DE2001549A1 - Process for the production of olefin polymers - Google Patents

Description

DR. ING. F. WtTBSTHOFF. θ MUNICH βθ ' DIPL. ING. G. PULS eCHWilQBBSTHlSSE 9 DH.K.T.PECHMANN TiLXrox SS Qe Bl XHt. IiVu * 1 *. XlifiiltiJSlVC »^ TKLKOBAl (If ADKKSSKl

-. - PBOTXOTPAT1NT ifOVOHIV

1A-37,348

B e s ehre i b u h g for the patent application of the

SHELL INTERNATIONAL RESEARCH MAATSGHÄPPIJ NV, 30, - Care. 1 van Bylandtlaan, Ώβη Haag / Netherlands

concerning! ·

" Process for the production of olefin polymers "

The invention relates to a process for the production of olefin polymers in the presence of catalysts known as Ziegler catalysts. It affects both Polymerization of olefins, such as the polyolefins produced, including copolymers, as well as the production of Ziegler catalysts suitable for use in the polymerization of olefins, as well as those obtained Catalysts themselves.

A Ziegler catalyst can be formed in that for example in a reactor for olefin polymerization a transition metal compound in which the transition metal has a valence level below the usual has the maximum valency level, e.g. titanium trichloride, with an organometallic compound, e.g. aluminum diethyl monochloride, the organometallic compound primarily as an activator for the transition metal compound is used, but also to intercept smaller amounts of impurities which deactivate the de ^ a, catalyst and in, de ». Polymerization reactor have been introduced.

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Such Ziegler-catalyst may be, and are optionally fed to the reactor with an additional organometallic compound outside the polymerization reactor fabric. ¹ The catalyst formation within the polymerization reactor in the above-mentioned manner is, however, a suitable method which is used in practice. The transition metal compound in a valence level below the usual maximum valency level is generally obtained by reducing the corresponding compound in which the metal is in the normal maximum valence level. For example, titanium trichloride is usually produced by reducing titanium tetrachloride using an aluminum alkyl compound or an aluminum alkyl halide compound as the reducing agent. The reduction stage can be carried out together with the catalyst preparation stage, in that the same aluminum alkyl compound is used both as a reducing agent and as an activator for the catalyst. The titanium trichloride used in the production of the catalyst is generated in situ under these conditions. However, it is now generally preferred to carry out the reduction of the transition metal as an independent step and then to add the organometallic compound to the reduced compounds formed, which is done either in the reactor or outside the reactor.

Usually the polymerization is carried out in a reaction medium consisting of an inert organic liquid e.g. an aliphatic hydrocarbon. The catalyst and one or more olefins are used in this Medium brought together in a suitable manner. A molecular weight regulator, usually hydrogen, is usually used the reactor is added to the formation of polymers

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with undesirably high molecular weight to suppress. Many Forms of Ziegler catalysts have been suggested. It is now known that there are many transition metal compounds and organometallic compounds that are used for the production of Ziegler catalysts can be used. Such catalysts can also consist of more than one transition metal compound in combination with one or more. Organometallic compounds exist and / or such catalysts may contain additional compounds that have a modifying effect have on the catalyst and / or on the course of the polymerization.

For economic reasons it is obviously desirable that the Ziegler catalyst should have a high catalytic activity during the polymerization Catalyst as such or by changing the polymerization conditions, for example by increasing the pressure, in order to achieve a maximum polymerization rate per unit weight of the usual catalysts, which practical considerations still allow, or by a combination of these factors. However, other considerations are also important. For example, market demands dictate the type of polymer to be made, which in turn affects the type of catalyst and / or the polymerization conditions that can be used without having to switch to cumbersome and expensive cleaning steps.

As already mentioned, the transition metal compound is generally obtained in a valency level below the usually maximum valency level in that the ent- ■■ '■: ■ - ■. ■ ".. '.. ■■; - ■'.; - 4 _; -

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speaking connection that the metal in the ordinary contains the maximum value level, is reduced. These Reduction is usually carried out as a reducing agent an organometallic compound based on the same metal as the activator is used metal used for the Ziegler catalyst, preferably aluminum. However, it is also possible to use the reduction stage to carry out so that an organometallic compound is used which is different from that which is used for activation of the Ziegler catalyst produced is used. For example, titanium tetrachloride can be mixed with an organomagnesium compound reduced and activated with an organic aluminum compound. To date, Ziegler catalysts have generally had does not have a sufficiently high activity to be found in a fluidized bed system in the absence of a solvent use as the final product contained excessive amounts of catalyst which are difficult to remove. Because of her surprising however, high activity has been found to be able to successfully produce organomagnesium compounds Catalysts are used whose activity is sufficiently high that they can be used in a satisfactory manner in gas phase polymerization of olefins can be used.

