DE69422392T3 - PROCESS FOR PRODUCING GRANULAR RESIN - Google Patents

Description

The This invention relates to a process for producing granular resin. In particular, the invention relates to a slurry process for the polymerization and copolymerization of ethylene in the presence from on carriers catalysts comprising metallocenes of transition metals.

The Use of metallocene compounds of transition metals as catalysts for the Polymerization and copolymerization of ethylene is a relative one new development in the polymerization and copolymerization of Ethylene.

Metallocenes can be described by the empirical formula Cp _m MA _n B _p . These compounds have been used together with alumoxane to produce olefin polymers and copolymers such as ethylene and propylene homopolymers, ethylene-butene and ethylene-hexene copolymers (see US-A-4542199 and US-A-4404344).

Methylalumoxane (MAO) is used as a cocatalyst with metallocene catalysts. It belongs to the class of alumoxanes comprising oligomeric linear and / or cyclic alkylalumoxanes represented by the general formula: R- (Al (R) -O) _n -AlR ₂ for oligomeric linear alumoxanes; and (-Al (R) -O-) _m for oligomeric cyclic alumoxane,
wherein n is 1 to 40, preferably 10 to 20; m is 3 to 40, preferably 3 to 20 and R is a C ₁ -C ₈ alkyl group, and preferably methyl.

Methylalumoxane is often prepared by reacting trimethylaluminum with water or with hydrated inorganic salts such as CuSO ₄ .5H ₂ O or Al ₂ (SO ₄ ) ₃ .5H ₂ O. Methylalumoxane can also be generated in situ in polymerization reactors by adding trimethylaluminum and water or aqueous inorganic salts. MAO is a mixture of oligomers with a very broad molecular weight distribution and normally with an average molecular weight of about 1200. MAO is typically held in toluene solution.

EP-A-0336593, DE-C-43 44 672 and US-A-5147949 each disclose a polymerization catalyst, which comprises a metallocene and an alumoxane, that of silica gel, the contains specific amounts of water become.

US-A-52407894 discloses a catalyst comprising a dehydrated silica support, a metallocene and an alumoxane. The catalyst is useful in the polymerization of propylene as a homopolymer or copolymer with other olefins. Example 9 describes ethylene polymerization using the catalyst in conjunction with tetraethylaluminum (TEAL). The reported density for the resulting polymer is 0.9479 g / cm ³ .

at current commercial slurry process Attempts to produce LLDPE have been unsuccessful because of the Polymer and / or catalyst solubilities limit the yields and equally efficient solvent separation and the solid transfer downstream prevent the reactor.

First typically swells the soluble Fraction, if the polymer is soluble in the solvent, what the proportion of polymer per unit of reactor or volume of solvent, and consequently the production volume is limited. The resulting gel structure usually contaminates the reactor. In addition, will Resins made with unacceptably low bulk density.

Secondly when the catalyst is in the solvent or monomer soluble is the polymer chains growing on the catalyst, an unacceptable Particle morphology. The resins from the soluble catalyst fraction are typically very small particles ("fine particles") that swell in the solvent and again give a gel-like structure.

The The present invention provides a solution to these limitations to disposal. By reaction of the metallocene / MAO solution with the reactive surface of a Carrier, will formed a new class of catalyst. Under controlled conditions This new class of catalyst produces a polymer with good morphology without the problems described above.

• (a) das Dispergieren eines Katalysators in dem aliphatischen Lösungsmittel unter im wesentlichen wasserfreien Bedingungen, um eine Aufschlämmung in einem Reaktionsgefäß zu bilden, wobei der Katalysator, getragen von einem dehydratisierten Träger, ein Metallocen und ein Alumoxan umfaßt;
• (b) das Halten der Aufschlämmung bei einem absoluten Druck unter 1000 psi (6,9 MPa) und einer Temperatur von 20°C bis 100°C;
• (c) das Einführen von Ethylen und einem alpha-Olefin, das aus 1-Buten, 1-Propen und alpha-Olefinen mit 6 bis 10 Kohlenstoffatomen ausgewählt wurde, in das Reaktionsgefäß, wobei der Partialdruck des Ethylens zwischen 20 und 1000 psi (0,14 bis 6,9 MPa) liegt; und
• (d) die Gewinnung von granulärem LLDPE, das eine Schüttdichte von 15 bis 36 lb./ft³ (240 bis 580 kg/m³), eine spezifische Dichte im Bereich von 0,91 bis 0,939 g/cm³, ein MFR von weniger als etwa 30 und eine durchschnittliche Teilchengröße von 300 bis 800 μm aufweist, aus dem Reaktionsgefäß, umfaßt, wobei das aliphatische Lösungsmittel aus der Gruppe, bestehend aus Isobutan, Pentan, Isomeren von Pentan, Hexan, Isomeren von Hexan, Octan, Isomeren von Octan, Decan, Dodecan und Gemischen hiervon, ausgewählt ist.

