CA2237434A1 - Aluminoxane process and product - Google Patents

Abstract

An aluminoxane product is prepared by reacting water which contains a stabilizing agent, such as a lithium halide, with a hydrocarbyl aluminum compound, such as trimethylaluminum, in an organic solvent.

Description

. CA 02237434 1998-0~-12 W O 97/18218 PCT~US96/~8244 ALUMlNOXANE PROCESS ANI~ P~ODUCT

t, This invention relates generally to the p~ lion of alllminox~nes and more particularly to the p~ ion of hydrocarbyl~ minc-xanes, such as methylaluminoxane, '1 by reacting a hydrocarbyl alumim~m compound with water which contains a stabilizing 5 agent, such as a metal salt, which solution is dispersed in an organic solvent.
Vandenberg, U. S. 3,219,591 reported the catalytic activity of compounds formed by the reaction of trialkyl alu~ with limited amounts of water in the polymeri7~tion of epichlorohydrin and other oxiranes. Shortly thereaf[er, Manyik, et al. U.S. 3,242,099 reported the use of aluminoxanes, made by reacting 0.85 - 1.05 moles of water with 10 hydrocarbyl al-l"l;..l~ll compounds such as kiisobutylal-.,..i.~l."" as co-catalysts with certain kansition metal compounds in the polymeri7~tion of mono-unsaturated alpha-olefins; e.g. ethylene and propylene. Isobutylaluminoxane was also made by adlding an equalmolequantityofwatertoaheptanesolutionoftriisobutylal-,."i"l.."
Manyik, et al. U.S. 3,300,458 prepared alkylaluminoxane by passing a hydro-carbon through water to form a wet hydrocarbon and mixing the wet hydrocarbon and an alkyl alumimlm/hydrocarbon solution in a conduit.
Schf-~n1h~l, et al. U.S. 4,730,071 show the ~ ~a~ion of methyl~ minc xane by dispersing water in toluene using an ultrasonic bath to cause the dispersion and then adding a toluene solution of trimethylz~ minllm to the dispersion. Schoenthal, et al. U.S.
4,730,072 is similar except it uses a high speed, high shear-in~ cing impeller to form the water dispersion.
Edwards, et al. U.S. 4,722,736 describe an aluminoxane process in which water is introduced below the surface of a solution of hydrocarbyl ~ minnm ~ rent to a stirrer which serves to immediately disperse the water in the hydrocarbon solution.
A problem associated with free water addition to trialkylalllminllm to produce t aluminoxane solutions in organic solvents is that the solutions may produce gell and/or small particles which aggregate to form gel on et~n~ling Even when the particles and/or gel are removed by filtration, additional gel can forrn in the solution after 2 or 3 weeks, especially when originally-prepared dilute solutions are concentrated to contain higher aluminoxane contents which are convenient for storage, shipment and use.

W O 97/18218 PCT~US96/18244 Sangokoya, U.S. Patent No. 5,157,137 describes a process for treating ~AO with an anhydrous salt and/or hydroxide of an alkali or ~Ik~lin~ earth metal to inhibit gel and gel forming compounds.
We have now discovered a process for making alurninoxanes by free water S addition which provides unique, gel free, stable products.
In accordance with this invention there is provided a process for making an aluminnx~ne, said process compt~i~in~ reacting water which contains a stabilizing agent with a hydrocarbyl aluminum compound in an organic solvent so as to produce an aluminoxane product.
Also provided is a new stable aluminoxane product prepared by this novel process.
~ydrocarbylaluminoxanes may exist in the form of linear, cyclic, caged or polymeric structures with the simplest compounds being a tetraalkylaluminoxane such as tetramethylaluminoxane, (CH3)2AIOAl(CH3)2, or tetraethyl~ minoxane, (C: 2H5)2AlOAl-(C2H5)2. The compounds p.~re.led for use in olefin polymerization catalysts usually contain about 4 to 20 ofthe repeating units:

