Recycling Superabsorbent Polymer via Extensional Flow
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Solution Overview
Problem
Current methods for recycling superabsorbent polymers (SAP) into poly(acrylic acid) (PAA) require high energy and long times, often leading to decarboxylation and inferior product properties, which hinders the efficient recycling and reuse of SAP in absorbent hygiene products and other applications.
Innovation Solution
The use of an extensional flow device with short residence times and optional cavitation to degrade SAP into PAA, achieving a concentration greater than 1 wt% and requiring less than 50 MJ/kg of energy, while maintaining the carboxylic groups and producing a product with a weight-average molecular weight less than 1,000,000 g/mol.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional methods are used to degrade SAP into PAA, then complete degradation can be achieved, but high energy consumption and long processing time are required
Solution Approach 1:
The invention changes the physical parameters of the degradation process by using extensional flow conditions with specific residence times (0.1-120 seconds) and extension rates (0.1-100 s⁻¹), along with controlled temperature and pressure parameters, to achieve rapid SAP degradation into PAA with molecular weight less than 1,000,000 g/mol while consuming less than 50 MJ/kg energy, thus resolving the contradiction between degradation completeness and energy efficiency
2Reliability
If conventional degradation methods are used, then SAP can be converted to PAA, but decarboxylation occurs leading to inferior product properties
Solution Approach 1:
The invention applies extensional flow conditions with residence times of 0.1-120 seconds to rapidly degrade SAP into PAA before decarboxylation can occur. The high extension rates (0.1-100 s⁻¹) enable the degradation process to complete quickly, producing high-quality PAA with molecular weight less than 1,000,000 g/mol while maintaining carboxylic groups and avoiding the time-loss decarboxylation problem
3Productivity
If long residence times are used for SAP degradation, then complete conversion to PAA is achieved, but energy consumption increases and product properties deteriorate
Solution Approach 1:
The invention uses dynamic extensional flow conditions with residence times of 0.1-120 seconds and extension rates of 0.1-100 s⁻¹ to control the degradation process. This dynamic approach allows complete SAP conversion to PAA while maintaining molecular weight less than 1,000,000 g/mol and avoiding over-degradation, thus resolving the contradiction between conversion efficiency and molecular weight control
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 method effectively degrades SAP into PAA with improved molecular weight distribution and energy efficiency, enabling the recycling of SAP into high-quality products that can be reused in various applications, such as adhesives, coatings, and water treatment, while reducing environmental impact.
Implementation Method 1
a feed stream comprising SAP is fed into the extensional flow device and a product stream is produced, which comprises essentially poly(acrylic acid) (PAA)
Implementation Method 2
Recycling of superabsorbent polymer with an extensional flow device at short residence times, with optional and additional cavitation
Data Source
AI summary
Poly(acrylic acid)-based superabsorbent polymer (SAP) in a feed stream is converted into poly(acrylic acid) (PAA) in an extensional flow device. The total energy used to degrade the SAP into PAA is less than about 50 MJ/kg SAP.