Adipic Acid Polyester Viscosity Index Improvers for Aircraft Hydraulic Fluids
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Solution Overview
Problem
Current hydraulic fluids for aircraft face challenges such as high toxicity, environmental hazards, limited fire resistance, and unsuitable viscosity profiles across varying temperatures, particularly at high altitudes, due to the use of trialkyl phosphates and triaryl phosphates, which require additional hazardous additives for compatibility and stability.
Innovation Solution
A hydraulic fluid composition comprising polyesters with 30-50 mol% adipic acid residues and 25-50 mol% specific repeating units, combined with trialkyl phosphates like tributyl phosphate, which eliminates the need for triaryl phosphates, providing improved low-temperature compatibility and viscosity stability without the health and environmental hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If trialkyl phosphates are used as base stock, then fire resistance is improved, but viscosity at increased temperatures becomes too low and wear characteristics worsen
Solution Approach 1:
The patent combines trialkyl phosphate base stock with a specific polyester viscosity index improver containing adipic acid residues and propylene glycol polyesters. This composite formulation maintains the fire resistance of trialkyl phosphate while adding the viscosity enhancement needed for high-temperature operation, eliminating the need for triaryl phosphate additives.
Solution Approach 2:
The patent modifies the viscosity characteristics by introducing a polyester with specific compositional parameters (30-50 mol% adipic acid residues, 25-50 mol% propylene glycol polyester repeating units). This changes the fluid's viscosity-temperature profile to maintain adequate viscosity at elevated temperatures while preserving fire resistance.
2Temperature
If viscosity index improvers are added to trialkyl phosphates, then viscosity at high temperatures is improved, but compatibility at low temperatures deteriorates
Solution Approach 1:
The patent specifies precise compositional parameters for the polyester viscosity index improver: 30-50 mol% adipic acid residues and 25-50 mol% propylene glycol polyester repeating units. This specific parameter range ensures compatibility with trialkyl phosphate at low temperatures while providing the needed viscosity improvement at high temperatures.
Solution Approach 2:
The patent creates a viscosity index improver with non-uniform molecular structure through the specific combination of adipic acid residues and propylene glycol polyester units. This local structural quality allows the polymer to maintain compatibility with trialkyl phosphate across the full temperature range, particularly at low temperatures where phase separation would normally occur.
3Stability of the object's composition
If triaryl phosphates are added to improve low-temperature compatibility, then viscosity stability is improved, but toxicity and environmental hazards worsen
Solution Approach 1:
The patent extracts and eliminates the harmful triaryl phosphate component from the hydraulic fluid formulation. Instead, it uses a polyester viscosity index improver based on adipic acid and propylene glycol polyesters, which provides the necessary low-temperature compatibility without the neurotoxicity and environmental hazards of triaryl phosphates.
Solution Approach 2:
The patent replaces the hazardous triaryl phosphate with a safer, biodegradable polyester additive system. This substitution uses environmentally friendly materials that do not persist in the environment or pose health risks, effectively replacing the harmful substance with a benign alternative.
4Temperature
If polymethacrylate-type viscosity index improvers are used, then viscosity at high temperatures is improved, but compatibility with trialkyl phosphates at low temperatures deteriorates
Solution Approach 1:
The patent changes the chemical structure of the viscosity index improver from polymethacrylate type to polyester type with specific compositional parameters (adipic acid residues and propylene glycol polyester units). This structural parameter change fundamentally alters the compatibility characteristics, enabling low-temperature compatibility with trialkyl phosphate while maintaining high-temperature viscosity improvement.
Data Source
AI summary
The invention is related to a composition for use in hydraulic systems of an aircraft. The composition typically comprises an adipic acid-based polyester in a phosphate ester base stock substantially consisting of trialkyl phosphates.