According to the present invention there is provided a process for preparing a linear low density polyethylene (LLDPE) in granular form, the process comprising:

• (a) dispersing a catalyst in the aliphatic solvent under substantially anhydrous conditions to form a slurry in a reaction vessel, the catalyst supported by a dehydrated carrier comprising a metallocene and an alumoxane;
• (b) maintaining the slurry at an absolute pressure below 1000 psi (6.9 MPa) and a temperature of 20 ° C to 100 ° C;
• (c) introducing ethylene and an alpha-olefin selected from 1-butene, 1-propene and alpha-olefins having 6 to 10 carbon atoms into the reaction vessel, wherein the partial pressure of ethylene is between 20 and 1000 psi (0 , 14 to 6.9 MPa); and
• (d) recovering granular LLDPE having a bulk density of 15 to 36 lb./ft ³ (240 to 580 kg / m ³ ), a specific gravity in the range of 0.91 to 0.939 g / cm ³ , an MFR of less than about 30 and having an average particle size of 300 to 800 microns from the reaction vessel, wherein the aliphatic solvent is selected from the group consisting of isobutane, pentane, isomers of pentane, hexane, isomers of hexane, octane, isomers of octane , Decane, dodecane and mixtures thereof.

advantageously, in step (d) the ethylene and the alpha-olefin are copolymerized, around the granular Resin that is substantially insoluble in the solvent and an average particle size of 300 up to 800 μm (Microns) has.

The specific gravity is preferably less than 0.93.

In the preferred embodiment, the carrier comprises silica which is amorphous and porous and has a pore volume of from 0.1 to 5 cm ³ / g, the silica having a lower concentration of silanol groups than 2.5 mmol per gram of silica.

It is also preferred that the Silica with a volume of a mixture containing a metallocene and alumoxane comprises, is contacted, wherein the volume of the mixture is not greater than the total pore volume of the dehydrated silica is.

The metallocene preferably has the formula Cp _m MA _n B _p , where Cp is a substituted cyclopentadienyl group, m is 1 or 2; M is zirconium or hafnium; each A and B are selected from the group consisting of a halogen atom, a hydrogen atom and an alkyl group; and m + n + p is equal to the valency of the metal M and that the alumoxane has the following formula (a) or (b): R- (Al (R) -O) _n -AlR ₂ (a) for oligomeric linear alumoxanes; (-Al (R) -O-) _m (b) for oligomeric cyclic alumoxane has; wherein n is 1 to 40, m is 3 to 40, and R comprises a C ₁ -C ₈ alkyl group; and the contacted silica is an activated catalyst.

Desirably the catalyst is in particle form with a particle size in the range from 1 to 500 μm (Micrometers).

The relationship from aluminum to the transition metal from the metallocene in the catalyst is preferably 70 to 350.

It it is preferred that the Amount of the transition metal (on elemental basis) is between 0.001 and 10 weight percent and the amount of aluminum (elemental based) between 1 and 2 40 percent by weight and that the Al: transition metal ratio (on Elementary basis) is between 25 and 10,000.

Of the Catalyst comprises preferably a metallocene selected from the group those of bis (n-butylcyclopentadienyl) metal dihalides, bis (n-butylcyclopentadienyl) metal hydridohalides, bis (n-butylcyclopentadienyl) metal monoalkyl monohalides; Bis (n-butylcyclopentadienyl) metal dialkyls; (Tetrahydroindenyl) metal halides and bis (indenyl) metal dihalides. Most preferably, the catalyst comprises a metallocene selected from the group consisting of bis (isobutylcyclopentadienyl) zirconium dichloride, Bis (pentamethylcyclopentadienyl) zirconium dichloride, bis (tetrahydroindenyl) zirconium dichloride, Bis (indenyl) zirconium dichloride, bis (1,3-dimethylcyclopentadienyl) zirconium dichloride, Bis (methylcyclopentadienyl) zirconium dichloride and bis (n-butylcyclopentadienyl) zirconium dichloride consists.

The solvent is preferably an alkane, the alpha-olefin being in the solvent desirably a concentration of 0.1 to 50 weight percent, better 0.1 to 30 weight percent, delivers.

The Alkan contains preferably 4 to 19 carbon atoms. The solvent is most preferred selected from the group, that of isobutane, pentane, isomers of pentane, hexane, isomers of hexane, Heptane, isomers of heptane, octane, isomers of octane, decane, dodecane and mixtures thereof.

Desirably is the boiling point of the solvent less than 180 ° C.

Of the Pressure in step (b) is preferably below 600 psi (4.1 MPa).

Conditions of the slurry process

Of the Catalyst is in the solvent by stirring distributed. Stirring is during the polymerization (copolymerization) by conventional means maintained. The polymerization is carried out under anhydrous conditions.

The catalytic slurry polymerization The invention is carried out at a total pressure of less than 1000 psi (6.9 MPa) performed. In general, the total pressure is between 20 and 1000 psi (0.14 to 6.9 MPa), and more preferably between 100 and 600 (0.69 to 4.1 MPa).

