Polyolefin pipe

Patent metadata

Field	Value
Publication number	US-9963573-B2
Application number	US-201414787865-A
Country	US
Kind code	B2
Filing date	Apr 23, 2014
Priority date	May 3, 2013
Publication date	May 8, 2018
Grant date	May 8, 2018

Abstract

This invention relates to a polymeric pipe, and more particularly a polymeric pipe where the pipe comprises a crosslinked polyolefin formed from extruded polyolefin comprising a photoinitiator and a reactive extrusion species. More particularly, this invention relates to the manufacturing of plastic pipes and tubing by utilizing co-rotating twin screw extrusion combined with photo-induced crosslinking, of thermoplastic polymers such as polyethylene, to produce PEX pipes and tubing.

First claim

The invention claimed is:

1. A polymeric pipe formed from a mixture consisting of:
a polyethylene structural polymer;
a photoinitiator in an amount of 0.02 to 3% by weight;
a co-agent in an amount of 0.02 to 10%, by weight;
a phenolic antioxidant in an amount of 0.1 to 1% by weight; and
optionally a hindered amine light stabilizer in an amount of 0.05 to 1% by weight;
wherein the photoinitiator is a compound of the following formula:

wherein:
R 1 is —(CH 2 ) m (C═O)[O(CH 2 ) n ] p O(C═O)(CH 2 ) q —;
R 3 is selected from group consisting of —H, -halo, —OH, —(C 1 -C 4 )alkyl, —(C 2 -C 4 )alkenyl, —O(C 1 -C 4 )alkyl, and —O(C 2 -C 4 )alkenyl;
m is 0, 1 or 2;
n is 2, 3, 4, 5 or 6;
p is 2, 3, 4, 5, 6, 7, 8, 9 or 10; and
q is 0, 1 or 2;

wherein the co-agent comprises at least one carbon-carbon double bond;
wherein when tested in accordance with the ASTM F 876 Hoop Stress Stabilizer Test, the pipe demonstrates effective stabilization for over 12500 hours;
wherein the pipe is a cross-linked polyethylene pipe with the characteristics of a pipe obtainable by:
extrusion of a mixture comprising the polyethylene structural polymer, photoinitiator, co-agent, phenolic antioxidant, and optional hindered amine light stabilizer from a co-rotating twin screw extruder to form an extruded pipe; and
cross-linking the structural polymer by irradiating the extruded pipe with UV radiation.

2. The pipe of claim 1 , wherein m and q are both 1, n is 4 and p is 3, 4, 5 or 6.

3. The pipe of claim 1 , wherein the photoinitiator is

wherein r is 2, 3, 4, 5, 6, 7, or 8.

4. The pipe of claim 1 , wherein the photoinitiator is in an amount of 0.3 to 1.5% by weight.

5. The pipe of claim 1 , wherein the co-agent comprises at least two reactive carbon-carbon double bonds.

6. The pipe of claim 1 , wherein the co-agent comprises at least one of triallylcyanurate, polybutadiene, or trimethylolpropane triacetate.

7. The pipe of claim 1 , comprising the hindered amine light stabilizer in the amount of 0.05 to 1% by weight.

8. The pipe of claim 7 , wherein the hindered amine light stabilizer comprises:

which has a molecular weight of 2000 to 3100 g/mol, or

which has a molecular weight of 3100 to 4000 g/mol,
wherein R 5 is a C 2 -C 24 alkyl group.

9. The pipe of claim 1 , wherein the antioxidant is a phenolic antioxidant.

10. The pipe of claim 1 , wherein the polyethylene structural polymer comprises high density polyethylene (HDPE) with a melt flow index (MFI) of at least 2, or with a melt flow index of at least 5.

11. The pipe of claim 1 , where in the pipe is a cross-linked pipe.

12. A method of producing a cross-linked polyolefin pipe comprising:
extrusion of a mixture from a co-rotating twin screw extruder to form an extruded pipe; and
cross-linking a polyolefin structural polymer by irradiating the extruded pipe with UV radiation,
wherein the extrusion mixture comprises the polyolefin structural polymer, a photoinitiator in an amount of 0.02 to 3% by weight, a co-agent in an amount of 0.02-10% by weight, and a phenolic antioxidant in an amount of 0.1 to 1% by weight;
wherein the photoinitiator is a compound of the following formula:

wherein:
R 1 is —(CH 2 ) m (C═O)[O(CH 2 ) n ] p O(C═O)(CH 2 ) q —;
R 3 is selected from group consisting of —H, -halo, —OH, —(C 1 -C 4 )alkyl, —(C 2 -C 4 )alkenyl, —O(C 1 -C 4 )alkyl, and —O(C 2 -C 4 )alkenyl;
m is 0, 1 or 2;
n is 2, 3, 4, 5 or 6;
p is 2, 3, 4, 5, 6, 7, 8, 9 or 10; and
q is 0, 1 or 2;

and wherein the co-agent comprises at least one carbon-carbon double bond.

13. The method of claim 12 , wherein the polyolefin structural polymer is one of polyethylene, polypropylene, polybutylene, polyolefin copolymers or any copolymers thereof.

14. The method of claim 12 , wherein the mixture further comprises a hindered amine light stabiliser in an amount of 0.05 to 1% by weight.

15. The method of claim 12 , wherein the cross-linked polyolefin pipe has a degree of crosslinking in the range of about 60 to about 90%.

16. The method of claim 12 , wherein the polyolefin structural polymer and at least one component are separately injected into the extruder;
wherein the at least one component is one of the photoinitiator, the co-agent, the phenolic antioxidant, or a combination thereof; and
wherein the polyolefin structural polymer and the at least one component are mixed by a mixing element of the twin-screw extruder.

17. The method of claim 12 , wherein the extrusion is performed at an extruder output of greater than 100 kg/h.

18. The pipe of claim 1 , wherein the polyethylene structural polymer is in an amount of at least 85% by weight.

Assignees

• Uponor Innovation Ab

Inventors

• Ericsson Jan
• Ortquist Andrew
• Menssen Todd
• John Jacob
• Meeker Josh

Classifications

• B29C48/09

  Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels · CPC title

• C08K5/132

  Phenols containing keto groups {, e.g. benzophenones} · CPC title

• B29C48/28

  Storing of extruded material, e.g. by winding up or stacking · CPC title

• B29C48/37

  Gear pumps · CPC title

• B29C35/10

  for articles of indefinite length · CPC title