The role of proton-donors in cyclotrimerization of isocyanates by the action of an amine-epoxide catalytic system

2768

3 . A. SH~B~--~OVA e~ a/.

10. A. L. BUCHACHENKO and A. M. VASSERMAN, Stabil'nyye radJkaly, Khimiya, Moscow, 1973 11. A. L. BUCHACHENKO, A . L . KOVARSKH and A. M. VASSERMAN, (book), Uspekhi khimii i fiziki polimerov, Khimiya, Moscow, 1973 12. E. Ire. TOMASHEVSKII and A. I. S L U T S K E R , Zavodsk. lab. 29: 9, 994, 1963 13. S. N. ZHURKOV, B. Ya. LEVIN and A. V. SAVITSKII, Dokl. A ~ SSSR 186: 1, 132, 1969 14. V. B. STRYUKOV, E. (L R O Z A N T S E V , A. I. KASHLINKSII, N. G. MAL'TSEVA and I. F. TIBANOV, Dokl. A_~ SSSR 19O: 4, 895, 1970 15. N. Ya. RAPOPORT, S. I. B E R U L A V A , A. L. K O V A R S K I I , I. N. MUSAELYAN, Yu A. Y E R S H O V and V. B. MILLER, Vysokomol. soyed. A17: 11, 2512, 1975 (Translated in Polymer Sei. U.S.S.R. 17: 11, 2901, 1975) 16. H. G. OLF and A. PETERLIN, J. Polymer Sei. A-2, 9: 8, 1449, 1971 17. E. A. MELWYN-HUGHES, Fizicheskya khimiya (Physical Chemistry). Izd. inostr, lit., Moscow, 1962 18. L. I. PAVLINOV, (book), Svoistva veshehestv i stroyeniye molekul (Properties of Material and Molecular Structure). Kalinin, 72, 1977 19. T. M. BIRSHTEIN and 0. B. PTITSYN, Konformatsii makromolekul (Macromoleoular Conformation). Nauka, Moscow, 1964 20. V. V. SYCI~EV, Slozhnyye termodinamicheskiye sistemy (Complex Thermodynamic Systems). Energiya, Moscow, 1970 21. F. Kh. SAI)YKOV, Khimich. volokna, 2, 45, 1971 22. L UORD, Mekhanicheskiye svoistva tverdykh polimerov (Mechanical Properties of Solid Polymers). Khimiya, Moscow, 1975

Polymer Science UIS.S.R. Vol. 24, ~fo. 11, pp. 2768-2778, 1982

:Printedin Poland

0032-3950~82 $7.50-~.00 © 1983 Pergamon Pre~ Ltd.

THE ROLE OF PROTON-DONORS IN CYCLOTRIMERIZATION OF ISOCYANATES BY THE ACTION OF AN AMINE-EPOXIDE CATALYTIC SYSTEM* N . A. SHIBANOVA, A. K . ZHITI~KIlgA, L. V. TURETSKII a n d N. V. V ~ T S O V A All-Union Scientific Research Institute of Synthetic Rubbers

(Received 31 June 1981) A kinetic study was made of eyclotrimerization of phenylisocyanate by the action of a 2-methyl-diazabicyelooetane-phenylglyeidyl ether catalytic system in the presence of proton-donors and of variations taking place in the catalytic system itself over a period of time. Water, methanol, phenol, diphenyluroa, methyl-~-phonylurethane and methyl-a,y-diphe~ylallophanato wore used as porton-donors. I t was shown that during the interaction of all three components of the catalytic system products of quaternary ammonium bases are formed with high basicity and much * Vysokomol. soyed. A24: No. 11, 2408-2415, 1982.

Role of proton-donor~ in eyclotriraerization of isocyaitates

2769

higher catalytic activity in the process examined t h a n the mnine--epoxide binary system. Diphenylurea has the highest activity as proton-donor. A proportionality was established between the rata of cyclotrimerization and the ooneentration of active adduct formed in the ternary system.

