Process for the preparation of solutions of oligomeric methylaluminoxanes

DESCRIPTION

The present invention relates to the preparation of oligomer solutions of methylaluminoxanes possibly having long chain alkyl groups containing trimethyl aluminum in their free and / or complexed form. As solvents, aliphatic, cycloaliphatic or aromatic hydrocarbons may be used.

Long chain alkymer alkyl and / or alkylamers with simplified structures

<img file="PT96751B_D0001.tif" />

RR \ (-Al-O)_no-Al

R ~ R (linear)

<img file="PT96751B_D0002.tif" />

(cyclic) compounds are known compounds which are used as catalyst components for the preparation of highly effective catalysts for polyolefins, and are preferably cited with methylaluminoxanes (MAO) oligomers with R = CHg (DE-A-30 07-

<td> 725,</td><td>EP-B-0</td><td> 069</td><td> 951,</td><td>DE-A-32</td><td> 40</td><td>382, EP-A-0 170 059, DE-A-34</td><td> 43</td>

<td> 087,</td><td>EP-B-0</td><td> 128</td><td> 046,</td><td>US-A-4</td><td> 665</td><td>046, EP-A-0 232 595, US-A-4</td><td> 668</td>

<td> 838,</td><td>US-A-4</td><td> 665</td><td> 047,</td><td>EP-A-0</td><td> 241</td><td>560 WO 87/03887, EP-A-0 237</td><td></td>

294).

A known process for preparing alkylaluminoxanes is the transformation of aluminum trialkylates with water into inert hydrocarbons. However, especially for the preparation of oligomeric methylaluminoxanes (MAO) from trimethyl aluminum (TMA), other processes are preferably referred to, as it is well known from the literature that it is possible to according to the method described in US-A-3,242,099 of the slow addition of water to trimethyl aluminum (TMA) only very difficult and very low yield MAO (EP-A-018189) is obtained furthermore, In this way, compounds are obtained which together with the transition metal components do not provide any highly effective catalyst systems (EP-B-0 069 951).

No J. Polymer Science, 23, N^s 8 (p.2120) expressly refers in this regard: Simple synthetic routes to the aluminum-aluminoxane PO-Al (CH ^) are not availaJ i

<img file="PT96751B_D0003.tif" />

ble owing to the extremely high reactivity of the trimethylalane relative. This notwithstandig, the sybnthesis through direct reaction between Al (CH_O)_no and H „0 in a 1: 1 molar ratio in ο ο ά toluene solution has been reported. We found this method not very reliable. The degree of oligomerization of the aluminoxane result was scarcely reproducible and the 'reaction rathér uncontrollable.

These deficiencies were supposedly eliminated by the transformation of trimethyl aluminum (TMA) with salts containing crystallization water, such as aluminum sulfate. hydrate (EP-A-0 108 561), or in another process by transforming TMA with inorganic compounds containing water bound by absorption or adsorption, such as fine silicon dioxide (W0-A-89/02453, oxide (WO-A-89/02453), aluminum hydroxide (EP-A-0 315 234) or molecular filters (Diss. I. Her-wig, University of Hamburg, 1979).

These latter processes cited naturally require greater technological and economic expenditure; have the major disadvantage that the solid compounds used, to be well dosed, must generally be ground and sieved (especially salts containing water of crystallization), and that their moisture content must be accurately and contrarily adjusted, to achieve objective and reproducible transformation.

Moreover, they require prolonged reaction times and, at least at the beginning of the reaction, often reduced temperatures (EP-A-0 315 234, W0-A-89/02453), which not only result in reduced space / time yield, as well as a higher technological and energy expenditure.

Thus there was a need for a simplified process for the preparation of oligomeric MAOs, which provided in good yield an inert hydrocarbon soluble compound and formed with special transition metal compounds, highly effective catalyst systems for the polymerization of olefins.

i ί

<img file="PT96751B_D0004.tif" />

Such a process is provided by the present invention. In accordance with the process of the present invention, methyl aluminoxane (MAO) oligomer solutions, optionally having long chain alkyl groups containing trimethyl aluminum in its free and / or complexed form, are reacted by reacting a TMA solution and optionally 'other alkylaluminums, inert, aliphatic, cycloaliphatic or aromatic hydrocarbons, preferably toluene, with water in the molar ratio of Η ^ Ο / ΤΜΑ from 0.65 to 0.75, and then separating the insoluble secondary compounds formed during the reaction. Clear solutions obtained from oligomeric MAOs can be used directly, without any purification steps, in the preparation of polymerization catalysts.

