Pipeline Field Joint Coating for Stronger PP Bonding
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Solution Overview
Problem
Existing pipeline field joint coatings made from non-polypropylene materials face challenges in achieving maximum bond strength with polypropylene pipe coatings, leading to potential fractures and corrosion due to differential expansion and contraction, which can result in cracking and water penetration.
Innovation Solution
A method involving a coating material composition of propylene polymer and substantially linear or linear ethylene copolymers, which form co-continuous phases, is applied to the field joint, ensuring compatibility and enhanced bonding between polypropylene pipe coatings and non-PP field joint coatings, using injection molding techniques to create a durable and resistant barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-polypropylene field joint coating materials are used, then the coating cycle time is reduced and mold complexity is decreased, but the bond strength between the field joint coating and polypropylene pipe coating deteriorates, leading to cracking and corrosion
Solution Approach 1:
The patent introduces a polypropylene adhesive layer as an intermediary between the non-polypropylene field joint coating and the polypropylene pipe coating. This adhesive layer acts as a mediator that ensures strong bonding between the incompatible materials, preventing cracking and corrosion while allowing the use of chemically curable materials that reduce coating cycle time and mold complexity requirements.
2Strength
If polypropylene field joint coating is used, then the bond strength with pipe coating is maximized, but the coating cycle time increases due to heating and cooling requirements
Solution Approach 1:
The patent changes the bonding mechanism parameter from thermal bonding (requiring heating and cooling) to chemical bonding. By using chemically curable field joint materials that cure through chemical reaction rather than thermal processes, the coating cycle time is significantly reduced while the polypropylene adhesive layer ensures maximum bond strength is maintained through chemical adhesion rather than thermal fusion.
3Device complexity
If non-polypropylene field joint coating materials are used, then the mold design becomes simpler and more compact, but internal stresses during curing cause cracking in the insulation
Solution Approach 1:
The patent applies a polypropylene adhesive layer beforehand on the polypropylene pipe coating surface before applying the non-polypropylene field joint coating. This preparatory step cushions and prevents the development of internal stresses that would otherwise cause cracking during the curing process of the chemically curable material, thereby maintaining insulation reliability while allowing for simpler mold designs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces internal stresses and cracking, enhancing the bond strength between polypropylene pipe coatings and non-PP field joint coatings, thereby preventing corrosion and ensuring the integrity of the pipeline insulation.
Implementation Method 1
wherein the propylene polymer and the substantially linear ethylene copolymer (SLEP), a linear ethylene copolymer (LEP), or mixtures thereof form co-continuous phases
Data Source
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AI summary
The present invention relates to a method of coating a pipeline field joint comprising the steps of (a) applying a layer of a coating material composition comprising (i) a propylene polymer and (ii) a substantially linear ethylene copolymer, a linear ethylene copolymer, or mixtures thereof, to the uncoated region of the field joint, preferably the coating is applied by injection molding.