Aqueous Ink Composition Using Butenediol-Vinyl Alcohol Copolymer
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Solution Overview
Problem
Conventional aqueous ink compositions for writing instruments face issues with dryup resistance and writing quality due to flocculation of resin particles, leading to reduced discharge properties and elevated viscosity with aging, while existing solutions either fail to prevent clot formation or result in inferior writing performance.
Innovation Solution
An aqueous ink composition containing at least 5% by mass of resin particles with a median particle diameter of 0.3 µm or more, combined with 0.05 to 10% by mass of butenediol•vinyl alcohol copolymer, which forms a stable core-shell structure to maintain dispersion stability and prevent viscosity increase, enhancing dryup resistance and writing quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If resin particles are blended in aqueous ink composition to endow specific function, then the ink composition can provide enhanced performance, but the dispersion stability of resin particles deteriorates due to flocculation when moisture volatilizes
Solution Approach 1:
A dispersant is introduced as an intermediary substance between resin particles and water to prevent flocculation. The dispersant adsorbs onto resin particle surfaces, creating electrostatic or steric repulsion that maintains stable dispersion even when moisture volatilizes during storage or writing operation.
Solution Approach 2:
The surface properties of resin particles are modified through surface treatment or selection of particles with specific surface charge characteristics. By adjusting parameters such as surface potential, hydrophobicity, or particle size distribution, the resin particles maintain stable dispersion without flocculation during moisture loss.
2Duration of action of stationary object
If flocculation is prevented or loose flocculation is created to form a 'cover' mechanism, then dryup resistance is improved, but the clot behaves like a highly viscous substance that transfers onto drawn lines and reduces quality
Solution Approach 1:
A lubricant is introduced as a mediator between the ink clot and the writing surface. The lubricant reduces friction and prevents the formation of a highly viscous clot, allowing smooth ink transfer to the paper without blobbing or quality degradation, while still maintaining sufficient dryup resistance.
Solution Approach 2:
The viscosity and rheological properties of the ink composition are optimized by adjusting the balance between resin particle concentration, dispersant amount, and lubricant content. This creates an ink that maintains stable dispersion without forming excessive clots, ensuring high-quality line drawing while preserving dryup resistance.
3Duration of action of stationary object
If ethylene oxide-modified polyvinyl alcohol is blended to enhance non-drying property, then dryup resistance is improved, but clot formation occurs in the beginning of writing after cap off and viscosity is elevated with aging
Solution Approach 1:
Instead of relying on ethylene oxide-modified polyvinyl alcohol which causes long-term stability issues, the invention uses a combination of dispersant and lubricant that provides effective dryup resistance through a different mechanism. This alternative approach avoids the harmful side effects of clot formation and viscosity elevation with aging.
Solution Approach 2:
The invention employs a composite system combining dispersant and lubricant components that work synergistically to achieve dryup resistance without the adverse effects of modified polyvinyl alcohol. The composite formulation maintains stable resin particle dispersion and prevents clot formation during storage and initial writing operations.
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 composition achieves excellent dryup resistance and writing performance without deteriorating dispersion stability or increasing viscosity, ensuring consistent line quality and preventing clot formation on drawn lines.
Implementation Method 1
maintain dispersion stability
Implementation Method 2
prevent flocculation of the resin particles
Implementation Method 3
prevent viscosity increase
Implementation Method 4
excellent in a dryup resistance
Data Source
Figure 1A~1C
AI summary
Provided is an aqueous ink composition for a writing instrument containing at least, 5% by mass or more of resin particles having a median particle diameter; D50 of 0.3 µm or more based on volume and 0.05 to 10% by mass of a butenediol•vinyl alcohol copolymer, wherein the aqueous ink composition is excellent in a dryup resistance without reducing a dispersion stability of the resin particles, and the aqueous ink composition is suited to writing instruments such as ballpoint pens, marking pens of an aqueous ink.