Waterborne Epoxy-Phenoxy Coating for Corrosion and Conductivity
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Solution Overview
Problem
Conventional aqueous-based coatings face challenges in achieving corrosion resistance and electrical conductivity without using toxic heavy metals, while also dealing with limitations in prepolymer dispersibility and VOC emissions.
Innovation Solution
A waterborne thermoset cured coating formulation using a water-dispersed phosphonated or sulfonated epoxy resin co-cured with a phenoxy resin, combined with a corrosion-inhibiting metal salt and electrically conductive particulates like aluminum or zinc, which are free from chromium, lead, and cadmium, to provide both corrosion resistance and electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If aqueous coating dispersions are used to reduce VOC emissions and toxicity, then environmental safety and health are improved, but corrosion resistance deteriorates due to low prepolymer loading and film pinholes
Solution Approach 1:
The patent combines epoxy resin with phenoxy resin to create a composite aqueous coating system. The epoxy resin provides corrosion resistance while the phenoxy resin enhances water dispersibility and film continuity, eliminating pinholes. This composite approach allows the coating to maintain both environmental safety (aqueous base) and reliability (corrosion resistance) simultaneously.
Solution Approach 2:
The patent modifies the chemical structure of the prepolymer by incorporating phenoxy resin groups, which change the physical and chemical parameters of the coating. This structural modification enables better water dispersibility and higher prepolymer loading in the aqueous phase, thereby improving corrosion resistance without sacrificing environmental benefits.
2Ease of operation
If prepolymer is derivatized to increase water dispersibility, then dispersibility is improved, but corrosion resistance deteriorates due to increased water wetting
Solution Approach 1:
The patent creates a composite system where phenoxy resin-modified epoxy prepolymer combines the water dispersibility of phenoxy groups with the corrosion-inhibiting properties of epoxy resin. The synergistic interaction between the two resin components allows the coating to achieve both good water dispersibility and maintained corrosion resistance, resolving the trade-off between these two properties.
3Ease of operation
If electro-coating techniques are used to achieve electrical conductivity and improved coating deposition, then conductivity and deposition uniformity are improved, but corrosion resistance deteriorates due to formulation compromises
Solution Approach 1:
The patent formulates a composite aqueous dispersion of epoxy-phenoxy resin that is inherently suitable for electro-coating. The phenoxy resin component provides excellent water dispersibility and film-forming properties that ensure uniform deposition during electro-coating, while the epoxy resin maintains corrosion resistance. This composite formulation eliminates the need to compromise corrosion resistance to achieve electro-coating compatibility.
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 formulation achieves effective corrosion resistance and electrical conductivity on various substrates, including metals and polymers, without the use of toxic metals, while reducing VOC emissions and improving handling properties, making it suitable for electrostatic discharge and powder coating applications.
Implementation Method 1
a water dispersed or emulsified phosphonated epoxy resin, or water dispersed or emulsified sulfonated epoxy resin that is co-cured with a phenoxy resin
Implementation Method 2
A curative is provided to induce cure with the epoxy resin and phenoxy resin
Implementation Method 3
With the inclusion of electrically conductive aluminum or zinc particulate the formulation is rendered more corrosion resistant as well as electrically conductive
Implementation Method 4
A corrosion inhibiting metal salt is also present having a salt anion of phosphate, biphosphate or tetraborate
Data Source
AI summary
A waterborne thermoset cured anticorrosion formulation includes a water dispersed or emulsified phosphonated or water dispersed or emulsified sulfonated epoxy resin that is cured with a phenoxy resin having a polyhydroxyl ether backbone and terminal alpha glycol moieties. Water is present as a predominant volatile in which the epoxy resin and phenoxy resin are present in a weight ratio of epoxy resin to phenoxy resin of between 0.1 and 3:1. An aqueous curative is provided to induce cure between the epoxy resin and phenoxy resin, A corrosion inhibiting metal salt is also present having a salt anion of phosphate, biphosphate or tetraborate and a metal cation with the proviso that the metal cation formulation as a whole is devoid of chromium, lead, cobalt, and cadmium. Ideal curatives include aqueous aminoplast crosslinkers, aqueous unblocked isocyanates, aqueous blocked isocyanates, and a mixture thereof. With the inclusion of electrically conductive aluminum or zinc particulate the formulation is rendered corrosion resistant as well as electrically conductive to make an inventive coating amenable to powder coating.