The educts are used in such amounts that the MAO concentration in the solvent used is between 1-20 wt%, preferably 1-10 wt%. The concentrations may then be increased by condensation of the solvent under moderate conditions, preferably to 10-50% by weight of MAO. In this way it is even possible to obtain solid methylaluminoxanes (MAO) by completely eliminating the solvent.

Untransformed TMA, which in part also passes upon solvent condensation, can again be advantageously used for the preparation of MAO.

Solvents may include hydrocarbons aromatic, in particular alkyl benzols, eg toluene or xylol, as well as aliphatic or cycloaliphatic saturated hydrocarbons, eg heptane.

The reaction is preferably carried out by adding water to a TMA solution in one of the above hydrocarbons, maintaining the reaction temperature between -50 ° C.^s and +100²C. However, it is usually sufficient to work at a temperature of 0-50 ° C.⁹Ç.

In order to avoid uncontrolled reactions due to the relatively high exotherm of the reaction of TMA with

<img file="PT96751B_D0005.tif" />

In addition to water, the addition of water to the TMA solution should be done slowly while being careful to maintain sufficient exhaust for the developed heat. The insoluble secondary compounds that are formed are eliminated from solution by usual procedures such as filtration, centrifugation or decantation.

Due to the reactivity of tMA and MAO in relation to air oxygen, it must be worked under an inert gas atmosphere during the preparation of the MAOs.

The reaction product obtained is a solution of a methylaluminoxane (MAO) containing unprocessed TMA, in its free and / or complexed form. Such a solution is especially suitable as a catalyst component for the preparation of highly effective catalysts for the production of polyolefins. MAOs may also, as described in Example 1 be isolated in its solid form, the solid compound is an oligomer with an average molecular weight of approx. 800 - 3000 g / Mol.

In accordance with the process of the present invention it is also possible to prepare methylaluminoxanes which further have longer chain alkyl groups (eg ethyl, butyl, isobutyl, hexyl, octyl) in the proportion of 5-20 Mol% relative to methyl groups. preferably 10-15 Mol-%. The introduction of longer chain alkyl groups results in better solubility in hydrocarbons, which is particularly advantageous in aliphatic hydrocarbons, e.g. heptane (example 7), since pure MAO is only difficult to soluble in such solvents (example 6).

Contrary to the general opinion so far among experts, that for the preparation a molar ratio of H2 O / TMA of approx. 1 (US-A-3 242 099, EP-Ao 241 560, EP-A-0 208 561), and according to which with the addition of water to the TMA (see eg US-A-3 242 099 or J. Polymér Science, 23, p. 2120) It would not be possible to obtain a catalytically effective MAO.

<img file="PT96751B_D0006.tif" />

molar ratio of 0.65 - 0.75 if MAO solutions are obtained which, when associated with special transition complexes, are characterized by a high catalytic activity in the olefin polymerization. From this proportion, a very active MAO having a high enough average molecular weight and good solubility in alkyl benzols, eg toluene, is obtained. By the process described in Examples 1 to 3, MAO is obtained in 46-48% yield relative to the isolated solid compounds. The percentage of insoluble secondary compounds is relatively small and can be easily separated.

It has been found that above a molar ratio of H₂0 / TMA of 0.75, especially close to the 1 molar ratio, soluble MAO yield decreases dramatically. Furthermore, the reaction proceeds with great foaming, and a heavy precipitation of a white compound is observed (comparison example 1).

If, on the contrary, reducing the molar ratio below the limits of the present invention from 0.65-0.75, the yield of MAO decreases rapidly, thus making the process expensive (comparison examples 2 and 3).

