Flame-Retardant Polyurethane Coatings via Phosphinate Grafting

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Solution Overview

Problem

Current aqueous polyurethane dispersions with flame retardants are limited in producing clear coats and often impair material properties, as phosphorus-containing additives are incompatible with binders, restricting gloss levels and compatibility with polyurethane coatings.

Innovation Solution

Incorporating phosphorus-containing monomers with hydroxyl groups into the polyurethane polymer chain, where the phosphorus atom forms a phosphinate group separated by a carbon atom, allowing for a stable and compatible flame-retardant polyurethane dispersion that maintains film-forming properties and allows for clear coat production.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If phosphorus-containing additives are mixed into polyurethane coatings, then flame retardancy is improved, but compatibility with the binder deteriorates and gloss level is reduced

Engineering Contradiction:

Improveflame retardancyVSAvoidbinder compatibility

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent combines the flame retardant phosphorus compound with the polyurethane binder into a single integrated polymer structure. The phosphinate group is incorporated into the polyol component, creating a graft copolymer where phosphorus-containing side chains are covalently bonded to the polyurethane backbone. This merging eliminates the phase separation and incompatibility issues that occur when phosphorus additives are simply mixed into conventional polyurethane coatings.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention creates a composite polymer structure combining polyurethane chains with grafted phosphorus-containing side chains. This composite material integrates the fire-retardant properties of phosphorus compounds with the film-forming and adhesive properties of polyurethane, achieving both flame retardancy and binder compatibility in a single material system.

Inventive Principle:

Principle #40Composite materials

2Reliability

If inorganic flame retardants are added to coatings, then flame retardancy is improved, but material properties are impaired due to high addition amounts

Engineering Contradiction:

Improveflame retardancyVSAvoidmaterial properties

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the chemical structure and molecular weight parameters of the phosphorus compound by incorporating it into the polymer chain. Instead of using high amounts of low molecular weight inorganic phosphorus additives that impair material properties, the invention uses low amounts of phosphorus incorporated into the polymer structure, achieving flame retardancy with minimal impact on viscosity, flexibility, and other material properties.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If phosphorus compounds are incorporated into polyurethane, then flame retardancy is improved, but film-forming properties are affected

Engineering Contradiction:

Improveflame retardancyVSAvoidfilm-forming properties

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by placing phosphorus-containing side chains at specific locations along the polyurethane backbone rather than uniformly distributing them. The phosphinate groups are grafted onto the polyol chains, creating localized fire-retardant zones that do not interfere with the overall film-forming process. This localized incorporation maintains the continuity and integrity of the polyurethane matrix during film formation.

Inventive Principle:

Principle #3Local quality

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

This approach enables the production of clear, flame-retardant polyurethane coatings with minimal impact on material properties, maintaining film-forming characteristics and stability, and allows for high phosphorus content without impairing polymer properties or requiring toxic solvents.

Implementation Method 1

Incorporating phosphorus-containing monomers with hydroxyl groups into the polyurethane polymer chain

Methodology Applied

Scientific EffectPolyaddition reaction: Chemical Bonding

Implementation Method 2

aqueous, anionically stabilized via carboxyl or sulfonate groups, dispersions

Methodology Applied

Scientific EffectElectrostatic stabilization: Electrostatics

Data Source

PatentEP3150646B1Aqueous dispersions of pre-polymers containing isocyanate-terminated phosphorus and coatings made from same and use

Publication Date: 2023.09.20 SYNTHOPOL CHEM DR RER POL KOCH GMBH & CO KG

AI summary

The present invention relates to isocyanate-terminated prepolymers dispersed in water with organophosphorus compounds incorporated into the polyurethane polymer structure, coatings produced with such polyurethane dispersions and their use in flame-retardant aqueous coating materials, such as aqueous air-drying varnishes, aqueous stoving varnishes and aqueous two-component varnishes.