Method for carrying out radical ethylene high-pressure polymerization while preventing undesired polymer deposits

• US 20030008982A1
• Filed: 07/31/2002
• Published: 01/09/2003
• Est. Priority Date: 02/16/2000
• Status: Active Grant

• Current Assignee: BASF AG (BASF SE), Basell Polyolefine GmbH (Lyondellbasell Industries NV)
• Original Assignee: BASF AG (BASF SE), Basell Polyolefine GmbH (Lyondellbasell Industries NV)
• Inventors: Deckers, Andreas, Evertz, Kaspar, Littmann, Dieter, Mahling, Frank-Olaf, Sutoris, Heinz Friedrich
• Granted Patent: US 6,562,915 B2
• Time in Patent Office: Days
• US Class Current: 526/82
• CPC Class Codes: C08F 110/02 Ethene
• CPC Class Codes: C08F 2/00 Processes of polymerisation
• CPC Class Codes: C08F 2/005 by addition of a scale inhibitor to the polymerisation medium
• CPC Class Codes: C08F 2/40 using retarding agents
• CPC Class Codes: C08F 2500/26 Use as polymer for film forming
• CPC Class Codes: C08F 297/08 polymerising mono-olefins
• CPC Class Codes: C08F 4/34 Per-compounds with one peroxy-radical

Abstract

The invention relates to a method for polymerizing or copolymerizing ethylenically unsaturated monomers in the presence of radically decomposing polymerization initiators in a continuously operating polymerization device. Said polymerization device is composed of a fresh gas supply, a pre-compressor, a post-compressor, a reactor, a pressure maintaining valve, of a high-pressure circuit, which is provided with a high-pressure product separator and with a high-pressure circuit gas return, and of a product valve and a low-pressure circuit, which is provided with a low-pressure product separator and with a low-pressure circuit gas return. The inventive method is characterized in that nitrogen monoxide or oxygen is added in a dosed manner as an inhibitor into the high-pressure circuit, into the low-pressure circuit and/or into the pre-compressor.

Claims

1. A process for the polymerization or copolymerization of ethylenically unsaturated monomers in the presence of polymerization initiators which decompose to form free radicals in a continuously operated polymerization apparatus comprising a fresh gas feed line (a), a precompressor (b), a postcompressor (c), a reactor (e), a pressure maintenance valve (f), a high-pressure circuit (g) having a high-pressure product separator (i) and a high-pressure circulation gas return line (l), a product valve (m) and a low-pressure circuit (n) having a low-pressure product separator (o) and a low-pressure circulation gas return line (q), wherein nitrogen monoxide or oxygen is introduced as inhibitor into the high-pressure circuit (g), into the low-pressure circuit (n) and/or the precompressor (b).

2. A process as claimed in claim 1, wherein an inhibitor concentration of not more than 25 ppm is established after introduction of the inhibitor.

3. A process as claimed in claim 1 or 2, wherein nitrogen monoxide is introduced as inhibitor.

4. A process as claimed in claim 1 or 2, wherein oxygen is introduced as inhibitor and an inhibitor concentration of from 1 to 10 ppm is established after the introduction.

5. A process as claimed in claim 4, wherein an inhibitor concentration of from 2 to 5 ppm is established.

6. A process as claimed in any of claims 1 to 5, wherein the inhibitor is introduced into the precompressor.

7. A process as claimed in claim 6, wherein the inhibitor is introduced at a pressure of <

20 bar.

8. A process as claimed in any of claims 1 to 7 in which ethylene is polymerized.

9. The use of oxygen as inhibitor in a process as defined in any of claims 1 to 8.

10. The use of nitrogen monoxide as inhibitor in a process as defined in any of claims 1 to 8.

High-pressure, free-radical polymerization of ethylene with avoidance of undesirable polymer deposits

In a process for the polymerization or copolymerization of ethylenically unsaturated monomers in the presence of polymerization initiators which decompose to form free radicals in a continuously operated polymerization apparatus comprising a fresh gas feed line, a precompressor, a postcompressor, a reactor, a pressure maintenance valve, a high-pressure circuit having a high-pressure product separator and a high-pressure circulation gas return line, a product valve and a low-pressure circuit having a low-pressure product separator and a low-pressure circulation gas return line, nitrogen monoxide or oxygen is introduced as inhibitor into the high-pressure circuit, into the low-pressure circuit and/or the precompressor.