Plastics pipes of polyolefins

• US 7,485,685 B2
• Filed: 10/19/2006
• Issued: 02/03/2009
• Est. Priority Date: 11/23/2001
• Status: Expired due to Term

• Current Assignee: Basell Polyolefine GmbH (Lyondellbasell Industries NV)
• Original Assignee: Basell Polyolefine GmbH (Lyondellbasell Industries NV)
• Inventors: Beuermann, Ilka, Vogt, Heinz, Mihan, Shahram
• Primary Examiner(s): RABAGO, ROBERTO
• Application Number:
  US11/551,121
• Publication Number:
  US 20070065613A1
• Time in Patent Office: 838 Days
• Field of Search: 526/106, 526/130, 526/348, 526/352, 264/464, 264/472, 264/476, 264/477, 264/563
• US Class Current: 526/106
• CPC Class Codes: C08F 210/14 Monomers containing five or more carbon atoms
• CPC Class Codes: C08F 210/16 Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
• CPC Class Codes: C08F 2500/04 Broad molecular weight distribution, i.e. Mw/Mn > 6
• CPC Class Codes: C08F 2500/07 High density, i.e. > 0.95 g/cm3
• CPC Class Codes: C08F 2500/11 Melt tension or melt strength
• CPC Class Codes: C08F 2500/12 Melt flow index or melt flow ratio
• CPC Class Codes: C08F 2500/18 Bulk density
• CPC Class Codes: C08F 4/22 of chromium, molybdenum or tungsten
• CPC Class Codes: C08F 4/24 Oxides
• CPC Class Codes: Y10T 428/1352 Polymer or resin containing [i.e., natural or synthetic]

Abstract

Plastics pipes comprise polyolefins which can be prepared by means of a fluorine-modified chromium catalyst and are used for transporting gases and liquids.

Claims

1. A method for producing a polyolefin pipe comprising:

preparing a polyolefin by polymerization in a single-line plant in the presence of a silica-xerogel-supported chromium catalyst activated with air and modified with an inorganic fluorinating agent,

combining said polyolefin with further additives in an amount of from 0 to 10% by weight; and

shaping said combination into the form of a pipe by means of melt extrusion.

2. A method according to claim 1 wherein the polyolefin thus prepared has a density of from 0.943 to 0.955 g/cm³, a melt flow rate HLMI (190°

C./21.6 kg) of from 4 to 12 g/10 minutes, and a molar mass distribution M_w/M_n from 8 to 18.

3. A method according to claim 1 further comprising:

crosslinking said polyolefin.

4. A method according to claim 3 wherein said polyolefin has a molar mass distribution M_w/M_n from 8 to 18.

5. A method according to claim 1 wherein the catalyst employed in the preparation of the polyolefin is prepared by a process which comprises:

a) providing a finely divided silica xerogel;

b) loading the xerogel with chromium from a solution of chromium trioxide or of a chromium compound; and

c) activating the product obtained in stage (b) in an anhydrous gas stream, containing oxygen in a concentration of more than 10% by volume at from 400 to 1,100°

C.; and

wherein the chromium compound is converted into chromium trioxide under the conditions of stage (c); and

wherein the modification of the catalyst with the fluorinating agent is conducted in stage (a), in stage (b), or in stage (c).

6. A method according to claim 1 wherein the polyolefin is a homopolymer of ethylene.

7. A method according to claim 1 wherein the polyolefin is a copolymer of ethylene.

8. A method according to claim 1 wherein the polyolefin is a copolymer of ethylene with a 1-alkene of 3 to 10 carbon atoms.

9. A method according to claim 3 wherein the crosslinking of said polyolefin is obtained by radiation crosslinking.

10. A method according to claim 5 wherein the polyolefin is a homopolymer of ethylene.

11. A method according to claim 5 wherein the polyolefin is a copolymer of ethylene.

12. A method according to claim 5 wherein the polyolefin is a copolymer of ethylene with a 1-alkene of 3 to 10 carbon atoms.

13. A method according to claim 3 wherein the crosslinking of said polyolefin is obtained by radiation crosslinking, and wherein the catalyst employed in the preparation of the polyolefin is prepared by a process which comprises:

a) providing a finely divided silica xerogel;

b) loading the xerogel with chromium from a solution of chromium trioxide or of a chromium compound; and

c) activating the product obtained in stage (b) in an anhydrous gas stream, containing oxygen in a concentration of more than 10% by volume at from 400 to 1,100°

C.; and

wherein the chromium compound is converted into chromium trioxide under the conditions of stage (c); and

wherein the modification of the catalyst with the fluorinating agent is conducted in stage (a), in stage (b), or in stage (c).