PVDF Pipe Coating Adhesion via Thermoplastic Interlayer

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Solution Overview

Problem

Existing coatings for metallic pipes do not provide strong adhesion to withstand pressure drops in oil and gas production pipelines nor are they impermeable to both liquids and gases simultaneously.

Innovation Solution

A three-layer coating system comprising a layer of epoxy resin with free hydroxyl groups, a thermoplastic adhesive layer of anhydride modified polyolefin or acrylic acid modified polyolefin, and a layer of polyvinylidene fluoride (PVDF) applied to the inside of metallic pipes, with the adhesive layer ensuring strong adhesion and the PVDF layer providing impermeability and impact resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single-layer plastic coating is applied to the inside of the pipe, then the coating provides some protection, but it cannot strongly adhere to the metal pipe surface to withstand pressure drops in oil and gas production pipelines

Engineering Contradiction:

Improveadhesion strengthVSAvoidcoating structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The coating system is divided into three distinct layers: an epoxy adhesive layer that bonds to the metal substrate, a thermoplastic adhesive layer that provides intermediate bonding, and a PVDF protective layer that provides corrosion and abrasion resistance. This segmentation allows each layer to perform its specific function optimally, achieving strong overall adhesion while maintaining structural integrity under pressure drops.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses a composite coating structure combining different materials with complementary properties: epoxy resin for strong metal adhesion, thermoplastic adhesive for intermediate bonding, and PVDF for environmental resistance. This composite approach achieves adhesion strength and protective properties that no single material could provide alone.

Inventive Principle:

Principle #40Composite materials

2Reliability

If existing coatings are applied to pipes, then they provide some corrosion protection, but they are not impermeable to both liquids and gases simultaneously

Engineering Contradiction:

ImproveimpermeabilityVSAvoidcorrosion and abrasion

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The PVDF layer provides impermeability by creating a dense, non-porous barrier that prevents penetration of both liquid and gaseous substances. The thermoplastic adhesive layer is applied at elevated temperatures to ensure proper fusion and eliminate micro-defects, achieving complete impermeability. This combination of material selection and process control ensures protection against both liquids and gases simultaneously.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If a thermoplastic coating is applied without adhesive layers, then the application process is simpler, but the coating cannot withstand pressure drops present in oil and gas production pipelines

Engineering Contradiction:

Improvecoating applicationVSAvoidpressure resistance

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The thermoplastic adhesive layer acts as an intermediary between the epoxy adhesive and the PVDF protective layer, ensuring strong bonding between these components. This intermediate layer facilitates stress distribution and prevents delamination under pressure drops, while the epoxy layer provides the primary bond to the metal substrate. The multi-layer adhesive system maintains strength without complicating the application process.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 coating system achieves strong adhesion to withstand pressure drops and ensures impermeability to liquids and gases, offering superior protection against corrosion and abrasion, with the PVDF layer providing a tough and flexible barrier.

Implementation Method 1

a layer of thermoplastic adhesive applied directly onto the layer of epoxy resin

Methodology Applied

Scientific EffectAdhesion: Adhesive

Implementation Method 2

applying heat at a temperature higher than the point of softening of the thermoplastic material, but without damaging the material

Methodology Applied

Scientific EffectThermal softening: Melting

Implementation Method 3

offering superior protection against corrosion and abrasion

Methodology Applied

Scientific EffectCorrosion resistance:

Implementation Method 4

offering superior protection against corrosion and abrasion

Methodology Applied

Scientific EffectAbrasion resistance:

Implementation Method 5

ensures impermeability to liquids and gases

Methodology Applied

Scientific EffectImpermeability:

Data Source

PatentEP3683042A1Internal anticorrosive and abrasive resistant protection coating for pipes

Publication Date: 2020.07.22 PATAGONIA SHALE SERVICES SA

Figure 1

AI summary

The present invention includes an inner anticorrosive and abrasive resistant coating (10) for metallic pipes (1) used for the transport of fluids. The coating includes: a layer of epoxy resin (2) having free hydroxyl groups, which are applied directly to the inside (1a) of the metallic pipe (1); a layer of thermoplastic adhesive (3) applied directly onto the layer of epoxy resin; and a layer of a plastic material (4) containing polyvinylidene fluoride or polyvinylidene difluoride (PVDF).