IN the development of polymer materials with increased thermal and fireresistance, cyclotrimerization of isocyanates is widely used; this process is usually carried out in the presence of compounds with a mobile hydrogen atom--hydroxyl-containing oligoethers or esters, glycols and polyols, water, etc. [1-4]. Tertiary amines together with epoxides [1, 2, 4-6] are often used as catalysts. Various scientists [1, 6] noted the co-catalytic role of water in cyclotrimerization of isocyanates, catalysed by a tertiary amine-epoxide system, however, the effect of proton-donors on a given reaction has not been examined from a kinetic point of view [1, 5-8]. It was shown previously [9-11] that the catalytic activity of the amine-epoxide system in relation to cyclotrimerization of isocaynates increases considerably on keeping amine with the peroxide previously. With an increase in the moisture in the system, the increase in catalytic activity is more clearly expressed. Based on results it was assumed that catalysis of cyclotrimerization of isocyanates is effected using a product formed from tertiary amine, epoxide and a hydroxylcontaining compound, the presence of which in these systems is inevitable [12]. I t was noted also that, in addition to typical proton-donors (water, alcohols), products of primary and second~.'y interaction with isocyanate, namely urethane, allophanate, urea and biuret may also have co-catalytic activity in the reaction examined. This paper deals with a more detailed study of the role of proton-donors in catalysis of cyclotrimerization of phenylisocyanate (PIC) by the action of a 2-methyl-diazabicyclooctane (metyl-DABCO)-phenylglycidyl ether (PGE) catalytic system in the presence of various proton-donors (PD). In order to establish the type of active product formed, conversions taking place in the amineepoxide-PD catalytic system itself during retention were examined. Cyclotrimerization of PIC was carried out in chlorobenzene under isothermal conditions at 25 ° and under adiabatic conditions at a n initial temperature of 25 o. I n view of the limited solubility of components of the catalytic system in chlorobenzene, it was prepared in the form of a solution in DMF with the following concentrations: [methyl-DA_BCO] : 0 . 2 , [ P G E ] : 0 . 4 and [ P D ] : 0 . 4 mole/1. The product of cyclotrimerization was identified by I R spectroscopy according to absorption bands at 1420 and 1710 em -1 corresponding to tripher~ylisocyanurabe. Kinetic of eyclotrimerization of PIC were monitored under isothermal conditions chemically b y the conversion of NCO groups, while trader adiabatic conditions, nearest to real processes for obtaining expanded polyisocyanurates b y thermometry [9, 13, 14], using parameters such as the induction period a n d initial velocity. The catalytic system was examined b y argentometric, dielectrometric and potentiometric titration. Argentometric titration which controls the content of epoxy groups in the catalytic system, was carried out using a Ph-340 device and a glass-silver electrode pair. The dielectric constant 8 of catalytic systems in benzene was measured using a " T a n g e n t "

2770

~ . A. SHIBA~OVA et al.

