Patent DE-3566806-D1 (DE)
Title: Process for preparing relatively low density polyethylenes by means of a ziegler catalyst
Inventor: FUNK GUIDO DR
IPC: C08F4/16
Filed: 1985-12-13
Granted: 1989-01-19
Abstract: 1. A process for the preparation of an ethylene polymer having a relatively low density by polymerization of ethylene at from 20 to 160 degrees C and under from 1 to 100 bar in the presence of hydrogen, using a Ziegler catalyst system which comprises (1) a binary titanium-containing component consisting of (1.1) a first titanium-containing sub-component, consisting of a titanate of the formula Ti(OR**1 )4 where R**1 is an aliphatic and/or aromatic C1 -C12 -hydrocarbon radical, and (1.2) a second titanium-containing sub-component which furthermore contains chlorine, and (2) an aluminum-containing component, consisting of an organoaluminum compound of the formula AlR**2 where R**2 is R**3 or OR**3 , and R**3 is C1 -C8 -alkyl ;, with the provisos that the atomic ratio of titanium from (1) to aluminum from (2) is from 1 : 5 to 1 : 500 and the ratio of titanium from (1.1) to titanium from (1.2) is from 1 : 0.01 to 1 : 1, wherein a binary titanium-containing component (1) is used whose second titanium-containing sub-component (1.2) consists of a finely divided solid which is obtainable by a method in which (1.2.1) first (1.2.1.1) a finely divided, porous, inorganic oxidic substance (I) which has a particle diameter of from 1 to 1,000 mu m, a pore volume of from 0.3 to 3 cm**3 /g and a specific surface area of from 100 to 1,000 m**2 /g and is of the formula SiO2 - aAl2 O3 where a is from 0 to 2, and (1.2.1.2) a solution (II), as obtained by combining (IIa) 100 parts by weight of an alcohol of the formula R**4 -OH where R**4 is a saturated C1 -C8 -hydrocarbon radical, (IIb) from 0.01 to 6 parts by weight (calculated as titanium) of a titanium trichloride of the formula TiCl3 . nAlCl3 , where n is from 0 to 0.5, and (IIc) from 0.01 to 4 parts by weight (calculated as magnesium) of magnesium chloride (MgCl2 ), are brought into contact with one another with formation of a dispersion of (III), with the proviso that the weight ratio of the inorganic oxidic substance (I) to titanium in the titanium trichloride (IIb) is from 1 : 0.01 to 1 : 0.2 and the weight ratio of the inorganic oxidic substance (I) to magnesium in the magnesium chloride (IIc) is from 1 : 0.01 to 1 : 0.25, the dispersion is evaporated to dryness at below 200 degrees C and above the melting point of the alcohol (IIa) used, a solid-phase intermediate (IV) being formed, and (1.2.2) then (1.2.2.1) the solid-phase intermediate (IV) obtained from stage (1.2.1) and (1.2.2.2) an aluminum component (V) which is dissolved in an inert hydrocarbon and contains not only aluminum but also a C1 -C12 -hydrocarbon radical are brought into contact with one another with formation of a dispersion, the resulting dispersed solid-phase product (VI) being the second titanium-containing sub-component (1.2), with the proviso that the aluminum component (V) used in stage (1.2.2) is one which consists of (1.2.2.2.1) from 25 to 100 mol % of a complex which is soluble in the inert hydrocarbon and of the empirical formula  see diagramm : EP0188740,P11,F1  where m is 2, 3 or 4, R**5 and R**6 are each a C1 -C12 -hydrocarbon radical and R**7 is a C1 -C12 -hydrocarbon radical or chlorine, and (1.2.2.2.2) from 0 to 75 mol % of an aluminum compound which is soluble in the inert hydrocarbon and of the formula  see diagramm : EP0188740,P11,F2 where R**5 and R**6 are each a C1 -C12 -hydrocarbon radical and R**7 is a C1 -C12 -hydrocarbon radical or chlorine, and with the provisos that (i) the sum of the percentages under (1.2.2.2.1) and (1.2.2.2.2) is 100 and (ii) the atomic ratio of titanium in the solid-phase intermediate (IV) to aluminum in the aluminum component (V) is from 1 : 1 to 1 : 30.