The effect of active trace impurities on the polymerization of propylene on complex catalysts

Polymerization of propylene on complex catalysts

1383

CONCLUSIONS

(1) I t is shown t h a t it is possible to obtain f~om epichlorohydrin polyetherglycols of comparatively low molecular weight ( ~ 3000) with Al(iso-C4H9) ~ as catalyst and diethanolamine as co-catalyst. (2) I t is suggested t h a t when tri-isobutylaluminium reacts with co-catalysts the alkyl groups are partially replaced by alkoxy groups. (3) I t has been established t h a t the monomer takes part in formation of a more active catalyst during the polymerization process. (4) Yfhen epichlorohydrin is polymerized on the Al(iso-C4H9)3-diethanolamine catalyst system there is an induction period, the length of which is dependent on temperature. Translated by E. O. PHILLIPS REFERENCES

1. P. E. EBERT and C. C. PRICE, J. Polymer Sei. 46: 455, 1960 2. C. C. PRICE and M. OSGAN, J. Amer. Chem. Soc. 78: 4787, 1956 3. R. O. COLCLOUGH,G. GEE, W. C. HIGGINSON, J. B. JACKSONand M. LITT, J. Polymer Sci. 34: 171, 1959 4. L. A. BAKALO, B. A. KRENTSEL' and A. V. TOPCHIEV,Vysokomol. soyed. 4: 1361, 1962 (Translated in Polymer Sci. U.S.S.R. 4: 3, 429, 1963) 5. J. FURUKAWA and T. SAEGUSA,Polimerizatsiya al'deyidov i okisei (Polymerization of Aldehydes and Oxides). 242, Izd. "Mir", 1965 (Russian translation) 6. A. M. PAKEN, Epoksidnye soyedineniya i e'poksidnye smoly (Epoxide Compounds and Epoxide Resins}. 926, State Scientific and Technical Publishing House, 1962 7. K. S. KAZANSKII, V. V. YEVREINOV and S. G. ENTILIS, Izv. Akad. Nauk SSSR, ser, khim., 274, 1964

THE EFFECT OF ACTIVE TRACE IMPURITIES ON THE POLYMERIZATION OF P R O P Y L E N E ON COMPLEX CATALYSTS* S. 1~I. MEZm~OVSKH, YU. V. Y~ssI~ and N. M. CHIRKOV Institute of Chemical Physics, U.S.S.R. Academy of Sciences (Received 3 May 1966)

THE monomers and solvents (n-heptane, propane, petroleum fractions etc.), used in the production of polyolefins, can contain impurities such as sulphur compounds, acetylenes, dienes, carbonyl compounds, oxygen, ethylene, alcohols, water, butenes etc., depending on their method of preparation or their origin. The use in polymerization on complex catalysts of olefins and solvents of a * Vysokomol. soyed. Ag: No. 6, 1243-1248, 1967.

1384

S. M. IVI~z~L~aOVSr~Uet al.

high degree of purity (usually 99.8-99.9%) does not guarantee a process of normal rate (as in the absence of impurities) or following the desired direction. I t has been reported for example [1] that 0.0008~ of impurities such as C2H2, CO, CO2, sulphur compounds and H20, or 0.0005~ of 02, retard polymerization. According to reference [2] 1-1.5 × 10-3 mole ~/o concentrations of COS and CS~ practically inhibit polymerization. In references [1-5] trace impurities are regarded as passivators and the main stress in these communications is on determination of the maximal permissible concentrations of impurities in the monomer and solvent. Recently however publications have appeared (mainly patents) in which addition to the reaction zone of H~O, alcohols, CO, 02 etc. is recommended for the purpose of increasing the polymerization rate and modifying the properties of the products [6-9]. From analysis of these data it follows firstly that most of the above compounds have a considerable effect on the polymerization process and on the properties of the polyolefins (depending on the concentration of the trace impurities and on t h e nature of the reactions of the impurities with the catalyst components and with the catalyst system). Secondly, both on the basis of the experimental work and of analysis of these data there is not a unified opinion about what role the trace impurities play in the polymerization process and in the formation of a stereoregular product, and about what effect they have on molecular weight and physicomechanical properties. Reference [10], which reports a study of the effect of water and alcohols on the polymerization of various monomers in the presence of complex catalysts, clearly exemprifies this. After showing that water takes an active part in the polymerization of styrene, isoprene, butadiene and vinyl ether the authors of reference [10] are forced to admit that as yet there is insufficient information on which to base an unequivocal solution to the problem of the effect of water on the polymerization of propylene. The present work is the first attempt at a systematic study of the effect of trace impurities on the polymerization of propylene on complex catalysts.