Of the Ethylene partial pressure is substantially between 20 and 1000 psi (0.14 to 6.9 MPa), preferably substantially between 60 and 600 psi (0.41 to 4.1 MPa). Optionally, hydrogen may be included in the slurry polymerization introduced become. The hydrogen partial pressure can be between 0 and 20 psi (0 to 0.14 MPa) and is preferably less than 10 psi (0.069 MPa).

The Temperature of the catalytic polymerization is in the range of 25 ° C to 100 ° C; the upper limit depends from the solvent from. For the production of a resin with a lower specific density as about 0.94, the temperature may be less than 90 ° C to a low level from 40 to 45 ° C be. Preferably, the temperature is between 55 ° C and 75 ° C, better about 60 ° C up to about 70 ° C when pressed of about 125 psi (0.86 MPa). The residence time can be between 1 and 4 hours are. Under these conditions becomes dispersed polymer in the slurry reactor in the solvent educated. The mean particle size of the product in the slurry reactor is between 300 and 800 μm. Typically, the average particle size of the product is in the slurry reactor in the range of 450 to 650 μm.

The solvent is selected from the group consisting of isobutane, pentane and isomers hereof, hexane and isomers thereof, octane and isomers thereof selected. Petroleum fractions, which generally contain these compounds as an admixture, can be used as well.

In the experiments contained herein, the slurry contains from 0.0047 to 0.01175 percent by weight of catalyst or 40 to 100 mg of the catalyst in 1000 cm ^{3 of} solvent. Typically, the operation is carried out at 70 mg of catalyst per 1000 cm ³ .

The Amount of alpha-olefin for the copolymerization with ethylene provides a concentration in the solvent from 0.1 percent by weight to 50 percent by weight, preferably 0.1 to 30 weight percent, more preferably about 10 weight percent. The alpha-olefin is selected from propylene, 1-butene and alpha-olefins having 6 to 10 carbon atoms, including 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene, selected. Preferably, the alpha-olefin is one with 6 to 8 carbon atoms.

Preferred catalyst compositions

The Anhydrous catalysts used in the invention (which suitably free from water) comprise a dehydrated one Carrier, an alumoxane and at least one metallocene. The catalyst is free flowing and disperse in the form of dry powder particles having a particle size of about 1 μm to about 250 μm, preferably about 10 microns up to about 150 μm. The catalysts, which are only a transition metal in the form of a metallocene, have an activity of at least 200 kg polymer / g transition metals. The aluminoxane and metallocene loading on the support is such that the amount of aluminum the carrier (elemental-based) provided by the aluminoxane, between 1 and 40 weight percent, preferably 5 and 30 weight percent, and the strongest preferably 5 and 15 percent by weight. The optimal MAO loading is in the range of 3 to 15 mmol per gram of the silica support; if a silica carrier overloaded with MAO is, the catalyst activity reduced and the catalyst particles agglomerate, bringing the Problems of transmission of the catalyst are connected.

The Amount of metallocene on the carrier, on transition metal elemental basis, is between 0.001 and 10% by weight, preferably 0.05 and 1.0 weight percent, better 0.05 and 0.5 weight percent. Accordingly can the relationship Al: Zr (elemental based) in the catalyst between 25 and 10,000, normally in the range of 50 to 1,000, but preferably about 75 to 300, better 100 to 200 are.

To form the catalysts of the invention, all of the catalyst components can be dissolved with alumoxane and impregnated into the carrier. The catalyst preparation is carried out under anhydrous conditions and in the absence of oxygen. In a single process, the support material is impregnated with alumoxane, preferably methylalumoxane, by the procedure described below. The class of alumoxanes includes oligomeric linear and / or cyclic alkylalumoxanes represented by the formula: R- (Al (R) -O) _n -AlR ₂ for oligomeric linear alumoxanes; and (-Al (R) -O-) _m for oligomeric cyclic alumoxane,
wherein n is 1 to 40, preferably 10 to 20; m is 3 to 40, preferably 3 to 20 and R is a C ₁ -C ₈ alkyl group, and preferably methyl. MAO is a mixture of oligomers having a broad molecular weight distribution and normally having an average molecular weight of about 1200. MAO is typically held in toluene solution.

The Volume of solution, an alumoxane and a solvent for that can in dependence of the catalyst to be produced vary. At a preferred embodiment Alumoxane incorporation into the carrier is one of the regulatory factors in the catalyst synthesis by Alumoxaneinlagerung in the carrier material the pore volume of the silica. In this preferred embodiment is the method of impregnation of the carrier material by infusing the alumoxane solution without formation of a slurry of the carrier material like silica in the alumoxane solution. This Step is done with stirring.

