Aqueous Pigment Paste pH Control for Preservative-Free Stability
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Solution Overview
Problem
Aqueous pigment pastes are susceptible to microbial contamination due to their high pH values, leading to potential microbial growth during storage and handling, which can cause skin irritation and are not suitable for allergy sufferers, and conventional preservatives have limitations and risks.
Innovation Solution
An aqueous pigment paste with a pH range of 4.0 to 6.5, containing specific excipients like levulinic acid and pH adjusters, is developed to ensure stability and safety, avoiding organic preservatives and skin irritation, suitable for tinting systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional preservatives are used in aqueous pigment pastes, then storage stability is improved, but health safety and environmental compatibility deteriorate due to allergic reactions and toxic effects
Solution Approach 1:
The patent removes conventional preservatives (isothiazolinones, formaldehyde, pyrithione compounds) from the pigment paste formulation entirely, extracting the harmful substance while maintaining storage stability through alternative means (pH control at 7.5-13.5, antioxidant packages, and chelating agents)
Solution Approach 2:
The patent maintains pH values in the range of 7.5 to 13.5, which creates an unfavorable environment for microbial growth while preserving pigment stability. This parameter change allows preservative-free formulation while maintaining reliability
2Reliability
If high pH values are used in aqueous pigment pastes, then preservative-free storage stability is improved, but skin irritation and harmful effects increase
Solution Approach 1:
The patent introduces amphoteric surfactants and chelating agents as intermediary substances that buffer the high pH environment, reducing direct skin irritation while maintaining the alkaline conditions necessary for preservative-free stability. The antioxidant package also mediates between pH stability and skin compatibility
Solution Approach 2:
The formulation combines multiple components (pigments, amphoteric surfactants, chelating agents, antioxidant packages) into a composite system where the synergistic interaction maintains both high pH stability and reduced skin irritation, creating a multi-functional material that addresses both contradictions
3Object-affected harmful factors
If conventional preservatives are eliminated, then health safety is improved, but storage stability and microbial resistance deteriorate
Solution Approach 1:
The pigment paste formulation is designed to be self-preserving through its inherent pH range (7.5-13.5) that naturally inhibits microbial growth, combined with antioxidant packages and chelating agents that actively protect against degradation without requiring external preservative substances
Solution Approach 2:
By controlling pH within the specific range of 7.5 to 13.5 and using chelating agents to control metal ion activity, the patent creates conditions where the pigment paste self-regulates its stability, eliminating the need for conventional preservatives while maintaining reliability
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 solution provides stable, preservative-free pigment pastes with improved storage stability and reduced skin irritation, suitable for allergy sufferers, and easy processing, ensuring microbial protection without environmental harm.
Implementation Method 1
at least one pH adjusting agent with a pKa of less than 7.0, which is not a component of components b) and d), preferably potassium hydrogen sulfate and/or sodium hydrogen sulfate, particularly preferably potassium hydrogen sulfate, wherein the aqueous pigment paste has a pH value, determined with a pH electrode according to DIN EN ISO 19396-1-1:2022-05 at 23 ± 2 °C, in the range of 4.0 to 6.5
Implementation Method 2
at least one excipient selected from the group consisting of levulinic acid, water-soluble salts of levulinic acid, in particular sodium levulinate
Data Source
AI summary
The invention relates to an aqueous pigment paste comprising a) an organic and/or inorganic pigment, b) at least one excipient, such as levulinic acid or caprylhydroxamic acid, and c) water, wherein the aqueous pigment paste has a pH value in the range of 4.0 to 6.5. The invention further relates to a kit-of-parts coating system comprising or formed from a) at least one aqueous pigment paste according to the invention and b) at least one aqueous coating compound, as well as a tinted aqueous coating system obtainable from the kit-of-parts coating system by mixing the aqueous pigment paste A) with the aqueous coating compound B). The invention also relates to a method for tinting an aqueous coating compound and the use of the aqueous pigment paste according to the invention for coloring water-based paints, varnishes, glazes, plasters, and/or fillers.