Epoxy Primer Coatings for Wet, Rusted Substrates With Low VOCs
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing coatings struggle to adhere and provide effective corrosion protection on damp, moist, wet, or rusted substrates, particularly those prepared using ultra-high pressure water jetting, which can leave residual water and flash rust, and require high wet film thickness, leading to issues with volatile organic compounds and slow cure rates.
Innovation Solution
A primer coating composition comprising epoxy resin, silane, glycol ether solvent, and microspheres, which can be applied on damp, moist, or rusted substrates, offering low VOC content, long pot life, and excellent adhesion, with a high volume solids ratio and low viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ketimine or aldimine based curing agents are used to achieve wet surface tolerance, then the coating can be applied on moist or wet substrates, but volatile organic compounds (ketones and aldehydes) are released which have negative health and safety impacts
Solution Approach 1:
The patent changes the chemical parameters of the curing agent system by using polyamine curing agents instead of ketimine/aldimine, and incorporates silane modifiers that change the reaction mechanism. This allows wet surface tolerance to be achieved through hydrolysis of silane groups rather than through ketone/aldehyde release, eliminating the harmful VOCs while maintaining the ability to apply on moist substrates.
Solution Approach 2:
The patent introduces silane compounds as intermediary substances that mediate the curing process. The silane groups hydrolyze to form silanol intermediates which then react with the polyamine curing agent, creating a crosslinked network without requiring ketone or aldehyde intermediates. This intermediary mechanism enables wet surface tolerance while avoiding VOC release.
2Quantity of substance
If high wet film thickness is applied to ensure adequate coating coverage, then the substrate is fully protected, but the release of ketone or aldehyde is hindered leading to entrapped volatile components
Solution Approach 1:
The patent changes the curing chemistry parameters by using silane-modified polyamine systems. The silane groups provide a controlled hydrolysis mechanism that releases water instead of volatile ketones or aldehydes. This parameter change in the curing mechanism allows high wet film thickness to be applied without trapping harmful volatiles, as the curing process occurs through water release rather than volatile intermediate formation.
3Adaptability or versatility
If ketimines and aldimines are used to achieve wet surface tolerance, then application on moist substrates is enabled, but the coatings have challenges associated with production and storage due to hydrolytic instability
Solution Approach 1:
The patent changes the chemical stability parameters by selecting polyamine curing agents with appropriate molecular structures and incorporating silane modifiers that provide hydrolytic stability. The silane groups hydrolyze to form stable siloxane crosslinks that do not undergo further degradation, providing long pot life and storage stability while maintaining wet surface tolerance capability.
Solution Approach 2:
The patent creates a composite curing system combining polyamine curing agents with silane modifiers. This composite approach combines the wet surface tolerance of polyamines with the stability of silane crosslinked networks. The resulting hybrid curing mechanism provides both the ability to apply on moist substrates and the storage stability required for practical manufacture and distribution.
4Manufacturing precision
If ketimine or aldimine cured products are applied in too dry conditions, then the substrate is properly prepared, but very slow cure results because moisture is required for hydrolysis
Solution Approach 1:
The patent changes the curing mechanism parameters by using silane-modified polyamine systems that cure through hydrolysis of silane groups followed by condensation. This mechanism can proceed at reduced rates in low-moisture conditions without requiring the rapid moisture-dependent hydrolysis of ketimine/aldimine systems. The silane hydrolysis provides a more flexible curing rate that can accommodate varying substrate moisture conditions while maintaining proper substrate preparation requirements.
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 composition provides effective anti-corrosive protection on wet or rusted substrates with good adhesion and long pot life, reducing volatile organic compounds and ensuring rapid application without the need for intermediate curing steps.
Implementation Method 1
Ketimines and aldimines are hydrolysed in the presence of water to provide the free amines and a ketone or an aldehyde. The liberated amine reacts with the epoxy functional resin
Implementation Method 2
a glycol ether solvent... low viscosity for good application properties
Implementation Method 3
1.0 to 9.0 wt % microspheres... high volume solids ratio (low content of volatile organic compounds (VOC))
Implementation Method 4
application of coatings on moist or wet substrates... excellent adhesion
Data Source
AI summary
A primer coating composition comprising: (i) an epoxy resin; (ii) 2.0 to 15 wt % of silane; (iii) a curing agent; (iv) a glycol ether solvent; and (v) 1.0 to 9.0 wt % microspheres.