Determination of the rate of reaction of water with the components of the a-TiCla-Al(G2tts)a catalyst system. In order to find the effect of water on the stereospeoific polymerization of propylene it is first necessary to discover whether trace quantities of water react with the catalyst components and what is the nature of this reaction. The subject of this paper is the study of the kinetics of the reaction of water wi~h the a-TiCla-Al(C~Hs) a catalyst system during the process of polymerization of propylene. EXPERIMENTAL

Propylene was polymerized in a liquid propane-propylene mixture (50-80~/o propylene). The gas was purified and dried .by the method of reference [11]. In addition the gas was fractionally distilled twice and passed twice through a column with 13-x and 4-A molecular sieves.

Polymerization of propylene on complex catalysts

1385

Within the limit of experimental error of 1-2 parts per million (p.p.m.) the gas contained no moisture or oxygen, nor was ethylene found. The quantity of ethane did not exceed 10 p.p.m, and the quantity of sulphur-containing compounds (expressed as elementary sulphur) was not greater than 0.003 g S/m a of gas. Propane free from propylene, as determined chromatographically to within 0.5 moles % of propylene, was obtained by rectification of a propane-propylene fraction containing 95~o of propane, which had previously been purified and dried by the method described above, with additional drying. The heterogeneous component of the catalyst system was a sample of ~-TiCls obtained by reduction of TiC4 with silicon. Analysis of this sample gave the following results: TiCI~ 0.16%; insoluble matter 0"1~o; Fe nil; surface area 7 ma/g. The homogeneous component of the catalyst was AI(C,Hs)s free from hydroxy compounds, hydrides and chlorine compounds. Measured amounts of g-TiCl8 in sealed ampoules under dry, oxygen-free argon were placed in the reactor. The ampoules were broken by the action of the stirrer. The AI(C,Hs)s was introduced into the reaction zone by means of a special metal syringe. Moist n-heptane * (containing 0"015~o of water as determined by the Fischer method [12], corresponding to the solubility of water in n-heptane [13J) was added to the system in portions. The experiments were conducted in a high pressure apparatus with a glandless stirrer and a diffuser [lll. The volume of the reactor was 0"7 1. RESULTS AND DISCUSSION

I n this work w a t e r was b r o u g h t into c o n t a c t w i t h the c a t a l y s t c o m p o n e n t s a t different stages, t h e c o n c e n t r a t i o n s o f H~O a n d t h e c a t a l y s t c o m p o n e n t s were v a r i e d a n d we also v a r i e d t h e t i m e of c o n t a c t of t h e c a t a l y s t c o m p o n e n t s w i t h water. F i g u r e 1 shows, in semilogarithmic coordinates, some kinetic curves of polym e r i z a t i o n of p r o p y l e n e o n t h e a-TiCla-Al(C~Hs) 3 c a t a l y s t s y s t e m in t h e presence a n d absence o f w a t e r (control e x p e r i m e n t ) . I t is seen t h a t on this c a t a l y s t s y s t e m p o l y m e r i z a t i o n begins a t once a n d proceeds a t a c o n s t a n t r a t e (control e x p e r i m e n t , curve 1). T h e presence of w a t e r t in t h e s y s t e m a t first causes complete inhibition o f t h e reaction, followed b y a period in which t h e process is nonlinear, a n d finally t h e p o l y m e r i z a t i o n r a t e becomes constant. T h e length of t h e i n d u c t i o n period was d e t e r m i n e d b y e x t r a p o l a t i o n of the linear section of t h e curve t o t h e p o i n t of intersection w i t h the abscissa. T a b l e 1 a n d Fig. 2 show the d e p e n d e n c e of the i n d u c t i o n period on t h e t i m e o f c o n t a c t of w a t e r with t h e c a t a l y s t c o m p o n e n t s before f o r m a t i o n of t h e c a t a l y s t system, a n d on t h e c o n c e n t r a t i o n of w a t e r in a n d t h e n a t u r e of t h e m e d i u m in which t h e r e a c t i o n is carried out. I t is seen from these results t h a t : 1) the i n d u c t i o n p e r i o d is n o t d e p e n d e n t on the t i m e of c o n t a c t o f H~O w i t h a-TiC13 (Table 1); 2) t h e i n d u c t i o n period * Spectroscopic grade n-heptane was used for preparation of the solution. In the experiment in which water was added, the solutions were made up in the same way as those in electroseopic grade n-heptane.