device at a frequency of l0 s Hz using PD solutions as titrant, Dipole moments were calculated according to Debye. The relative basicity of catalytic systems ill nitromethane or DMF was determined from results of potentiometric titration using a Ph-340 device, a glass-ehloro-silver electrode pair and 0-05 )r HC104 solution in dioxane as titrant. Diphenylguanidine was the standard. Relative basicity was determined from the difference between potentials of semi-neutralization JE½ of the system studied and diphenylguanidine (DPG). All solvents were purified and dried according to methods previously described [15]. I_u eblorobenzene ([Cl-]<0-001~o) the content of chlorine ions was controlled. PIC was kept over calcium oxide and to reduce the concentration of the chlorine ion below 0-001% it was further retained for 1 hr with dimcthylethanolamine ( ~ 1 wt. % of PIC), then filtered and distilled in vacuum, using a fraction of b.p. 67°/13.3 gPa and with a C1 content <0.001 w*.%. Methyl-DABCO was freed from traces of moisture, prhnary and secondary amines by retention for 30-40 mill with 1-2 wt.~o toluylenediisocyanate, filtered and distilled in vacuum, using a fraction of b.p. 72-74°/13.3 gPa. PGE was dried over calcium hydride and distilled i n v a c u o (b.p. 101-105°/6.6 gPa). Methyl-N-phenylurethane was obtained by adding PIC dropwise to dehydrated methanol and recrystallized from methanol; it was identified according to absorption bands at 1220 and 1760 em -1 in the IR spectrum. Methyl-g,y-diphenylallophanate were obtained from a PIC dimer and methanol mad identified according to absorption bands at 1240, 1280, 1695 and 1740 cm -1. Diphenylurea was synthesized by slow addition of water to PIC and absorption bands at 1220, 1230 and 1708 cm -1 in the IR spectrum were used for identification. W e h a v e previously established [9-11] t h a t catalytic a m o u n t s o f P D a n d i s o c y a n a t e t r i m e r a d d e d t o t h e reaction s y s t e m a t t h e same t i m e as the a m i n e - e p o x ide b i n a r y catalyst, do n o t m a r k e d l y accelerate cyclotrimerization o f isocyanates. A s t u d y o f the effect o f previous contacting of P D with an amine cpoxide c a t a l y t i c s y s t e m on kinetics o f cyclotrimerization shows t h a t during r e t e n t i o n o f this t e r n a r y s y s t e m its c a t a l y t i c a c t i v i t y m a r k e d l y increases o v e r a period o f t i m e a n d depends on t h e t y p e o f P D a n d concentrations o f c o m p o n e n t s in the system. W i t h a c a t a l y s t c o n c e n t r a t i o n (at m e t h y l - D A B C O ) I> 10 -2 mole/1, t h e i n d u c t i o n p e r i o d practically disappears a f t e r 2-4 h r r e t e n t i o n of the c a t a l y t i c s y s t e m (Table 1) a n d the time r e q u i r e d for achieving m a x i m u m catalytic a c t i v i t y u n d e r t h e conditions studied is in t h e i n t e r v a l o f 4-24 hr. The a c t i v i t y in cyclotrimerization o f P I C achieved during r e t e n t i o n o f the s y s t e m does n o t decrease for a long period o f t i m e (10-30 days). A s t u d y o f t h e c o n c e n t r a t i o n d e p e n d e n c e o f t h e a c t i v i t y o f a catalytic s y s t e m p r e v i o u s l y k e p t for 24 h r shows t h a t it depends on t h e c o n c e n t r a t i o n o f e v e r y comp o n e n t in t h e system. P a r t i c u l a r orders o f t h e r e a c t i o n studied for each compon e n t o f the catalytic s y s t e m are equal t o one and the c o n c e n t r a t i o n order f o r P I C is two (Fig. 1). P r e v i o u s contacting of P D with amine alone or w i t h o n l y epoxide does n o t increase the catalytic a c t i v i t y o f the a m i n e - e p o x i d e - P D s y s t e m . Results t h e r e f o r e p r o v e t h a t all ingredients o f the a m i n e - e p o x i d e - P D t e r n a r y c a t a l y t i c s y s t e m t a k e p a r t in the f o r m a t i o n o f a p r o d u c t , which is a m u c h m o r e active c a t a l y s t o f cyclotrimerization of isocyanates t h a n the a m i n e - e p o x i d e b i n a r y system.

Role of proton-donors in cyclotrlmerization of isocyanates

2771

I o~:JZUm= [m ole/L .m in_7 a

1"0

0~5

L

S I

2.E

o.5

z~elad, L/mole

b /a

1

I

2 1.5 - log c Cmole/l.] Fro. 1

J ,/.'P"

x"

i

0 0"2 lo~ C [mole~l_]

!

