High temperature polymerization of ethylene on titanium-magnesium gel immobilized catalysts

382

V. A. IfA~A~TOV d aL

2. V. A. KABANOV, V. I. SMETANYUK and V. G. POPOV, Dokl. Akad. N a u k SSSR 225: 1377, 1975 3. V. A. KABANOV, V. I. SMETANYUK, V. G. POPOV, M. A. MARTYNOVA and V. I. MATYUZHOVA, Kompleksnye metalloorganicheskie katalizatory polimerizatsii olefinov, sb. VI (Organo-metal Complex Catalysts for an Olefines Polymerization, issue VI), p. 18, Chernogolovka, 1977 4. Yu. N. BOCHAROV, V. A. KABANOV, M. A. MARTYNOVA, V. I. SMETANYUK a n d V. V. FEDOROV, Russian Authors' Cert. 492298, 1973; Byul. izobret., l~o. 43, 1975; Belgian Pat. 818000; Brit. Pat. 1477825; French Pat. 7425529

Polymer Science U.S.S.R.Vol. 22, pp. 382-390.

0032-3950]80/0201-0382507.50/~

Pergamon Press Ltd. 1980. Printed in Poland

HIGH TEMPERATURE POLYMERIZATION OF ETHYLENE ON TITANIUM-MAGNESIUM GEL IMMOBILIZED CATALYSTS* V. A . KABAI~OV, S. S. IVAI~CHEV, V. I. SMETAi~IYUK, A . A. BAULIlV,

M. A. MARTYI~OVAand V. M. KOVYLOV A. V. Topchiyev I n s t i t u t e of Petrochemical Synthesis, U.S.S.R. Academy of Sciences "Plastpolimer" Research Organization (Received 6 December 1978)

A study has been made of some peculiarities of the high temperature polymerization of ethylene on t i t a n i u m - m a g n e s i u m gel immobilized catalytic systems. The polymerization kinetics have been investigated, as well as the extent to which the polymerization rate m a y be influenced b y the nature and structure of the gel-like carrier a n d b y the ratio of the catalyst components. Some molecular characteristics have been investigated and the mechanical properties of the polyethylene examined.

Among TItE present day objectives in technological research in the field of polyethylene production on complex metalorganic catalysts that would combine efficiency with facilitated removal of catalyst residues from the polymer with no deleterious effect on the quality of articles. This would obviate the laborious technological process of end product extraction. If the reactions are to be carried out in solvents, it is better and more economical for the reaction temperatures to be in the region of 140-220 °, i.e. above the PE melting point. While it is true that many of the existing complex metalorganic catalysts would rapidly become inactive under these conditions, it was recently reported [1] that a high tern* Vysokomol. soyed. A22: No, 2, 345-350, 1980.

