Pipe comprising ethylene base polymer

Details Pipe comprising ethylene base polymer Pipe comprising ethylene base polymer

2002-02-22

2004-04-13

Rabago, Roberto (Department: 1713)

Stock material or miscellaneous articles

Hollow or container type article

Polymer or resin containing

C428S036800, C428S036900, C138S118000, C138S177000, C138SDIG007, C526S348000

Reexamination Certificate

active

06720048

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a pipe comprising an ethylene base polymer, more specifically to a pipe comprising an ethylene base polymer which is excellent in a creep characteristic (durability), a rigidity and an impact resistance and which is suited to uses for large diameter pipes receiving a high internal pressure.
RELATED ART
In recent years, ethylene base polymers are increased in use in the pipe field because of characteristics thereof such as an excellent impact resistance. The most important characteristic required to the pipes of the ethylene base polymers is to have such an excellent durability that they are not broken even under pressure exerted by gas and city water over a long period of time. However, conventional polyethylene pipes have a problem on any of a rigidity, a long-term durability and an impact resistance, and the existing situation is that particularly when they are used for large diameter pipes receiving a high internal pressure, they can not be used because of an unsatisfactory creep characteristic and are specialized in use for branch pipes having a small diameter.
Then, various proposals have been made in order to apply them to uses receiving a high internal pressure. A polyethylene resin composition for a pipe is proposed in, for example, Japanese Patent Application Laid-Open No. 57638/1986. However, this composition has the defect that it has a high density and therefore is liable to be susceptible to brittle fracture in a creep test. Further, a polyethylene-made pipe having excellent mechanical characteristics is proposed in Japanese Patent Application Laid-Open No. 301933/1996, but this has the problem that it is inferior in fluidity.
Further, a production process in which annealing conditions are specified in order to obtain a pipe having an excellent low temperature toughness is proposed in Japanese Patent Application Laid-Open No. 44219/1998, but it is not preferred in terms of heat balance to heat again an article once cooled to subject to annealing treatment and further cool it down, and a long production line is required in actual molding.
DISCLOSURE OF THE INVENTION
The present invention has been made under such circumstances, and an object thereof is to provide a pipe comprising an ethylene base polymer which is excellent in a durability, a rigidity and an impact resistance and which is suited to uses for a large diameter pipe receiving a high internal pressure.
The present inventors have repeated intensive researches in order to achieve the object described above. As a result thereof, they have found that a pipe made of an ethylene base polymer satisfying fixed ranges in four properties of (1) residual stress, (2) crystallinity, (3) gradient of the crystallinity against a thickness of the pipe and (4) a thickness of the pipe has desired physical properties and is a pipe meeting the above object. The present invention has been completed based on such knowledge.
That is, the present invention provides a pipe comprising an ethylene base polymer comprising ethylene and &agr;-olefin having 3 to 20 carbon atoms, wherein (A) a maximum value of the residual stress is 0.13 MPa or less; (B) the crystallinity is 0.630 to 0.850; (C) a gradient of the crystallinity against a thickness of the pipe is 0.465 or less; and (D) the pipe has a thickness of 5 to 50 mm.


REFERENCES:
patent: 2002/0045711 (2002-04-01), Backman et al.
patent: 9-151280 (1997-06-01), None
patent: 11-286557 (1999-10-01), None
patent: 2001-114838 (2001-04-01), None

Affiliated with

Also associated with

Rating

Pipe comprising ethylene base polymer does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Pipe comprising ethylene base polymer, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pipe comprising ethylene base polymer will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3263382