Since it is advantageous to ensure a good mixture of the compounds in reaction, various technical measures have been proposed, such as ultrasound (EP-A-0 257 695) or the use of high shéar-inducing impeller -EP stirrers. -A-0 258 824).

However, with the use of these techniques, no improvement of the process to which the present invention relates was observed. Only MAO yields of 42% and 44% of the theoretical value, respectively, were obtained with respect to the isolated solid compounds (comparison examples 4 and 5).

Using the mixing techniques according to the above-mentioned EP-A-0 257 695 and EP-A-0 258 924 and following the techniques and ratios given therein, very low concentration MAO solutions are obtained (1 -2% by weight).

ϊ

<img file="PT96751B_D0007.tif" />

outside the limits of the H2 O / TMA molar ratio of 0.65-0.75 by adding to the TMA solution in a circulating system hydrocarbon turbulence produced in the external circulatory system of a liquid transport system. For the formation of such a turbulence field a rotor / stator reaction apparatus is particularly suitable. The construction and operation of such a rotor / stator reaction apparatus are described for example in DE-A-2 363 888.

As can be seen from Figure 2, there are in a bitula (2.1) a stator instrumental game (2.2) and a rotor instrumental game (2.3) respectively. Both sets are made up of concentricly mounted individual circular instruments which have milled slots or holes in a radical arrangement. Their construction is such that they can work with a small gap between the slots.

stator instrumental play is fixedly mounted on the apparatus while the rotor instrumental play is moved with a high number of rotations. Thus, the rotor instrumental game rotates in the grooves of the rings between the individual rings of the stator instrumental game so that an instrumental ring works in space between two other instrumental rings.

When passing through the apparatus, the reaction components are alternately accelerated by centrifugal force in the rotor instrumental game, reaching a great perimeter velocity, and in the following fixed stator instrumental game they are again decelerated and directed radially. Thus great forces of cutting are formed. This process occurs thanks to the number of revolutions and the configuration of the apparatus so often that agitation of the especially effective compounds is achieved. which allows a reagent compound to be introduced into the system.

<img file="PT96751B_D0008.tif" />

through a dosing hole (4) at a suitable point in the bead, whether fractions of a second are homogeneously incorporated into the reaction mixture and circulated in the apparatus, are capable of reacting spontaneously. It is irrespective of whether the apparatus is placed inside a conventional stirrer or mounted externally.

The process referred to in the present invention is best illustrated with the aid of Figure 1.

Preferably, the TMA solution is placed in a conventional stirrer (1), which works in connection with the rotor / stator reaction apparatus (2), with the contents of the reci. stirring vessel introduced into the rotor / stator reaction apparatus by free-flow or a pump (3) and after leaving the rotor / stator reaction apparatus, again returned to the agitation vessel.

The reaction of TMA with water is carried out in the externally mounted reaction apparatus (2) into which the water is metered in the turbulence field with the aid of a dosing pump (6). The homogeneous incorporation of the water described above is supported and is enhanced by the methane gas formation that occurs upon TMA transformation. 0 contents of the stirring vessel (4) circulating through the reaction apparatus, returning again to the stirring vessel (1), where the reaction heat which has only been formed is the heat additionally produced by the operating power is evacuated thereto. Heat exchange vials (5) are the amounts of any gas eventually formed which are separated from the liquid and eliminated through the exhaust pipe (7).

As can be seen from examples 4 and 5, this process using a rotor / stator reaction apparatus is a surprisingly simple variant for cost-effective preparation of MAO from TMA and water on an industrial scale. It is characterized above all by the high yield of MAO yield by high space-time yield.

<img file="PT96751B_D0009.tif" />

Solid secondary compounds are only produced on a small scale. The very simple technical construction is, at the same time, the easy conduction of the reaction, allowing the preparation of MAO with a very short reaction time and reproducible quality. In this way it is possible to achieve an increase in soluble MAO yield of more than 20%. In addition, the reaction can conveniently be carried out at room temperature, which means remarkable energy savings for cooling.

