pH-Responsive Associative Thickener for Tinted Coatings
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Solution Overview
Problem
Existing associative thickeners in aqueous polymer systems experience a significant drop in viscosity when colorants are added, requiring high surfactant concentrations or organic solvents to maintain viscosity, which are costly and environmentally unfriendly.
Innovation Solution
An aqueous associative thickener composition with a polyoxyalkylene or polysaccharide backbone and oligomeric hydrophobes containing secondary, tertiary amines, or phosphines, which are protonated or deprotonated to adjust solubility and viscosity, allowing for high active solids content without volatile organic solvents or costly additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high solids concentration is used in associative thickeners, then thickening efficiency is improved, but viscosity becomes too high for pourability
Solution Approach 1:
The patent applies parameter changes by modifying the chemical structure of hydrophobic groups (using secondary/tertiary amines or phosphines instead of traditional groups) and adjusting pH to protonate these groups. This protonation changes the hydrophobicity parameter, allowing the thickener to maintain high solids concentration (5-50% or higher) while reducing aqueous viscosity to pourable levels through the suppression of hydrophobic associations at low pH.
2Productivity
If conventional associative thickeners are used in tinted systems, then initial viscosity is achieved, but viscosity drops significantly when colorant is added
Solution Approach 1:
The patent uses parameter changes by selecting hydrophobic groups with ionizable functionality (secondary/tertiary amines or phosphines) whose hydrophobicity can be modulated by pH. In the presence of colorants and surfactants, the pH-dependent association behavior maintains viscosity stability, as the protonated form prevents excessive disruption of the thickening network.
Solution Approach 2:
The patent employs composite materials by combining the polymeric backbone with specific oligomeric hydrophobe blocks containing ionizable groups. This composite structure allows the thickener to function effectively in complex tinted systems, where the hydrophobic blocks provide the necessary associations for viscosity while the ionizable groups offer responsiveness to environmental changes from colorant addition.
3Ease of operation
If surfactant or cyclodextrin is used to suppress viscosity, then pourability is improved, but cost increases and thickening efficiency decreases
Solution Approach 1:
The patent applies the taking out principle by removing the need for external viscosity-suppressing additives like surfactants or cyclodextrin. Instead, the thickener molecule itself contains ionizable groups that can be protonated to suppress viscosity, eliminating the requirement for separate suppressant components and their associated costs and complexity.
Solution Approach 2:
The patent implements self-service by designing the thickener to regulate its own viscosity through pH-dependent protonation of its hydrophobic groups. The thickener molecule self-regulates its association state based on environmental pH, eliminating the need for external agents to control viscosity, thereby reducing formulation complexity and cost.
4Ease of operation
If organic solvent is added to achieve high solids concentration, then pourability is improved, but environmental compliance becomes problematic due to VOC content
Solution Approach 1:
The patent applies parameter changes by using pH control to protonate the ionizable hydrophobic groups, which suppresses hydrophobic associations and reduces viscosity. This allows achievement of high solids concentration with pourable viscosity using only water as the solvent, eliminating VOC-containing organic solvents and meeting environmental compliance requirements.
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 maintains viscosity in tinted systems without surfactant or cyclodextrin, providing cost-effective and environmentally friendly thickening, ensuring pourable viscosity and effective film build in coatings.
Implementation Method 1
sufficient acid to substantially protonate the secondary amine, or the tertiary amine, or the tertiary phosphine, or combination thereof
Implementation Method 2
aqueous associative thickener polymer composition... comprising blocks of oligomeric hydrophobes... wherein said blocks of oligomeric hydrophobes are attached to or within the polymer backbone
Data Source
AI summary
A polymer composition with blocks of hydrophobes attached to or within the backbone of an associative thickener. The blocks are composed of two or more units of the same or different hydrophobes whereby the hydrophobe is reversibly switched between being hydrophilic and hydrophobic in nature. When the hydrophobe is rendered hydrophilic, the aqueous thickener is pourable and readily incorporated into aqueous polymer compositions. When this hydrophobe is rendered hydrophobic, the thickener performs its thickening function efficiently, especially in tinted systems. Switching is readily accomplished by adjusting the pH of the associative thickener composition and the aqueous polymer composition being thickened.