Catalyst components for the polymerization of olefins and catalysts therefrom obtained

Abstract

A catalyst component for the polymerization of olefins obtained by a process comprising: (a) reacting in an inert hydrocarbon suspension medium a Mg(OR1)(OR2) compound, in which R1 and R2 are identical or different and are each an alkyl radical having 1 to 10 carbon atoms, with a tetravalent transition metal compound having at least a Metal-halogen bond, used in amounts such that the molar ratio metal / Mg is from 0.05 to 5, thereby obtaining a solid reaction product dispersed in a hydrocarbon slurry and (b) contacting the product obtained in (a) with ethylaluminum dichloride.

Description

TITLECATALYST COMPONENTS FOR THE POLYMERIZATION OF OLEFINS AND CATALYSTS THEREFROM OBTAINEDFIELD OF THE INVENTION

[0001] The present invention relates to catalyst components for the polymerization of olefins CH2=CHR, wherein R is hydrogen or hydrocarbon radical having 1-12 carbon atoms. In particular, the invention relates to catalyst components suitable for the preparation of homopolymers and copolymers of ethylene and to the catalysts obtained therefrom.

[0002] Specifically, the present invention relates to preactivated solid catalyst components, comprising titanium magnesium and halogen, and obtainable by using a specified pre-activating agent.BACKGROUND OF THE INVENTION

[0003] In the field of non-solution olefin (po)polymerization, the catalyst characteristics have primary affect a number of product features. For example, a narrow particle size distribution of the catalyst is usually replicated on the polymer with consequent beneficial results in plant operation. The catalyst, also impacts, through its polymerization activity, on plant productivity and polymer properties such as molecular weight distribution and melt flowability.

[0004] WO93 / 099882 describes catalyst components for the preparation of polyolefins, particularly through the slurry process, characterized by high polymerization activity and narrow particle size distribution. The catalyst is obtained by pre-activating a precursor containing a Mg alkoxy compound and a titanium compound with an aluminum alkyl chloride compound.

[0005] While maintaining the same catalyst performances, it would be desired using a preactivation procedure employing a lower amount of aluminum compound.SUMMARY OF THE INVENTION

[0006] Accordingly, one of the objects of the present disclosure is a catalyst component for the polymerization of olefins obtained by a process comprising:

[0007] (a) reacting in an inert hydrocarbon suspension medium a Mg(0R1)(0R2) compound, in which R1and R2are identical or different and are each an alkyl radical having 1 to 10 carbon atoms, with a tetravalent transition metal compound having at least a Metal-halogen bond, used in amounts such that the molar ratio metal / Mg is from 0.05 to 10, thereby obtaining a solid reaction product dispersed in a hydrocarbon slurry,

[0008] (b) contacting the product obtained in (a) with ethylaluminum dichloride.DETAILED DESCRIPTION OF THE INVENTION

[0009] In step (a) of the preparation of the catalyst component, R1and R2are preferably alkyl groups having from 2 to 10 carbon atoms or a radical -(CH2)nOR3, where R3is a Ci-C4-alkyl radical and n is an integer from 2 to 6. Preferably R1and R2are Ci-C2-alkyl radical. Examples of such magnesium alkoxides are: magnesium dimethoxide, magnesium diethoxide, magnesium di-i- propoxide, magnesium di-n-propoxide, magnesium di-n-butoxide, magnesium methoxide ethoxide, magnesium ethoxide n-propoxide, magnesium di(2-methyl-l -pentoxide), magnesium di(2-methyl-l -hexoxide), magnesium di(2-methyl-l -heptoxide), magnesium di(2-ethyl- 1 - pentoxide), magnesium di(2-ethyl-l -hexoxide), magnesium di(2-ethyl-l -heptoxide), magnesium di(2-propyl-l -heptoxide), magnesium di(2-methoxy-l -ethoxide), magnesium di(3 -methoxy- 1- propoxide), magnesium di(4-methoxy-l-butoxide), magnesium di(6-methoxy-l -hexoxide), magnesium di(2-ethoxy-l -ethoxide), magnesium di(3 -ethoxy- 1 -propoxide), magnesium di(4- ethoxy-l-butoxide), magnesium di(6-ethoxy- 1 -hexoxide), magnesium dipentoxide, magnesium dihexoxide. Preference is given to using the simple magnesium alkoxides such as magnesium diethoxide, magnesium di-n-propoxide and magnesium di-i-butoxide. Magnesium diethoxide is the preferred one. It can be used as a suspension or as a gelatineous dispersion. The suspension or the gel can be prepared starting from commercially available Mg(OC2Hs)2 usually having average particle diameter ranging from 200 to 1200 pm preferably from 500 to 800 pm.

