Plasticiser Ester Purification via Alkali Treatment and Filtration
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Solution Overview
Problem
The existing purification processes for plasticiser esters, such as those used in polyvinyl chloride and polyurethane production, face issues with high sodium levels leading to pre-polymerization of isocyanates and reduced filterability due to titanium hydroxide agglomeration, resulting in suboptimal electrical properties and filtration efficiency.
Innovation Solution
A process involving treatment of crude esters with an alkaline aqueous solution using less than stoichiometric amounts of alkali metal salts and controlled water levels, followed by filtration and water removal under vacuum, to minimize sodium content and prevent titanium hydroxide agglomeration, enhancing filterability and electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional purification processes using aqueous alkali are used to neutralize crude esters, then catalyst residues and mono-esters are removed, but high sodium levels remain in the final product
Solution Approach 1:
The patent changes the chemical parameter by substituting sodium hydroxide with potassium hydroxide as the neutralizing agent. This substitution maintains the neutralization effectiveness while changing the alkali metal residue from sodium to potassium, thereby resolving the contradiction between purification effectiveness and sodium content control
Solution Approach 2:
The patent employs a multi-stage filtration system using disposable filter aids (diatomaceous earth, activated carbon, clay) that are sacrificed during the process to capture and remove alkali metal residues and other contaminants. These filter aids are consumed in the process, allowing effective removal of impurities without contaminating the final product with reusable filter media
2Reliability
If excess water is used in the neutralization process, then hydrolysis and neutralization are enhanced, but filtration efficiency decreases due to agglomeration
Solution Approach 1:
The patent applies different water amounts at different stages of the process. A controlled amount of water (0.7-1.4 wt%) is used during neutralization to prevent excessive agglomeration, while subsequent filtration stages use dry filter aids. This localized control of water distribution resolves the contradiction between neutralization completeness and filtration efficiency
Solution Approach 2:
The patent introduces filter aids (diatomaceous earth, activated carbon, clay) as intermediary substances that mediate between the aqueous neutralization mixture and the final filtered product. These intermediaries capture alkali metal residues and organic contaminants while maintaining filter permeability, thus resolving the contradiction between thorough neutralization and efficient filtration
3Productivity
If titanium catalyst is used for esterification, then catalytic activity is high, but titanium hydroxide residues cause pre-polymerization of isocyanates
Solution Approach 1:
The patent systematically extracts titanium catalyst residues through multiple filtration stages using specialized filter aids. The diatomaceous earth, activated carbon, and clay filters work together to adsorb and remove titanium hydroxide particles from the ester product, thereby eliminating the harmful pre-polymerization effect while maintaining the benefits of titanium catalysis during production
Solution Approach 2:
The patent employs consumable filter aids that are sacrificed during the filtration process to capture titanium residues. These disposable filter media (diatomaceous earth, activated carbon, clay) are designed to be consumed in the process, effectively removing titanium hydroxide without introducing reusable filter media that could contaminate the final product
4Reliability
If stoichiometric amounts of alkali are used for neutralization, then complete neutralization is achieved, but sodium levels in the final product increase
Solution Approach 1:
The patent changes the alkali metal parameter by substituting sodium hydroxide with potassium hydroxide. This substitution allows complete neutralization to proceed while changing the residue from sodium to potassium, thereby resolving the contradiction between neutralization completeness and sodium content control in the final product
Solution Approach 2:
The patent uses consumable filter aids (diatomaceous earth, activated carbon, clay) that are sacrificed during filtration to capture and remove alkali metal residues. These disposable filter media enable complete neutralization while preventing alkali metal contamination of the final product through their sacrificial filtration action
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 process produces plasticiser esters with reduced sodium levels, improved filterability, and enhanced electrical resistivity, suitable for high-quality applications in PVC electrical insulation and polyurethane production, while maintaining stability and preventing pre-polymerization issues.
Implementation Method 1
contacting the crude ester with aqueous alkali such as sodium hydroxide or sodium carbonate. The addition of the water and the alkali hydrolyses and/or neutralises catalyst residues and neutralises any undesirable mono-ester that may be present
Implementation Method 2
The addition of the water and the alkali hydrolyses and/or neutralises catalyst residues
Implementation Method 3
Finally any excess alcohol and water may be removed by flashing or stripping with a vapour, e.g., with steam or nitrogen
Data Source
AI summary
Compositions including a C6 to C13 phthalate ester containing titanium but in an amount less than 0.01 ppm by wt of titanium, prepared by titanium catalyzed esterification, and containing from 0.1 to 2.0 wt % of an antioxidant, are provided.