Reactive Polyurethane Dispersion pH Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Commercially available reactive polyurethane dispersions used in UV-curable inkjet inks are prone to pH instability under basic aqueous conditions, leading to hydrolysis and a significant drop in pH, which affects the ink's jetting performance and stability.
Innovation Solution
The development of reactive polyurethane dispersions with specific combinations of functional groups in the polymer backbone and capping units, including styrene-containing monoalcohols and ionic stabilizing groups, which are incorporated into the polymer strands to enhance pH stability and UV curability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional reactive polyurethane dispersions are used in UV-curable inkjet inks, then the ink can be cured to form a durable coating, but the dispersion is prone to pH instability under basic aqueous conditions leading to hydrolysis and pigment precipitation
Solution Approach 1:
The invention changes the chemical parameters of the polyurethane dispersion by incorporating specific functional groups (carboxylic acid groups with pKa 4-6 and ionic stabilizing groups) to modify the pH behavior and prevent hydrolysis under basic conditions
Solution Approach 2:
The invention creates a composite polyurethane structure combining multiple functional groups (carboxylic acid groups, ionic stabilizing groups, and UV-curable groups) within the same polymer backbone to achieve simultaneous pH stability and curability
2Reliability
If ionic stabilizing groups are incorporated into the polymer strands, then pH stability is enhanced, but the complexity of the polymer structure increases
Solution Approach 1:
The invention merges multiple functions (pH stabilization, hydrolysis prevention, and UV curability) into a single polyurethane polymer structure, eliminating the need for separate stabilizing agents and simplifying the overall formulation
3Strength
If the polyurethane dispersion is designed for UV curability, then a durable cross-linked coating is formed, but the presence of reactive groups may accelerate hydrolysis under basic conditions
Solution Approach 1:
The invention places different functional groups at specific locations within the polymer structure - carboxylic acid groups and ionic stabilizing groups are positioned to provide pH stability, while UV-curable groups are positioned to enable cross-linking, with each region performing its specialized function
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 reactive polyurethane dispersions maintain pH stability over time, preventing pigment precipitation and ensuring the ink's jetting performance and durability, even under accelerated shelf-life conditions, while allowing for UV curing to form a durable printed image.
Implementation Method 1
one terminal capped with one or more ionic stabilizing groups... maintain pH stability over time, preventing pigment precipitation
Implementation Method 2
UV-curable polyurethane coatings can be applied in liquid form and then cured very quickly using UV radiation to produce a hard, durable cross-linked coating
Data Source
Figure 1
Figure 2
AI summary
The present disclosure is drawn to a reactive polyurethane dispersion including a polymer strand having a polymer backbone that has two ends terminating at a first capping unit and a second capping unit. The polymer backbone can include polymerized monomers including a reactive diol and a diisocyanate. The reactive diol can be an acrylate-containing diol, a methacrylate-containing diol, a styrene-containing diol, or combination thereof. The first capping unit can be a styrene-containing monoalcohol reacted with an isocyanate group of the diisocyanate. The second capping unit can be an ionic stabilizing group.