High temperatur~ polymerization of ethylene

s8:~

l~erature process that was advantageous from both technical and economic standpoints had been develol~ed. The advantage lies in the fact that during its lifetime, however short, the catalyst is able to produce a sufficiently large amount of polymer. The drawback inherent in processes based on this principle is invariably the marked extent to which technical and economic factors are dependent on catalyst efficiency. Some loss of catalyst activity, which may occur in he course of a reaction, e.g. owing to a deterioration in the quality of the stock, may render the entire proce~'s uneconomical. Moreover if the need should arise to modify PE by eopolymerization with ~-olefins, or to regulate the molecular weight of the polymer by the addition of hydrogen, it would be practically impossible tO maintain catalyst activity at the required level. Another way of approaching the problem would be to carry out ethylene polymerization by a continuous scheme involving the use of catalytic contacts that are long term and stable in their operation. In this case one finds that even in the case of relatively low specific rates of polymerization the overall efficiency of the catalysts may, in view of their prolonged operation, exceed the levels attained by the most active of the known catalyst systems that operate until they are "burnt out". Unfortunately the normal type of catalytic compositions are of no use for this purpose: granules are rapidly broken up by polymer forming in their pores, and are reduced to dust. The practicability of the second method is apparently related to use of the recently proposed gel immobilized catalytic systems [2-5], which are capable of maintaining a constant rate of ethylene l~olymerization for a long time, even up to 200 ° . The systems in question are specially constructed macroscopic sized pieces of composite polymeric material (granules, ]amellae, films, etc.), in whose volume are catalytically active transition metal compounds bound in a complex. The particles swell to some extent in the reaction medium and form firm gels that are permeable to monomer and to the reaction product. Polyethylene formed in the volume of swollen granules of gel immobilized catalytic systems are expelled quite rapidly from the latter into the reaction solution, and can readily be removed along with solvent from the reaction zone, making room for a fresh portion of monomer. The general principles of synthesis of the catalysts of interest have been described [5]. According to [5] titanium-magnesium systems were found to be the most efficient for ethylene polymerization processes. The present paper gives some results obtained in our kinetic investigation of the high temperature polymerization of ethylene, using the systems in question. Polymeric carriers for the titanium-magnesium catalytic systems were synthesis on the basis of an ethylene-propylene-diene ternary copolymer (SKEPT). In the first SKEPT variant polymethaerylic acid (PMAA) or polyallyl alcohol (PAA) were grafted as ligands by a radical mechanism. In the second variant 1,2-polybutadiene (PB) was grafted to SKEPT first, followed b y PMAA or P A A grafting. After the grafting the resultant materials were moulded, and were t h e n

~84

V. A. KAB~mov ee a/.

cured through residual double bonds ~mtil a three dimensional chemical bond network was formed between base-polymer macromolecnles. Thus each bit of ~arrier is in the form of a chemically crosslinked system that is capable of only limited swelling in solvents. Next, hydroxyl or carboxyl groups on the grafted polymeric ligands of the -carrier were modified by treatment with excess Grignard reagent, chemisorption of titanium tetrachloride was carried out, and the resulting complex was activated w i t h organoaluminium compounds. The following could be taken as an example of procedure typical for the laboratory synthesis of gel immobilized catalytic systems. 10 g of repreeipi'tated S K E P T (30~o content of propylene units, 2°/o content of ethylidenenorbornene) were placed in a 500 ml three necked flask fitted with stirrer and reflux condenser, and decanted into 200 ml of heptane. S K E P T was dissolved, while stirring, at room temperature, the solution was purged with argon for 30 rain, and the flask was charged with 1 g of methacrylic acid and 0.15 g of dinitrile o f isobutyric acid, and thermostat heating was switched on. Grafting was carried out at 70 ° in an argon atmosphere for 10 hr, then the thermostat was switched off, and the mixture cooled to room temperature; then 0-15 g of benzoyl peroxide was added, and heptane was removed under vacuum. The resulting graft copolymer was dried and cured b y heating at 100 ° for 30 rain, and was then discharged from the flask in the form of a film of thickness 0.1-0.2 ram. The carrier film was cut into pieces measuring 1-5 m m and placed in a 500 ml flask, after which 100 ml of dehydrated sulphurie ether was added, and the contents were kept for 1 hr at room temperature. 30 ml of a 1 M solution of allyl magnesium bromide i n sulphurie ether was then added, and left standing for 16 hr in the sealed flask. The resulting product was washed 5 times with sulphuric ether, thrice with heptane and was dried i n v a c u o . The degree of swelling in n-heptane was determined for the obtained polymeric carrier. 1 g of the magnesium containing carrier was then placed in a 40 ml glass reactor, 4 ml of a 0.5 M solution of TiCl~ in heptane was added, and kept for 4 hr. The reaction system was then heated at 100 ° for 1 hr, and cooled to room temperature, after which uncombined TiCI~ was removed from the product by fivefold extraction with heptane. The resultant complex (SKEPT-PMAA-RMgX-TiCl~)* was treated with a 0.5 ~ solution of diisobutyla l u m i n i u m hydride in heptano at room temperature, was kept for 2 hr and then washed with beptane, dried i n v a c u o , and placed in ampoules. The method used for ethylene polymerization on gel immobilized catalytic systems has been described [5]. The process was carried out in non-continuous reactors fitted with a magnetic stirrer, as well as in an autoclave equipped with an electromagnetic stirrer provided with an ampoule breaking device. The only difference in experimental procedure in one or cther of the two cases was that in the former instance (non-continuous reactor) the catalytic system was placed in the reactor and subjected to swelling in a solvent in the absence of ethylene at room temperature, before the start of an experiment, whereas in the latter ease (autoclave) the ampoule containing dry pieces of c~talyst was broken after the pre-set temperature and ethylene pressure had been established in the autoclave. Intrinsic viscosity determinations for the P E were carried out in deealin at 135 ° in a n argon atmosphere, and the corresponding viscosity average molecular weights were given b y the formula [6]: [ g ] l a s ~ 3 . 3 4 × 10 -4 ~ I °'~4. * To abbreviate designations of the gel immobilized catalytic systems the chemical formulae of the metal compounds have been added to designations of the respective graft polymeric carriers ill the order in which the compounds were applied.