α The process according to the invention for the preparation of olefin polymers by polymerizing an olefin in the presence of a catalyst is characterized in that the polymerization is carried out at least partially in the gas phase in the absence of a solvent and a catalyst is used which is obtained by reducing a compound of a transition metal in the usual maximum Valence stage with an organomagnesium compound and activation of the reduction product by adding an organoaluminium compound has been produced as an activator .

Although the entire reaction is carried out in the gas phase

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This can, if necessary, "cause certain technical problems. It is therefore preferred to use a two-stage process in which the gas phase polymerization takes place only after a prepolymerization stage is solvent fed into a polymerization reactor, which is subsequently, when a copolymer is to be produced sat! charged with the olefin monomer or monomers, and preferably also fed with hydrogen as molecular weight regulator. the Vorpölymerisation may be overall M suitable pressing performed, although it is preferred to use above atmospheric pressures, preferably

2 below 100 at and especially at about 1.4 to 14 kg / cm.

After prepolymerization is complete, the solvent becomes stripped off and the further polymerization is carried out in the gas phase, preferably by a fluidized bed process. Without relying on a theoretical explanation of the invention To establish better catalyst activity, it is assumed that the reduction is lower than the controlled Conditions according to the invention is carried out, leads to the fact that magnesium atoms in a particularly effective manner the solid phase of the reduced transition metal compound ^

be incorporated and that the presence of these atoms in the ER M preserved activated Ziegler catalyst is one of the reasons for the increased activity of the catalysts used in this invention.

Any transition metal compound or a mixture of such compounds, which are an organomagnesium compound of the usually maximum, can serve as a catalyst for the olefin polymerization. Valence level can be reduced and whose lower valence level is effective for olefin polymerization as a catalyst in the presence of an organometallic activator. Any organometallic compound can also be used

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which is known to activate Ziegler catalysts for olefin polymerization to produce the to activate reduced transition metal compounds. Suitable Transition metal compounds are the halides of titanium, vanadium, chromium, molybdenum and zirconium. Suitable organometallic compounds are alkyl compounds and alkyl halide compounds of aluminum, zinc and magnesium. As is known per se is, however, the most useful Ziegler catalysts are those produced by the reduction of titanium tetrachloride and by activating the obtained trichloride with an aluminum alkyl compound and an aluminum alkyl halide, respectively. Therefore, the present invention is intended to be related to this catalyst system will be explained in more detail, although it is not limited to such systems, but in general on the production of all kinds of Ziegler catalysts is applicable.

Many kinds of organomagnesium compounds can be used as reducing agents in the present invention. In general however, for practical reasons, it is preferred to use compounds of a kind produced by the reaction between a Organohalide compound of the general formula RX in which a R is a hydrocarbon group and X is a halogen atom, and metallic magnesium. Such compounds are often referred to as "Grignard compounds". This term will therefore also be used in the following. It must be noted, however, that at times the term “Grignard compounds” in the narrower sense for the designation of ether complexes of organomagnesium halides is needed, which was created by the mentioned reaction in ether as a solvent. According to the registration, the expression however, in the broadest sense used to denote any type of organomagnesium compound resulting from the aforesaid general reaction gives · For example, in the following the term "Grignard compounds" does not denote aur

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Hydrocarbon-magnesium halides of the general formula: HMgX, which may be present in solvated form, but also the dihydrocarbon-magnesium ^{compounds of the general formula: Rp M} S together with the forms of both types of compound that are obtained when the Grignard reaction is carried out in an inert, i.e. non-hydrating Solvent such as a hydrocarbon; is carried out·

Although any "Grignard compound" can be used in the present invention, it is believed that the ether complexes which result from the reaction of magnesium with a hydrocarbon halide in the presence of an ether are not always very effective. It is therefore preferred according to the invention to use those Grignard compounds which have been obtained by reacting a hydrocarbon halide of the formula BX with magnesium metal in the absence of an ether. Without wishing to be bound by theoretical discussions, it is believed that such ether-free Grignard compounds are often present in molecularly associated form. For economic reasons, it is preferred to use compounds in whose formula X denotes a chlorine or bromine atom, while optimum activity in the activated catalyst obtained as the end product is generally achieved by using a Grignard compound in whose formula H an alkyl group with at least 4 and preferably at least 8, in particular 12 carbon atoms. The higher alkyl Grignard compounds, however, usually require more expensive agents to prepare them, and therefore the choice of a suitable Grignard alkyl compound is usually determined by economic considerations, ease of handling and optimal effectiveness.

