Self-Dispersing Pigment Surface Modification for Decor Paper
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Solution Overview
Problem
In the production of decor paper and paper laminates, titanium dioxide pigments often interact negatively with furnish components, leading to issues such as reduced paper tensile strength, mottled appearance, and poor opacity, due to compatibility issues.
Innovation Solution
A process for preparing self-dispersing titanium dioxide pigments involves adding a dual functional compound with an acidic aluminum salt and a base to form a turbid solution, which is then added to a slurry of inorganic particles, depositing hydrous alumina and the dual functional compound on the pigment surface, thereby enhancing compatibility and maintaining pigment particles dispersed in an aqueous medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional titanium dioxide pigments are added to paper furnish, then brightness and opacity are improved, but paper tensile strength deteriorates due to negative interactions with furnish components
Solution Approach 1:
A dual-functional compound is introduced as an intermediary substance that modifies the surface of titanium dioxide pigment particles. This compound contains an anchoring group that attaches to the pigment surface and a basic amine group that interacts favorably with paper furnish components, thereby mediating between the pigment and the paper matrix to prevent negative interactions while maintaining brightness enhancement
Solution Approach 2:
The isoelectric point of the pigment surface is changed from its conventional value to at least about 8 through surface modification with the dual-functional compound. This parameter change alters the electrostatic properties of the pigment particles, improving their compatibility with paper furnish components and preventing strength deterioration
2Illumination intensity
If conventional titanium dioxide pigments are added to paper furnish, then opacity is improved, but uniformity deteriorates due to mottled appearance
Solution Approach 1:
The dual-functional compound acts as a mediator that promotes uniform distribution of pigment particles throughout the paper furnish. The basic amine group interacts with furnish components to prevent aggregation and ensure even dispersion, eliminating the mottled appearance while maintaining improved opacity
Solution Approach 2:
The self-dispersing pigment utilizes its own surface-modified properties to achieve uniform distribution without requiring additional dispersing agents or complex processing. The zeta potential and isoelectric point modifications enable the pigment to self-disperse uniformly in the aqueous phase and maintain uniformity in the final paper product
3Stability of the object's composition
If pigment particles are suspended in aqueous medium, then dispersion is achieved, but agglomeration occurs due to insufficient repulsive forces
Solution Approach 1:
The zeta potential of the pigment particles is modified through surface treatment to enhance electrostatic repulsion between particles. By adjusting the isoelectric point to at least about 8, the pigment particles maintain sufficient like-charge in the aqueous medium, creating strong repulsive forces that prevent agglomeration and maintain stable dispersion
Solution Approach 2:
The pigment surface is transformed into a composite structure combining the inorganic pigment core with the organic dual-functional compound coating. This composite structure provides both the optical properties of the pigment and the electrostatic properties needed for stable dispersion, combining benefits of different material types
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 treated titanium dioxide pigments exhibit improved compatibility and dispersion, maintaining sufficient zeta potential to prevent agglomeration, resulting in enhanced paper properties like increased opacity and tensile strength, and a higher isoelectric point that facilitates better interaction with paper fibers and wet strength resins.
Implementation Method 1
adding the mixture from step (b) to a slurry of inorganic particles whereby a hydrous alumina and the dual functional compound are deposited on the pigment surface
Implementation Method 2
the pigment zeta potential becomes a dominant force keeping pigment particles separated, i.e., dispersed in the aqueous phase
Data Source
AI summary
The disclosure provides a process for preparing a self-dispersing pigment having an isoelectric point of at least about 8 comprising: (a) adding a dual functional compound with an acidic aluminum salt to form an aqueous solution, wherein the dual functional compound comprises an anchoring group that attaches the dual-functional compound to the pigment surface, and a basic amine group comprising a primary, secondary or tertiary amine; (b) adding a base to the mixture from step (a) whereby the pH is raised to about 4 to about 9 to form a turbid solution; and (c) adding the mixture from step (b) to a slurry of inorganic particles whereby a hydrous alumina and the dual functional compound are deposited on the pigment surface. The self-dispersing pigments prepared by this process are useful in making décor paper that may be used in paper laminates.