The volume of the alumoxane solution is sufficient to fill the pores of the carrier material without forming a slurry in which the volume of the solution exceeds the pore volume of the silica; accordingly, and preferably, the maximum volume of the alumoxane solution is equal to, but not exceeding, the total pore volume of the carrier material sample. The maximum volume of the alumoxane solution ensures that no slurry of the silica in the solvent is formed in this step. For example, if the pore volume of the support material is 1.65 cm ³ / g, the volume of the alumoxane will be equal to or less than 1.65 cm ³ / g of the support material. Thus, the maximum volume of the solution (metallocene and alumoxane) is equal to the total pore volume of the carrier, for example, silica, which is the pore volume in, for example, cm ³ / g times the total weight of the carrier used. As a result of this measure, the impregnated carrier material will appear to be dry immediately after impregnation, although the pores of the carrier may be filled, inter alia, with solvent. The preferred solvent for the aluminoxane, for example methylaluminoxane, is toluene. The advantage is that the impregnation is carried out in a single solvent system.

The solvent can be made from the alumoxane-impregnated Pores of the carrier material removed by heating and / or under vacuum or by heat in a Inert gas such as nitrogen are washed. When elevated temperatures are used, the temperature conditions in this step so regulated that the Agglomeration of the impregnated carrier particles and / or reduces, if not eliminates, the crosslinking of the alumoxane becomes. In this step, the solvent can evaporate be removed, which at relatively low elevated temperatures of about 40 ° C and below about 60 ° C causes agglomeration of the catalyst particles and crosslinking of the alumoxane.

Preferably the drying is at 45 ° C or less 5 to 7 hours. Although the solvent by evaporation at relatively higher Temperatures as defined by the above range above 40 ° C and below about 60 ° C can be removed Very short heating time programs are used to agglomeration the catalyst particles and crosslinking of the alumoxane, which with a Reduction of catalyst activity are avoided. Accordingly, an active catalyst is at an evaporation temperature of 110 ° C (In less than 10 seconds), while at 45 ° C drying over a Period of 24 hours can be.

In a preferred embodiment the metallocene is added to the alumoxane solution prior to impregnation of the carrier with the solution added. Again, the maximum volume of the alumoxane solution is also contains the metallocene, the total pore volume of the substrate sample. The molar ratio of the aluminum provided by the alumoxane, expressed as Al, to metallocene metal, expressed as M (eg Zr) is between 50 and 500, preferably 75 and 300, better 100 and 200. Another advantage of the present invention is that this Al: Zr ratio can be regulated directly. In a preferred embodiment the alumoxane and metallocene compounds at ambient temperature 0.1 to 6.0 hours before use in the infusion step with each other mixed. The solvent for the Metallocene and the alumoxane can suitable solvents such as aromatic hydrocarbons, halogenated aromatic hydrocarbons, Ethers, cyclic ethers or esters; it is preferably toluene.

The metallocene compound has the formula Cp _m MA _n B _p , in which Cp is an unsubstituted or substituted cyclopentadienyl group, M is zirconium or hafnium, and A and B belong to the group including a halogen atom, hydrogen or an alkyl group. In the above formula of the metallocene compound, the preferred transition metal atom M is zirconium. In the above formula of the metallocene compound, the Cp group is an unsubstituted, mono-, or polysubstituted cyclopentadienyl group. The substituents on the cyclopentadienyl group may preferably be straight-chain or branched-chain C ₁ -C ₆ -alkyl groups. The cyclopentadienyl group may also be part of a bicyclic or tricyclic moiety such as indenyl, tetrahydroindenyl, fluorenyl or a partially hydrogenated fluorenyl group as well as a portion of a substituted bicyclic or tricyclic moiety. If m in the above formula of the metallocene compound is 2, the cyclopentadienyl groups may also be represented by polymethylene or dialkylsilane groups such as -CH ₂ -, -CH ₂ -CH ₂ -, -CR'R "- and -CR'R". -CR'R "- where R 'and R" are short alkyl groups or hydrogen, -Si (CH ₃ ) ₂ -, -Si (CH ₃ ) ₂ -CH ₂ -CH ₂ -Si (CH ₃ ) ₂ - and similar bridging groups to be bridged. When the A and B substituents in the above formula of the metallocene compound are halogen atoms, they belong to the group of fluorine, chlorine, bromine or iodine. When the substituents A and B in the above formula of the metallocene compound are alkyl groups, they are preferably straight or branched C ₁ -C ₈ alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, n Hexyl or n-octyl.