1386

S. M. M_EzmovsY.tI etal.

is dependent on the time of previous contact of H20 with AI(C2Hs)8 (Table 1); 3) a t low water contents the induction period is proportional to the water concentration (Fig. 2, curves 1, 3 and 4); 4) in experiments in which H20 was previously mixed with the AI(C~Hs) 8 (Fig. 2, curves 3 and 5) the induction periods are always shorter t h a n when the w~ter is previously in contact with the a-TiC1a (Fig. 2, curves 1 and d). I t follows from this t h a t under the given conditions H20 does not react with a-TiCl 8 but does react with AI(C2Hs)a, both in the absence and presence of a-TiCla, i. e. in the homogeneous phase and on the solid surface. This leads to the suggestion t h a t the induction period in this process is caused by adsorption of the water molecules on the surface of the ~-TiC] 3 (blocking the active centres of polymerization of the propylene), from where t h e y a r t

I'

log 1_" ~

z

5°I o-1 o-3 O-/d

so

T#ne,min FIG. 1

/oo

o

za

ao ,'g/.q8o [,,-,lo--'r~ct~o]

z¢-5

60

j

100

FIa. 2

FIG. 1. Semilogarithmle rate curves of polymerization of propyleno on the g-TiC1,-A1(C~Hs)s system in the presence and absence of H~O: /--control experiment, [H20] ----0, [TiCls] -----0.27 g/1., Ti : A1-- 1 : 3; 2--[H80]=29"2 × 10-4 g/l. of TiCl,, [TIC13]=0"31 g/1., Ti : AI=I : 3. FIG. 2. Dependence of induction period (rind) on concentration of water: 1--H20+a-TiCls in monomer (tr=10 rain); 2--H~O+g-TiC18 in monomer (tr=0, 30, 60 min); 3--HlO +AI(C~H~)8 in monomer (tT=10 min); 4--HaO+~-TiCla in pnopano (tr=10 min); 5 - - H I t +AI(CIH6)s in propane (tr= 10 min). removed b y reaction with the Al(C~H6)3. I t m a y be assumed t h a t the rate of adsorption of water on to the surface of TiC13 is so great t h a t the time for establishment of equilibrium between the water molecules in the solution and on t h e solid surface is negligibly small. Thus the length of the induction period is an objective criterion for determining the end of the reaction between /kl(C~Hs) a a n d H~O *. * Strictly speaking the method used for determining the induction period gives the time when no water is left in the solution but a fraction, a/e, remains o n t h e surface of t h e ~-TiCls. Under our conditions this is always less than 2 % of the total quantity of water added. To present the precise mathematical basis of this would be cumbersome and would require special consideration.

1387

Polymerization of propylene on complex catalysts TABLE 1.

EFFECT

ON THE INDUCTIOlq PERIOD OF WATER WIT~

OF THE TIME OF PREVIOUS

CONTACT

THE CATALYST COMPONENTS

(70 °, medium--liquid propane-propylene mixture, surface area of ~-TiC13, S0 = 7m~/g)

g/1.