High temperature polymerization of ethylene

385

The number of double bonds and methyl groups in the PE chain, as well as the melting point and the main mechanical properties of the PE (maximum breaking stress as, tensile yield point ay and the breaking elongation Al/1) were determined by the methods described [7]. In cases where the ethylene is practically free of corrosive impurities (water and oxygen) and where no cocatalyst decomposition takes place, the titaniummagnesium catalysts synthesized b y these procedures all exhibit stable and reproducible catalytic activity in high-temperature ethylene polymerization processes (Fig. 1). Stationar:(, reaction rates, i.e. where there are eqlml a b s o l u t e valnes for flows of monomer and of forming P E over the surface of catalyst, w ,,.q PE/voTi.hr

2ooo !

cl v, gpE/g c~talys~ 2 ~- 9,

!

5

IO00

I

/

I

I

2

I

3

I

II

I

5

l

7

I

/

I

3

I

I

I

0.5

1

1"5

;t

I

I

6

If

T/me ~hr

FIO. 1. Plots of the ethylene polymerization rate w (a) and of the degree of catalyst swelling in PE V (b) vs. time for titanium-magnesinm gel immobilized catalytic systems: 1, 2-SKEPT-BP-3RMgX-TiCI,, 160°, pressure 20 arm, eocatalyst HA1R2, solvent n-heptane; the catalyst underwent prior swelling in n-heptane (1) and was loaded into the reactor in the dry form (2); 3--SKEPT-PAA-RMgX-TiCI~, 200°, pressure 15 arm, cocatalyst A1RIC1, solvent n-heptane; the catalyst underwent prior swelling in n-heptane; 4--SKElYr-BP3RMgX-TiCI,, 160°, pressure 4 arm, cocatalyst A1R3,solvent n-deeane, the catalyst underwent prior swelling in n-deeane. pieces, are established in approximately 1 hr. The kinetic curves are characterized b y initial non-stationary regions, where the reaction rate is a fwaction o f the physical state of the catalytic system at the start of all experiment. For. systems that have come into contact with a reaction medium in the form of " d r y " catalyst pieces, the reaction rate during the non-stationary period increases in line with increased swelling of catalyst pieces in the monomer solution. The polymerization rate during the non-stationary period decreases for these same pieces that have been brought to the equilibrium degree of swelling in the solvent before coming into contact with monomer. In either case the stationary rates are identical, i.e. do not depend on the w a y in which the initial catalyst pieces pass into the stable working condition (cp. curves 1 and 2). Additional swelling:

V, A. KABA~OVet al.