Suitable metallocene compounds include bis (n-butylcyclopentadienyl) metal dihalides, bis (n-butylcyclopentadienyl) metal hydride halides, bis (n-butylcyclopentadienyl) metal monoalkyl monohalides, bis (n-butylcyclopentadienyl) metal dialkyls, and bis (indenyl) metal dihalides, wherein the metal is zirconium or hafnium, the halide groups are preferably chlorine and the alkyl groups are C ₁ -C ₆ -alkyls. Illustrative but non-limiting examples of metallocenes include bis (n-butylcyclopentadienyl) zirconium dichloride, bis (n-butylcyclopentadienyl) hafnium dichloride, bis (n-butylcyclopentadienyl) zirconium dimethyl, bis (n-butylcyclopentadienyl) hafnium dimethyl, bis (n-butylcyclopentadienyl) zirconium hydride chloride, bis ( n-butylcyclopentadienyl) hafnium hydride chloride, bis (1,3-dimethylcyclopentadienyl) zirconium dichloride, bis (pentamethylcyclopentadienyl) zirconium dichloride, bis (pentamethylcyclopentadienyl) hafnium dichloride, bis (isobutylcyclopentadienyl) zirconium dichloride, cyclopentadienylzirconium trichloride, bis (indenyl) zirconium dichloride, bis (4,5 , 6,7-tetrahydro-1-indenyl) zirconium dichloride and ethylene [bis (4,5,6,7-tetrahydro-1-indenyl)] zirconium dichloride. The metallocene compounds used in the practice of this technique can be used as crystalline solids, as solutions in aromatic hydrocarbons, or in supported form.

The carrier material is a solid, particulate, porous, preferably inorganic material such as a Oxide of silicon and / or aluminum. In the most preferred embodiment, the carrier is silica in the form of spherical particles obtained, for example, by a spray-drying process. The carrier material is used in the form of a dry powder having an average particle size of from about 1 μm to about 500 μm, preferably from about 1 μm to 250 μm, more preferably 10 μm to 150 μm. If necessary, the final catalyst containing the support material can be sieved to ensure the exclusion of large catalyst particles. Currently, the exclusion of catalyst particles having a particle size greater than 500 microns, preferably the exclusion of larger particles than 250 microns particle size, better the exclusion of larger particles than 150 microns particle size, considered possible. The sieving of the material is preferably carried out after the impregnation of the carrier with the metallocene and the aluminoxane. This is highly desirable in the practice of the invention in which the catalyst contains only a transition metal in the form of a metallocene and which is used to form narrow molecular weight distribution LLDPEs, reduce and / or eliminate gels in the final polyolefin product, and eliminate reactor overheating zones ,

The surface area of the support is at least about 3 m ² / g, preferably 5 to 1200 m ² / g, more preferably at least about 50 m ² / g up to about 350 m ² / g. The pore volume of the support will be between 0.1 and 5 cm ³ / g, preferably between 0.1 and 3.5 cm ³ / g. The carrier material should be dry, that is free of absorbed water.

Preferably is the carrier Silica containing [OH] groups. The hydroxyl group content of the silica may be greater than 0 to 2.5 mmol / g silica, but preferably should it appears to be below 0.5 to 2.5 mmol / g. This area is due to lower drying, dehydration and / or Calcination temperatures are preferred.

The Silica hydroxyl groups (herein, silanol and silica hydroxyl used interchangeably) are detected by IR spectroscopy. Quantitative determinations of the hydroxyl concentration on the silica are obtained by contacting a silica sample with methyl magnesium iodide and measuring methane evolution (by pressure determination).

The Dehydration of the silica material may be by heating at about 100 ° C to about 600 ° C, preferably about 150 ° C up to about 300 ° C, better at about 250 ° C be effected.

Silica dehydrated at 600 ° C (for about 16 hours) will have a surface hydroxyl concentration of about 0.7 mmol per gram (mmol / g) of silica. Silica dehydrated at 800 ° C will be silica with 0.5 mmol silica hydroxy per gram of silica. The silica of the most preferred embodiment is an amorphous silica with a high surface area (surface area = 300 m ² / g, pore volume 1.65 cm ³ / g) and is a material sold under the trade name Davison 952 or Davison 955 by the Davison Chemical Division of WR Grace and Company. On delivery, the silica is not dehydrated and must be dehydrated prior to use.

The effect of silica hydroxyl groups on catalyst activity and productivity is reflected in the examples below. The synthesis of the catalyst of the invention showing highest activity dictates that the silica contains hydroxyl groups for contact with the solution containing aluminoxane and metallocene as described below. It has been determined that the reaction of the hydroxyl groups of the silica with radical scavengers such as trialkylaluminum compounds, for example trimethylaluminum (TMA), reduces the activity of the prepared catalyst as compared to a catalyst reacting with a silica having hydroxyl groups which did not react with such a radical scavenger. was formed. Silica containing higher hydroxyl numbers produces catalysts with higher activity than lower hydroxyl number silica; It can be shown that treatment of the silica with trimethylaluminum for reaction with the silanol or silica hydroxy groups [which reduces the hydroxyl concentration to 0 (zero) with appropriate molar amount of TMA, as shown by IR] prior to catalyst synthesis, has a catalyst with one Productivity of about 200 kg (polymer) / g transition metal produced. However, this activity is a good activity, and the catalyst exhibiting such activity is useful in this process. In comparison, catalysts having a hydroxyl group content of 1.8 mmol / g silica show a productivity of about 1000 kg (polymer) / g transition metal. The amount of hydroxyl groups, in mmol / g silica, can be affected by the dehydration temperatures used to condition the silica. More specifically, the dehydration temperatures of about 600 ° C reduce the amount of reactive hydroxyl groups available for contact with the solution of the aluminoxane and the metallocene. In comparison, the dehydration temperatures of about 250 ° C increase the amount of reactive hydroxyl groups used for contact with the solution of alumi noxans and the metallocene, based on the silica which has been heat treated at 600 ° C for the dehydration purpose. Consequently, it has been found that the catalyst prepared with the silica subjected to dehydration temperatures of 250 ° C is more active than the catalyst prepared with the silica subjected to drying temperatures of 600 ° C. Accordingly, dehydration and / or calcination temperatures below 300 ° C and preferably at about 250 ° C are preferred.

