], mole/1. bobs× 108, sec -1

3.8 5.6 0.104 0.108 1.4 1.4

5.0 3-3 4.3 0.294 0.300 0.870 3-4 3-1 9.9

Table 2 shows rate constants of the reaction studied, according to the waterdioxane solvent composition in PO excess. An increase of keff with an increase of water concentration, water functioning as polar component of the solvent, TABLE 2. RATE CONSTANTS OF I1WTEI~ACTIOZWOF T E D A W I T H P O I N .A.W A T E R - - D I O X A N E SYSTEM AT 250; [TEDA] ~ I0 -6 MOLE/L. [P0]

] [H,0] mole]l.

0.1-1.0 1.00 1"01 0.85 0"80 0.97 0.81 2.80 0.56

55.5 36.3 27.9 17.5 10.9 5.0 3.5 2.6 1.9

eofthe mixture 78"0 52-0 37-5 20.0 10.7 5.1 4.1 ' 3-6

3-2

koba x l 0 ~, ~eff X 10 ~, see -x L/mole. sec * 62 38 13 6.5 3-9 1.7 4-7 0-46

110 62 38 15 8.1 4.0 2.1 1.7 0.82

* Results concerning kob,in water are given above. * As shown b y kinetic curves a n d their t r a n s f o r m a t i o n s (Fig. 4b) a b r i e f i n d u c t i o n p e r i o d is o b s e r v e d a t t h e beginning of t h e r e a c t i o n o f T E D A w i t h P O , which could n o t b e e x p l a i n e d in t h i s s t u d y .

~inetics and mecb~-iRm of c,,,?clio trimerization of isocyanates

491

is easy to understand since charge separation takes place in the Bmlgng stage of the reaction, which is promoted b y an increase of the dielectric constant o f the medium. According to the electrostatic theory of the effect of solvent [13] in monomolecular transformation of a polar molecule, taking place with charge separation, a linear relation is observed between log betr and 1/8, where s is the dielectric constant of the medium. As shown b y Fig. 5a, this relation does not hold good in the entire range of E. In spite of this, the linear section m a y be extrapolated to pure dioxane (e-----2.23) and the rate constant of C* formation derived, kerr~~_2 × 10 -s 1./mole.sec. Deviations from the electrostatic theory are due to specific solvation of reacting particles and the intermediate sf~f~ as a result of the formation of a H bond with water. Using the equilibrium constant of T E D A H=O in dioxane ( K = 0 . 2 3 L/mole [7]) it m a y be shown that in the region of 8 > 2 0 (~>0.8) a larger part of T E D A is present in the system as a complex with water (Fig. 5b). Within the framework of the electrostatic theory of the effect of medium [13] an increase in the gradient in coordinates log b ~ - l / 8 in this range of 8 values m a y be due to the increase of dipole moments of T E D A and the intermediate state as a result of complex formation with the hydrogen bond.

Ic keff

keff,fg 3 12-

"2 A3

3

8-

#

%"NJ 0.1

I 0"3

I

o.51/e

Fzo. 5. Relation between keu of the reaction of TEDA with PO and l/e: /---dilute dioxane, 2--water, 3--ethanol, 4---dioxane (a) and relation between/cet ~and the molar fraction of of amine combined with a hydrogen bond with water (b).

Relation between the rate of trlmerization and the concentration of active centres. Using the rate constant of the reaction of T E D A with PO in dioxane derived b y extrapolation of kinetic curves which were plotted under conditions ensuring chain breakage at the stage of zwitterion formation, the rule of C* formation in the system [G*] = [TEDA]o( 1 -- e-k=t'[Ox]°t) being known, we evaluate [C*] in experiments of trimerization of CPIC. Table 1 shows C* values in relation to moments ~ d and ~m~x with different concentrations of components of the catalytic system. I t can be seen that the

492

•

R.P.

Tzo~

~ M.

concentration of gctive centres in the system is lower b y 2 orders of magnitude than the initial concentration of TEDA. The value of [C*] w i ~ ~m~ is only 1,5 times higher than [C*] with ~lnd, although the rate of trimerization b y ~m~x moment of time increases very suddenly, compared with the rate of the reaction b y Tlud moment of time. The relation between Wm~x and [C*] with ~m~x is shown in Fig. 6. It follows from this relation in bilogarithmic coordinates that the order of the reaction in relation to active centres varies from first to about third. I t should be noted t h a t the value of [C*] was calculated without considering the consumption of these centres at subsequent stages of chain extension and breakage of polyoxyl~ropylene glycol. The calculation of the consumption of C* should result in a sharper form of the dependence of wmax on [C*] at ~m~x.

