Silane-Modified Polyurea Binders for Fast-Curing Coatings

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Solution Overview

Problem

There is a need for fast-curing, isocyanate-free binders with improved technical properties, particularly for use in corrosion protection systems, as existing silane-modified polyurea compounds take longer to dry and pose toxicological risks due to free isocyanate groups.

Innovation Solution

A silane-modified polyurea compound is produced by reacting a polyisocyanate based on isophorone diisocyanate with isocyanurate and allophanate groups with an aminosilane, resulting in a binder with reduced free isocyanate content and enhanced curing properties, including faster pendulum hardness development and lower viscosity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If silane-modified polyurea compounds are used as binders in coatings, then crosslinking ability and coating performance are improved, but drying time is extended

Engineering Contradiction:
Improvecoating performanceVSAvoiddrying time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent changes the chemical parameters of the silane modification by using specific aminosilanes with different alkoxyl groups (methoxyl, ethoxyl, propoxyl) and varying the ratio of polyisocyanate to aminosilane. This optimization of chemical parameters achieves faster curing rates while maintaining coating performance, directly resolving the contradiction between crosslinking ability and drying time.

Inventive Principle:
Principle #35Parameter changes

2Productivity

If polyisocyanates with free isocyanate groups are used as binders, then reactivity and curing speed are improved, but toxicological danger increases

Engineering Contradiction:
Improvecuring speedVSAvoidtoxicological danger
Core Design Contradiction:
ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent converts the potentially harmful free isocyanate groups into beneficial allophanate and isocyanurate structural units through controlled reaction. These structural units maintain the reactivity and curing speed benefits while eliminating the toxicological dangers, effectively transforming a harmful feature into a beneficial one.

Inventive Principle:
Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent optimizes the reaction parameters including the molar ratio of polyisocyanate to aminosilane (1:0.5 to 1:2), reaction temperature (30-80°C), and catalyst selection to achieve complete consumption of free isocyanate groups. This parameter optimization ensures high curing speed while maintaining low toxicity, resolving the contradiction between productivity and safety.

Inventive Principle:
Principle #35Parameter changes

3Strength

If conventional silane-modified binders are used, then coating resistance is improved, but viscosity is high requiring more solvent

Engineering Contradiction:
Improvecoating resistanceVSAvoidsolvent amount
Core Design Contradiction:
StrengthVSQuantity of substance

Solution Approach 1:

The patent changes the molecular structure parameters by selecting specific aminosilanes with different chain lengths and alkoxyl groups, and optimizing the polyisocyanate to aminosilane ratio. These parameter changes reduce the viscosity of the binder while maintaining or improving coating resistance, thereby reducing the solvent requirement and aligning with environmental regulations.

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 new binder achieves faster drying times, improved hardness development, and reduced solvent usage, while being toxicologically harmless due to low free isocyanate levels, making it suitable for quick-drying coatings in corrosion protection systems.

Implementation Method 1

produced by reaction of a polyisocyanate based on isophorone diisocyanate, which has isocyanurate and allophanate structural units, with an aminosilane

Methodology Applied
Scientific EffectChemical reaction: Chemical Bonding

Implementation Method 2

The compounds have terminal alkoxysilane groups, which have the property of hydrolyzing to organosilanols upon contact with small amounts of moisture

Methodology Applied
Scientific EffectHydrolysis: Hydrolysis

Implementation Method 3

polymerizing to organosiloxanes by subsequent condensation. This polymerization leads to crosslinking of the silane-modified polyurea compound

Methodology Applied
Scientific EffectCondensation: Condensation

Data Source

PatentEP3732225B1Silane-modified polyurea compounds based on polyisocyanates with isocyanurate and allophanate groups
Publication Date: 2021.11.17 COVESTRO INTELLECTUAL PROPERTY GMBH & CO KG

AI summary

The invention relates to a polyurea compound that can be produced by reacting a polyisocyanate based on isophorone diisocyanate, which has isocyanurate and allophanate groups, with an amino silane according to general formula (I): R1 a(R1O)(3-a)Si(CH2)nNHCHR2CH2COOR3 (I), wherein the groups R1 are selected independently from one another from C1-C20-alkyl or C6-C20-aryl, a is a whole number between 0 and 2, n is a whole number between 1 and 4, R2 is selected from H, C1-C20-alkyl, C6-C12-aryl and –COOR3, and R3 is a respective C1-C20-alkyl. The invention also relates to the use of the compound as a binder for producing coatings.