~ Al - O ~
where R is C,-C8 alkyl and is preferably methyl. The exact structure of ~lllminoxanes has not been defined and they may contain linear, cyclic, caged and/or cross-linked species.
Methylaluminoxanes (MAOs) normally have lower solubility in organic solvents than higher alkylaluminoxanes and the methylaluminoxane solutions tend to be cloudy or gelatinous due to the separation of particles and agglomerates. In order to improve the solubility of the methylaluminoxane, higher alkyl groups, e.g. C2 to C20 can be included such as by hydrolyzing a mixture of trimethylalllmin--m with a C2 to C20 alkylzlll-min--m compound such as, for example, triethylal--min--m, tri-n-propyl-al--minl-m, triisobutyl-minl-nn, tri-n-hexylalllmin~lnn~ tri-n-octylal--minum or a triarylal~-min--m Such mixed methyl higher alkyl or aryl ahlmin- x~n~s are included in the term "methylaluminoxane"
as used herein.
Any hydrocarbyl alllminnm compound or mixture of compounds capable of reacting with water to form an aluminoxane can be used. This includes, ~or example, CA 02237434 1998-0~-12 trialkylalllminllm, triarylalllmimlm, or mixed alkyl-aryl alllmimlm The preferred hydrocarbyl aluminum compounds are the alkyl alllminllm compounds, especially trialkylal~lmimlrn compounds such as trimethylall~mimlm, triethylalllminl-m, triisobutylalllminum, tri-n-hexyl~lllminllm, or trioctyl~ll..,.i..-l", Of 5 these, the more preferred are the ki-cl-4-alkylalllminllm compounds.
Of the various hydrocarbyl aluminoxanes, methylaluminoxane and ethyl-aluminoxane are the more difficult to prepare because of the extreme reactivity of trimethylalllmimlm and triethylalllminllm with water. The most reactive is trimethyl-s~luminllm and, accordingly, the prer~ d use of the process of the invention is ~o make 1 0 methylaluminoxane.
The reaction is carried out in an inert solvent. Any inert solvent can be used. The d solvents are aliphatic and aromatic hydrocarbons. Aromatic hydrocarbons are more preferred such as toluene, xylene, ethylbenzene, cumene, or mesitylene. The most preferred solvent is toluene.
The concentration of the hydrocarbyl alul llhlulll compounds in the inert solvent can range from about 1-30 weight percent. A ~lc;r~ d concentration is about 5-10 weight percent, more preferably 10-15 weight percent.
The stabilizing agents are combined with the water used to hydrolyze the hydrocarbyl al~ lll.l compounds. The term "stabilizing agent" as used herein includes any water soluble inorganic compound which is effective to provide aLI~yl~lllmin~ xanes having improved solubility in organic solvents when added to the water used to hydrolyze the hydrocarbyl alllminllm compound. Preferred are water soluble (at least I gram/100 mL H2O at 25~C) metal salts and their ammonium analogs and especially alkali andzllk~line earth metal hsllicles Non-limi~ing examples of such compounds include, NaBr, NaF, NaCI, LiCl, LiBr, LiF, LiI, Kcl, MgCl2, or MgI. Halide salts of other metals as well as ammonium and metal nitrates, nitrites, sulfates, sulfites, phosphates, phosphites, borates, and carbonates can be used, for example Na2SO4, LiBO2, LiCO3, LiNO2, Li2SO4, MgSO4,NaNO3, NaNO2, NaPO3, Na2SO3, Al2(SO4)3, or Na3PO4. Hydroxides such as LiOH, Ba(OH)2, KOH, CsOH, or NaOH can also be used.
The stabilizing agents are added to make from about 0.05 percent by weight up tosaturated solutions in water. Preferably from about 0.1 to 50 percent by weight aqueous W O 97/18218 PCT~US96/18244 solutions of stabilizing agents are used to hydrolyze the hydrocarbyl aln.. l compounds.
The stabilizing agent Cont:~inin~ a~ueous solutions can be combined with the r hydrocarbyl al---.~ -- compound in an inert organic solvent by any suitable manner such Sas the various ways which are known in the art. For exarnple, the process which is described in U.S. Patent No. 4,908,463 where water dispersed in an organic solvent is mixed with a solution of the hydrocarbyl al-lminl-m in a "T-shaped" reactor. The amount of water dispersed in the solvent is preferably from about 0.25 to 5.0 weight percent, based on the weight of solvent. A more preferred amount is about 0.5 to 3.0 weight 10percent and most preferred is about 1.0 to 2.5 weight percent. The r~cts~nt~ are combined in proportions to provide from about 0.5 to 4.0 moles of hydrocarbyl ahTmin~lm compound per mole of water and from about 5.0 to 10,000 moles of hydrocarbyl alnminllm compound per mole of stabilizing agent and, preferably, from about 50 to 5,000 moles of hydrocarbyl alll..lit~l.... compound per mole of stabilizing agent.
The invention is further illustrated by, but is not intended to be limited to, the following examples.