Hlaecial features of the "auto-catalytic" effect of the trimer and matri~ mechanism of exttatysis. The absence of proportionality between the concentration of zwitterions and the maximum rate of trimerization suggests that active centres are transformed during the reaction, thus increasing catalytic activity. This assump-

! I

2 [c*J',mo/e/z.

Fro. 6

2o

60

1oo "b T/me, m/n

~o

Fro. 7

Fio. 6. Relation between w=~ of t~nerization and [C*]'--the concentration of active c e n t , s C* at Tmaxwithout considering the consumption of C*. Fxo. 7. Effect of trimer additives on the rate of trimerization: a: 1--trimer (0-08 mole/].) obtained with only TEDA; 2--trimer (0"06 mole/L), obtained using TEDA-PO; b:/--reaction before the addition of a fresh monomer sample; 2--reaction with a fresh monomer samples (added at zero moment of time after discontinuity on the abscissa) in the system with [TEDA]----0.195 × 10-I, [PO]~ 1.95 mole~l.

Kinetics and mechanism of cyclic trimerizafion of isocyana~es

495

tion may be further substantiated by several experimental facts obtained when studying the effect of trimer additives on the rate of tdmerization of CPIC a n d the shape of kinetic curves. As shown by Fig. 7a, trimer additives synthesized using TEDA without a cocatalyst, in the absence of TEDA and PO in dioxane, do not result in trimerization of isocyanate, whereas in the presence of a trimer obtained using a TEDA-PO system the reaction takes place very rapidly and without an induction period. Similar results were obtained without preliminary separation of the trimer. Thus, after the complete disappearance of the monomer, a fresh monomer sample was introduced into the system containing the trimer formed and the initial catalyst components. The reaction took place without an induction period in this case (Fig. 7b). When trimerization was carried out using only TEDA, the addition of a new monomer sample after completing the process, in contras~ to the experiment described, did not result in a sudden increase in the consumption of 1~C0 groups. Results simply point to the existence of interaction between C* and the trimer formed during the reaction, which results in a modification of the active centre. There' is information in the literature concerning the high complex forming ability of isocyanate trimers [14, 15]. Complexes of trimers with organic solvents such as acetone and DMF are formed very easily and are so strong that they only break down in vacuum on heating to 100-200 °. Assuming that complexes of trimer with C* are formed in our case it can be understood why the trimer obtained using the TEDA-PO system, being separated by simple reprecipitation from solution, actively undergoes trimerization. The experimental reaction order (close to third) for [C*] and monomer concentration by Zmaxmoment of time suggests that the trimer functions as a matrix, on which three active centres are arranged. This structure of the new, matrix catalyst "enables three monomer molecules to be coordinated on it at once. The problem concerning the type of matrix catalyst formed during trimerization is being dealt with in a special study. It may be assumed in first approximation that the same zwitterions or ionic pairs which initiate trimerization in the initial period of the reaction, are "attached" practically unchanged to the trimer molecule. The fact, however, that the matrix catalyst contains threo active centres, hardly raises any doubt. The activities of several catalytic systems of trimerization [1] such as amineoxide, amine-aldehyde, amine-amine, metal alcocholates, salts of some carboxylic acids, etc, may be explained from single standpoints using theories o f matrix catalysts. Cyclic trimer associates may be formed in every case on a matrix trimer, which consist of either catalyst-cocatalyst components, interacting with each other with rupture or partial polarization of bonds, or ionic pairs of the type of RO-Me +, RCOO-Me +. 2,4,6-tri-(dimethylaminomethyl)phenol containing three amino-groups attached by the CH2 group to the benzene ring [2] is a special analogue of the matrix catalyst of trimerization. As shown

~94

R . P . T ~ a ~ ~ a/.

previously, this catalyst without a cocatalyst undergoes trimerization much more actively t h a n T E D A and without an induction period. I t should be noted finally t h a t the idea concerning the formation of a new catalyst, more active t h a n C* in the course of the reaction m a y be used to control

C,mole/I. 0.6-

20

6O tO0 rime, rein

NO

I~G. 8. Effect of the formation of a matrix catalyst on the form of the kinetic curve and the ~ate of trimerization with [TEDA]=--2.2× 10-s, [PO]=2.0 mole/l: /--without trimer ad. ditives; 2---with the simultaneous addition of 0.52 mole/l, trimer and monomer, TEDA and 1)0; 3--trimer (0.51 mole/l.} was added to the TEDA-PO system 70 rnin (~m~) before the addition of the monomer. the rate of trimerization. Thus, keeping the T E D A - P O catalytic system with trimer for a certain length of time required to obtain Wmaxat given concentrations of T E D A and PO, the induction period m a y be practically removed (Fig. 8). These results are easy to understand from the point of view of matrix catalysis: a catalyst of trimerization, more active t h a n without the trimer, is formed during retention. Changing retention time and the concentration of the m a t r i x - - t r i m e r , reaction rate m a y be varied within wide limits and if necessary, the process can be carried out without an induction period altogether. The kinetic system of matrix catalysis in cyclo-trimerization of isocyanates will be analysed by the authors at a later stage. Trana~e_~ by E. S ~ R Z REFERENCES

1. 2. 3. 4.