2

3

[ool/[Ad , ~ote/~ole Fro. 2

FIG. 1. Bilogarithmic dependences of the rate of cyclotrimerization of PIC on the concentration of components of the catalytic system methyl-DABCO (1), phenol (2), PGE (3) (a) and on PIC cocentration for urethane (1), methanol (2), urea (3) (b). a: 1 - - [ P G E ] = p h e nol-----8× 10-8 mole/1.; 2--[methyl-DABCO]----4× l0 -3, [ P G E ] = 8 × 10-a mole/1.; 3--[methyl-DABCO]=4 × l0 -3, [phenol]: 8 × 10 -a, [PIC] = 1.44 mole/1.; b: 1--[methyl-DABCO] = 1.6 × 10 -3, [PGE] =[urethane] = 3-2 × l0 -3 mole/1.; 2--[methyl-DABCO] = 0.8 × 10 -~-, [PGE] = [methanol] = 1.6 × 10-2 mole/1. ; 3--[methyl-DABCO] : 1.6 × 10-3, [PGE] :[urea] ~ 3.2 x × l0 -a mole/1. FIG. 2. Curves of dielectrometric titration of a Iaethyl-DABCO-PGE system with methanol (1, 2) and phenol (3, 4) without retention (1, 3) and with retention at each point for 4 hr (2, 4). A0--(methyl-DABCO+PGE), B0--proton-donor. I n v i e w o f t h e foregoing it is o f p r a c t i c a l a n d t h e o r e t i c a l i n t e r e s t to e x a m i n e processes t a k i n g place in t h e t e r n a r y s y s t e m a n d establish t h e t y p e of p r o d u c t f o r m e d . I n this s t u d y this p r o d u c t was m a i n l y s t u d i e d using a m i n e - e p o x i d e - p h e nol (or m e t h a n o l ) c a t a l y t i c s y s t e m s , h o w e v e r , t h e d e p e n d e n c e s e s t a b l i s h e d are also t y p i c a l of o t h e r s y s t e m s studied. T a b l e 2 shows results of a r g e n t o m e t r i c t i t r a t i o n of c a t a l y t i c s y s t e m s a t differe n t stages of r e t e n t i o n . I t can be seen t h a t on r e t e n t i o n t e r n a r y s y s t e m s e p o x i d e g r o u p s d i s a p p e a r , t h e r a t e of t h e i r c o n c e n t r a t i o n change increasing w i t h a n increase in t h e a m o u n t of P D a n d on r e p l a c i n g m e t h a n o l b y phenol. I n t i t r a t i o n of t h e a m i n e - e p o x i d e s y s t e m w i t h a P D solution it was f o u n d t h a t w i t h o u t p r e v i o u s r e t e n t i o n o f t h e t e r n a r y s y s t e m the value of ~ is d i r e c t l y prop o r t i o n a l to P D c o n c e n t r a t i o n (Fig. 2, curves 1 a n d 3) a n d w i t h s u b s e q u e n t r e t e n t i o n o f t h e t e r n a r y c a t a l y t i c s y s t e m e increases o v e r a p e r i o d o f time. T h e v a l u e o f for a m e t h y l - I ) A B C O - P G E - p h e n o l solution c h a n g e s f r o m 2.402 to 2.466 in 24 hr, t h e m a x i m u m r a t e o f increase being o b s e r v e d in t h e initial period of r e t e n -

2772

l~. A . S m ~ o v A

~ a/.

TABr.~ 1. ~ O T OF P ~ v x o u s ~ o ~ " o~' ~ . - ~ ' ~ , a x , . - D A B C O - P G E - P D CATAT,X"~O SYS~M O7 ~ O S OF CYCLO~rJ~ZATION OF P i e AT 25 ° r~ C~mOnOB~ZE~ ([PIC]0~ 1"44 mole/L)

Proton-donor

![Methyl. DABCO] x x l0 s

[PGE] X x 10a

[PD] X 10'

Retention time, hr

molefl.

