Biodegradable PAG Hydraulic Fluids With Low Foaming Rheology Control
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Solution Overview
Problem
Existing water-based lubricants, particularly those containing high molecular weight polyalkylene glycols, suffer from low biodegradability and excessive foaming, which is undesirable for applications in metalworking, gear oils, and hydraulic fluids, especially in subsea environments.
Innovation Solution
A composition comprising low molecular weight oxyethylene/oxypropylene block copolymers with a biodegradability of at least 60% and low allyl content, prepared using a Double Metal Cyanide catalyst for the oxypropylene block and Potassium Hydroxide for the oxyethylene block, to maintain rheology and reduce foaming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high molecular weight polyalkylene glycols are used as rheology modifiers, then sufficient thickening efficiency is achieved, but biodegradability deteriorates
Solution Approach 1:
The patent changes the molecular weight parameter of polyalkylene glycols from high (12,000 g/mol or higher) to low (less than 4,000 g/mol), which fundamentally alters both the thickening efficiency and biodegradability characteristics. This parameter change enables the fluid to achieve adequate rheology properties while significantly improving biodegradability to 60% or higher.
2Reliability
If conventional polyalkylene glycols are used in water-based hydraulic fluids, then desired rheology properties are maintained, but foaming increases
Solution Approach 1:
The patent modifies the molecular weight parameter of polyalkylene glycols from high to low, which directly reduces foaming tendencies while preserving rheology properties. The low molecular weight PAGs (less than 4,000 g/mol) exhibit significantly lower foam stability and faster foam collapse rates compared to conventional high molecular weight PAGs.
3Object-generated harmful factors
If low molecular weight polyalkylene glycols are used, then biodegradability improves, but thickening efficiency deteriorates
Solution Approach 1:
The patent optimizes the molecular weight parameter to a specific range (less than 4,000 g/mol but sufficient to provide adequate thickening), and combines this with specific compositional parameters (oxyethylene content of 20-80%, low allyl content) to achieve both high biodegradability and sufficient rheology modification.
4Reliability
If high molecular weight polyalkylene glycols are used, then sufficient rheology control is achieved, but environmental impact worsens
Solution Approach 1:
The patent changes the molecular weight parameter from high to low, which fundamentally improves environmental impact by increasing biodegradability to 60% or higher. This parameter change allows the fluid to maintain adequate rheology control while being much more environmentally friendly and suitable for subsea applications where environmental protection is critical.
Data Source
AI summary
A composition comprising water and a polyalkylene glycol having an allyl content of less than 20 μeq/g, which composition has reduced foaming properties and preferably a biodegradability of at least 60% as determined using OECD 301F. The polyalkylene glycol can be made by forming a first intermediate comprising an oxypropylene block by reacting propylene oxide with a polyol initiator in the presence of a Double Metal Cyanide catalyst, and then reacting the first intermediate with ethylene oxide in the presence of a KOH catalyst.