Titanium Dioxide Pigment Surface Treatment for UV Lightfastness
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Solution Overview
Problem
Titanium dioxide pigments used in paper laminates tend to turn gray upon exposure to UV light due to the formation of Ti3+ ions, which affects their lightfastness and increases costs due to the use of retention aids and other additives.
Innovation Solution
A process involving treating titanium dioxide pigment with a source of phosphorus and aluminum, followed by drying and thermal treatment at temperatures between 300° C to 800° C, to create a surface-treated pigment with improved lightfastness, characterized by an isoelectric point greater than pH 6 and negative zeta potential, thereby reducing color change upon UV exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If titanium dioxide pigment is used in paper laminates, then brightness and opacity are improved, but lightfastness deteriorates due to gray color change upon UV exposure
Solution Approach 1:
An inorganic surface treatment layer comprising aluminum phosphate and phosphorus is applied to the titanium dioxide pigment surface. This intermediary layer acts as a protective barrier between the UV light and the titanium dioxide, preventing the formation of Ti3+ ions that cause gray color change, while allowing the pigment to maintain its brightness and opacity functions
Solution Approach 2:
The surface treatment modifies the chemical and physical parameters of the titanium dioxide pigment surface by incorporating aluminum phosphate and phosphorus. This changes the surface properties to be more resistant to UV-induced reduction, thereby improving lightfastness without sacrificing the optical properties of the pigment
2Stability of the object's composition
If retention aids and additives are used to maintain pigment stability, then pigment dispersion is improved, but manufacturing cost increases
Solution Approach 1:
The patent extracts and removes the need for additional retention aids and dispersants by incorporating the stabilizing function directly into the pigment surface treatment. The inorganic surface treatment layer itself provides the stability and dispersion properties that would otherwise require separate chemical additives, thereby reducing manufacturing costs while maintaining pigment stability
3Reliability
If thermal treatment is applied to remove surface hydroxyl groups, then lightfastness is improved, but energy consumption increases
Solution Approach 1:
The inorganic surface treatment with aluminum phosphate and phosphorus is applied in advance during pigment manufacturing, creating a protective layer that pre-prevents UV-induced degradation. This preliminary action reduces or eliminates the need for subsequent high-temperature thermal treatment to remove surface hydroxyl groups, thereby improving lightfastness while significantly reducing energy consumption
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 pigment exhibits a significant decrease in delta E* (color change) of at least 40% compared to untreated pigments, maintaining brightness and enhancing the lightfastness of paper laminates.
Implementation Method 1
drying the treated mixture to form a treated pigment having surface hydroxyl groups; removing a major proportion of the surface hydroxyl groups of the treated pigment
Implementation Method 2
removing a major proportion of the surface hydroxyl groups of the treated pigment
Implementation Method 3
The type of resin and laminate paper used, and composition of the final assembly, are generally dictated by the end use of the laminate. Decorative paper laminates can be made by utilizing a decorated paper layer as upper paper layer in the unitary core structure
Data Source
AI summary
The present disclosure relates to a process for making a decorative base paper for a paper laminate comprising impregnating a base paper with a pigment mixture of titanium dioxide and water wherein the titanium dioxide pigment is made by treating a mixture of titanium dioxide pigment and water with a source of phosphorus and a source of aluminum; drying the treated mixture to form a treated pigment, the treated pigment having surface hydroxyl groups; and removing a major proportion of the surface hydroxyl groups of the treated pigment. Preferably the surface hydroxyl groups are removed by thermal treatment, for example at temperatures ranging from 300° C. to 800° C. The source of phosphorus is typically phosphoric acid and the source of aluminum is typically sodium aluminate. The pigment can be characterized by an isoelectric point which is greater than pH 6 and a negative zeta potential of at least 20 mV at a pH of 7.5 or more and wherein the pigment has improved light fastness.