Titanium Dioxide Pigment Surface Treatment via pH Adjustment
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Solution Overview
Problem
The existing methods for surface-treating titanium dioxide pigments with organosilicon compounds are hindered by the slow reaction rate of alkyltrialkoxysilanes and dialkyldialkoxysilanes at mildly acidic pH, leading to increased manufacturing cycle times and reduced efficiency in achieving desired bonding with the pigment surface.
Innovation Solution
A process involving the adjustment of the pH of a titanium dioxide slurry to between 3.5 and 7 using a monoprotic acid fluidizing agent, allowing for the effective application of alkyltrialkoxysilanes and dialkyldialkoxysilanes as surface treatments, and subsequent spray drying to promote bonding and reduce cycle times, while maintaining high solids content for efficient fluidization and energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alkyltrialkoxysilanes and dialkyldialkoxysilanes are used to treat titanium dioxide pigments at mildly acidic pH, then the bonding with pigment surface is improved, but the reaction rate becomes slow and manufacturing cycle time increases
Solution Approach 1:
The patent changes the pH parameter from mildly acidic to strongly acidic (pH 1-3) to dramatically accelerate the reaction rate of alkyltrialkoxysilanes and dialkyldialkoxysilanes with titanium dioxide pigment surface, reducing manufacturing cycle time from hours to minutes while maintaining effective bonding
Solution Approach 2:
The patent performs preliminary pH adjustment to strongly acidic conditions before adding the organosilicon compounds, preparing the pigment surface in advance to facilitate rapid reaction and reduce subsequent processing time
2Reliability
If titanium dioxide pigment is handled as finely divided powder, then opacifying properties are improved, but powder flow characteristics and dust properties deteriorate
Solution Approach 1:
The patent changes the surface chemical parameters of titanium dioxide by applying organosilicon compound treatments that modify surface polarity and interparticle forces, transforming the powder from inherently dusty with poor flow to free-flowing with low dust properties while maintaining fine division for opacifying performance
Solution Approach 2:
The patent creates a composite surface structure on titanium dioxide particles by depositing organosilicon compounds that form a coating layer combining the opacifying properties of TiO2 with the flow-enhancing characteristics of the organosilicon treatment
3Ease of operation
If inorganic metal oxide and metal hydroxide coatings are deposited on titanium dioxide surface, then wetting and dispersing properties are improved, but opacifying properties are reduced
Solution Approach 1:
The patent changes from inorganic coatings to organosilicon compound coatings, altering the chemical nature of the surface treatment to provide organic-based wetting and dispersing improvement that does not compromise the optical opacifying properties of titanium dioxide
Solution Approach 2:
The patent uses thin-film organosilicon coatings that provide sufficient surface modification for improved wetting and dispersing without forming thick layers that would interfere with light scattering and opacifying performance
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
This approach enhances the processibility and dispersibility of the surface-treated titanium dioxide pigments, reducing grit levels and improving gloss and tint strength when formulated into plastics and coatings, while also reducing energy costs and manufacturing time.
Implementation Method 1
adjustment of the pH of a titanium dioxide slurry to between 3.5 and 7 using a monoprotic acid fluidizing agent
Implementation Method 2
spray drying to promote bonding and reduce cycle times
Implementation Method 3
spray drying to promote bonding and reduce cycle times
Data Source
AI summary
An improved process for making an organosilicon compound surface-treated titanium dioxide material, comprising (a) forming a mixture of the titanium dioxide material in water, (b) wet milling the mixture, (c) adjusting the pH of the slurry resulting from step (b) to between about 5.0 and about 8.5, (d) after step (c), removing the titanium dioxide material from the mixture by vacuum or pressure filtration, (e) after step (d), washing the titanium dioxide material so removed, (f) after step (e), converting the washed titanium dioxide material to a fluid dispersion having a pH of from about 3.5 to less than about 7 via addition of a fluidizing agent comprising a water-soluble monoprotic acid, (g) after, or concurrently with, step (f), adding to the resulting dispersion of titanium dioxide material an organosilicon compound, with mixing, and (h) spray drying the dispersion of the washed titanium dioxide material resulting from step (g) to yield a dry titanium dioxide pigment powder.