Wm~,

molefl. • -min

~'0~

Without PD

1-6 1-6 1"6 1"6 1.6

3"2 3"2 3.2 3"2 3-2

u

0 2 4 10 24

0.04 0-08 0.17 0•27 0.59

50 25 10 3"3 1"0

Methanol

1.6 1.6 1.6 1.6 1.6 1.6

3.2 3.2 3.2 3.2 3.2 3.2

3"2 3"2 3"2 3"2 3.2 3.2

0 2 4 6 24 48

0-04 1.72 3"42 6•84 11.60 12.00

50 0"25

3"2 3.2

0 0"1 2 4 6 10 24

0"09 1.32 11.6 13.72 18.28 22.00 24.00

0 1 4 24

3.06 8.00 4"28

,J

Phenol

1.6

3"2

3"2

1.6 1.6 1.6

3.2 3.2 3.2 3.2 3-2

3"2 3.2

1-6 1.6 Urea

Urethane

Allophanate

3•2

!

0.8 0.8 0.8 0"16

1"6 0"32

1"6 1"6 1"6 0.32

0.8 0.8 0.8 0-16

1"6 1.6 1"6 0.32

1•6 1-6 1"6 0"32

0 1 4 24

0.31 2"00 1"2

0.8 0.8 0.8 0-8 0.16

1.6 1"6 1"6 1-6 0.32

1"6 1.6 1.6 1"6 0"32

0 1 2 4 24

1"92 4.40 13"20 2'35

1.6 1"6

16"7 0"t

>60 0.22 0"1 0'1 >60 4.8

0.3 0"7 >60 0.30 0.10 0.05 0.05

tion. These results confirm that although on mixing the catalytic system the proton-donor undergoes noticeable polarization, other donor-aeceptor complexes are n o t f o r m e d i n s t a n t a n e o u s l y , while d u r i n g r e t e n t i o n of the t e r n a r y s y s t e m a p r o d u c t o f h i g h e r p o l a r i t y t h a n t h e i n i t i a l c o m p o n e n t s is f o r m e d •

Role of proton.donors in cyulotrimerization of isoeyanates

2773

Figure $ (curves 2 and 4) shows rosults of measuring the value of 8 during titration of a methyl-DABCO-PGE solution with a PD solution with rontention o f minimum 4 hr in each concentration point. I t can be seen t h a t under these conditions strong adducts are formed, the polarity of which is much higher t h a n the polarity of the initial components. For example, dipole moments for methanol and phenol in benzene are 1.65 and 1.70 D, respectively, while in catalytic adduets TABLE

2. DEPENDENCE

OF ' P ~

DEGREE

METRYL-DABCO-PGE-PD C A T A L Y Z e

OIr CONVERSIOI~ OF E P O X I D E GI~OUPS ~e

IN THE

S Y S T E M ON R E T E N T I O N T I M E A N D T H E T Y P E OF P R O T O N DONOR

([MethyLDABCO]~0.3; [PGE]~[PD]~0.6 mole/L; ehlorobenzene, 25°) ~e, ~o for various PD Retention I time, hr without PD methanol phenol

Retention time, hr

~e, % for vaa'ious PD without PD methanol phenol

4

6 24

5.3 8.1

48.6 65"6

] t

63.5 84-5

48 96

22.2 70.0

92.4 100.0

92.6 100"0

TABLE 3. CHARACTERISTICSOF THE RELATIVE B&SICITY OF ADDUCTS FORMSEDIN THE METHYL-DABCO-PGE-PD SYSTEM ([Methyl-DABCO]= 0.2; [PGE] = [PD] = 0.4 mole/1.; retention time 24 hr; DMF, 25°) PD Water Methanol

AEIIt,

mV

PD

210 220

Phenol Urethane

~El/2 ,

mV

PD

270 225

Allopha nate Urea Without PD

AElf~ ,

mV

160 220 60

t h e y have values of 3.53 and 4.04 D. The adducts formed, as shown by Fig. 2, have an eqnimolecular composition if PD is one of the components and t h e m e t h y l - D A B C 0 - P G E system, the other. The validity of using this method for calculating dipole moments and for determining the composition of adducts formed in the system is described in another paper [10]. Figure 3 and Table 3 show results of potentiometric titration of the catalytic systems studied. The dependence of relative basicity of the system on time, the same as in dielectrometry, was studied for a m e t h y l - D A B C 0 - P G E - p h e n o l t e r n a r y system. The curve of potentiometric titration of a freshly prepared system fully agrees with the titration curve of methyl-DABC0 alone and in Fig. 3 t h e y are shown b y curve I alone. On retaining the catalytic system for 1 hr the curve of potentiometric titration undergoes a qualitative change: a new change appears in the range of 600---450 mV, which is evidence of the formation of a new product in the system. As the duration of retention of the catalytic system increases, the concentration of the product formed is higher and the concentration