R. P. TIGER, L. I. SARYNINA and S. G. ENTELIS, Uspekhi khimii 41: 1672, 1972 L. NICHOLAS and G. T. GMITTER, J. Cellular. Plast. 1: 85, 1965 GERHARD and J. DETLEF, Plaste und Kautschuk 28: 177, 1976 A. FARKAS and G. MH.T.S, Sb. Kataliz. Polufunktsional'nyye kataliza~ory i slozhnyye reak~ii (Semi-functional Catalysts and Complex Reactions). "Mir", 1965 5. B. D. BEITCHMAN, Indnstr. and Eng. Chem. Prod. Res. Dee. 5: 35, 1968 6. (L N. PETROV, L. Ya. RAPPOPORT and F. S. KOGAN, Vysokomol. soyed. BU: 828, 1969 (Not translated in Polymer Sci. U.S.S.R.) /

Co-oligomerization of t e t r a h y d r o f u r a n with propylene oxide

495

• Y. R. P. TIGER, I. G. BABAYEVA a n d S. P. BONDARENKO, K i n e t i k a i kataliz 18: No. 1, 1977 8. DZh. F U R U K A W A a n d T. SAEGUSA, Polimerizatsiya al'degidov i okisei (Polymerization of Aldehydes and Oxides). "Mir", 1966 9. J. TANAKA, M. TOMIO and H. KAKIUCHI, J. Macromolec. Sci. A I : 471, 1967 10. J. HANSOON, A Kinetic S t u d y of the Addition of Amines to Propylene Oxide, Lund, 1955 11. J. HANSSON, Svensk. Kern. Tidskr. 66: 287, 351, 1954 12. J. HANSSON, Svensk. Kern. Tidskr. 67: 246, 256, 263, 1955 13. S. G. ENTELIS and R. P. TIGER, K i n e t i k a rcaktsii v zhidkoi raze (Liquid-Phase Reaction Kinetics). " K h i m i y a " , 1973 14. Y. I W A K U R A , K. UNO a n d V. KABAYASHI, Bull. Chem. Soc. J a p a n 89: 2551, 1966 15. R. TSUZUKI, K. ICWI]K~,WA and N. KASE, J. Organ. Chem. 25: 1009, 1960

THE MECHANISM OF CO-OLIGOMERIZATION OF TETRAHYDROFURAN WITH PROPYLENE OXIDE IN THE PRESENCE OF METHACRYLIC ANHYDRIDE* A. A. BERLIN, L. N. TUROVSKAYi and N. G. MATV~.YEVi I n s t i t u t e of Chemical Physics, U.S.S.R. A c a d e m y of Sciences

(Received 21 September 1976) A s t u d y was m a d e of t h e effect of the order of adding propylene oxide (PC) a n d a c a t a l y s t on process mechanism, molecular weight a n d functionality of oligomers formed b y co-oligomerization of t e t r a h y d r o f u r a n with P C b y the action of SbClt in the presence of methacrylic ahnydride (MA). I t was shown t h a t MA takes no p a r t in practice in initiation of oligomerization. Chain extension is effected on active centres of the t y p e of cyclic zwitterions and ionic pairs of different properties on counterions. The ratio of these active centres depends on the order or adding P C a n d the catalyst. A possible mechanism of adding m e t h a c r y l a t e groups into oligomer molecules is described. The overall functionality in relation to methacrylate groups a n d chlorine of oligomers obtained on adding P C after SbC15 is higher t h a n for oligomers synthesized on adding the catalyst into a m o n o m e r - M A mixture, b u t is less t h a n 2 in both cases. The lack of functional groups m a y be due to t h e presence of macrocyclic oligomers.

IT is known that cyclic a-oxide additives function as activators, taking part in the formation of active centres [1-3] in homopolymerization of tetrahydrofuran (THF). On the other hand, it is universally adopted that during copolymerization of T H F with propylene oxide (PO) in the presence of glycols initiation only takes place with glycols [4-6]. However, during copolymerization of these monomers on BF3 esterate with 1,2-propanediol as co-catalyst [7] it was shown that * Vysokomol. soyed. A19: No. 2, 428-433, 1977.