EXAMPLE 1

In a 2-liter, three-necked flask equipped with a stirrer, refrigerator, 10 ml 3-ring syringe and a nitrogen buffer system, place 1047 g of a solution of 92,3 g (1,28 mol). of trimethyl aluminum (TMA) is 954.7 g of toluene. Cool the solution to 2²C. Cooling thoroughly, then dropwise add 15.8 g (0.88 mol) of distilled water over 2 hours by stirring the mixture always while maintaining an internal temperature of 2-6 ° C.^TheG. The methane gas formed during¹ The reaction is conducted to a wind. The molar ratio of H20 / TMA is 0.7.

At the beginning of the reaction a fuzzy formation can be observed in the gas space and a cloudiness of the reaction solution. As water is added further, the formation of a white compound insoluble in the reaction mixture begins.

After the addition of water is complete, heat the reaction mixture to 50 ° C.^sC and boiling under reflux is reduced pressure (approx. 100 mbar) in order to eliminate dissolved methane. Then separate the insoluble secondary compounds by filtration under a nitrogen atmosphere. The amount of insoluble secondary compounds was, after vacuum drying, 25 g or 27% (relative to the TMA used).

The filtrate yielded 925.5 g of a clear solution which is colorless, which contains MAO in soluble form.

<img file="PT96751B_D0010.tif" />

TMA not transformed. The Al content of the solution is 2.5% by weight. Thus, this solution contains 23.1 g (0.86 g-atom) of Al. The yield of Al in solution relative to the TMA used is therefore 67%. The percent Al that could be determined by isoquinoline titration was 1.0% by weight, corresponding to 9.24 g (0.34 g-atom) of Al. They were distilled off in vacuum under moderate conditions 104 g of the solution thus obtained. Thus 4.8 g MAO was isolated as a white solid compound, corresponding to a yield of 46% relative to Al in the TMA used. The Al content of the isolated solid compound was 39.6% by weight. Titration with isoquinoline gave 8.3 wt.% Al. Hydrolysis of the solid compound formed 533 NmL / g methane. The average molecular weight was calculated as 1500g / mol (cryoscopy in benzene).

EXAMPLE 2

In anology with Example 1, water was reacted in TMA at a molar ratio of 0.65.

As filtrate 912 g of a clear, colorless solution containing soluble MAO and untransformed TMA were obtained. The Al content of the solution was 2.7% by weight.

Then the filtrate was concentrated in a distillation apparatus and 501 g of toluene was distilled off under reduced pressure (approx. 100 mbar). In distilled toluene was 8 g of TMA, ie 8.7% of the TMA used.

400 g of a clear colorless solution containing soluble MAO and residual TMA were obtained as a concentrate. The Al content in the concentrate was 5.1 wt%. Thus, the concentrate contained 20.4 g (0.76 g-atom) of Al, corresponding to a 59% yield relative to Al in the TMA used. The Al content determined by isoquinoline titration is 1.5% by weight, corresponding to 6.0 g.

<img file="PT96751B_D0011.tif" />

(0.22 g-atom) of Al. Of the 400 g of concentrate, 60 g under vacuum distillation under moderate conditions. Thus, 6.7 g of MAO was isolated as a white solid compound. Thus, the yield of isolated oligomeric MAO was 48% relative to Al in the TMA used.

Al content of the isolated solid compound was 42.4% by weight. Titration with isoquinoline revealed 7% by weight of Al. 515 Nml / g of methane was formed on hydrolysis of the compound. The average molecular weight was calculated at 1200 g / mol (benzo cryoscopy).

EXAMPLE 3

In analogy to example 1, water and TMA were reacted at a molar ratio of 0.75.

The yield of isolated oligomeric MAO was 48%, relative to Al in TMA used. The average molecular weight was approx. 2500 g / mol (benzoic cryoscopy).

EXAMPLE 4

On a 100 l stainless steel transformer coupled to a rotor / stator apparatus (Supraton type, Krupp), a 7.6 Kg (105.5 mol) TMA solution was reacted in 40.0 Kg of toluene. , with 1.211 kg (67.3 mol) of distilled water. The dosing of the water was done with the aid of a plunger metering pump (Lewa type, 3 mm in diameter, dosage duration: 3.5 h, 30 min post-reaction time). After filtration, 41.5 kg of MAO solution with a 5.5% content of Al weight (82% of the theoretical value of Al to Al) was obtained. Moderate vacuum distillation of an aliquot portion of the solution gave a solid oligomeric MAO content of 11.1 wt.% (68% of the theoretical theory.