2774

N. A. S m ~ a ~ o v A e~ a/.

~f methyl-DABC0 decreases at the s a m e time so that the overall concentration of the product and methyl-DABCO remains constant. Table 3 indicates that during retention in all the systems examined a product is formed, the relative basicity of which considerably exceeds the basicity of methyl-D'ABCO, while in the system with phenol (Fig. 3, curves 2-4) the basieity E~mV

0

-400

/ I

1

~

I

I

I

J

i

I

7

5

VHClO+ ~m l

FIG. 3. C~rves of potentiometric titration of a m e t h y l - D A B C O P G E - p h e n o l catalytic system (l-d), methyl-DABCO (1'), diphenylguanidine (5) and tetramethylarnmonitun hydroxide (6) system in nitromethane; retention time of the catalytic system 0

(1), 1 (2), 4 (3) and 24 (4). of the product exceeds the basicity of quaternary ammonium base taken for comparison. According to IR spectroscopy [17], interaction of components of the catalytic system is aceomla~nied by a marked structural change-over o f all PD studied, particularly strong ionization of O - - H or N - - H bonds in them. Results of a composite study of a tertiary amiuc-epoxide-PD catalytic system suggest that during the interaction of all the three components of this system adduets are formed of the type of quaternary ammonium derivative with the hypothetical structure b+

6-

6+ 6-

RsN-- CHs-- CH-- O...H...R',

of high polarity and basicity, these being effective catalysts in cyclotrimerization. Figure 4 shows kinetic curves and their semi-logarithmic transformations for cyclotrimerization of PIC under isothermal conditions; these experiments were carried out with about the same concentrations of the catalytic adduct, obtained with different proton-donors, except for the adduct based on urea. Figure 5 shows the variation of kinetic curves with the concentration variation of a catalytic adduct obtained from methanol and phenol. The concentration of the catalytic adduct was determined by potentiometric titration of the catalytic system imme-

Role of proton-donors in oyolotrimeriz~tion of isocyanatms

EPIC.I,mole/l.

l- [PIC]o "C~c/

a

2775

D

1"0

I

0"5

I q2 I

0

5

,,,

0 T/me ~rain

10

5

I

10

FIa. 4. Kinetic curves (a) and semi-logarithmic transformations (b) for cyclotrimerization of PIG b y the action of catalytic systems of m e t h y l - D A B C 0 - P G E - P D at 25 in ehlorobenzene for various PD; 1--allophanate, concentration of the catalytic adducts being 3.4x104; 2 - - u r e t h a n e , 3.8)<10-4; 3--methanol, 3-2×10-4; d--water, 3-2× 10-4; 5 - - u r e a , 1.4 × 10-4; 6--phenol, 4 × 10 -4 molell.

[PIC.~,rnole/l.

I_ fPscTo n-~

a

1.2

1"2

0.8

0"8

O.q!

0"4 •

I

I

i

I

1'6i

t'J,

1.2

0,8

0.8

O.q

O'q I

0

20

qO

I

I

60 T i m e, rain

Ill

20

40

Fxc. 5. Kinetic curves (a, e) a n d semi-logarithmic transformation~ (b, d) for cyelotrimerization of PIC by the action of m e t h y l - D A B C O - P G E - P D catalytic systems in chlorobenzene a t 25° with methanol (a, b) a n d phenol as P D (c, d); concentration of the adduc~ 0.4 × 10 -4 (1), 0.8× 10-4 (2), l>6x 10-' (3) and 2.4)< 10-4 mole/1. (4).