[0010] Preferably before the reaction with the transition metal halide the magnesium alcoholate is suspended in an inert, saturated hydrocarbon. In order to lowering the magnesiumalcoholate particle size, the suspension can be subject to high shear stress conditions by means of a high-speed disperser (for example Ultra-Turrax or Dispax, IKA-Maschinenbau Janke & Kunkel GmbH) working under inert atmosphere (Ar or N2). Preferably the shear stress is applied until a gel-like dispersion is obtained. This dispersion differs from a standard suspension in that it is substantially more viscous than the suspension and is gel-like. Compared with the suspended magnesium alcoholate, the dispersed magnesium alcoholate settles out much more slowly and to a far lesser extent.

[0011] The magnesium alkoxide is firstly reacted with the tetravalent transition metal compound of the formula (II)MXm(OR4)4-m(II), where M is titanium, zirconium or hafnium, preferably titanium or zirconium, more preferably titanium, R4 is an alkyl radical having from 1 to 9, preferably from 1 to 4 carbon atoms and X is a halogen atom, preferably chlorine, and m is from 1 to 4, preferably from 2 to 4.

[0012] Examples which may be mentioned are: TiCh, TiCh(OC2H5), TiCh(OC2H5)2, TIC1(OC2H5)3, TIC13(OC3H7), TIC12(OC3H7)2, TIC1(OC3H7)3, T1CI3OC4H9), TIC12(OC4H9)2, TIC1(OC4H9)3, T1C13(OC6H13), TIC12(OC6HI3)2, TIC1(OC6HI3)3, ZrCl4, preference is given to using TiCh or ZrCk Particular preference is given to TiCk

[0013] The reaction of the magnesium alkoxide with the tetravalent transition metal compounds is carried out at a temperature at from 50 to 140°C, preferably from 60 to 120°C, more preferably from 70 to 90°C over a period of from 0.1 to 20 hours, preferably within 1 to 10 hours, more preferably within 1 to 7 hours. Suitable inert hydrocarbon suspension media for the abovementioned reactions include aliphatic and cycloaliphatic hydrocarbons such as butane, pentane, hexane, heptane, cyclohexane, isooctane and also aromatic hydrocarbons such as benzene and xylene. Petroleum spirit and hydrogenated diesel oil fractions which have carefully been freed of oxygen, sulfur compounds and moisture can also be used.

[0014] The magnesium alkoxide and the tetravalent transition metal compound can be reacted in a molar ratio of Metal / Mg ranging from 0.05 to 5, preferably from 0.1 to 1. At the end of the reaction a solid product is obtained by removing of the liquid phase.

[0015] Optionally, one or more washing step with inert hydrocarbon are carried out until the supernatant mother liquor has Cl and Ti concentrations of less than 10 mmol / dm3. The washing step can be carried out with the same hydrocarbon medium used in step (a) at a temperature rangingfrom 10°C to the boiling point of the medium used. Preferably, it is carried out under mild conditions and more preferably at room temperature when working at Ti / Mg molar ratios in the range of 0.1 to 1. Washings at higher temperature are suitable for higher Ti / Mg molar ratios.

