CA1158223A - Catalysts for the polymerization of ethylene, process for preparing them, and polymerization process using these catalysts - Google Patents

Abstract

Ethylene polymerization catalysts, process for their manufacture and a polymerization process using said catalysts. The catalysts have the formula: (TiC13,? AlCl3) x (MCl3) x (MgX2) y in which 0.3? x? 30 ? y? 20, M is a transition metal from groups VB and VI B of the Periodic Table and X is a halogen, and are prepared by contacting the syncrystallized titanium trichloride with aluminum chloride, the metal trichloride M and, if necessary, the anhydrous magnesium halide and by subjecting these chlorides to a grinding step during which the grinding energy is at least equal to 3 KWh per kg of treated solid material. The catalysts make it possible to polymerize ethylene under a pressure of 300 to 2,500 bars and at a temperature of 180.degree. at 300.degree.C, in the presence of an activator chosen from hydrides and organometallic compounds of metals from groups 1 to III of the Periodic Table, the atomic ratio of the metal of the activator to the sum Ti + M being understood between 0.1 and 10, and the average residence time of the catalytic system in the polymerization reactor being between 2 and 100 seconds.

Description

2 ~ 3 The present invention relates to polymerization catalysts.
tion of ethylene and, more particularly, of the type catalysts Ziegler having a solid solution structure.
Many varieties of Ziegler-type calalyzers are already known for the polymerization of ethylene and ~ -olefins. These cat-lysers generally include the catalytic component properly said, consisting of at least one halogen compound of a transition metal groups IV ~ V of the Periodic Table, and an activator C} Loisi among hydrides and organometallic compounds of metals of groups I to III of the Periodic Table. The constituent cata-lytique comprising the transition metal can, if necessary, be fixed on an inert support such as alumina, silica, magnesia, halo-magnesium genures, etc ...
The present invention relates more particularly to Ziegler type catalysts comprising at least two halogenated compounds.
transition metals, one of which is a halogenated titanium compound syncrystallized with a halogenated compound of a metal from group III of the Periodic Classification and the other of which is a halogenated compound of metal of groups VB and VIB of the Periodic Table, these cata-lysers which can be fixed on an inert support.
The literature gives some examples of type catalysts ~ iegler comprising two halogenated compounds of deuY metal ~ transition different: for example French patent n 1,348,983 describes catalytic constituents for polymerizing in particular ethylene having 25 for formula (TiCl3, VCl3) ~, x being between 0.25 and 4, and allowing sant a catalytic yield of 15 grams of polymer per milliatome of titanium and vanadium and per hour at 40C. Likewise the American patent n 3.223.651 describes a catalyst of formula:
y TiCl3, (1-y) VCl3, 0.33 AlCl3, 30 including between 0.5 and 0.97, capable of producing a synergistic effect gie for the polymerization of ~ -olefins at a lower temperature 100C and under a pressure below 35 bars. -`
On the other hand, it is known to polymerize ethylene under a pressure between approximately 300 and 2500 bar and at a temperature 35 between 180C and 300C approximately. As part of such a procedure we seek to improve on the one hand the production yield compared to the catalyst used and on the other hand the quality of the polymer produced in modifying in particular the following parameters: density, mass molecular distribution of molecular masses. The purpose of this "