2776

N, A. SHIBANOVA el a~.

diately before being introduced into the reaction medium. Figure 4 indicates t h a t the adduct which is based on urea is the most active. Adducts with phenol also have increased activity, whereas remaining PD examined form adducts of similar catalytic activity. An increase in activity on transition from water and methanol to phenol of high acidity, m a y be explained by an increase in the polarity and basicity of the catalytic adduct formed. A relatively high catalytic activity of the system with urea cannot be explained from these points of view and probably depends on the specific structure of the adduct formed; this structure cannot be evaluated within the framework of this study. All kinetic curves of cyclotrimerization of PIC (Figs. 4 and 5) are S-shaped and characterized by the existence of an induction period, after which the reaction begins to take place at a rate which is close to the maximum. With an increase in the concentration of the catalyst, the maximum rate of cyclotrimerization Wm=x increases and the duration of the induction period t0 decreases. Figure 6

-los uJ = (,,ole/l..roi,J j

-loS1 Erniz _rz

£PIC.], rno/e/l.

~<-o-x--(:y.---x--%

(2"8ol

o~

1"2 I q

I

s.5-tosc Fio. 6

1,1

20

t 40

2,2' 'Z'~.min

FI(~. 7

Fio. 6. Bilogarithmic dependences of the rate of cyclotrimerization of PIC. (1) and of the induction period (2) on the concentration of the adduct for catalytic systems with phenol (1) and methanol as PD (II); [PICJ0=mole/1., ehlorobenzene, 25°. FIo. 7. Kinetic curves of cyclotrimerization of PIC in the presence of a trimer (1,' 2') and without a trimer (1, 2). Solvent -- ehlorobenzene. shows the dependence of maximum rate of cyclotrimerization and of the value which is the inverse of the induction period, on the concentration of catalytic adduct in bilogarithmic coordinates. I t can be seen t h a t a particular reaction order for the catalytic adduct in these cases is equal to one. As shown by the transformations in Figs. 4 and 5, the time order of cyclotrimerization for PIC is also equal to one. I t is impossible to explain the type of kinetic curve of cyclotrimerization using the matrix mechanism of catalysis of the reaction studied [8] proposed recently since, to our mind, this is contradicted by kinetic considerations and by the results obtained which prove the absence of an effect of trimers on kinetics of cyclotrimerization of PIC under the conditions examined (Fig. 7).

Role of proton-donors in cyelotrimerization of isocyanates

2777

1~O co-catalysis was observed in ~ previous s t u d y either [18] w i t h a t r i m e r i a c y c l o t r i m e r i z a t i o n of i s o c y a n a f c s in t h e presence o f similar catalysts. A t the same time we established t h a t kinetics of c y c l o t r i m e r i z a t i o n of i s o c y a n ares, p a r t i c u l a r l y t h e i n d u c t i o n period a n d m a x i m u m reaction rate are m a r k e d l y influenced b y acidic inhibitors, e.g. h y d r o g e n chloride, t h e possible presence of w h i c h in i s o e y a n a t e s a n d in ehlorobenzene should be t a k e n into account. I t m a y be a s s u m e d f r o m these results t h a t the i n d u c t i o n period of the r e a c t i o n s t u d i e d is d e t e r m i n e d b y t w o factors, n a m e l y the a c t i o n o f the inhibitor a n d t h e slow f o r m a t i o n of active centres. More detailed analysis of these effects requires f u r t h e r investigations. Translated by E. ,~.'I']MERFREFERENCES

1. 2. 3. 4. 5.