Grignard compounds are known from the chemical literature, which describes many processes for their preparation

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are. For the preparation of the alkyl magnesium halides preferred according to the invention a suitable method is the method according to Bryce Smith in Ohern. & Ind. (1960), page 1533, metallic magnesium and an alkyl halide in a hydrocarbon solvent in the presence of an alcohol, preferably 1.0 mol% ethanol, are heated as a catalyst. Another useful manufacturing method has been described by Zakharkin, Qkhlobystin and Strunin in Tetrahedron Letters (1962), p. 631, with many Grignard compounds can be obtained by using magnesium and the alkyl halide in isooctane as solvents

S heats up. By these methods sludges are usually obtained, the desired Grignard reducing agent partly in the liquid phase and partly as undissolved contain solid material. All of the reaction product present as a sludge can be used as a reducing agent in the invention Process are used. However, the presence of "insoluble" ingredients can create difficulties. Often is therefore preferred to use the Grignard compound as soluble Separate product. This can best be accomplished by containing the organomagnesium compound Reaction product extracted with a suitable solvent, either after the reaction of the magnesium with can be added to the hydrocarbon halide or

If is at least partially present during the implementation. At least two portions of the solvent are required in each pail to achieve a reasonably complete extraction. Therefore, the preferred method for the preparation of the Grignard compound is sium metallic Magne and implement a hydrocarbon halide optionally in the presence of a solvent, such as isooctane or toluene, and optionally in the presence of catalytic amounts of an alcohol and the Reaktionsgemiech with a geeig Neten solvent at fiückf Luss -to heat and the extracted desired Grignard compound from the obtained

Separate solution. The term "Grignard connection" in the-

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This description means the product that by implementation of metallic magnesium and a hydrocarbon halide whether the product is used in the reaction sludge or has been separated from the insoluble products by solvent extraction is. The latter type of product is particularly known as the "Grignard solution" designated.

This Grignard compound can with the titanium tetrachloride in a manner known per se to reduce this compound to be used for titanium trichloride. However, it has been found that the best way to use the Grignard compound is to use a Solution of titanium tetrachloride converts into the same hydrocarbon Solvent is dissolved, as it was used to make the Grignard compound. These reactants can be added in any order. It However, it has been found that better results, e.g. higher bulk densities of the polymers, are often obtained by that one uses the so-called. Reverse addition method in which the titanium tetrachloride is added to the reducing agent becomes, in this case, the Grignard connection. For this reason, this order of addition is preferred. The concentration the Grignard compound in the mud of the reaction. mixture, the concentration of the .titanium tetrachloride solution used and the relative amounts of the two reactants can vary within wide limits, to adapt them to special procedural needs.

The temperature at which the reducing Grignard compound is reacted with the titanium tetrachloride, is important because it is the physical IOrm and affects the activity of the Ziegler catalysts obtained and also the physical properties of the .Polymer produced influenced * Accordingly, a preferred Process characteristics according to the invention

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Use of a reduction temperature below ^{0 0} O, since this results in a higher catalyst activity and higher bulk densities in the polymers. If catalysts are prepared at other reduction temperatures, but the other variables are adjusted ffcst, it is found that a drop in temperature from room temperature to ^{0 0} leads to a decrease in catalyst activity, but surprisingly, with a further decrease in temperature, the catalyst activity is sharply increased and becomes significantly greater than the activity that is achieved in the reduction at room temperature. To achieve a useful effective increase in catalyst activity, the temperature should substantially be below 0 ⁰ C, and is preferably at most -30 C, preferably not higher than -60 ⁰ C. A further considerable advantage of the use of reduction temperatures below 0 ° C according to of the invention is that a better bulk density of the polymer is obtained. This property is found to be inversely proportional to the reduction temperature of the catalyst. A continuous increase in the bulk density of the polymer is thus achieved when the reduction temperature is lowered from room temperature to -60 ⁰ C. Although it is sometimes possible to achieve catalyst activities in a reduction at room temperature which are comparable to those achieved at reduction temperatures below 0 ^° C, especially if the reduction ^{temperature is not very much below 0} ° C, it is usually not possible to to achieve the combined effect of both a high catalyst activity and a high bulk density without the catalyst reduction being carried out ^{below 0 ° C.}

The rate of addition of the titanium tetrachloride should of course be adjusted so that the heat developed can be distributed without the reaction temperature rising above the desired limit. After this addition « \ Ψά% τ sjü

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Warm the mixture to tree temperature and stand in a suitable manner overnight until the. Reaction is complete, stirring during this time. The slurry of titanium trichloride can then optionally a certain time, are heated to 60 ⁰ G, for example, 6h; to achieve optimal activity. .