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11 ~ 8223 invention therefore consists in developing usable catalysts to polymerize ethylene under high temperature conditions and high pressure defined above and capable of improving the yield and quality of the polymer produced.
The ethylene polymerization catalysts according to the invention has the formula:
(TiC13. 3 AlC13) (MX3) X (NgX2) y in which 0.3 ~ x ~ 3.0 ~ y ~ 20, M is a metal of transition from groups V3 and VIB of the Periodic Table and X is a halogen.
These catalysts have a Ti-M binary solid solution structure which can be characterized by the size of its crystallites.
We have found that, from the point of view of the efficiency of these catalysts, this dimension determined by the radiocrystal analysis method-lographic (Sherrer's law) in the perpendicular direction on the plan (3 l should preferably be less than or equal to 100 any5-troems (~). As can be understood by their structural formula, these catalysts can, if appropriate, (when y ~ O ~ be fixed on an inert support consisting of halide of magnesium anhydrous sium. Among the metals M, vanadium and chromium are preferred, but molybdenum and tungsten can be used.
The halogen of the magnesium halide and that of the halogen-metal M may be the same or different and are chosen from fluorine, chlorine, ~ bromine and iodine.
The behavior of the catalysts according to the invention with respect to of the polymerization of ethylene includes an important aspect which makes them specially suitable for use in conditions of high pressure and high temperature: indeed, that, unlike the catalysts of the prior art already cited, they do not exhibit the ~ phenomenon ~ of synergy of pro-duction in low pressure conditions but only in high pressure and temperature conditions.
The preferred method of manufacturing the catalysts according to the invention consists in bringing titanium trichloride into contact syncrystallized with aluminum chloride, metal halide M and, where appropriate, the anhydrous magnesium halide for one long enough for the dimension (determined as above) of the crystallites of the solid solution obtained either ~ 1 ~ 8 ~ 23 2a less than 100 angstroems. This can be achieved effectively by subjecting the three aforementioned chlorides to a step of grinding in the water the grinding energy would be at least equal at 3 KWh per kg of solid matter treated. More specifically, we have ~ 8 ~ 23 observed that the effectiveness of these catalysts in the polymerization ~ ion of e- -the higher the grinding energy, the greater the thylene high. However, in order to optimize this efficiency given the cost operating and the need to save energy there is usually grinding energy is not required to be greater than about Z5 ~ 'h per kg of solid matter treated.
It has also been found that, with a view to employment in low pressure and moderate temperature conditions, it is desirable to select catalysts according to the invention for which 2 ~ y ~ 20.
This particular category of catalysts according to the invention therefore finds more varied applications since it can be used in all the ethylene polymerization processes whatever their temperature and pressure conditions.
The present invention also relates to poly-mereneization of ethylene using the catalysts previously defined under selected conditions. A first method according to the invention consists in putting ethylene, under a pressure between 300 and 2500 bars approximately and at a temperature between 180 and 300C approximately, in presence of a catalytic system comprising (a) at least one catalyst for (iC13 3 AlC13) QMX3) x ~ MgX2) y in which 0.3 S x ~ 3 O ~ y ~ 20, M is a transition metal from groups VB and VIB of the Periodic classification and X is a halogen and (b) at least one activa-teur chosen from hydrides and organometallic compounds of metals of groups I to III of the Periodic Table, the atomic ratio of the metal of the activator has the sum Ti ~ M being between 0.1 and 10, and the average residence time of the catalytic system in the reactor polymerization being understood between 2 and 100 seconds. This residence time depends on the temperature in the reactor in the sense that it is ~ as much higher than the temperature is lower. This first process can bring into play, especially when the temperature and / or pressure of polymerization is not very high, the presence of a hydrocarbon inert preferably having me ~ of 5 carbon atoms such as by example propane or butane.
A second process for the polymerization of ethylene according to the invention is to put ethylene, under a pressure between 1 and 200 bars, in solution or in suspension in an inert liquid hydrocarbon having at least 6 carbon atoms preferably chosen from alipha-~ ics or saturated cycloaliphatics and aromatics, in the presence 1 1 ~ 822 ~

of a catalytic system comprising (a) at least ~ m catalyst of formula (TiCl ~, fUC13) (~ g ~; 2) y in which 0.3 ~ x ~ 3, 2 ~ y ~ 20, ~ 1 is a transition metal from groups ~ B and VIB of the Classification Periodic and X is a halogen, and (b) at least one activator chosen among hydrides and organometallic compounds of the metals of groups I to III of the Periodic Table, the atomic ratio of metal of the activator at the sum Ti + I ~ i being between 1 and 1000.
In this type of process, the average residence time of the catalytic system in the polymerization reactor is usually several minutes and can reach up to a few hours.
When in the high pressure process a reactor is used autocla ~ e or tubular having several reaction zones, it can be advantageous, in order to produce certain qualities of polymers, adopt a specific arrangement of the polymerization installation like for example one of those described in French patents n 2,346,374 and 2.3S5,745. Often it will be useful for checking the index fluidity of the polymer, in particular of the polyethylene, to carry out the polymerization in the presence of a chain transfer agent such as hydrogen. In the high pressure process, this agent will be used at 0.04 to 2% by volume based on ethylene.
The method according to the invention allows, as regards the polymerization or copolymerization of ethylene, to produce any a range of polymers whose density is between 0.905 and 0.960 g / cm3 and whose melt index is between 0.1 and 100 dg / min approximately. Relatively low density polymers, for example between 0.905 and 0.935 g / cm ~, are obtained in copoly-deserving of ethylene with a fine ~ -ol ~ having 3 to 8 carbon atoms, for example propene at 15 to 35 ~ 0 by weight, or butene-at a rate of 15 to 60% by weight.
The methods according to the invention make it possible to improve by a share the production yield compared to the catalyst used and secondly the quality of the polymer produced by modifying the parameters density, molecular mass and molecular weight distribution.
Other advantages of the invention appear ~ in the leccure of the examples following doMees ~ for illustration and not limitation.
E. ~ IE'LES 1 to 3 In a batch ball mill, we introduce on the one hand titanium trichloride syncrystallized with aluminum chloride TiC13, s AlCl3, on the one hand chromium trichloride CrCl3 (and, for ~.