Accordingly is the silica used in the embodiments of the invention will, a greater silanol concentration (OH) as 0.7 mmol OH per gram of silica; preferably it's a bigger one 0.7 mmol to 2.5 mmol OH per gram of silica. In preferred embodiments the concentration is between 1.6 and 1.9 mmol / g of silica.

polymerization and copolymerization products

Low density products (0.91 to 0.939 g / cm ³ ) with high bulk density, low (hexane) extractability and granular morphology can be prepared in the slurry reactor without fouling. The produced resin has a high molecular weight, narrow molecular weight distribution and homogeneous branching distribution. The catalyst ash contains small amounts of Al and Zr (from the catalyst), e.g. Less than 1 ppm Zr and 40 ppm Al (from the catalyst). The high activity of the catalysts of the invention, which also exhibit long catalyst life and produce high bulk density products, are clear factors for the unexpected efficiency of these catalysts in catalytic polymerizations and copolymerizations of olefins.

In particular, the copolymer products contain 0.1 to 2 ppm Zr. The product has an average particle size of 0.015 to 0.035 inches (0.38 to 0.89 cm) and a shaker bulk density of 15 to 36 lb / ft ³ (240 to 580 kg / m ³ ). The particles of the product are free-flowing. The low density, narrow molecular weight distribution copolymers have been prepared with MI of one (1) and less than 1, up to 0.01. The low density products of the invention exhibit MI between 0.01 and 5, preferably 0.5 and 4, better 0.8 and 2.0.

Accordingly, the products in the slurry reactor are characterized by an MI of less than 10, preferably less than 5, more preferably less than 3. The low density products of the invention exhibit a melt flow ratio (MFR) of less than 30, generally 15 to 25, preferably 16 to 22; Products with an MFR between 16 and 22 have been produced; MFR is the ratio I ₂₁ / I ₂ [wherein I _{21 was} measured according to ASTM D-1238, Condition F, at 190 ° C, and I _{2 was} measured according to ASTM D-1238, Condition E]. The differential scanning calorimeter data indicate that the polymerization product shows very low hot tack temperatures. When processed into films, the films of the copolymer exhibit balanced tear strength as measured by ASTM D-1922. Furthermore, the LLDPE of the invention exhibits greater dart drop impact values than 800 measured by ASTM D-1709. The catalytic products with the catalyst of the invention are essentially gel-free. The films show low haze values measured by ASTM D-1003.

EXAMPLES

catalyst Preparation

Example 1: no TMA on the silica 988

5 g silica PQ 988, which have been dehydrated at 600 ° C, a solution of (n-butylCp) 2ZrCl · ₂ and MAO in toluene were treated with 11.2 cm ^3. Gas evolution was observed. Schering's MAO solution contained 13.2 weight percent Al. The Al: Zr ratio was 200: 1. The catalyst was dried under flowing N ₂ at 38 to 42 ° C for 2 hours. The catalyst was labeled 1A and contained 14.3 wt% Al and 0.18 wt% Zr.

Example 2: 0.75 mmol TMA / g on silica 988

5 g of PQ 988 silica dehydrated at 600 ° C was slurried in 25 ml of heptane and treated with 2.9 ml of TMA solution (14% by weight in heptane), which corresponds to 0.75 mmol TMA / g of silica. Gas evolution was observed during TMA treatment. The slurry was dried at 80 to 90 ° C until free-flowing powder was obtained. The TMA-treated Silici dioxide was treated with 11.1 ml of the MAO / Zr solution described in Example 1. At this point, no gas evolution was observed. The catalyst was dried under flowing N ₂ at 42-44 ° C for 2 hours and labeled 2B. It contained 11.9 weight percent Al and 0.13 weight percent Zr.

Example 3: 0.75 mmol TMA / g on silica 988

5 grams of PQ 988 silica dehydrated at 600 ° C were slurried in 25 mL of heptane and treated with 6 mL TMA solution (14 percent by weight in heptane), which corresponds to 1.5 mmol TMA / g silica. Gas evolution was observed during TMA treatment. The slurry was dried at 80 to 90 ° C until free-flowing powder was obtained. The TMA-treated silica was treated with 11.1 ml of the MAO / Zr solution described in Example 1. At this point, no gas evolution was observed. The catalyst was dried under flowing N ₂ at 42-44 ° C for 2 hours and labeled 3A. It contained 11.1 weight percent Al and 0.12 weight percent Zr.

