Mercapto-Terminated Polysulfide Preparation Using Di-Aldehyde Branching
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Solution Overview
Problem
Conventional branching agents for polysulfide polymers, such as 1,2,3-trichloropropane, pose health risks and handling challenges due to cancer-causing properties and high volatility, necessitating the need for safer alternatives that improve ease of handling and reaction efficiency.
Innovation Solution
The process involves reacting formaldehyde with a halo-alcohol in the presence of di-aldehydes or their corresponding acetals and hemiacetals as branching agents, which react with sodium polysulfide or a mixture of sodium hydrosulfide and sulfur to form mercapto-terminated liquid polysulfides, eliminating the need for hazardous substances and enhancing reaction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If 1,2,3-trichloropropane is used as branching agent, then the polysulfide achieves good elastic properties and reinforced hardness, but it causes health risks and handling difficulties due to cancer-causing properties and high volatility
Solution Approach 1:
The patent changes the chemical parameters of the branching agent by substituting 1,2,3-trichloropropane with di-aldehydes (such as glyoxal, glutaraldehyde) and their acetals/hemiacetals. This parameter change maintains the crosslinking functionality while eliminating the harmful properties of the original agent, thereby resolving the contradiction between achieving good elastic properties and avoiding health risks.
Solution Approach 2:
The patent employs di-aldehydes and their derivatives as alternative branching agents that are safer, less volatile, and do not possess carcinogenic properties. These substitutes fulfill the functional requirement for crosslinking without the long-term health hazards associated with trichloropropane, effectively replacing the harmful substance with a safer alternative.
2Strength
If 1,2,3-trichloropropane is used as branching agent, then the polysulfide achieves good elastic properties, but it requires closed system handling and high expenditure for vapour absorption
Solution Approach 1:
The patent modifies the physical and chemical parameters of the branching agent by using di-aldehydes and their acetals/hemiacetals instead of 1,2,3-trichloropropane. This substitution reduces volatility and eliminates carcinogenicity, thereby simplifying handling requirements and reducing the need for expensive closed-system infrastructure and vapour absorption equipment.
3Strength
If conventional branching agents are used, then the polysulfide achieves good mechanical properties, but the reaction process is slow and requires high expenditure
Solution Approach 1:
The patent changes the chemical composition of the branching agent to di-aldehydes and their derivatives, which exhibit improved reactivity compared to 1,2,3-trichloropropane. This parameter change accelerates the crosslinking reaction, thereby improving productivity and reducing the time and cost associated with the manufacturing process while maintaining good mechanical properties.
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 approach allows for the production of polysulfides with improved handling and formulation characteristics, reduced health risks, and enhanced mechanical properties, such as Shore A hardness, while maintaining the chemical resistance and elasticity of the cured polymers.
Implementation Method 1
The branching agent serves to form a three dimensional crosslinked structure after curing of the polysulfide and, consequently, a reinforced hardness with good elastic properties of the cured polymer
Implementation Method 2
reacting (para)formaldehyde with a halo-alcohol to form a reaction mixture comprising bis(2-dihaloalkyl)formal
Implementation Method 3
reacting the reaction mixture of step a) with either (i) sodium polysulfide or (ii) a combination of sodium hydrosulfide and sulfur
Data Source
AI summary
Process for the preparation of a mercapto-terminated liquid polymer comprising the steps of: a) reacting (para)formaldehyde with a halo-alcohol to form a reaction mixture comprising bis(2-dihaloalkyl)formal and b) reacting the reaction mixture of step a) with either (i) sodium polysulfide or (ii) a combination of sodium hydrosulfide and sulfur, wherein the process is performed in the presence of a branching agent selected from the group consisting of di-aldehydes and their corresponding actetals and hemiacetals.