Fluoropolymer composition for oil pipe

a technology of fluoropolymer and composition, which is applied in the direction of transportation and packaging, mechanical equipment, coatings, etc., can solve the problems of lack of adhesion between the lining and the inability of mechanical restraint on the movement of the lining, and the separation of the lining from the interior surface of the vessel, so as to achieve better adhesion

Inactive Publication Date: 2005-01-27
EI DU PONT DE NEMOURS & CO
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] The present invention finds that rotolining compositions of TFE / PPVE copolymer and certain metal powders present in small amounts in the composition adhere to the interior surface of hollow articles when applied to such surface in a rotolining process. It has been discovered, however, that the rotolining composition in which TFE / PEVE copolymer is used in place of the TFE / PPVE copolymer provides much better adhesion. The present invention, therefore is directed to the improved rotolining composition using TFE / PEVE copolymer and the use of this composition in the rotolining process.

Problems solved by technology

The reason why the lining is loose arises from the high shrinkage of the perfluorinated polymer when the lined vessel is cooled from the rotolining operation, the shrinkage of PFA even exceeding that of FEP, causing the lining to separate from the interior surface of the vessel.
While this is satisfactory in some applications, the lack of adhesion between lining and interior surface of the vessel becomes disadvantageous in such vessels as pipes, wherein the opportunity for mechanical restraint on movement of the lining is limited, especially as the length of the pipe increases.
The passage of corrosive material, such as oil through the pipe, especially when the flow of the material varies, subjects the lining to mechanical stress, which can cause the lining to crack and fail.
The presence of the fine powder, however, causes another problem, namely that the fine powder can deposit on the surface of the coating to become a contaminant in the chemical stored in the vessel.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0031] A series of rotolinings were conducted at oven temperature of 740° F. (380° C.) for 120 min of mold rotation, in which the test panels are 304 stainless steel which has been grit blasted with a blend (16 grit) of alumina particles and glass beads and in which the amount of rotolining composition added to the mold is sufficient to form a lining 90 mils (2.3 mm) thick.

[0032] When the rotolining material consists solely of TFE / PEVE copolymer particles or TFE / PPVE copolymer particles, the resultant lining does not adhere to the interior surface of the mold, in particular to the test panels forming the major interior surface of the mold.

[0033] When the rotolining material is a composition of either copolymer plus 0.5 wt % zinc powder, the resultant linings adhere to the interior surface of the mold, but the adhesion of the TFE / PEVE copolymer-containing lining is substantially greater. The peel strength of the TFE / PEVE copolymer lining is 77.4 lb / in (13.55 kN / m), while the peel s...

example 2

[0036] A series of rotolinings are conducted under the same parameters as Example 1 to compare stabilized TFE / PEVE copolymer with unstabilized TFE / PEVE copolymer. The stabilized TFE / PEVE copolymer particles are prepared by treating the particles of the copolymer with fluorine to obtain the copolymer having less than 10 unstable end groups per 106 carbon atoms. Each rotolining composition contains 1 wt % of the zinc powder. For the carbon steel panels, the peel strength of the unstabilized copolymer-containing lining is 109 lb / in (19.16 kN / m), while for the stabilized copolymer-containing lining, the peel strength is 53 lb / in (9.28 kN / m). Both linings are smooth and bubble-free.

[0037] As the metal powder concentration is increased from 1 wt % for both copolymer compositions, the peel strength diminishes. At 5 wt % zinc powder concentration, the peel strength of the stabilized copolymer-containing lining drops to 14 lb / in (2.45 kN / m).

example 3

[0038] The linings of Examples 1 and 2 are overcoated with stabilized TFE / PPVE copolymer which does not contain any metal powder by adding particles of the copolymer in sufficient amount to the interior of the lined mold to provide an overcoat thickness of 100 mils (2.5 mm). The rotolining temperature is 650° F. (343° C.), and the time of mold rotation is 180 min. The resultant overcoat adheres to the lining (undercoat) and is smooth and bubble-free.

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Abstract

The present invention relates to a composition of tetrafluoroethylene/perfluoro(ethyl vinyl ether) copolymer particles and metal powder which enables the composition to the used for rotolining an interior surface of a hollow article, wherein the resultant lining adheres to such surface. The invention further relates to oil pipe having its interior surface rotolined with fluoropolymer, the rotolining containing an effective amount of metal powder to cause the rotolining to adhere to said interior surface and a process for rotolinig the interior of the oil pipe.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to fluoropolymer compositions and to the use of such compositions for rotolining of the interior surface of a hollow article. [0003] 2. Description of Related Art [0004] J. Scheirs, Modern Fluoropolymers, John Wiley & Sons (1997) describes the rotolining process, which involves the adding of sufficient fluoropolymer in powder form to a steel vessel to coat the interior surface of the vessel with the desired thickness of the fluoropolymer, followed by rotating the vessel in three dimensions in an oven, to melt the fluoropolymer, whereby the fluoropolymer covers the interior surface of the vessel and forms a seamless lining (p. 315). The resultant fluoropolymer lining protects the vessel from corrosive materials stored or handled by the vessel, by virtue of the chemical inertness of the fluoropolymer forming the lining and the lining being continuous with respect to the interior surface of the v...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B05D7/22C08K3/08F16L9/14
CPCC08F214/18C08K3/08Y10T428/139Y10T428/1393C08L27/18Y10T428/31544Y10T428/3154
Inventor LAHIJANI, JACOB
Owner EI DU PONT DE NEMOURS & CO
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