DE1645172C - Process for the polymerization of ethylene and a catalyst for carrying out this process - Google Patents

Description

30th

The preparation of normally solid polymers of 1-olefins by the polymerization of such olefins in the presence of a catalyst, the chromium oxide in combination with silicon dioxide, Contains aluminum oxide, zirconium oxide and / or thorium oxide, with at least part of the chromium hexavalent is described in U.S. Patent 2,825,721. This procedure leads to thermoplastic polymers that can be shaped to produce any object any shape and which can be extruded and cold drawn to produce threads or that can be made into films. The molecular weight distribution of these olefin polymers however, it is a bit too wide.

The narrowing of the molecular weight distribution of olefin polymers with the catalyst and according to the process of US Pat. No. 2,825,721 with the addition of ammonium fluosilicate the chromium oxide catalyst is described in U.S. Patent 3,130,188.

It has now been found that an even narrower molecular weight distribution can be achieved by using heavy metal fluosilicates.

The invention relates to a process for the polymerization of ethylene, alone or together with other low molecular weight 1-olefins, in the presence of catalysts made of chromium oxide, at least an oxide of silicon, aluminum, zirconium or thorium as a carrier and a fluosilicate as Agent for narrowing the molecular weight distribution, which is characterized in that in the A heavy metal fluosilicate has been incorporated into the catalyst used.

The invention also relates to a catalyst for carrying out this process, consisting of chromium oxide, at least one oxide of silicon, aluminum, zirconium or thorium as a carrier and a fluosilicate as an agent for narrowing the molecular weight distribution characterized by is that it contains a fluosilicate of a heavy metal

The use of fluosilicates of metals of the I. subgroup of the periodic table is preferred, d. H. of copper, silver and gold.

In a preferred embodiment, a catalyst is used which, after the addition of the fluosilicate has been activated by heating. A preferred catalyst is one, copper fluosilicate has been added in an amount of 0.1 to 8 percent by weight.

The procedures, concentration ranges, reaction conditions, Diluents and the like disclosed in U.S. Patent 3,130,188 are applicable.

The molecular weight distribution is represented by the ratio of the weight average molecular weight M _w to the number average molecular weight M _n . A high value for this ratio indicates a broad molecular weight distribution. Both weight average and number average molecular weights were determined by gel permeation chromatography as described by JCMoore, J. Polymer Science, Part A, Vol. 2, pp. 835-843 (1964). The calibration was carried out by membrane osmometry (M _n ) and light scattering (M _w ). The molecular weight distribution is also represented by the ratio of the high-load melt index to the regular melt index according to the determination method ASTMD 1238-62 T (conditions F or E). A higher value for this ratio for a given melt index indicates a broader molecular weight distribution. This relationship is sometimes referred to as "shear sensitivity" or "shear behavior".

To explain the invention, experiments were carried out using voa catalysts, that of a microspheroidal silicon oxide as a carrier, the 0.1 weight percent aluminum oxide and had an average pore diameter of about 225 Å after they had been impregnated with the individual catalyst components, 5 Hours at 621 ° C. The compositions and other details of the catalyst preparations are shown in the following table I:

Table I.

Attempt no. Cr,
Weight percent Used addition Weight percent , Remarks . 1*) 0.98 none - Carrier, impregnated with aqueous
CrO ₃ solution and at 149 ° C
dried

*) Comparative tests.

continuation

Attempt no. Cr,
Weight percent Used addition Weight percent Remarks 2 *) 0.90 NH ₄ fluosuicate 1.0 Carrier, impregnated with aqueous CrO ₃ -LoSiUIg, dried at 149 ° C and dry mixed with the addition 3 0.98 Cu fluosilicate 1.0 Carrier, impregnated with aqueous CrO ₃ -LoSiUIg, dried at 149 ° C and dry mixed with that Additive hexahydrate

*) Comparative tests.

The polymerization batches were stirred in a 1.3 liter reaction vessel using the The following working technique was carried out: the reaction vessel was heated and flushed with dry nitrogen and with 0.05 to 0.15 g of catalyst - suspended in about 340 g of a hydrocarbon reaction medium, which contained about 85 percent by weight cyclohexane and 15 percent substituted cyclopentanes and branched heptanes - loaded. The reaction vessel was heated to the indicated reaction temperature and it became Ethylene was added to maintain a pressure of 30.6 atm for 1 hour.

Table II

attempt
No. Tempe
rature
C. Polymer
yield
g / g
catalyst H OCH
jelasting
melting
index More regular
Enamel
indcx Melt index
High load stress indcx Molecular weight Afc M, M * / M- _r la *)
Ib *)
2a *)
2 B*)
2 c *)
3a
3b
3c 140
149
135
140
149
135
140
149 1135
888
1300
1450
1595
1310
1360
1645 364
654
191
305
571
204
351
700 11.30
25.70
6.48
11.10
21.50
7.35
13.65
28.90 Regular melting index 95,000
85000
84000 18000
16000
20000 5.38
5.20
4.11 32.2
26.0
29.5
27.6
26.6
27.8
25.7
24.2

*) Comparative tests.
The quotient

High stress melt index
Regular melt index

was plotted against the regular melt index for these runs, and the following values

for the quotient

High load melt index

Regular melt index

which were read from the curves at a regular melt index of 20 are in Table III reproduced. ·

It is obvious that the catalysts modified according to the invention are comparable or higher Polymer yields and a narrower molecular weight distribution than those not modified adorned

Table III

additive

none

NH ₄ -fluosilicate

Cu fluosilicate

quotient

Heavy Duty Melting Index

Regular melt index at regular melt index of 20

27.9 26.4 24.8

Catalysts according to US Pat. No. 2,825,721 or the modified catalyst according to US Pat U.S. Patent 3,130,188.

The production of copolymers from ethylene with 1-olefins with 3 to 12 carbon atoms, 65 such as propylene, 1-butene, isobutylene, 1-pentenes, the 1-hexenes, the 1-octenes or the 1-dodecenes, and also with 1-butadienes, is also within the scope of the invention.

Claims (4)

Patent claims: 1. Process for the polymerization of ethylene, alone Gder together with other low molecular weight 1-olefins, in the presence of catalysts of chromium oxide, at least one oxide of silicon, aluminum, zirconium or thorium as a carrier and a fluosilicate as an agent for narrowing the molecular weight distribution, characterized in that a fluosilicate in the catalyst used Heavy metal has been incorporated. 2. Catalyst for carrying out the method according to claim 1, consisting of chromium oxide, at least one oxide of silicon, aluminum, zirconium or thorium as a carrier and one Fluosilicate as an agent for narrowing the molecular weight distribution, characterized in that that the catalyst contains a fluosilicate of a heavy metal. 3. Catalyst according to claim 2, characterized in that it after the addition of the fluosilicate has been activated by heating. 4. Catalyst according to claim 2 or 3, characterized in that copper fluosilicate in one Amount of 0.1 to 8 percent by weight has been added.