AI(C~H,h concentration, mole/1. × 10~

Quantity of H~O, g/g TiCls × × 104

0"175 0"180 0'178 0"28 0"50 0'27 0"20 0"30 0"23 0"36 0"28

0"82 0"81 0"81 0"61 0"87 0"91 0"80 1 "03 0"74 1"06 0"88

44.4 44.3 44.7 14.5 14.4 15-7 30.1 32.2 39.0 33.0 34.o

a-TiC13 concentration,

Time of contact of H~O with a-TiC18 in absence of AI(C2Hs)3, rain

Time of contact of H~O with AI(C~H~h in absence of of ~-TiCla, rain

o 30 60 0 10 15 0 lO 35 60 90

Induction period (rind),

min

50 52 52 43 23 17 50 27 24 0 0

F o r the r e a c t i o n occurring on the surface t h e r a t e of c o n s u m p t i o n of water, dN/dt, is of zero order w i t h respect t o water, i.e. it is d e p e n d e n t o n l y o n t h e c o n c e n t r a t i o n of t r i e t h y l a l u m i n i u m (cA1), t h e c o n c e n t r a t i o n of a-TiC13 (CTi), its surface area (So) a n d t h e degree of coverage of t h e a-TiC13 with w a t e r (a). (We assume t h a t in t h e region of complete inhibition of p o l y m e r i z a t i o n a : 1 a n d in t h e nonlinear region a < l ) . F o r t h e reaction occurring in solution t h e r e a c t i o n b e t w e e n H 2 0 a n d AI(C2Hs)a is of t h e first order w i t h respect t o w a t e r a n d triethylaluminiuxa. T h e r a t e of disappearance of w a t e r is r e p r e s e n t e d b y the equation. dN dt --k'1%i cA1So a ÷ k ~ cA1N

(I)

dN dt ~ - k l ~ k 2 N ,

(II)

k l : k ' 1 S OaCTi CA1 ,

(III)

/~2----k'2 cA1-

(IV)

or

where

1388

S. M. MEZHIKOVSKIIet ed.

By integrating equation (II) we obtain --ln(1 +~:N)=k2 t+c and bearing in mind that when t=0, N=:N o (:No is the initial concentration of water) In ( 1 + ~k2 lgo)--In(1 + ~ N) =k2 t .

(V)

When t=Zin d, N = 0 and equation (V) takes the form k2 ln(1 +~No)=k2,nd

(VI)

(rind is the induction period). Solving equation (VI) with respect to vind (taking account of III and IV) we obtain

1

(

,

zlna= k~ cA---~ In 1+ kl So aCTi ]

(vii)

We now transform equation (vii) in terms of the new variables No/CTt and T~d CAt, which we can vary in experiments: 1

ke

zina cA1= ~ In I + k 1'S Oa

(VIII)

After simple transformations we obtain

\ CT,/ =k; aSo+k ~:N°. d (Tind CA1)

(IX)

CTi

For a series of experiments in which CTI and cx~ are kept constant it is easy to see that d:N° = kl+k2 :No

(X)

d~tnd

In a series of experiments we varied the time of reaction (tr) of water with the aluminium alkyl in the absence of the heterogeneous component, i.e. the a-TiC1a was added at different intervals after the initial reaction between H20 and AI(C~Hs)a. In this case the rate of fall in the concentration of water in the solution is given by arN , =k2 cAlN.

Polymerization of propylene on complex catalysts

1389

Hence the quantity of water remaining at time t r is given b y N~=No/e~,,

~r .

