Polyurethane Resin-Bonded Pigment for Inkjet Printing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Aqueous pigment inks face challenges in achieving high image density, dispersibility, storage stability, and resolubility due to the strong interparticle cohesive forces of pigments and their weak affinity with organic polymers and water, leading to issues like image penetration, curling, and nozzle clogging in high-speed printing applications.
Innovation Solution
A polyurethane resin-bonded pigment is produced by reacting self-dispersible carbon black with a basic compound and a water-dispersible polyurethane resin having isocyanate end groups, forming a urea bond to create a highly crosslinked resin structure on the pigment surface, enhancing dispersibility and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a dispersant is adsorbed on the surface of the pigment to improve dispersibility, then dispersibility is improved, but storage stability deteriorates due to shear force during discharge or long-term storage removing the dispersant
Solution Approach 1:
The patent applies preliminary action by pre-coating the pigment surface with a water-dispersible polyurethane resin before use. This resin forms a stable base layer that prevents pigment aggregation during storage. Then, a polyisocyanate compound is added just before printing to provide temporary dispersant action during high-speed discharge, which is subsequently removed without affecting the underlying resin coating.
Solution Approach 2:
The patent implements dynamics by making the dispersant system changeable over time. The polyisocyanate compound is added dynamically at the timing of printing rather than being permanently attached during storage. This allows the dispersant to be present when needed for high-speed discharge and easily removable afterward, preventing both aggregation during storage and clogging during printing.
2Productivity
If the amount of ink discharged per unit time is increased to match high-speed printing, then printing speed is improved, but image density decreases due to insufficient pigment concentration
Solution Approach 1:
The patent applies parameter changes by modifying the physical state and concentration parameters of the pigment dispersion. The water-dispersible polyurethane resin creates a stable colloidal dispersion that maintains high pigment concentration without aggregation. The subsequent addition of polyisocyanate compound further optimizes the dispersion parameters during printing, enabling high pigment load at high discharge rates while maintaining image density.
3Stability of the object's composition
If a highly crosslinked resin structure is formed on the pigment surface to enhance stability, then storage stability is improved, but nozzle clogging occurs due to reduced resolubility
Solution Approach 1:
The patent applies partial action by forming a crosslinked resin structure on only the surface of the pigment particles rather than throughout the entire material. The water-dispersible polyurethane resin provides this partial crosslinking on the surface for storage stability, while the core pigment material remains accessible. The polyisocyanate compound adds temporary crosslinking during printing that is subsequently removed, preventing permanent clogging.
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 polyurethane resin-bonded pigment achieves excellent image density, dispersibility, storage stability, and resolubility, forming an ink film with marker resistance and rubfastness, while preventing nozzle clogging and maintaining performance in high-speed printing.
Implementation Method 1
reacting self-dispersible carbon black with a basic compound and a water-dispersible polyurethane resin having isocyanate end groups, forming a urea bond to create a highly crosslinked resin structure on the pigment surface
Data Source
AI summary
A polyurethane resin-bonded pigment may exhibit excellent image density, dispersibility, storage stability, and resolubility, and may form an ink film that exhibits marker resistance and rubfastness. The polyurethane resin-bonded pigment is produced by bringing (I) a pigment having a surface acidic group into contact with (II) a basic compound having two or more amino groups selected from a primary amino group and a secondary amino group in its molecule in an aqueous medium to obtain a pigment having an unreacted surface amino group, and bringing the pigment having an unreacted surface amino group into contact with (III) a water-dispersible polyurethane resin having an isocyanate end group and (IV) a polyisocyanate compound to bond the pigment having an unreacted surface amino group and the water-dispersible polyurethane resin (III) having an isocyanate end group via a urea bond.