[0016] Optionally, after the washing the solid product coming from (a), preferably still in form of a concentrated slurry, is subjected to another contact step with a tetravalent titanium compound of formula TiXm(OR4)4-m where X and m have the same meaning disclosed above. Preferred titanium compounds are TIC14, TIC13(OC2H5), TIC12(OC2H5)2, TIC1(OC2H5)3, TIC13(OC3H7), TIC12(OC3H7)2, TIC1(OC3H7)3, TIC13OC4H9), TIC12(OC4H9)2, TIC1(OC4H9)3, TIC13(OC6HI3), TiCl2(OC6Hi3)2, TiCl(OC6Hi3)3. TiCh being the most preferred. In the optional contact stage the molar ratio of Ti / Mg may range from 0.001 to 1, preferably from 0.01 to 0.1. At the end of the reaction a solid product is obtained by totally or partially removing of the liquid phase.

[0017] In step (b), ethyl-aluminum dichloride (EADC) is reacted with the solid reaction product of step (a).

[0018] EADC can be added in a molar ration of 0.1 to 2.5, preferably from 0.3 to 2.0 with respect to magnesium alkoxide. The reaction is carried out in suspension under stirring at a temperature ranging from 0 to 150°C, preferably from 60 to 120°C within 0.5 to 7 hours, preferably from 1 to 5 hours.

[0019] At the end of the preparation process the particle size of the catalyst component (component A) preferably ranges from 5 to 30pm.

[0020] As already explained, the catalyst component obtained with this process keeps unaltered its performances while at the same time using a lower molar amount of Al with respect to the pre-activation step carried out with ethyl aluminum sesquichloride (EASC).

[0021] The catalyst component of the invention can be used in combination with a trialkylaluminum (component B) having from 1 to 6 carbon atoms in the alkyl radical, e.g. triethylaluminum, triisobutylaluminum, triisohexylaluminum, Preference is given to triethylaluminum and triisobutylaluminum.

[0022] The mixing of the component (A) and the component (B) can be carried out in a stirred vessel at a temperature of from -30°C to 150°C prior to the polymerization. It is also possible to combine the two components directly in the polymerization vessel at a polymerization temperature of from 20°C to 200°C.

[0023] It is also possible firstly to prepolymerize the preactivated catalyst system with alphaolefins, preferably linear C2-C 10-1 -alkenes and in particular ethylene or propylene, and then to use the resulting prepolymerized catalyst solid in the actual polymerization. The mass ratio of catalyst solid used in the prepolymerization to monomer polymerized onto it is usually in the range from 1:0.1 to 1 :2.

[0024] It is also possible to isolate the catalyst in the non-prepolymerized form or in the prepolymerized form and store it as a solid and re-suspend it on later use.

[0025] The catalysts systems of the invention are particularly suited for liquid phase polymerization process. In fact, the small average particle size of the component (A) , such as less than 30pm, preferably ranging from 5 to 20 pm, is particularly suited for slurry polymerization in an inert medium, which can be carried out continuously stirred tank reactor or in loop reactors. In a preferred embodiment the polymerization process is carried out in two or more cascade loop or stirred tank reactors producing polymers with different molecular weight and / or different composition in each reactor. In addition, to the ethylene homo and copolymers mentioned above the catalysts of the present invention are also suitable for preparing very-low-density and ultra-low- density polyethylenes (VLDPE and ULDPE, having a density lower than 0.920g / cm3, to 0.880 g / cm3) consisting of copolymers of ethylene with one or more alpha-olefins having from 3 to 12 carbon atoms, having a mole content of units derived from ethylene of higher than 80%; elastomeric copolymers of ethylene and propylene and elastomeric terpolymers of ethylene and propylene with smaller proportions of a diene having a content by weight of units derived from ethylene of between about 30 and 70%.