386

occurs during the non-stationary period in catalyst pieces which have attained the equilibrium degree of swelling in solvent after coming into contact with monomer; along with the additional swelling there is a parallel process of accumulation, within each particle, of P E formed there, the amount of PE reaching a m a x i m u m simultaneously with establishment of the stationary polymerization rate and stationary degree of swelling (Fig. lb, curve 1). In other words "superequilibrium" swelling of crosslinked catalyst pieces is due to an increased concentration of macromolecules within the previously formed three dimensional network of the polymeric carrier. * Let Vst be the volume of the gel immobilized catalytic system in the stationary working state, whereupon V s t ~ Veq+AV', where Veq is the volume of the system in question t h a t has attained the equilibrium degree of swelling in pure solvent, and A V' is the additional volume increment due to "super equilibrium" swelling of the three dimensional structure of the initial gel. The work of enlargement of the catalyst system b y A V' v,,

A=~ p(V)dr

is done at the expense of the free energy of ethylene polymerization, and gives rise to additional stress appearing in the elastic network of the catalyst. TABLE

1.

STATIONARY

RATES

OF

ETHYLENE

POLYMERIZATION

ON

VARIOUS

TITANIUM-

MAGNESIUM GEL IMMOBILIZED CATALYTIC SYSTEMS

(Pressure 10 arm, temperature 145°, cocatalyst--A1R2C1) Catalyst

Solvent

SKEPT-BP-PAA-RMgX-TiC1 ~ SKEPT-PAA-RMgX-TiC14 IKEPT-PMAA-3RMgX-TiCI~ ~KEPT-BP-PMAA-3RMgXTIC14 Ditto

Heptane Ditto ~9

Toluene Chlorobenzene

Degree of swelling, g/g carrier in solvent I in heptano

w, g PE/g Ti.hr

4.9 4.8 4-5

4.9 4.8 4.5

800 240 170

4.4 8"0 1"6 2"4

4.4 8.0 1.6 1.6

670 1140 540 720

3.1

1.6

880

Since the magnitude of the additional stresses is a function of the P E concentration in cross]inked catalyst particles, it can be seen t h a t these m a y simply disintegrate if the polymerization rates are too high. I t is this factor that determines the upper limit of t h e specific productivity of the catalytic system. * The additional swelling cannot be attributed to solvent quality improving on account o f the addition of monomer to the system, since the degree of s~elling for nonaotivatecl

~atalytic systems will, in the circumstanoes, remain practically eonstant.

High temperature polymerization of ethylene

387

T h e r a t e o f e t h y l e n e p o l y m e r i z a t i o n o n t i t a n i u m - m a g n e s i u m c a t a l y s t s , is a linear function of pressure, as in the case of other types of gel immobilized syst e m s [5], a n d g o e s t h r o u g h a p o o r l y d e f i n e d m a x i m u m a t 160 °. TABLE 2. EFFECT OF THE NATURE OF THE ORGANOALUmNIU1V[COMPOUND O1WTHE SPECIFIC ACTIVITY OF GEL IMMOBILIZED CATALYTICSYSTEMS A~NDMOLECULARWEIGHT OF P E (Pressure 20 arm, temperature 160% catalyst concentration 1.0-1.3 g/1., coeatalyst concentration 0.5 g/1.)

!

Catalyst

S KEPT-BP-PMAA-RMgX-TiC14

7 × h0

A1R~H

AIRa AIR2CI

AIR2H AIR2CI

SKE PT-BP-PMAA-3RMgX-TiC1,

A1R~H A1R~

670 520 390

4.7 4.1 2-2

403.8 335-7 144.7

2200 1400 620 330

4.0 2.6 3.9 3'9

324.7 181.3 313-7 313.7

The catalytic activity of titanium-magnesium catalysts may be regulated by varying the nature of the polymeric complexing agent, the solvent and the organoaluminium compound. Tables 1 and 2 give some data demonstrating the influence of these factors on the ~tationary rate of ethylene polymerization. TABLE

3. I ~ O L E C U L A R

CHARACTERISTICS AND

THESIZED

PHYSICO-CHEMICAL PROPERTIES

OF

PE

SYN-

ON A G E L I M M O B I L I Z E D C A T A L Y T I C S Y S T E M

ME Catalyst

? .°

SKEPT-BP-PMAARMgX-TiC14 SKEPT-BP-PMAA3RMgX-TiC1, SKEPT-PAA-RMgXTiCI~ TiCI~-AI(CsH6)CI* * Commercial catalyst.

