Waterborne Polyurethane Coatings for Anti-Graffiti via Fluorinated Polyol

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Solution Overview

Problem

Current anti-graffiti coatings struggle to effectively limit the diffusion and penetration of graffiti paint, making removal difficult due to the dye and solvents in graffiti paint, and most existing solutions focus on modifying polyols in two-component waterborne polyurethane systems.

Innovation Solution

A waterborne polyurethane coating composition comprising a fluorinated polyol and a blend of hydrophilically modified trimer polyisocyanates, specifically a hydrophilic ally modified trimer of hexamethylene diisocyanate and isophorone diisocyanate, which provides improved barrier properties and anti-graffiti performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fluorinated polyol is used to reduce surface energy and dewet graffiti paint, then anti-graffiti performance is improved, but the coating formulation complexity increases

Engineering Contradiction:

Improveanti-graffiti performanceVSAvoidcoating formulation complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent uses a composite approach by combining fluorinated polyol with specific polyisocyanate trimers (HDT and IPDT) in a controlled ratio. This composite formulation achieves superior anti-graffiti performance through synergistic effects while maintaining manageable formulation complexity through defined compositional ranges.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent optimizes specific parameters including the ratio of fluorinated polyol to other polyols (1-40% by weight), the NCO/OH ratio (1.2-3.0), and the blend composition of polyisocyanates. These parameter optimizations resolve the contradiction by achieving high anti-graffiti performance within controlled formulation boundaries.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If polyol modification is focused on reducing surface energy, then graffiti paint contact is reduced, but the barrier properties against dye diffusion may be compromised

Engineering Contradiction:

Improvegraffiti paint contactVSAvoidbarrier properties

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies local quality by using fluorinated polyol specifically for surface energy reduction to dewet graffiti paint, while simultaneously incorporating hydrophilically modified polyisocyanates that provide barrier properties. Different components of the coating system perform different functions: fluorinated polyol handles surface dewetting, while the polyisocyanate blend provides the barrier against diffusion.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The composite formulation combines materials with complementary properties: fluorinated polyol for low surface energy and dewetting capability, and hydrophilically modified polyisocyanates for barrier properties. This composite approach allows simultaneous achievement of both dewetting and barrier functions without compromise.

Inventive Principle:

Principle #40Composite materials

3Loss of substance

If waterborne polyurethane system is used to achieve low VOC, then environmental compliance is improved, but the anti-graffiti performance may be reduced compared to conventional systems

Engineering Contradiction:

ImproveVOC contentVSAvoidanti-graffiti performance

Core Design Contradiction:

Loss of substanceVSReliability

Solution Approach 1:

The patent changes key formulation parameters to optimize anti-graffiti performance in waterborne systems: using 1-40% fluorinated polyol, controlling NCO/OH ratio at 1.2-3.0, and employing specific polyisocyanate trimers. These parameter adjustments enable waterborne systems to achieve anti-graffiti performance comparable to or exceeding conventional solvent-based systems while maintaining low VOC compliance.

Inventive Principle:

Principle #35Parameter changes

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 achieves excellent anti-graffiti properties with high gloss, chemical resistance, and recoatability, while maintaining low VOC levels, effectively preventing graffiti paint penetration and facilitating easy removal.

Implementation Method 1

use perfluoro-, fluorine-, or silicone-modified materials, including polyols, to reduce the surface energy of the coating and thereby dewet any graffiti paint and reduce contact

Methodology Applied

Scientific EffectSurface energy reduction: Surface Tension

Implementation Method 2

the dye molecules tending to diffuse or penetrate into the coating after the graffiti paint is applied onto a coating surface

Methodology Applied

Scientific EffectDiffusion barrier: Diffusion

Data Source

PatentUS7875672B2Two component waterborne polyurethane coatings for anti-graffiti application

Publication Date: 2011.01.25 RHODIA OPERATIONS SAS

AI summary

Two component (2K) waterborne polyurethane coating compositions which when cured achieve excellent anti-graffiti properties at low VOC level (below 100 g/L) are disclosed. The composition comprises (A) a fluorinated polyol and optionally a non-fluorinated polyol; and (B), a blend of polyisocyanates comprising a hydrophilically modified trimer of hexamethylene diisocyanate (HDT) and a hydrophilic ally modified trimer of isophorone diisocyanate (IPDT). The glass transition temperature of the ambient cured coatings, crosslinked network structure, and fluorine content at the surface enable excellent anti-graffiti properties. The waterborn coatings of the invention have excellent recoatability and exceptional chemical resistance.