Amphoteric Polyurethane Binder for Ink-Jet Viscosity Stability
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Solution Overview
Problem
Ink-jet printing technologies face challenges with ink stability, particularly when printing on non-absorbent media, as slow-drying inks can stick to heated rollers and transfer onto subsequent prints, leading to image quality issues and substrate damage.
Innovation Solution
Development of an aqueous ink-jet ink composition containing a self-stabilized amphoteric polyurethane binder with tertiary amine groups and anionic acid groups, which maintains viscosity stability and prevents ink transfer during high-speed paper handling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If anionic polyurethane particles are used as binder to provide fast drying and improve image durability, then image quality is improved, but viscosity and pH of the ink change upon storage over time especially after oven aging
Solution Approach 1:
The patent changes the chemical parameters of the polyurethane binder by introducing amphoteric groups (both cationic and anionic charges) instead of using only anionic polyurethane. This parameter change in the binder's charge characteristics enables the ink to maintain stable viscosity and pH during storage and oven aging while still achieving fast drying and durable images.
2Reliability
If slow-drying ink is used to print on non-absorbent media, then image durability is improved, but ink transfers onto heated rollers and subsequent prints
Solution Approach 1:
The amphoteric polyurethane binder acts as an intermediary that enables the ink to dry at an optimal rate on non-absorbent media. The dual charge characteristics of the binder facilitate controlled evaporation and adhesion, preventing ink transfer to heated rollers while still forming durable images, thus mediating between the conflicting requirements of drying speed and image durability.
3Productivity
If heated rollers are used to transfer media in wet-press, then productivity is improved, but drying ink sticks to rollers causing image quality problems
Solution Approach 1:
The ink formulation uses amphoteric polyurethane binder that preemptively prevents sticking to heated rollers by controlling the drying characteristics. The binder's unique charge properties create a protective effect during the heating and transfer process, preventing the ink from adhering to the rollers before the media is transferred, thus maintaining image quality while enabling high-speed production.
Data Source
AI summary
The present disclosure provides aqueous ink-jet inks having improved stability containing an aqueous vehicle, a colorant, and an amphoteric polyurethane as a binder. The amphoteric polyurethane contains a plurality of tertiary amine groups derived from an amine-containing monomer, and a plurality of anionic acid groups.