The titanium dichloride produced by the reduction of the Grignard compound can then be used by any method known for the production of Ziegler catalysts. The reaction product can thus be used as such or it can first be freed from unreduced titanium tetrachloride and other soluble compounds by means of vials, in a suitable manner by decanting and reslurrying, the latter process being preferred. The titanium trichloride can also preferably, but not necessarily, be used as a slurry, as is obtained in the reduction stage and is not separated off before use _. can be used. In any case, the trichloride can be mixed with the aluminum alkyl compound as activator and added to the polymerization reactor, or the trichloride and the aluminum compound as activator can both be added separately to the polymerization reactor.

The polymerization of olefins can be achieved by using the Grignard reduction product activated by customary activators used in the production of Ziegler catalysts as the catalyst. It has been found, however, that the use of aluminum dialkyl halides as activators frequently leads to the formation of polymers which have a low melt index. Accordingly, a preferred method of the invention is the use of a silicon hydrogen aluminum compound, in particular a trialkyl aluminum compound, - - '. ■■■: "■'■" ■■ ^: / - ■., "■ ': ■ .-. ■ -'- 12'-

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as an activator in combination with the Grignard reduction product. It has also been found that in many cases Aluminum trialkyl compounds with long carbon chains result in a more active catalyst than the usual compounds, like triethylaluminum, although the carbon chains must not be excessively long, as this leads to a reduction in activity. Preferred activators are therefore aluminum trialkyl compounds, in which each alkyl chain has at least 4, but not more than 11 carbon atoms. A a suitable activator is triisobutylaluminum.

The relative amounts of titanium trichloride and the aluminum alkyl compound can be set within the usual limits, e.g. a molar ratio of 1: 1 to 1:40, in order to obtain catalysts which are adapted to certain polymerization conditions. In general, the more active catalysts obtained by using a molar ratio of activator to titanium trichloride of 10: 1 to 33 si will. In accordance with conventional procedures, the aluminum alkyl compound is preferably in solution in a suitable one Use hydrocarbon as a solvent, preferably the same solvent as in the Slurry of the reduced titanium trichloride is present. Hexane and isooctane are examples of technical and industrial scale suitable solvents.

The invention is particularly applicable to the production of ethylene polymers or copolymers with other monomeric 1-olefins which can be polymerized using Ziegler catalysts, for example propylene. The invention therefore includes, inter alia, a catalyst which is suitable for use in olefin depolymerization and a process for the preparation of such a catalyst «

The invention is explained in more detail by the following example

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B e i s ρ i e 1

"0.11 g of atom magnesium powder was dried by heating in a -250 ml flask" at 120 ° C. under a stream of pure nitrogen for 1 hour. The flask was cooled. 0.03 gmol of n-dodecyl bromide was added to the metallic magnesium. The mixture was heated until the n-dodecyl bromide boiled, indicating the beginning of the reaction. Subsequently, 0.07 gmol n-dodecyl bromide was dissolved in 100 ml SBPA (commercially available solvent, aliphatic hydrocarbon, bp. To 11O ⁰ G 90) was added over 20 to 30 min. The temperature of the reaction mixture was adjusted to 80 to 90 ° 0 ää. By the end of the reaction was heated to 80 ⁰ O. The concentration of the Grignard compound was determined by removing a sample, adding the sample to water and titrating against 1/10 η hydrochloric acid. The Grignard reagent formed a gray slurry in the solvent which has been cooled to -60 ⁰ C. As quickly as possible, an equimolar amount of titanium tetrachloride as a 2 molar solution in SBPA was added while the reactor contents were maintained at Q -5 ° G. The slurry was vigorously agitated during this procedure. After all of the titanium tetrachloride had been added, the slurry was allowed to warm to room temperature and stirred overnight. The titanium trichloride obtained was allowed to settle and the supernatant m

.Liquid was decanted and replaced with fresh solvent replaced. This was repeated 3 times. It became a washed one Obtained sludge from titanium trichloride.

