Microcapsule Pigment Density Control for Ink Dispersibility
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Solution Overview
Problem
Conventional microcapsule pigments and aqueous ink compositions for writing instruments face challenges in maintaining dispersibility and controlling the specific gravity and particle diameter, particularly with pigments like titanium oxide and carbon black, which are difficult to disperse effectively.
Innovation Solution
A microcapsule pigment is developed using a poorly water-soluble medium with a specific gravity less than 1 at 20°C, such as aliphatic carboxylate esters, which enhances dispersibility and allows for controlled specific gravity and particle diameter, achieved through microcapsulation with a shell layer formed from thermosetting resins like urethane or epoxy, enabling improved color developability and particle size distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dispersant is used to maintain dispersion stability of pigment, then dispersibility is improved, but the system becomes more complex and requires optimal selection for every pigment and medium combination
Solution Approach 1:
The patent uses a poorly water-soluble medium with specific gravity less than 1 as an intermediary substance to disperse pigments having large specific gravity. This medium acts as a mediator between the pigment particles and water-based ink composition, providing dispersion stability without requiring complex dispersant systems. The medium's lower specific gravity creates a density difference that prevents pigment settling while maintaining homogeneous distribution.
2Ease of manufacture
If conventional microcapsule pigments are used, then pigment encapsulation is achieved, but dispersibility in water-based ink compositions remains insufficient
Solution Approach 1:
The patent changes the physical parameter of the encapsulation medium by using a poorly water-soluble medium with specific gravity less than 1, rather than conventional water-soluble or oil-based media. This parameter change in the medium's density and solubility characteristics enables the microcapsule pigment to maintain both ease of manufacture through standard encapsulation processes and superior dispersibility in water-based ink compositions due to the density difference with pigment particles.
3Illumination intensity
If pigment with large specific gravity is used, then color intensity is improved, but control of specific gravity and particle diameter becomes difficult
Solution Approach 1:
The patent applies the counterweight principle by using a poorly water-soluble medium with specific gravity less than 1 to offset the large specific gravity of the pigment particles. This density compensation allows pigment particles with high specific gravity (providing intense color) to be dispersed and controlled in a medium that counteracts their settling tendency, enabling precise control of both specific gravity and particle diameter in the final ink composition.
Data Source
AI summary
Provided are a microcapsule pigment, though it is a microcapsule pigment obtained by microcapsulating a pigment having a large specific gravity such as titanium oxide and carbon black having a little difficulty in dispersibility, which makes it easier to be improved in dispersibility and which makes it possible to control a specific gravity and a particle diameter as desired, and an aqueous ink composition for writing instruments prepared by using the same. The microcapsule pigment described above is characterized by comprising at least a pigment and a poorly water-soluble medium having a specific gravity of less than 1 at 20°C, and the aqueous ink composition for writing instruments described above is characterized by containing the microcapsule pigment described above.