B. D. BEITCHAMN, Industr. and Engng. Chem. 5: 1, 35, 1966 B. D. BEITCHAMN, U. S. Pat. 3154522, 1965, Publ. in Ref. Zh. Khim., 3S 265P, 1967 K. G. FRISCH, K. J. PATEL and R. D. MARSgH, J. Collulax Plast. 6: 5, 203, 1970 L. NIKOLAS and G. T. SMITTER, J. Cellular Plast. 1: 1, 85, 1965 G. N. PETROV, P. Ya. RAPPOPORT and F. S. KOGAN, Vysokomol. ~oyed. B l h 828, 1969 (Not translated in Polymer Sci. U.S.S.R.) 6. Y. N. ANDREYEV, G. N. PETROV, P. Ya. RAPPOPORT, F. S. KOGAN and Ye. P. SHCHIPKOVA, Vysokomol. soyed. B12: 656, 1970 {Not translated in Pnlymer Sei. U.S.S.R.) 7. L. A. ONOSOVA, Autoref. dis. na soiskaniye uch. st. kand. khim. nauk, Moscaw, im D. I. Mendeleyeva, 22, 1974

MKhTI

8. R. P. TIGER, I. G. BADAYEVA, S. P. BONDARENKO and S. G. ENTELIS, Vysokomol. soyed. A19: 419, 1977 (Translated in Polymer Sei. U.S.S.R. 19: 2, 484, 1977) 9. A. K. ZHITINKINA, O. G. TARAKANOV, N. A. TOLSTYKH, A. V. DENISOV and Z. N. MEDVED', Sintez i fizikokhimiya polimerov 21: 3, 1977 10. N. A. TOLSTYI
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E.P.

KALUTSg.AYA and S. S. Gus~.v

16. Ye. N. GUR'YANOVA, I. P. GOL'DSHTEIN and I. P. ROMM, Donorno-aktseptornaya

svyaz', Moscow, Khimiya, 38, 71, 1973 17. E . L . KORZYUK, V . V . ZHARKOV, A . K . ZHITINK1NA and N. V. VARENTSOVA, Tez. dokl. Vses. nau0hno.tekhnieheskogo soveshehaniya po khimii i tekhnologii pro. izvodstva, pererabotki i primeneniya poliuretanov i iskhodnogo syr'ya dlya nikh (Same as 10) Vladimir, V-NIISS, 262, 1976 18. I. S. BECHARA and R. L. MASCIOLI, J. Cellular Plast. 15: 6, 321, 1979

Polymer Science U.S.S.R.eel. 24, i~o.11, pp. 2778-2787, 1982 Printed in Poland

0032-3950]82 $7.50+.00 © 1983 Pergamon Press Ltd.

IR SPECTROSCOPIC STUDY OF HYDRATION OF CELLULOSE ACETATES AND POLYVINYL ACETATE* E. P. KALUTSKAYAandS. S. GuSEV Institute of Physics, B.S.S.R. Academy of Sciences

(Received 3 July 1981) By differential recording of spectra of moistened, relatively similar dry samples absorption spectra were obtained and interpreted of water, absorbed by cellulose acetates of different degrees of substitution and by PVA. I t was established that water molecules adsorbed by triacetate and PVA interact via weak hydrogen bonds with C~--O groups of polymers. Both OH bonds of water molecules are disturbed to about the same extent by hydrogen bridges. Cellulose acetate with incomplete substitution is characterized by interaction of water molecules both with C = O groups and with unsubstituted hydroxy groups. However, asymmetry in the stress of OH bonds of the water molecule is observed in associates with hydroxyls. Hydration with high relative humidity values (>50~/o)is accompanied by the formation of hydrate structures on previously adsorbed molecules. I t was shown that water adsorption by cellulose acetate films may change the three-dimensional arrangement of acetate groups and increase t h e degree of orientation ordering of polymer structure.

Twrs paper is concerned with a study of properties of molecular interactions of cellulose acetate (CA) and PVA with adsorbed water molecules according to the relative atmospheric humidity and acetate group content in the polymer. Showing specific spectroscopic manifestation of hydration of these polymers is of separate interest since I R spectroscopic analysis is widely used in laboratory practice and samples practically always contain adsorbed water. However, obtaining the requisite spectroscopic data is difficult as a consequence of the superposition of bond-stretching vibration bands of water molecules and unsubstituted hydroxy-groups. A differential method of recording spectra of moistened * Vysokomol. soyed A24: No. 11, 2416-2423, 1982.