200 ml of hexane was placed in a 1200 ml autoclave with a ribbon stirrer. The autoclave was filled with nitrogen and warmed to ⁰ 6Q G, after which 1 mmol iEriisobutyl · - aluminum was added with stirring. The nitrogen was replaced by a mixture of ethylene and hydrogen in proportion. Then 0.03 mmol of the above prepared

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Provided titanium trichloride was added, whereupon the polymerisation of the prepolymerisation stage started. The pressure was increased to 6 at (3 at ethylene and 3 at hydrogen) and then kept constant by adding ethylene. The temperature was raised to 80 ⁰ O. The prepolymerization was carried out for 15 minutes. The pressure was then released and the hexane was completely removed by stripping for 1 hour.

The dry mixture of catalyst and polymer that was obtained was used for fluidized bed polymerization in the same autoclave. In this case, at 3 ethylene and at 3, hydrogen was pressurized and heated to 80 ⁰ C again. The polymerization was carried out for 2 hours and then terminated by replacing the mixture of ethylene and hydrogen with nitrogen. About 10 g of polyethylene were produced during the prepolymerization, while 13 g of polyethylene were obtained in the fluidized bed.

PATEUTANSPBÜOHE:

009850/1997

Claims (17)

1A-37 PATENTlIiSPE ^ CHE-: 1) Process for the preparation of olefin polymers by polymerizing an olefin in the presence of a catalyst, characterized in that the Polymerization at least partially in the gas phase in the absence of a solvent is carried out and a catalyst is used which is obtained by reducing a compound of a transition metal in the ordinary maximum valence level with an organomagnesium compound and activating the. · ■ Reaction products by adding an organoaluminum compound has been produced as an activator. 2) Method according to claim 1, characterized in that g e k e nn - ζ Inet that the polymerization can be carried out in two stages carries out, the gas phase polymerization being a prepolymerization stage precedes, in which the catalyst with the monomeric olefin in the presence of a solvent in Is brought into contact. . 3) The method according to claim 1 or 2, characterized geke η η I show η et that polymerized at least during part of the polymerization in the presence of hydrogen. _; . "■" .-. ^) Method according to claim 1 to 3 »thereby g e k e η η ζ e i ch η et that the olefin is ethylene or a mixture of ethylene used with a higher 1-olefin. 5) Method according to claim 1 to ^, characterized ge ke η η ζ eich η et that an organomagnesium compound is used for the catalyst production, which is essentially free of ether compounds. 6) Verfanren according to claim 1 to 5, characterized g e k e η η - "■■■■■ ■■ ;. .. '■■;■■■; ■■ . \ . .___ ■ ;:; ^: _ ■ :.; -". - 16 - 009850/1997 1A-57 54-8 - 16 - draws that an organomagnesium compound is used for catalyst production, which is the reaction product between metallic magnesium and a hydrocarbon halide is. 7) Method according to claim 6, characterized in that one is an organomagnesium compound used for the production of catalysts made from metallic magnesium and a hydrocarbon halide under conditions has been obtained that the organomagnesium compound is obtained in the form of a solution. 8) Process according to claim 1 to 7 »characterized in that a catalyst is used that by reduction at a temperature below O C of a transition metal compound in the usually maximum valency level with an organomagnesium compound and activation of the reduction product by combination with a trihydrocarbon aluminum compound has been obtained as an activator. 9) Process according to claim 8, characterized in that the catalyst used is one in which the reduction of the transition metal compound from the usually maximum valence stage has been carried out ^{at a temperature not above -3O 0 C.} 10) Method according to claim 9> characterized in that the reduction at a temperature not above 60 ⁰ C has been carried out. 11) Process according to claim 1 to 10, characterized in that a catalyst is used in which the transition metal compound is a tetravalent titanium compound. - 17 -009850/1997 1A-37,348 12) Method according to claim 11, characterized in that ge k e η η that the transition metal compound is titanium tetrachloride. 13) Method according to claim 1 to 12, characterized in that g e that a catalyst is used whose activator is a trialkylaluminum compound is. ', 14.) Method according to claim 13, characterized in that g e k e η η - draws that the trialkylaluminum compound has the formula Al E ^, in which E is an alkyl group Means chain length of at least 4 carbon atoms but not more than 11 carbon atoms. 15) Method according to claim 14, characterized in that the trialkylaluminum compound Is triisobutyl aluminum. 16) Method according to claim 1 to 15 »characterized in this that the reduction is achieved by adding the transition metal compound to the organomagnesium compound has been carried out. 17) Method according to claim 1 to 16, characterized in that the entire polymerization is carried out in the gas phase. 009850/1997