[0026] The following examples are given in order to further describe the present invention in a non-limiting manner.EXAMPLES

[0027] The results for the elemental composition of the catalysts described reported in the examples were obtained by the following analytical methods:Ti: photometrically via the peroxide complexMg, Cl: titrimetrically by customary methodsMFR5 / 190: mass flow rate (melt index) in accordance with ISO1133, nominal load = 5 kg and test temperature = 190°CFRR21.6 / 5: Flow rate ratio in accordance with EN ISO1133:FRR21.6 / 5 — (MFR21.6 / 190 / MFR5 / 190)FRR21.6 / 2.16: Flow rate ratio in accordance with EN ISO1 133 :FRR21.6 / 2.16 = (MFR21.6 / 190 / MFR2.16 / 190)Bulk density: in accordance with DIN EN ISO 60D50 (catalyst mean particle diameter): in accordance with DIN ISO 22412Example 1

[0028] a) Preparation of the catalyst component A:114 g (1 mol) of commercial Mg(OC2Hs)2 were suspended in diesel oil (hydrogenated petroleum fraction having a boiling range of 140 - 170°C) (total volume: 1.2 dm3). The suspension was converted into a dispersion in a cylindrical glass vessel under inert gas (Ar) to exclude moisture and air (O2) using a high-speed stirrer (®Ultra-Turrax) with external cooling by means of an ice bath (time: about 8 hours). The dispersion had a gel-like consistency. A volume of 0.31 dm3(containing 0.25 mol of MgiOCvHsk) of the gel-like dispersion was transferred to a 1 dm3glass flask provided with reflux condenser, 2-blade blade stirrer and inert gas blanketing (Ar), and 0.19 dm3of diesel oil having a boiling range of 140 - 170°C (hydrogenated petroleum fraction) was added and the mixture was stirred at room temperature for 10 minutes at a stirrer speed of 100 rpm.

[0029] This gel-like dispersion was brought to 85°C while stirring at a stirrer speed of 250 rpm and 0.075 mol of TiCh was subsequently metered in over a period of 4 hours. After a post-reaction time of 0.5 hour, the suspension is cooled down to ambient temperature and the stirrer is switched off. After the solid had settled, the supernatant liquid phase (mother liquor) was taken off. The solid was subsequently re-suspended in fresh diesel oil (hydrogenated petroleum fraction having a boiling range from 140 to 170°C) and after a stirring time of 15 minutes and subsequent complete settling of the solid, the supernatant liquid phase was taken off again.

[0030] After a post-reaction time of 1 hour the suspension was heated to 110°C. Subsequently 0.263 mol of EADC (Cl / Mg mr 2.1; Al / Mg mr 1.05) in 250 cm3of diesel oil (hydrogenated petroleum fraction having a boiling range of 140 - 170°C) was metered in over a period of 2 hours while stirring at a stirrer speed of 250 rpm. The temperature was subsequently held at 110°C for a further 2 hours. Afterwards the suspension is cooled down to ambient temperature and the stirrer is switched off. After the solid had settled, the supernatant liquid phase (mother liquor) was takenoff. The solid was subsequently resuspended in fresh diesel oil (hydrogenated petroleum fraction having a boiling range from 140 to 170°C) and after a stirring time of 15 minutes the stirrer was switched off.

[0031] The molar ratio of the solid (=catalyst component A) was: Mg:Ti:Cl « 1.00:0.29:2.73.The titanium content of the solid catalyst component was 7.6 wt-%. b) Ethylene polymerization in suspension

[0032] The polymerization experiments were carried out batchwise in a 1.6 dm3reactor. This reactor was equipped with an impeller stirrer. The temperature in the reactor was measured and automatically kept constant. The polymerization temperature was 85°C.

[0033] The polymerization reaction was carried out in the following way:0.75 dm’ of diesel oil (hydrogenated petroleum fraction having a boiling range from 140 to 170°C) were placed in the Ar-blanketed reactor and heated to 85°C. Under a blanket of inert gas (Ar), 2.0 mmol of tri ethylaluminum diluted to 4.0 cm3with diesel oil were added as cocatalyst (catalyst component B) and the catalyst component A prepared as described under a) was subsequently introduced into the reactor in an amount corresponding to 0.015 mmol of titanium as a suspension diluted with diesel oil.

[0034] The reactor was pressurized a six of times with H2 (hydrogen) to 3 bar and depressurized again to remove the Argon completely from the reactor. Then, a hydrogen overpressure of 2.15 bars was added. The polymerization was started by opening the ethylene inlet. Ethylene was introduced to achieve an overpressure of 6.0 bars over the entire polymerization time.