(XI)

An experimental curve of the dependence of the induction period on water concentration is shown in Fig. 3 in the form of a plot of No/cTl against Tind CA1. B y graphical differentiation of curve 1, Fig. 3 we obtained a linear plot of d (N0/CTi)/~ Tind CA1 against N0/CTi, which forms an intercept on the ordinate of /~'laS0= 0.2 × 10-8 1./g. rain and the slope gives k~= 4.0 h/mole, rain. The values of N~ for experiments with different times of reaction between H~O and AI(C2I-Is)3 in the absence of =-TIC18 were calculated from equation (XI), taking k~=4.0 1./ /mole.rain. The points on curve 2 (Fig. 3) were obtained from these values

%

~ p ~/77/'/7

,lO~,mole/~qTiCI.3

1"5

2

50 A-2 o-I o / 40 o-3

!

1"0

30 &o

o

¢-4

<>-5

20 -

0"5

/

10 I

IO 20 30 40 TlndCAL~10z, min. too/eli.

1

~

I

I

10 20 3o 4o 5o "Eiod ,mio

FIG. 3

Fro. 4

Fzo. 3. Dependence of experimental values of the induction period on the concentration of water, in the coordinates of equation (VIII): 1 --time of previous contact between water and the aluminium alkyl t~= 0; 2--tr was varied from 10 to 35 rain. FIG. 4. Correlation between the experimental (Tind) and theoretical (Ttheor) values of the in. duction period tT (min): 1--0; 2--10; 3--15; 4--25; 5--35; 6--120. of N 0. Graphical differentiation of this curve gave k~=4.3 1./mole.rain and k~aS0=0.23×10 -3 1./g.min, which are in good agreement with the values obtained from the experiments where tr----0. In order to verify the correctness of these values of the constants we calculated the induction periods (rtheor.) b y means of equation (VII) (see Fig. 4 and Table 2), taking #~----4.0 1./mole.rain, k~aS0=0.2× 10-31./g.min and the appropriate values of CTI, CAI, and N0, and taking account of the value of tr in each experiment. The calculated times are in satisfactory agreement with the observed induction periods. CONCLUSIONS

(1) The kinetics of the reaction between H 2 0 and AI(C2Hs) 8 in the presence of ~-TiC13 have been studied.

1390

S. M. I~ZN,~OVSKII et ~ . TABLE 2. INDUCTIOI~ PERIODS (EXPERIMENTA~ AND THEORETICAL) AT DIFFERENT VALUES OF CTI , CAI, ~ o AIVD t r

70 °, m e d i u m - - l i q u i d propane-propylene mixture, So----7 mS/g) CTi

cA1

co-TiC1s A1 (CsHs) s concentration concentration, g/1. molefl. × l0 g

0"60 0"65 0"70 0'22 0'18 0"20 0"28 0"20 0"18 0"29 0"44 0"39 0'50 0"30 0"27 0"26 0"23 0"30 0"60

1"03 1"12 1"15 0"92 0"81 0"70 0"61 0"83 0"82 0"82 0"90 0"82 0"87 1"03 0"91 0'80 0"74 0"95 1"54

tr

:No

Quantity of H~O, mole × 104

0"049 0"076 0"131 0"073 0"055 0"103 0"160 0"189 0"141 0'043 0"134 0"146 0'217 0"375 0"105 0"300 0"276 0"271 0

rind

Ttheor

Time of reacInduction period tion of AI(C,Hs)s calculated with H20 in experimental, from formula absence of min (VII), rain a-TiCla, min 0 0 0 0 0 0 0 0 0 10 1O 10 10 10 15 25 35 120

9 12 16 24 28 34 43 50 47 3 9 20 23 27 17 29 24 0 0

7"8 10"8 14"0 17"7 22"8 35"4 42 "8 35"4 40"1 7"0 12"1 19"0 22"6 31"7 19"3 35'0 31"1 0"7