Fx~mple 1 An aqueous LiCl solution was pl~ed which contained 0.35 pounds (158.9 grams) of anhydrous LiCI salt in 3 gallons (11.36 liters) of solution. This salt solution was fed into a flow-through sonicating horn at a rate of 0.15 lbs. (68.1 gms) per hour and ~m~ if ied with toluene fed at a rate of 10 pounds (4.54 Kg) per hour. This emulsion was then reacted with a 12 weight percent trimethylaluminum (TMA) in toluene stream fed at a rate of 11 pounds (5.38 Kg) per hour. The TMA-to-water mol ratio was 2.2 to 1.
The reaction mixture was then discharged into an eductor, mixed with methylaluminoxane (MAO) product solution from a pump-around loop, and finally discharged into the vapor space of a deg~c~ing vessel. The toluene feed to the sonication horn was m~int~ined at a temperature of -2~C. The TMA feed stream was m~intzlined at a temperature of 5~C.
The f1eg~ing vessel was m~int~ined at a temperature of 20~C.
The crude product was sampled and it was noticed that there was practically no ~leg~in~ in the sample. This behavior is very dirre~ t from that observed for samples -of crude MAO prepared using plain water. Normally crude MAO will continue to degas for 3 to 4 hours after sampling. The solids formed in the new MAO product also appear to settle faster than the solids in normal MAO crude.
A sample of the new MAO was taken from the product skeam during the run and Y S was filtered. The solids produced from the reaction appear to filter easier than those formed by the standard MAO plain-water process. The filtered crude was then batch flashed to concentrate the product. The crude product was c~n~ntr~tecl by fl~hing of the solvent using a 104~C wall temperature, a 60~C bulk t~ cldl~lre, and a vacuurn of 100 mm Hg. The resulting solution was 8.86 weight percent Al. The TMA content of thesolution was 4.84 weight percent TMA. The sample c~nt~in~d less than 20 ppm Cl. The alllminllm content equates to a 15 weight percent solution of MAO. This 15 weight percent MAO solution was isolated from the flash pot as a clear liquid.
The increased stability of the new MAO was demonstrated by placing a 15 weight percent solution in an oven at 60~C for 4 days, along with a 30 weight percent solution of 15 conventional plain-water p,~aled MAO. After the 4 days the MAO was cloudy, but the new MAO was still clear. The oven ~elll~ldlule was then increased to 65~C for two more days. The new MAO remained clear. The oven temperature was then raised to 80~C.
After one day at 80~C the new MAO was still clear, but regular MAO was completely gelled.
After the oven test, the 15 weight percent MAO solution was used in a polymerization test to clet~rmine if it was active as a co-catalyst. Three mL of the 15 weight percent MAO solution were added to 100 mL of toluene. To this solution, 0.25 mL of a solution of 18 mg of zirconocene dichloride -- (C5H5)2ZrCl2 -- dissolved in 18 rnL
toluene was added. The solution was stirred and heated in an oil bath to 80~C. A constant pressure of ethylene (60 psig) gas was then placed on the reaction vessel. After 35 minlltes, the vessel was removed firom the oil bath and the pressure was released. The polyethylene product was collected by filtration, washed and dried. The final yield was 7.05 grams of polyethylene.
The polymerization test was repeated with standard plain-water prepared MAO.
A change was made in the volume of MAO solution added based on the calculated weight percent MAO. Two mL of 23 weight percent MAO was added to 100 mL of toluene and CA 02237434 1998-0~-12 then 0.25 mL of the zirconcene dichloride toluene solution was added. The reaction was performed under the same conditions for the same length of time as the above polymeri7~tion test. The polyethylene was collected, washed and dried. The final yield was 7.88 grams. Allowing for expe~ l error, this result equates to approximately the S same degree of reactivity as the new MAO which has been heat aged. This demonstrates that the improved stability of the MAO pl~cd in accordance with the process of the invention is achieved without loss of activity.