Examples 4 to 6

catalysts which correspond to the three examples above were used made of silica 955-600 by Davison as a carrier. they were labeled 4, 5 and 6. They contained 15.0, 14.6 and 14.5, respectively Weight percent Al and 0.18, 0.18 and 0.17 weight percent Zr.

Slurry for LLDPE

The following examples are for only for Reference purposes and are not within the scope of the present invention.

Example 7

The polymerization was carried out in a 2 liter slurry reactor at 70 ° C with 1 liter of polymerization grade heptane. Hexene-1 (100 cm ³ ) and triisobutylaluminum (TIBA = 2 cm ³ of 25 wt% in heptane) were added to the reactor. At the reaction temperature, ethylene (120 psi [0.83 MPa]) was added to saturate the liquids. About 80 mg of the catalyst of Example 1 was added to the reactor and the polymerization was allowed to proceed for 1 hour. A granular product was obtained in a yield of 83 g with I ₂ of 1.00, MFR of 17.4, a density of 0.914 g / cm ³ and a productivity of 959 g PE / g cat / hr / 100 psi C2 , The product was easily removed from the reactor and showed little, if any, evidence of reactor fouling.

Examples 8 to 12

table Figure 1 illustrates similar Polymerization results with the catalysts of Examples 1 to 6. The conditions were as given in Example 7.

Table 1

The productivity is given in g PE / g cat./h/100 psi C2 =. The densities were 0.914 to 0.918 g / cm ³ .

Slurry LLDPE Morphology

The non-polluting operation of a laboratory slurry reactor is associated with the formation of granular PE product. Two basic types of particle morphology can be formed in the reactor. A solid, transparent, spherical particle makes up the main ingredient of the product non-TMA pretreated cases (catalysts of Examples 1 and 4) with small amounts of an amorphous white-looking polymer that binds some particles together. As reactor fouling with the TMA pretreated catalysts increases, the relative amounts of the white rubbery phase increase.

The Silica PQ 988 produced under the conditions given above less white polymer binder as the 955 silica from Davison and is used for the manufacture of non-polluting granular LLDPE preferred. However, acceptable catalysts can be used with the silica 955, as shown by the following example.

Example 13

One Example 1 more similar Catalyst was prepared on silica 955-600. It No TMA was used to pretreat the silica. The Al: Zr ratio was 200: 1. The MAO loading was 7 mmol Al / g silica and 0.035 mmol Zr / g silica. The MAO was in this case obtained from the Ethyl Corporation, and has a little less free TMA as the above used MAO from Schering. Under the polymerization conditions from Example 7, 128 g of a granular polymer with an MI of 1.4, an MFR of 20, a productivity of 1100 g / g cat./h/100 psi C2 and a density of 0.916.

Example 14 Metallocene catalyst, that of silica, with different dehydration temperatures was treated is worn

Four Catalysts were prepared in the same manner and using the same Formulation as prepared in Example 13, except that silicas with respective Dehydration temperatures of 20 ° C (with vacuum), 110 ° C and 300 ° C used were. These catalysts were in a slurry reactor using methods similar to those in Example 7. The Results are listed in Table 2.

Table 2

In all cases the resin morphology was excellent without reactor pollution.

Example 15

Cp*Zr

Bis(pentamethylcyclopentadienyl)zirkoniumdichlorid

IndZr

Bis(indenyl)zirkoniumdichlorid

CpZr

Bis(cyclopentadienyl)zirkoniumdichlorid

MeCpZr

Bis(methylcyclopentadienyl)zirkoniumdichlorid

CpTi

Bis(cyclopentadienyl)titandichlorid

CpZr

Bis(pentamethylcyclopentadienyl)titandichlorid

The following examples illustrate that other metallocene compounds can also be used to prepare the catalyst, but catalyst productivity and resin density, FI and MFR are different. Catalysts were prepared similar to Example 13 except that different metallocene complexes were used. The silica dehydration temperature and the polymerization results are shown in Table 3. Table 3

Cp * Zr

Bis (pentamethylcyclopentadienyl) zirconium

IndZr

(Indenyl) zirconium

CpZr

Bis (cyclopentadienyl) zirconium

MeCpZr

Bis (methylcyclopentadienyl) zirconium

CpTI

Bis (cyclopentadienyl) titanium

CpZr

Bis (pentamethylcyclopentadienyl) titanium

In all cases the resin morphology was excellent without reactor pollution.

Example 16

The The following examples illustrate the high bulk density the granular Products, the average particle size and the resulting high Yield per reactor unit or solvent volume. Very high catalyst efficiency both in terms of the use of the metallocene complex and the use of the methylalumoxane is shown in the following examples just as clearly made.