EXAMPLE 5

We proceeded in analogy with example 4, only with the difference that 'the molar ratio of H₂0 / TMA was 0.5. The solution obtained after treatment containing 5.4% by weight of Al (87% of the theoretical value king. To Al). Removal of the solvent from 155 g of filtrate provided 12.5 g of solid MAO (51% of theoretical king to Al).

EXAMPLE 6

By analogy with example 1, 150.0 g (2.083 mol) of trimethyl aluminum was placed in 850 g of heptane and at 0 ° C²C, 23.8 g (1,322 mol) of water were dosed (molar ratio of H2 O: TMA = 0.64). After dosing is complete, stir the suspension for about 2 h at room temperature and then filter. 958 g of filtrate are obtained, the determined Al content of which is 4.04% by weight (yield: 65% of the theoretical value of Al). Removal of the solvent by vacuum distillation provided 25.4 g of solid compound (20% of R a to Al).

EXAMPLE 7

In analogy to example 1, 46.0 g (0.634 mol) of trimethyl aluminum and 18.5 g (0.091 mol) of triisobutyl aluminum were 196 g of heptane and 8.48 g was dosed. (0.471 mol) of water so that the temperature does not exceed 20²C. Treatment in analogy with Example 4 gave 213 g of filtrate with an Al content of 5.8 wt% (63% of theoretical A16 value.) Removal of the 180 g solvent from the filtrate provided. 21.0 g of solid compound (36% of the theoretical value R 1 to Al).

Comparison Example 1

<img file="PT96751B_D0012.tif" />

In a 1 liter three-necked flask equipped as in Example 1, a solution of 39.6 g (0.55 mol) of TMA in 409.4 g of toluene was poured. Thereafter, under conditions similar to those of Example 1, 9.9g (0.55 mol) of water (molar ratio of H2 O / TMA = 1.0) were added dropwise. addition of approx. 8 g of water (molar ratio H₂0 / TMA approx. 0.8), a strong foaming that prevented the entire stirring of the reaction mixture from stirring, necessitating a slower addition of water. After treatment, 28% of oligomeric MAO, relative to the TMA used. The percentage of toluene insoluble secondary compound was 54% relative to Al in TMA used.

Comparison Example 2

In analogy with Example 1, water and TMA were reacted at a molar ratio of 0.4.

Isolated oligomeric MAO yield was 29%, relative to Al in TMA used.

Comparison Example 3

In analogy to example 1, water and TMA were reacted at a molar ratio of 0.5.

The yield of isolated oligomeric MAO was 26%, relative to Al in TMA used.

Comparison Example 4

In analogy with example 1, 39 g (0.54 mol) TMA dissolved in 156 g of toluene with 6.3 g (0.35 mol) of distilled water corresponding to a molar ratio were made to rotate. HgOTIMA of 0.65. Instead of the KPG shaker an ultrasonic probe (20 KHz, 150 W) was used. 160 g of an absolutely clear colorless filtrate were obtained.

<img file="PT96751B_D0013.tif" />

of Al determined was 5.22% by weight (58% of the theoretical value rel. to Al in TMA). The filtrate solvents were removed from 100 g by vacuum distillation. Thus 11.0 g of the solid compound were obtained (= 42% of the theoretical vol. Al to Al in TMA).

Comparison Example 5

By analogy with example 1, 61 g (0.83 mol) of TMA was dissolved in 244 g of toluene with 9.7 g (0.54 mol) of distilled water corresponding to a molar ratio. HgO dec: TMA 0.65. Instead of the KPG shaker an Ultraturrax shaker was used. After filtration, 258 g of an absolutely clear colorless filtrate having an Al content of 5.6% by weight (65% of the theoretical-to Al ratio in TMA) were obtained. The solvent of 177 g of filtrate was removed by vacuum distillation. Thus 18.0 g of solid compound were obtained (= 44% of the theoretical rel Al value in TMA).