- ~ `13. ~ 223 r ~

Example 3, vanadium trichloride VCL3) in amounts such as atomic ratios Ti and V / Ti are equal to the values given in the Table I. After two hours of co-grinding, the catalyst obtained is dis-persed in methycyclohexane and activated by dimethylethyldiethylsilo-~ Yalane in an amount such that the atomic ratio Al / Ti is equal to 6.
The polymerization of ethylene is then carried out (where appropriate in presence of comonomeric propene according to the proportion by weight indicated in Table I) continuously under a pressure of 600 bars in a autoclave reactor with a volume of 0.6 1 maintained at a temperature of 230C in inject ~ nt the catalyst dispersion thus prepared so that the average residence time of the catalyst in the reactor is equal to 30 about seconds. Hydrogen is injected into the reactor according to the quantity indicated in Table I below indicates, in addition to the conditions the catalytic yield Rc expressed in kilograms of polyethylene per milliatome of titanium, the melt index IF measured according to standard AST ~ ID 1238 and expressed in dg / min, and the density expressed in g / cm3.

TABLE I

_ Example Cr / Ti V / Ti o ~ H2% C3 ~ 6 ~ IF ~
_ 1 0.33 0 0.5 0 3.0 3.6 0.948 2 1 0 0.2529.5 1.112.8 0.932

3 0.33 0.67 0.2529.5 3.1 3.2 0.932;

EXE ~ LES_4 and 5 In a batch ball mill we introduce on the one hand titanium trichloride syncrystallized with aluminum chloride TiCl ~, S
AlCl3, and on the other hand vanadium trichloride VCl3 in such quantities the atomic ratio V / Ti is equal to 6. The ethylene is then polymerized continuously under a pressure of 1200 bars in an autoclave reactor cylindrical volume 3 l divided, by means of screens, into three zones identical, the first of which is kept at a temperature of 260C. The temperature T2 of the second zone is variable according to the examples and 11 ~ 8 ~ 23 f, indicated in Table II. The ~ ispersion ~ e catalyst is injected in the dc reactor so that the average residence time of the catalyst in the reactor is around 30 seconds. Hydrogen is injected in the reactor, in the quantity indicated in table II, to control the melt index of the polyethylene produced. Table II below indicates, in addition to the operating conditions, the yield Rcex expressed in kg of polymer per milliatome of titanium and vanadi ~, the fluidite index IF, the density ~, as well as the molecular weight mcyenne en number ~ hl and the percentage B of molecular weights less than 5000 determined by gel permeation chromatography.
EXI ~ THE 6 AND 7 (COh ~. ~ RATIFS) We operate in an identical way to the experiences of examples 4 and 5 except that 1 ~ ca-talyseur introduced into the reactor is constituted only titanium trichloride TiC13 3 AlC13 for example 6, and only vanadiwn VC13 trichloride for example 7. The different operating conditions and the polymerization results are recorded in Table II below.
TABLE II
_ Example 4 5 6 7 V / Ti l 2 0 % H2 2, l 2.3 l, 7 1.0 RC 10.1 7 ~ 7 3.4 3.0 IF 7.3 7.2 6 ~ 2 6.9 f 0.958 0, g58 0.954 0.956 ~ In 17,000 17,500 11,500 9,000 B 5.9 5.8 l0.0 12.8 _ _.

Thus it appears clearly, by comparaisor, between the exempies

4 and 5 on the one hand, 6 and 7 on the other hand, that the catalysts according to the invention tion allow, for polymers with equivalent melt flow indices, strongly increase the catalytic yield as well as the molecular mass while decreasing the rate of low molecular mass and increasing the density.