(2) A m e t h o d is p r o p o s e d f o r c a l c u l a t i n g t h e r a t e c o n s t a n t s o f t h e r e a c t i o n b e t w e e n H 2 0 a n d AI(C2Hs)a i n s o l u t i o n a n d o n t h e s u r f a c e o f ~-TiC1 a. (3) T h e V a l u e s o f t h e r a t e c o n s t a n t s o f t h e r e a c t i o n b e t w e e n w a t e r a n d t r i e t h y l a l u m i n i u m a t 70 ° i n s o l u t i o n (in a l i q u e f i e d p r o p a n e - p r o p y l e n e m i x t u r e ) a n d o n t h e s u r f a c e o f a-TiC1 a h a v e b e e n f o u n d . (4) A f o r m u l a is p r o p o s e d f o r c a l c u l a t i n g t h e l e n g t h o f t h e i n d u c t i o n p e r i o d in the polymerization of propylene on the a-TiCla-Al(C2Hs) a catalyst system in the presence of water. Translated by E. O. PHILLIPS REFERENCES 1. Fed. Germ. Pat. No. 1122704, 1956; R Z H K h i m . , 10S172P, 1965 2. K. VESELY, J. AMBROZ, R. VILIM and O. HAMRIK, International Symposium on Macromoleeular Chemistry, Section I I , p. 337, Moscow, 1960 3. H. W. COOVER, ft. Polymer Sci. 4: 511, 1963

Polarizing interferometry in the sedimentation analysis of polymers

1391

4. E. H. ADEMA, Rec. tray. chim. 81: 225, 1962 5. Austrian Pat. No. 235017, 1961; RZ~Khlm., 12S15SP, 1965 6. Fed. Germ. Pat. No. 1022382, 1956; U.S. Pat. 3082198, 1958; U.S. Pat. 6405858, 1963; Chem. Abs. 62; 14854, 1965 7. Dutch Pat. No. 107937, 1957; RZHKhim., 12S149P, 1965; Fed. Germ. Pat. No. 1195496, 1956 8. U.S. Pat. 3083246; 1961; Fed. Germ. Pat. No. 110666, 1965 9. Belg. Pat. No. 552462; A. V. TOPCHIEV, B. A. KRENZEL' and L. G. SIDOROVA, Plast. massy, No. 2, 3, 1961 10. H. SINN and W. V. TII'TZ, Makromol. Chem. 48: 50, 1961 11. A. P. FIRSOV, V. I. TSVETKOVA and N. M. CHIRKOV, Vysokomol. soyed. 3: 1161, 1961; (Not translated in Polymer Sci. U.S.S.R.) V. I. TSVETKOVA, O. N. PIROGOV, D. M. LISITSYN and N. M. CHIRKOV, Vysokomol. soyed. 3: 496, 1961; (Not translated in Polymer Sci. U.S.S.R.) O. N. PIROGOV, Yu. V. KISSIN and N. M. CHIRKOV, Vysokomol. soyed. 5: 1327, 1963 (Translated in Polymer Sci. U.S.S.R. 7: 6, 1327, 1963) 12. J. MITCHELL, Akvametriya (Aquametry). Foreign Literature Publishing House, 1952 (Russian translation) 13. C. BLACK, G. C. JORIS and H. S. TAYLOR, J. Chem. Phys. 16: 537, 1948

POLARIZING INTERFEROMETRY IN THE SEDIMENTATION ANALYSIS OF POLYMERS* V. N. TSVETKOV A. A. Zhdanov State University of Leningrad (Received 3 May 1966) Sn~cE the appearance of the first paper [1] dealing with the development of t he t h e o r y and use of the polarizing interferometer as a mean of studying diffusion, this meth o d has been widely adopted b y investigators studying the diffusion of polymers in solution [3]. More recently polarizing interferometry has been used in studies of t he rapid sedimentation of polymers [4, 5, 6]. I t was shown experimentally t h a t the v e r y sensitive optical system and the simple met hod of adj ust m ent (owing to its sensitivity it m a y be used where the concentrations of the solutions are one order lower t h a n in the ease of the PhiIpot-Svensson method) make this the most suitable and accurate m e t h o d of measuring sedimentation constants required for determination of the molecular weight of polymers. Relatively little attention has been paid to the possibility of using polarizing intefferometry to ana!yze the molecular-weight distribution of the samples under investigation. The present paper is mainly a s t u d y of this problem. * Vysokomol. soyed. A9: 1~o. 6, 1249-1256, 1967.