1

4.1

135

0"1

0.9

200

210

300

2

4.4

136

0.1

0"9

190

180

370

1

4.5 4-7

136 134

0.1 0.5

1.0 0"1

220 215

210 1 56O 200

42O

388

V. A. KABA~OV eg a/.

I n addition, Table 2 gives results regarding the effect of the nature of the organo&]~mlnium on the intrinsic viscosity and viscosity average molecular weight of the resultant PE. :For the catalytic systems under s t u d y the optimal content of g r a f t e d polymeric ligand in the carrier amounts to 10-15 w t . % (Fig. 2).

,PE/g~'.hz,

~, gPE/#ca?alq~Lhr b

EO0

30

#o0f

20

~200

lO I

70

I

20

I

I0

J

I

20

EPMAA]w~% Fro. 2. Plots of activity referred to 1 g of Ti (a) and 1 g of catalyst (b) vs. polymeric ligand content L for the gel immobilized cat~lytic system with a fixed ratio of Ti : L = 1. Catalyst-SKEPT-BP-3RMgX-TiCI,, pressure 20 arm, 160°, solvent--n-hexane, cocatalyst A1Ra, AIRs concentration 0,5 g/1. With a late-set content of graft PMAA (10 wt.%) the rate of ethylene polymerization increases with increase in the initial [TiCI4]/[PMAA] ratio in t h e interval 0.2-1.0, and thereafter remains practically constant (Fig. 3). The m a x imal specific catalyst activity calculating for 1 g of titanium is obtained w h e n

w,#PE/#T/.hp 600

- ~

'Z~'l 2

qO0 200

]

0.2

]

I

O.G

I

I

I"0

J

1.4

[Ti] : EPMAA] Fxo. 3. Effect of the [Ti] : [L] ratio on the activity of the gel immobilized catalytic system. Catalyst-'SKEPT-BP-3RMgX-TiC14, pressure 20 atm, 160°, solvent--n-heptane; cocat~lyst. HA1Ps (1), AIR s (2).

High temperature polymerization of ethylene

389"

the Ti content in the catalyst system is ~ 1% (determined b y analysis) (Fig. 4a). Since it is important, from a practical standpoint, t h a t the specific productivity of a gel immobilized catalyst system should be reckoned in terms of unit weight o f the system as a whole, the optimal Ti content will be ~ 2 - 3 w t . % (Fig. 4b). Calculations show that an efficient process of ethylene polymerization is. theoretically practicable, provided that the long term stable work of titanium, magnesium catalysts has a productivity of 10 g PE/g catalyst.hr (500 g P E / g Ti.hr). I n the course of 1000 hr work 500 kg PE/g Ti is obtainable with a c a t a l y s t system of the type in question. With a circulating type of reactor (reaction volume 1 l.) one can p u t 50 g of swollen catalyst particles in the latter and t h e r e b y obtain 0.5 kg of P E with 1 1./hr. Thus a 20 m 3 reactor is sufficient for an plant, with an outl~ut of 80,000 tons of P E l~er year.

w,g! 'EliS 7"(,/7;"

w # PE/g catalL48f . h," ci

b

30

2400 1800

20 1200 10 600 ]

0.5

i

f

1.5

I

I

2.5

I

0.5

I

I

~.~

L

l

z.5

~

1

=

3.5

[Ti], wf.% FIG. 4. Plots of the activity, referred to 1 g of Ti (a) and 1 g of catalyst (b), vs. Ti content in catalytic systems prepared with treatment of the carrier with a twofold excess of TIC14. Catalyst--SKEPT-BP-3RMgX-TiCI~-A1Rs, 160°, pressure 20 atm, solvent--n-heptane.. Some of the molecular characteristics and mechanical properties of PE" prepared on titanium-magnesium catalysts were investigated. I t was found t h a t the main properties and characteristics are not inferior to those of commercia|:' high density P E (see Table 3). Translated by R. J. A. HEND~Y REFERENCES

