Low-Salt Polysulfide Synthesis via Segmented Pre-Polymer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional processes for synthesizing polysulfides lack control over the sulfur to oxygen ratio, leading to conflicting requirements for chemical resistance and compatibility with surfaces, and result in significant salt production with environmental and economic drawbacks.
Innovation Solution
A process involving the reaction of bis(2-chloroalkyl)formal with sodium polysulfide or a combination of sodium hydrosulfide and sulfur, in the absence of dihaloalkane, using a pre-polymer structure that allows adjustment of the sulfur to oxygen ratio, reducing by-product formation and salt production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional processes use bis(2-chloroalkyl)formal with fixed oxygen content, then the synthesis is simple, but the polarity control is limited
Solution Approach 1:
The process segments the synthesis into two independent stages: first forming a pre-polymer with controlled oxygen content from polyol and formaldehyde, then reacting with sodium polysulfide. This allows independent optimization of oxygen content in stage 1 and polysulfide content in stage 2, enabling precise control over the final S/O ratio and polarity.
Solution Approach 2:
The pre-polymer is prepared in advance with a specific oxygen content before reacting with sodium polysulfide. This preliminary action allows the oxygen framework to be established first, providing a controlled base for subsequent sulfur incorporation, thereby enabling precise polarity control in the final product.
2Adaptability or versatility
If higher oxygen content is introduced to improve polarity and surface compatibility, then compatibility with glass and metals improves, but chemical resistance against oil and fuel deteriorates
Solution Approach 1:
The process enables independent adjustment of oxygen content (via pre-polymer composition) and sulfur content (via sodium polysulfide amount), allowing optimization of the S/O ratio to simultaneously achieve desired polarity for surface compatibility and sufficient sulfur content for chemical resistance against oil and fuel.
3Ease of manufacture
If conventional processes use high chlorine content halides, then the synthesis is straightforward, but large quantities of salt are formed as by-product
Solution Approach 1:
The process extracts and eliminates the source of excessive salt formation by replacing conventional high-chlorine dihaloalkanes with a two-stage system using formaldehyde and sodium polysulfide. This removes the harmful by-product generation while maintaining synthesis feasibility.
Solution Approach 2:
The process converts the previously harmful high-chlorine reagents into a beneficial low-salt system by using formaldehyde and sodium polysulfide that produce minimal salt by-products, turning a harmful synthesis approach into an environmentally friendly one.
4Shape
If liquid polymers are prepared by splitting chains of solid polymers, then liquid polysulfides are obtained, but the sulfur content remains relatively high and polarity is low
Solution Approach 1:
Instead of splitting solid polymer chains to obtain liquid polysulfides (which preserves high sulfur content), the process inverts the approach by synthesizing liquid polysulfides directly from pre-polymer and sodium polysulfide. This allows control over the S/O ratio and polarity from the beginning, producing liquid polymers with adjustable polarity rather than fixed high-sulfur characteristics.
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
This process enables control over the polarity of polysulfides, improving compatibility and chemical resistance, while minimizing salt production and maintaining comparable application properties to conventional polysulfides.
Implementation Method 1
synthesizing polysulfide polymers by condensation polymerization reactions between organic dihalides such as dichloroalkanes and alkali metal salts of polysulfide anions
Implementation Method 2
The reaction is preferably performed by heating the reaction mixture to a temperature in the range 60 to 100°C, more preferably from 80 to 95°C and most preferably from 85 to 90°C
Data Source
AI summary
Process for the preparation of a polysulfide comprising the step of reacting a bis(2-dihaloalkyl)formal with either (i) sodium polysulfide or (ii) a combination of sodium hydrosulfide and sulfur, the reaction being performed in the absence of a dihaloalkane and in the presence of a prepolymer (I) according to structure X-(R2-O)n-CH2-O-(R1-O)m-CH2-(O-R2)p-X, wherein R1 and R2 can be the same or different and are selected from alkane chains containing 2-10 carbon atoms, X is a halogen atom, and n, m, and p are integers that can be the same or different and have a value in the range 1 - 6.