Fxzlmplç 2 MAO was prepared using the sarne I,iCl salt solution as in Example I, but the feed rates and temperatures were somewhat different.
The salt solution was fed at a rate of 0.16 Ibs (72.6 gms)/hr. The toluene stream was fed at 11.6 Ibs (5.26 Kg)/hr. The TMA stream was fed at 11.6 Ibs (5.26 Kg)/hr.
These feed rates produced a TMA-to-water mole ratio of 2.22 to I . The temperature of deg~ing vessel for the second run was m~int~ined at 1 0~C. The other feed t~ Ldtures were m~in~inP~l the same as in Fx~mple 1.
A sample of the MAO was taken from the second run and was filtered and flashed under the same conditions as the first run sample of Exarnple 1. The final weight percent Al of this sample was 11.4. The sample contained 7.96 weight percent TMA and 0.01 weight percent Cl. These results equate to an 18 weight percent MAO solution. This solution was clear upon leaving the flash pot. A portion of the sample was placed in an oven at 65~C for two days and it remained clear ang gel free. The oven was then increased to 80~C, and a sample of standard 10 weight percent MAO was placed in the oven. After one day the new MAO was still clear, but the 10 weight percent MAO began turning cloudy.
The solids filtered from the sarnple from Exarnple 2 were analyzed. The solids contained 11.5 weight percent Al, no detectable TMA, 0.35 weight percent Cl, and a gas/AI mole ratio of 1.47. This ratio is approximately equivalent to that of standard plain-water prepared MAO. These results indicate that these solids could be a higher molecular weight MAO. An experiment was conducted to determine if the solids could be used as both an activator and a support for a metallocene catalyst. The solid was rinsed from the W O 97/18218 PCT~US96/18244 bottle with toluene and collected on a coarse frit. The solids were then washed with isopentane and a fine white powder resulted. The solid was removed from the frit and slu}Tied with toluene. S;x mL of a 0.100 gram of zirconocene dichloride dissolved in 60 mL toluene solution was then added to the slurry and the resulting ~ Lu~e ~it~tet1 The S slurry began t~h~nging color from white to peach colored. After approximately one-half hour, the slurry was transferred to the coarse frit for filtering. The toluene was filtered from the solid. The peach-colored solid was then rinsed with isopentane. Upon rinsillg, the solid turned to a white powder. One-half gram of this solid was placed into a reaction vessel and 25 mL of toluene was added to produce a slurry. The vessel was then placed 10 in an oil bath at 80~C and the slurrv was stirred at this te~ dLul~. Ethylene was applied to the vessel at a continuous pressure of 60 psig while being m~int~in~(l at 80~C. After 10 minllte~, the vessel was removed from the oil bath and the pressure on the vessel was released. The polyethylene produced from this reaction was washed, filtered, and dried.
The final yield of polyethylene was 2.1 grams.

Claims (14)

1. A process for making an aluminoxane having increased resistance to gel formation, said process comprising reacting in an organic solvent medium (i) a hydrocarbyl aluminum compound with (ii) free, liquid water that has dissolved therein a stabilizer against gelation in the aluminoxane, such that an aluminoxane having increased resistance to gel formation is produced.

2. A process of claim 1 wherein said stabilizer is selected from the group consisting of metal salts and their ammonium analogs, including mixtures thereof.

3. A process of claim 2 wherein the metal of said salts is selected from the group consisting of alkali and alkaline earth metals.

4. A process of claim 1 wherein said stabilizer is a lithium halide.

5. A process of claim 4 wherein said stabilizer is lithium chloride.

6. A process of any of the preceding claims wherein the aluminoxane produced is a methylaluminoxane.

7. A process for making an aluminoxane having increased resistance to gel formation, said process comprising (a) dispersing in a hydrocarbon solvent, an aqueous solution of a stabilizing agent that inhibits gel formation in an aluminoxane, and (b) mixing the dispersion with a hydrocarbon solvent solution of a hydrocarbyl aluminum compound.

8. A process of claim 7 wherein said stabilizing agent is selected from the group consisting of alkali metal halides and alkaline earth metal halides, including mixtures thereof, and said hydrocarbylaluminum compound comprises trimethylaluminum.

9. A process of claim 7 wherein said stabilizing agent is a lithium halide.

10. A process of claim 9 wherein said lithium halide is lithium chloride.

11. A process of any of claims 7-10 wherein the amount of water dispersed in the hydrocarbon solvent is from 0.5 to 3.0 weight percent based on the weight of said solvent; and wherein the reactants are combined to provide (i) from 0.5 to 4.0 moles of the hydrocarbyl aluminum compound per mole of water, and (ii) from 50 to 5,000 moles of the hydrocarbyl aluminum compound per mole of the stabilizing agent.

12. A process of claim 11 wherein the hydrocarbon solvent is an aromatic hydrocarbon solvent.

13. A solution in an organic solvent of an aluminoxane comprising (A) the reaction product of free, liquid water which has an aluminoxane gelation inhibitor dissolved therein, and (B) a hydrocarbyl aluminum compound, said solution being characterized by remaining clear and gel-free longer than it would if made without said aluminoxane gelation inhibitor, and stored in the same way.

14. A solution of claim 13 wherein the aluminoxane is a methylaluminoxane and wherein the organic solvent is a hydrocarbon solvent.