Polyurethane Dispersion Thickening with Fresh Silica Sol

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Solution Overview

Problem

Aqueous polyurethane adhesive formulations exhibit low viscosity, leading to settling and penetration issues, and rely on toxic organic thickeners that increase volatile organic compounds (VOC), compromising storage stability and heat resistance.

Innovation Solution

An aqueous dispersion containing anionically hydrophilized polyurethane, fresh sol, and optional additives, which increases viscosity without using toxic thickeners and enhances heat resistance and storage stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If organic thickeners are used to increase viscosity, then viscosity is improved, but toxicological concerns and VOC content increase

Engineering Contradiction:

ImproveviscosityVSAvoidtoxicological concerns and VOC content

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters by replacing organic thickeners with inorganic silica sols, fundamentally altering the thickening mechanism from organic-based to inorganic-based, thereby eliminating toxicological concerns and VOC emissions while maintaining the desired viscosity increase

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs silica sols that can be easily removed or degraded, replacing persistent organic thickeners. The silica-based system provides the necessary viscosity without long-term environmental or health concerns, effectively treating the thickening agent as a temporary functional additive rather than a persistent component

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Reliability

If viscosity is increased to prevent sagging, then sagging is reduced, but storage stability and heat resistance are compromised

Engineering Contradiction:

Improvesagging preventionVSAvoidstorage stability and heat resistance

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The patent creates a composite system combining polyurethane dispersion with silica sols, where the silica particles form a network structure that provides both viscosity for sagging prevention and thermal stability for heat resistance, achieving multiple functions simultaneously rather than compromising one for another

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes the porous structure of silica sols to create a three-dimensional network within the adhesive formulation. This porous network provides mechanical reinforcement for heat resistance while the interconnected pores maintain fluidity for application, resolving the contradiction between viscosity for sagging prevention and thermal stability

Inventive Principle:

Principle #31Porous materials

3Temperature

If silica sols with large particle diameter are used, then initial heat resistance is improved, but viscosity increase is limited

Engineering Contradiction:

Improveinitial heat resistanceVSAvoidviscosity increase

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by using silica sols with specific particle size distributions (50-500 nm) that provide heat resistance in the bulk material while maintaining appropriate viscosity characteristics. The particle size is optimized locally to balance thermal stability with flow properties, rather than using uniformly large particles throughout

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs silica sols as an intermediary substance that mediates between the conflicting requirements of heat resistance and viscosity. The silica particles act as a bridging component that provides thermal stability while their surface properties and concentration can be adjusted to achieve the desired viscosity, rather than directly conflicting with either requirement

Inventive Principle:

Principle #24Intermediary (Mediator)

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 solution achieves stable viscosity, long-term storage stability, and improved heat resistance without increasing VOC content, while maintaining effective adhesive properties.

Implementation Method 1

the use of a fresh sol for achieving a thickening effect in an aqueous polyurethane dispersion

Methodology Applied

Scientific EffectThickening effect:

Implementation Method 2

the at least one polyurethane is anionically hydrophilized

Methodology Applied

Scientific EffectElectrostatic repulsion: Ion Repulsion/Attraction

Data Source

PatentUS20240018293A1Use of Raw Gel in Formulations on the Basis of Polyurethane Dispersions

Publication Date: 2024.01.18 COVESTRO DEUTSCHLAND AG

AI summary

The present invention relates to an aqueous dispersion at least containing (A) at least one polyurethane, (B) at least one fresh sol and (C) optionally further additives, wherein the at least one polyurethane is anionically hydrophilized, to a process for producing the dispersion, to the use of the dispersion for producing an adhesive composition, to a corresponding adhesive composition, to an adhesive laminate containing at least one substrate bonded with this adhesive composition, to a process for producing an adhesive laminate and to the use of a fresh sol for achieving a thickening effect in an aqueous polyurethane dispersion.