Polyurethane Dispersion Crosslinking via Carbodiimide
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing aqueous polyurethane and polyurea dispersions for adhesives and coatings have limitations such as short processing times, insufficient reactivity, and excessive hydrophilicity due to high acid numbers and sterically hindered carboxyl groups, leading to suboptimal adhesive properties and stability issues.
Innovation Solution
The development of aqueous polyurethane or polyurethane-urea dispersions with terminal carboxyl groups and pendant sulphonate and/or carboxylate groups, which react with carboxyl-reactive crosslinkers like polycarbodiimides to form high-quality, long-processing-time adhesives and sealants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydroxy-functional polyurethane or polyurethane-polyurea dispersions are combined with isocyanate-functional crosslinkers to improve adhesive properties, then good adhesive properties are achieved, but the processing time becomes relatively short (usually only a few hours) due to the reaction of the polyisocyanate crosslinker with the water
Solution Approach 1:
The patent changes the chemical parameters of the crosslinking system by using carbodiimide-functional crosslinkers instead of isocyanate-functional crosslinkers. This parameter change in the crosslinker type fundamentally alters the reaction kinetics, enabling long processing times (several days to months) while maintaining good adhesive properties through crosslinking of the polyurethane-polyurea dispersions with terminal carboxyl groups
2Duration of action of moving object
If carboxylate-functional dispersions are combined with carbodiimide-functional crosslinkers to extend processing time, then long processing times are achieved, but the reactivity and properties of the binder mixtures are often not sufficient to meet increased requirements
Solution Approach 1:
The patent applies local quality by incorporating specific functional groups (terminal carboxyl groups) at particular locations within the polyurethane-polyurea polymer chains. These terminal carboxyl groups are strategically positioned to react with carbodiimide crosslinkers, creating localized high-reactivity sites that enable both long processing times and sufficient reactivity for high-quality adhesive applications
3Quantity of substance
If dithylolpropionic acid or carboxyl-functional polyesters are used to incorporate carboxyl groups into the polyurethane dispersion, then carboxyl groups are introduced, but the carboxyl groups become sterically hindered and not optimally accessible to crosslinking reaction
Solution Approach 1:
The patent extracts the carboxyl groups from sterically hindered positions (such as dithylolpropionic acid structures) and relocates them to terminal positions of the polyurethane-polyurea chains. This extraction from hindered environments to terminal positions makes the carboxyl groups optimally accessible to crosslinking reactions while maintaining the necessary quantity of reactive groups
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
These dispersions enable the production of high-quality, crosslinked adhesives and sealants with extended processing times, improved reactivity, and enhanced stability, achieving superior bonding and heat resistance.
Implementation Method 1
aqueous, crosslinkable dispersions based on polyurethane or polyurethane ureas... which are suitable for the production of high-quality paints, sealants and in particular adhesives... have very good crosslinking properties... in combination with carboxyl-reactive crosslinkers
Implementation Method 2
the dispersion is applied to the substrate, after the water has completely evaporated, the adhesive layer is removed by heating
Implementation Method 3
activated with an infrared radiator and converted into an adhesive state. The temperature at which the adhesive film becomes tacky is called the activation temperature
Data Source
AI summary
The invention relates to aqueous, curable dispersions based on polyurethane or polyurethane urea, to a method for their production and to use thereof.