1. U.K. Pat. 1235062, 1971; West German Pat. 2159910, 1972 2. V. A. KABANOV, V. L SMETANYUK and V. G. POPOV, Dokl. A N SSSR 225: 1377, 1975. 3. V. A. KABANOV, V. L SMETANYUK, V. G. POPOV, M. A. MARTYNOV& and V~ ]~ MATYUZHOVA, Kompleksnye metalloorganicheskiye katalizatory poBmerizatsii o|efinov

(Complex Metalorganic Catalysts for Olefin Polymerization Proeesses). No. VL, p,. 18,. Chernogolovka, 1977

:390

M. G. K ~ O V Y A K et al.

-4. Yu. N. BOCHAROV, V. A. KABANOV, M. A. MARTYNOVA, V. G. POPOV, V. I. SMETANYIfK and V. V. FEDOROV, U.S.S.R. Pat. 492298, 1973; Byull. izob., No. 43, 1975;

Belgium Pat. 818000; U.K. Pat. 1477825; French Pat. 7425529 -~. V. A. KABANOV, V. I. SMETANYUK, B. G. POPOV, M. A. MARTYNOVA and M. V. ULYANOVA, Vysokomol. soyed. A22: No. 2, 1980 (Translated in Polymer Sci. U.S.S.R. 22: 2, 1980) -6. P. M. HENRY, J. Polymer Sei. 36: 3, 1959 7.

Ye. Ya. PARAMONKOV, M. I. LEITMAN, N. M. KOROBOVA, A. A. BAULIN, L. G. STEFANOVICH, A. S. SEMENOVA, Ye. I. NALIVAIKO and I. N. ANDREYEVA, Plast.

massy, No. 5, 3, 1973

:.,:Polymer Science U.S.S.R. Vol. 22, pp. 390-398. ~D Pergamon Press Ltd. 1980. Printed in Poland

0032-3950[80/0201-0390507.50/0

SPLITTING OF ANTHRYLMETHYLCARBOXYLATE BONDS IN POLYMER SYSTEMS* ] f f . G. KRAKOVYAK, T. D. AI~'AI~YEVA, YE. V. AI~UFRIYEVA, R . A. V. ]~. LUSHCHIK, N . S. SHELEKHOV a n d S. S. SKOROXHODOV

GROMOVA,

High P o l y m e r Institute, U.S.S.R. A c a d e m y of Sciences (Received 11 December 1978)

A study has been made of the reaction of splitting of ester bonds in anthrylmethylcarboxylate grodps located in side groups or in crosslinkages or branchings in polymer systems based on methyl methacrylate and styrene. I t is shown t h a t the action of trifluoroacetic acid on the polymers in dichloromethane at room temperature is accompanied b y a quantitative selective splitting of a n t h r y l m e t h y l c a r b o x y l a t e groups in linear polymers (having from 0-1 to 100 mole % contents of units containing anthrylmethylcarboxylate groups) as well as in crosslinked polymer systems (with less t h a n 2-2.5 mole % contents of bridges forming crosslinkages with anthrylmethylcarboxylate groups). Splitting of anthryhnethylcarboxylate bonds in polymer systems based on styrene under the conditions examined is accompanied b y a F r i e d e l - K r a f t s reaction between conversion products of a n t h r y l m e t h y l c a r b o x y l a t e groups and phenyl rings o f polymers. M E T H O D of protecting various functional groups b y blocking groupings is widely used i n the synthesis of large a n d complex organic molecules b a d e d on polyfunetional compounds, -e.g. in the synthesis of peptides [1]. Problems involving the necessity of selective blocking o f functional groups and (or) deblocking of groups (more often t h a n not, it will be a case of : ~ l e c t i v e splitting of particular chemical bonds) arise also in the chemistry of vinyl polymers, ~for instance, in the synthesis of polymers containing active functional groups, which are

"THE

L

* Vysokomol. soyed. A22: ~To. 2, 352-358, 1980.