[0035] The polymerization was stopped after 120 minutes. The polyethylene was filtered off and dried in vacuum. The dry polyethylene powder was weighed. For quantification of catalyst productivity the mileage is determined as follows:Mileage = kg polyethylene / g catalyst.The results of the polymerizations are shown in Table 1.Example 2

[0036] Example 2 was performed in the same way as described in example 1 ) with the difference that 0.35 mol of EADC (Cl / Mg mr 2.8; Al / Mg mr 1.4) were used.Comparative Example 1

[0037] Comparative example 1 was performed in the same way as described in example 1 with the difference that 0.175 mol of EASC (Cl / Mg mr 2.1; Al / Mg mr 1.4) were used.

[0038] The molar ratio of the solid (catalyst component A) was: Mg:Ti:Cl ~ 1.00:0.29:2.66. The titanium content of the solid catalyst component was 6.5 wt-%. The polymerization was carried out as described in Example 1. The results of the polymerizations are listed in Table 1.Table 1:

Claims

CLAIMSWhat is claimed is:

1. A catalyst component (A) for the polymerization of olefins obtained by a process comprising:(a) reacting in a inert hydrocarbon suspension medium a Mg(0Ri)(0R2) compound, in which Ri and R2 are identical or different and are each an alkyl radical having 1 to 10 carbon atoms, with a tetravalent transition metal compound having at least a Metal-halogen bond, used in amounts such that the molar ratio metal / Mg is from 0.05 to 5, thereby obtaining a solid reaction product dispersed in a hydrocarbon slurry and(b) contacting the product obtained in (a) with ethylaluminum dichloride.

2. The catalyst component according to claim 1 in which the Mg(ORi)(OR2) compound is magnesium ethylate.

3. The catalyst component according to claim 1 in which the transition metal compound of step (a) is MXm(OR4)4-m (II), where M is titanium, R4 is an alkyl radical having from 1 to 9, preferably from 1 to 4 carbon atoms and X is a halogen atom, preferably chlorine, and m is from 1 to 4, preferably from2 to 4. when b is 0 R1is a linear, branched, cyclic alkyl radical or aryl radical having from3 to 10 carbon atoms and a is 1.

4. The catalyst component according to claim 3 in which the reaction of the magnesium alkoxide with the tetravalent transition metal compounds is carried out at a temperature at from 50 to 140°C.

5. The catalyst component according to any of the preceding claims in which the transition metal compound is selected from the group consisting of TiCh, TiC13(OC2H5), TIC12(OC2H5)2, TIC1(OC2H5)3, TIC13(OC3H7), TIC12(OC3H7)2, TIC1(OC3H7)3,T1CI3OC4H9), TIC12(OC4H9)2, TIC1(OC4H9)3, TIC13(OC6HI3), TIC12(OC6HI3)2, T1C1(OC6H13)3 and ZrCl4.

6. The catalyst component according to any of the preceding claims in which in step (a) The magnesium alkoxide and the tetravalent transition metal compound can be reacted in a molar ratio of Metal / Mg ranging from 0.05 to 5, preferably from 0.1 to 1.

7. The catalyst component according to claim 1 in which the tetravalent transition metal compound used in step (a) is TiCk8. The catalyst component according to claim 1 in which in step (b) EADC can be added in a molar ration of 0.1 to 2.5, preferably from 0.3 to 2.0 with respect to magnesium alkoxide.

9. The catalyst component according to any of the preceding claims in which step (b) is carried out in suspension under stirring at a temperature ranging from 0 to 150°C, preferably from 60 to 120°C within 0.5 to 7 hours, preferably from 1 to 5 hours.

10. The catalyst component according to any of the preceding claims in which the average particle size of the catalyst component (component A) ranges from 5 to 30pm determined via light scattering technique in accordance with DIN ISO 22412.

11. Catalyst system for the polymerization of olefins obtained by reacting the solid catalyst component according to claim 1-10 with a trialkylaluminum (component B).

12. Process for the polymerization of olefins carried out in the presence of the catalyst system of claim 11.

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