Alkyl Lactate Sulfate Surfactant pH Stability
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Solution Overview
Problem
Sulfated esters of oligohydroxycarboxylic acids used as surfactants exhibit a tendency to hydrolysis, which negatively impacts their storage stability, leading to pH changes during storage at elevated temperatures.
Innovation Solution
Aqueous surfactant compositions comprising alkyl lactate sulfates, phosphoric acid and its salts, citric acid and its salts, and water, with specific weight ratios and pH ranges, are formulated to enhance storage stability by maintaining a stable pH over 90 days at 40°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sulfated esters of oligohydroxycarboxylic acids are used as surfactants, then strong foaming ability and cleaning power are achieved, but storage stability deteriorates due to hydrolysis tendency
Solution Approach 1:
Buffer substances (phosphoric acid and citric acid) are introduced as intermediary substances to mediate between the surfactant and the hydrolysis reaction. These buffers act as pH regulators that intervene in the chemical environment, preventing the ester groups from undergoing hydrolysis by maintaining the pH within the optimal range of 4.5-7.5.
Solution Approach 2:
The pH parameter is actively controlled and changed to a specific range (4.5-7.5) through the addition of buffer substances. This parameter change creates an unfavorable environment for hydrolysis while maintaining the surfactant's functional properties, thereby resolving the contradiction between stability and activity.
2Stability of the object's composition
If alkyl lactate sulfates are formulated without buffer substances, then simplicity of composition is maintained, but pH stability deteriorates during storage at elevated temperatures
Solution Approach 1:
Buffer substances serve as intermediary agents that stabilize the pH without requiring complex formulation strategies. The simple dual-buffer system (phosphoric acid + citric acid) provides robust pH stability, demonstrating that controlled complexity can enhance rather than hinder composition stability.
3Reliability
If buffer substances are added to alkyl lactate sulfate compositions, then storage stability is improved, but formulation complexity increases
Solution Approach 1:
The invention creates a composite surfactant formulation by combining alkyl lactate sulfates with a specific composite buffer system (phosphoric acid and citric acid in defined ratios). This composite approach provides synergistic stability while maintaining manageable formulation complexity through established weight ratio ranges.
Solution Approach 2:
By defining specific parameter ranges (weight ratios of 1:5 to 1:10 for buffers to surfactant, and 1:1.2 to 1:3 for phosphoric to citric acid), the formulation complexity is controlled through quantitative specifications rather than qualitative complexity, enabling scalable production.
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 compositions demonstrate improved storage stability, with a pH change of 1.2 or less after 90 days at 40°C, maintaining clarity and homogeneity, and showing better resistance to hydrolysis compared to unbuffered samples.
Implementation Method 1
one or more compounds (B) selected from the group comprising phosphoric acid and the mono-, di- and tri-salts thereof, one or more compounds (C) selected from the group comprising citric acid and the mono-, di- and tri-salts thereof
Implementation Method 2
these compounds exhibit a certain tendency to hydrolysis due to the ester groups, which has a negative impact on the storage stability
Data Source
AI summary
Compositions containingone or more alkyl lactate sulfate (A) of the general formula (I),R1(OCOCH(CH3))nOSO3M1 (I)in which the radical R1 is a linear or branched alkyl or alkenyl radical having 6 to 30 carbon atoms, the index n is a number in the range from 1 to 5, and the radical M1 is selected from H, Li, Na, K, Ca/2, Mg/2, ammonium, and alkanolamine,one or more compound (B) selected from phosphoric acid and the mono-, di- and tri-salts thereof, wherein the cation of these salts is selected from Li, Na, K, Ca, Mg, ammonium, and alkanolamine,one or more compound (C) selected from citric acid and the mono-, di- and tri-salts thereof, wherein the cation of these salts is selected from Li, Na, K, Ca, Mg, ammonium, and alkanolamine, andwaterwhere the following provisos apply:the weight ratio of the sum total of the compounds (B) and (C) to the sum total of the compound (A) is in the range from 1:5 to 1:10.the weight ratio of the sum total of the compound (B) to the sum total of the compound (C) is in the range from 1:1.2 to 1:3.the pH of the compositions is in the range from 4.5 to 7.5.