The Catalysts were prepared using the methods described in Example 13 Standard method produced. The silica dehydration temperature, MAO loading, metallocene loading and drying time were varied to show the ranges of these predictors.

The polymerization is carried out in a semi-batch reactor at 70 ° C and a pressure of 125 psig (0.96 MPa). The reactor volume is 2.5 liters. One liter of heptane and 100 cm ³ of hexene were introduced into the reactor. Ethylene was introduced into the reactor at a pressure of 125 psig (0.96 MPa) before a small catalyst sample is injected into the reactor. Tables 4 and 5 show the results.

Table 4

Table 5

Claims (14)

A process for producing a linear low density polyethylene (LLDPE) in granular form having a specific gravity in the range of 0.91 to 0.939 g / cm ³ and an average particle size of 300 to 800 microns, the process comprising: (a) dispersing a catalyst in an aliphatic solvent under anhydrous conditions to form a slurry in a reaction vessel, the catalyst supported by a dehydrated carrier comprising a metallocene and an alumoxane; (b) maintaining the slurry at an absolute pressure below 1000 psi (6.9 MPa) and a temperature of 20 ° C to 100 ° C; (c) introducing ethylene and an alpha-olefin selected from 1-butene, 1-propene and alpha-olefins having 6 to 10 carbon atoms into the reaction vessel, wherein the partial pressure of the ethylene is between 20 and 1000 psi (0, 14 to 6.9 MPa); and (d) recovering granular LLDPE exhibiting a bulk density of 15 to 36 lb./ft ³ (240 to 580 kg / m ³ ) and an MFR of less than about 30 from the reaction vessel, wherein the aliphatic solvent is selected from the A group consisting of isobutane, pentane, isomers of pentane, hexane, isomers of hexas, octane, isomers of octane, decane, dodecane, and mixtures thereof; includes. Process according to claim 1, characterized in that the specific gravity of the LLDPE is less than 0.93 g / cm ³ . A method according to claim 1, characterized in that the support comprises silica which is amorphous and porous and has a pore volume of 0.1 to 5 cm ³ / g and which has a lower concentration of silanol groups than 2.5 mmol per gram of silica. Method according to claim 3, characterized in that the Catalyst by contacting under anhydrous conditions of silica with a volume of a mixture containing a metallocene and alumoxane comprises wherein the volume of the mixture is not greater than the total pore volume of the silica support is produced. Process according to Claim 4, characterized in that the metallocene has the formula Cp _m MA _n B _p , in which Cp represents a substituted cyclopentadienyl group, m 1 or 2; M is zirconium or hafnium; each A and B are selected from the group consisting of a halogen atom, a hydrogen atom and an alkyl group; and m + n + p is equal to the valency of the metal M and that the alumoxane has the following formula (a) or (b): (a) R- (Al (R) -O) n-AlR ₂ for oligomeric linear alumoxanes; (b) (-Al (R) -O-) _m for oligomeric cyclic alumoxanes; wherein n is 1 to 40, m is 3 to 40, and R comprises a C ₁ -C ₈ alkyl group; and that the silica is an activated catalyst. Procedure according to each preceding claim, characterized in that the catalyst in particulate form having a particle size in the range of 1 to 500 microns. Method according to claim 1, characterized in that the relationship from aluminum to the transition metal in the catalyst is 70 to 350. Method according to claim 1, characterized in that the Amount of the transition metal in the catalyst (elemental basis) between 0.001 and 10 weight percent and the amount of aluminum in the catalyst (elemental-based) is between 1 and 40 weight percent and that the Al: transition metal ratio in the catalyst (on elemental basis) is between 25 and 10,000. Procedure according to each preceding claim, characterized in that the metallocene selected from the group consisting of bis (n-butylcyclopentadienyl) metal dihalides, bis (n-butylcyclopentadienyl) metal hydride halides, Bis (n-butylcyclopentadienyl) metal monoalkyl monohalides; Bis (n-butylcyclopentadienyl) metal dialkyls; Bis (tetrahydroindenyl) metal halides and bis (indenyl) metal dihalides. Method according to claim 9, characterized in that the Metallocene selected from the group consisting of bis (isobutylcyclopentadienyl) zirconium dichloride, Bis (pentamethylcyclopentadienyl) zirconium dichloride, bis (tetrahydroindenyl) zirconium dichloride, Bis (indenyl) zirconium dichloride, bis (1,3-dimethylcyclopentadienyl) zirconium dichloride, Bis (methylcyclopentadienyl) zirconium dichloride and bis (n-butylcyclopentadienyl) zirconium dichloride consists. Method according to claim 1, characterized in that the Concentration of the alpha-olefin in the solvent in the range of 0.1 to 50 weight percent. Method according to claim 11, characterized in that the Concentration of the alpha-olefin in the solvent in the range of 0.1 to 30 weight percent. Method according to claim 1, characterized in that the Boiling point of the solvent less than 180 ° C is. Method according to claim 1, characterized in that the Pressure in step (b) is below 600 psi (4.1 MPa).