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E ~ LES 8 to 11 In a discontinuous ball mill whose specific power that es ~ from 0, S ~ 'per kilogram of rr ~ tière treated we introduce é ~ uimolecular amounts of TiCl3 and VCl3. After an operation of co-grinding of duration t expressed in hours, the catalyst obtained is subjected to a X-ray crystallographic analysis allowing to determine, according to the Scherrer's law, the dimcnsion c of the crystallites in the plane ~ 3 0 0). We observe that the catalyst has a solid solution structure. After this analysis, the catalyst is dispersed in methylcyclohexane and activated with dimethylethyldiethylsiloxalane in an amount such that the ratio atomic TilV is equal to 6.
~ Ethylene is then polymerized continuously according to the same operating procedure as in examples 4 and 5, the temperature T2 being kept constant at 230C. Table III below indicates, in addition to the duration of grinding of the catalyst, the yield Rc expressed as in the tests 4 to 7, the density f, the molecular mass ~ In, the percentage B and the dimension c expressed in angstroems.
TABLE III
~ 0 Example t Rc B c _.
8 0 2.0 0.954 10,000 10.9 2,000 9 4 7.1 0.958 15,000 7.3 100 8 9.8 0.956 16 5 ~ 0 5.9 80 11 15 12.5 0.954 22,500 4.2 60 _ EXI ~ LE 12 The catal ~ seur obtained con ~ ormément exerr ~ the 9 is dispersed in meth ~ lcyclo} 1exaJ1e then activated by monofluorodiethylalurninium in quancité such that the atornic ratio Ti Al ~, is equal to 6. We then polymerizes ethylene continuously under a pressure of 600 bars in presence of 0.5 O in moles of hydrogen, in a cyclin autoclave reactor drique of volume 0.61 maintained at the temperature of 230C. The dispersion catalyst is injected into the reactor so that the time average stay of catalyst ~ ur in the reactor is of the order of 30 seconds .. ....
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2 2 .3 ~. ~
A polyethylene with a melt index equal to 3.2 dg / min is then obtained.
with a catalytic yield of 6.1 kg of polymer per milliatome of titanium and vanadium.

EXI ~ LES 1_ and 14 In a discontinuous ball mill, an energy of grinding of 4 kl ~ h per kg of material treated with a mixture of TiC13 3 AlC13 and VC13 in the molar proportions indicated in Table IV. The cataly-sor obtained, dispersed in methylcyclohexane and activated with dimethyl-thyldiethylsiloxalane in an atomic ratio Ti ~ = 6 is used to polymerize ethylene continuously under a pressure of 1,200 bars in a cylindrical autoclave reactor of volume 31 maintained at the temperature 240C, the average residence time of the catalyst in this reactor being about 30 seconds. Table IV below indicates, in addition to the report atomic V / Ti in the catalyst, measured polymerization results as for the previous examples.

TABlEAU rv Example V / TiRc ~ n B

13 0.5 6.2 0.959 22,000 3.9 14 3 6.0 0.959 21,500 4.0 EXI ~ LES 15 to 17 In a discontinuous ball mill we apply an energy of grinding E, expressed in ~ h per kg of treated material, to a mixture of TiC13 s AlC13, VC13 and MgC12 in the molar proportions indicated in Table V below. The catalyst obtained, dispersed in a section C11 -C12 of hydrocarbons and activated by dimethylethyldiethylsiloxalane according to an atomic ratio T ~ --- V = 100, is used to polymerize ethylene in solution in section C11 ~ C12 above ~ ée, in a self-reacting steel clave with a capacity of 1 liter, at a temperature of 200C and below a pressure of 6 bars, for a period of one minute. The solution is then recovered and the polymer separated by filtration after cooling.

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Table V below indicates, in addition to the operating conditions, the catalytic yield Rc expressed in grams of polymers per gram of titanium per minute and per atmosphere.

S TABLE ~ .UV
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Example V / Ti MgJTi E Rc 10 15 1 6 4.0 606 16 1 12 6.1 678 17 2 12 3.1 474 . _ _.

