Water-Based Ink Purification Using Chelating Resin
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Solution Overview
Problem
Current techniques fail to effectively reduce the total content of polyvalent metals as impurities in ink jet recording inks containing pigments to 5 ppm or less, leading to issues with long-term storage stability and ejection stability, especially in thermal jet-type ink jet recording systems, where Kogation and nozzle clogging occur due to insoluble pigments and high calcium ion content.
Innovation Solution
A contact treatment method using a chelating resin with both alkali metal-bonded and hydrogen-bonded chelating groups, in the form of particles or fibers, is employed to reduce the total content of polyvalent metals in the ink to 1.2 ppm or less, ensuring excellent dispersion and ejection stability by efficiently capturing calcium and other metal ions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional purification techniques (chelating resins, cation-exchange resins, salting-out) are used to reduce polyvalent metal content, then some reduction in metal content is achieved, but the total content cannot be reduced to 5 ppm or less in pigment-based inks
Solution Approach 1:
The invention changes the chemical parameters of the purification system by introducing a specific basic compound (guanidine or its derivatives) with strong metal-chelating capability in alkaline conditions. This compound has pKa values of 13.6 and 11.2, allowing it to effectively bind polyvalent metals at pH 8-11, achieving metal content reduction to 5 ppm or less that conventional methods cannot attain
Solution Approach 2:
The invention creates a composite purification system combining the basic compound (guanidine or derivative) with the anionic polymer. This composite approach leverages the strong metal-chelating ability of the basic compound while utilizing the polymer matrix for stability and controlled release, enabling superior purification performance that neither component could achieve alone
2Reliability
If pigment concentration is increased to maintain light fastness and water resistance, then colorant performance is improved, but polyvalent metal impurities increase leading to Kogation and nozzle clogging
Solution Approach 1:
The invention selectively extracts and removes polyvalent metal impurities from the ink system using the basic compound as a chelating agent. The metal ions are bound and removed, leaving the pigment particles intact. This allows high pigment concentration to be maintained without the harmful metal impurities that cause Kogation and clogging
Solution Approach 2:
The basic compound acts as an intermediary that mediates between the pigment particles and the metal impurities. It preferentially binds to metal ions, sequestering them and preventing their interaction with pigment surfaces and heating elements, thus eliminating Kogation while preserving pigment functionality
3Manufacturing precision
If chelating resins are used to capture metal ions in alkaline environment (pH 8 or more), then metal removal is attempted, but the resins are inefficient and generate colored precipitates that adhere to the resin
Solution Approach 1:
The invention changes the chemical parameters by using a basic compound with appropriate pKa values (13.6 and 11.2) that is specifically optimized for alkaline conditions (pH 8-11). Unlike conventional chelating resins that lose efficiency in alkaline environments, this compound maintains strong metal-binding capability, achieving effective purification without precipitate formation
Solution Approach 2:
The purification approach uses a cost-effective basic compound that can be easily added to the ink formulation. The compound performs its metal-chelating function and the resulting metal-complex can be removed through filtration. The simplicity of this approach makes it more economically viable than expensive, regenerable chelating resins
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 method achieves long-term storage stability and ejection stability comparable to dye-based inks while maintaining the light fastness and water resistance of pigment-based inks, with a simple and efficient process that does not affect the physical properties of the ink.
Implementation Method 1
a contact treatment with a specific chelating resin is effectively employed as a simple and convenient method for reducing the total content of polyvalent metals
Data Source
AI summary
Disclosed are an ink jet recording water-based ink having excellent long-term storage stability and ejection stability at a pigment concentration greater than or equal to a certain level and a simple and efficient method for producing such a water-based ink. The present invention provides an ink jet recording water-based ink in which the total content of polyvalent metals as impurities in the water-based ink is not more than 1.2 ppm in terms of 1 mass% of a pigment concentration. Furthermore, the present invention provides a method for producing an ink jet recording water-based ink; the method enables efficient production of the above-mentioned ink jet recording water-based ink through a contact treatment with a particulate chelating resin in which each resin particle contains both an alkali metal-bonded chelating group and a hydrogen-bonded chelating group.