Marine Lubricant Base Stock Density Control
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Solution Overview
Problem
Conventional lubricants, particularly polyalkylene glycol (PAG) base stocks, are not environmentally friendly due to low biodegradability and can cause harm when discharged into water, leading to undesirable sheening on water surfaces.
Innovation Solution
A lubricant base stock comprising at least 87 wt % of (EO)(PO)(EO) block co-polymers with specific kinematic viscosities and molecular weights, which allows temperature-dependent solubility and density variation, ensuring the lubricant is denser than seawater at lower temperatures and lighter at higher temperatures, preventing surface sheening if discharged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional polyalkylene glycol (PAG) base stocks are used, then lubrication performance is achieved, but environmental harm occurs due to low biodegradability and surface sheening
Solution Approach 1:
The invention changes the molecular structure parameters of PAG from random copolymers to block copolymers with specific (EO)5-(PO)25-(EO)5 architecture. This structural parameter change enables temperature-dependent solubility and density variations, allowing the lubricant to sink in cold water (preventing sheening) while maintaining lubrication performance across operating temperatures.
Solution Approach 2:
The invention uses a composite approach by blending different block copolymer variants with varying molecular weights and viscosity characteristics. The base stock comprises multiple block copolymers (e.g., C5P25E5/C5P30E5, C7P25E7/C7P30E7) to achieve both environmental compatibility and optimal lubrication properties that single components cannot provide alone.
2Object-affected harmful factors
If biodegradable lubricants are used to reduce environmental impact, then surface sheening is prevented, but lubrication effectiveness may be compromised
Solution Approach 1:
The invention exploits the dynamic temperature-dependent properties of block copolymers. At low temperatures, the lubricant is water-soluble and sinks (preventing sheening). At operating temperatures, the lubricant maintains appropriate viscosity and film-forming characteristics for effective lubrication. This dynamic behavior resolves the contradiction between environmental safety and performance.
Solution Approach 2:
The block copolymer structure enables controlled changes in solubility and density parameters with temperature. The (EO)5-(PO)25-(EO)5 architecture provides a cloud point around 20-40°C, creating a transition from water-miscible (cold) to water-immiscible (hot) state, thereby preventing sheening while maintaining lubrication effectiveness at operating temperatures.
3Object-affected harmful factors
If lubricant density is increased to prevent floating and sheening, then environmental compatibility improves, but lubrication performance may deteriorate due to excessive viscosity
Solution Approach 1:
The invention uses the dynamic density variation of block copolymers with temperature. At discharge temperatures (below 20°C), the lubricant density exceeds seawater density (1025 kg/m³), causing it to sink and preventing sheening. At operating temperatures (above 40°C), the density decreases, and the lubricant maintains appropriate flow characteristics for effective lubrication.
Solution Approach 2:
The block copolymer structure enables temperature-dependent density changes. The (PO)25 mid-block provides hydrophobic character that increases density, while the (EO)5 end-blocks provide water solubility at low temperatures. This parameter change with temperature resolves the contradiction between density (for environmental compatibility) and viscosity (for lubrication performance).
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 lubricant base stock is biodegradable, non-sheening, and suitable for marine environments, maintaining effective lubrication properties while minimizing environmental impact.
Implementation Method 1
The block structure of the co-polymers may allow the base stock to partition between water solubility and insolubility depending on temperature
Implementation Method 2
the base stock is denser than seawater at a temperature below about 20° C. but is lighter than seawater at a temperature above about 40° C.
Data Source
AI summary
The present invention relates to a lubricant base stock, lubricant formulations, a method of lubricating a rotating shaft within a stern tube and the use of a lubricant base stock. The base stock and lubricant formulations may be particularly suited for use in aqueous environments (including fresh water or salt water). A lubricant base stock comprising a first (EO)(PO)(EO) block co-polymer and a second (EO)(PO)(EO) block co-polymer which is different from the first (EO)(PO)(EO) block co-polymer in a marine lubricant formulation wherein the lubricant base stock has a density of at least 1028 kg/m3 at 20° C. and at most 1022 kg/m3 at 40° C. in particular is provided.