EXr ~ LES 18 to 20 The catalyst obtained in accordance with Example 15 is dispersed in methylcyclohexane then activated with dimethylethyldiethylsiloxa-lane (e ~ emples 18 and 19) or by an equimolecular mixture of monochloro-diethylaluminium and trioctylaluminium ~ example 20) according to a report atomic Ti ~ l V equal to 6. Ethylene is then polymerized in the presence of this catalytic system: -- in a cylindrical autoclave reactor with a volume of 0.6 l maintained at a temperature of 230C and under a pressure of 600 bars, for which concerns example 18 ~
- in a cylindrical autoclave reactor of volume 3l maintained at a temperature of 240C and under a pressure of 1,200 bars, for which concerns examples 19 and 20, the muyen residence time of the catalyst in the reactor being of the order 30 seconds. Table VI below indicates the polymer results.
sation, and in particular the yield Rc, the density ~ ~ the molecular mass Mn and the percentage B.
EXI ~ THE 21 The catalyst obtained in accordance with e ~ example 17, dispersed in methylcyclohexan ~ then activated by dimé ~ hyléthyldiéthylsiloxa-lane in an atomic ratio ~ V equal to 6, is used for poly-merize ethylene in a 3 liter cylindrical autoclave reactor maintained at a temperature of 240C and under a pressure of 1,200 bars, the average residence time of the catalyst in the reactor being of the order 30 seconds.

: ' ~ 1 ~ 8 ~ 2 ~
l () Table VI below indicates the results of this polymerization.

TABLE VI

S Example Rc ~ ~ In B
_ 18 9.5 0.958 12,500 5.4 19 6.5 0.957 29,500 2.4 ~ o 7.4 0.956 18,500 ~, 5 21 6.5 0.962 24,000 ~, 2 EXE ~ THE ZZ
The catalyst obtained in accordance with Example 16, dispersed in methylcyclohexane and activated with dimethylethyldiethylsiloxane according to an TiAl V atomic ratio equal to 6, is used to copolymerize ethylene and propene ~ 30 O by weight) in an autoclave reactor cylindrical with a volume of 0.6 l maintained at a pressure of 600 bars and at a temperature of 230C, in the presence of 0.25 ~ in moles of hydrogen. A
copolymer with density 0.939 g / cm3 and melt index 7.2 dg / min is produced with a catalytic yield of 4.1 kg per milliatome of titanium and vanadium.

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Claims (10)

The embodiments of the invention, about which a exclusive right of property or privilege is claimed, are defined as follows: 1. Ethylene polymerization catalysts comprising at least minus two halogenated transition metal compounds, one of which is a titanium trichloride syncrystallized with aluminum chloride, charac-terrified in that they have the formula:
(TiCl3,? AlCl3) (MCl3) x (MgX2) y in which 0.3? x? 30 ? y? 20, M is a transition metal of groups VB and VI B of the Periodic Table and X is a halogen. 2. Catalysts according to claim 1, characterized in that that they have a Ti-M binary solid solution structure whose crystals-lites have a dimension less than or equal to 100 angstroems. 3. Catalysts according to claim 1, characterized in that 2? y? 20. 4. Method for manufacturing the catalysts according to the resale dication 1, characterized in that the trichloride is brought into contact titanium syncrystallized with aluminum chloride, trichloride metal M and, where appropriate, anhydrous magnesium halide and in that these chlorides are subjected to a grinding stage during which the grinding energy is at least equal to 3 KWh per kg of solid material processed. 5. Process for the polymerization of ethylene under a combined pressure taken between 300 and 2,500 bars and at a temperature between 180 ° and 300 ° C, characterized in that the ethylene is placed in the presence of a system catalytic including:
(a) at least one catalyst according to claim 1, and (b) an activator chosen from hydrides and organometallic compounds of metals from groups I to III of the Periodic Table, the atomic ratio of the activator metal to the sum Ti + M being understood between 0.1 and 10, and the average residence time of the catalytic system in the polymerization reactor being between 2 and 100 seconds. 6. Method according to claim 5, characterized in that the polymerization is carried out in the presence of an inert hydrocarbon having preferably less than 5 carbon atoms such as for example propane or butane. 7. Process for the polymerization of ethylene under pressure between 1 and 200 bars and at a temperature between 20 ° and 200 ° C, in solution or in suspension in an inert liquid hydrocarbon having at least 6 carbon atoms, characterized in that ethylene is put in the presence of a catalytic system comprising:

(a) at least one catalyst according to claim 3, and (b) an activator chosen from hydrides and organometallic compounds of metals from groups I to III of the Periodic Table, the atomic ratio of the activator metal to the sum Ti + M being understood between 1 and 100. 8. Manufacturing method according to claim 4, characterized in that the grinding energy is not more than 25 KWh per kg of solid matter treated. 9. Method according to claim 5, characterized in that the polymerization is carried out in the presence of 0.04 to 2% by volume of a chain transfer agent. 10. Method according to one of claims 5, 6 and 9, character-se in that it is applied to the copolymerization of ethylene with 15 to 35% by weight of an .alpha.-olefin having 3 to 8 carbon atoms.