Alkaline Subcritical Water Depolymerization of Thermoplastic Polyesters
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Solution Overview
Problem
Existing chemical recycling technologies for thermoplastic polyesters face challenges such as high energy costs, low efficiency, and difficulty in recycling materials composed of multiple polymers.
Innovation Solution
A method involving the use of subcritical water to depolymerize thermoplastic polyesters, where the reaction conditions are optimized to achieve high yields of recycled monomers like dicarboxylic acids and diols, while minimizing energy consumption and preventing overreaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-temperature and high-pressure water is used for depolymerization, then the recovery rate of dicarboxylic acid is enhanced, but the depolymerization time becomes extremely long or the temperature needs to be extremely high
Solution Approach 1:
The patent changes the chemical parameters of the water by adding alkali (sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate) to create alkaline water. This parameter change enables effective depolymerization at moderate temperatures (100-250°C) and reduces depolymerization time while maintaining high recovery rates of dicarboxylic acid, resolving the contradiction between recovery rate and time/temperature requirements.
2Adaptability or versatility
If multiple polymers are simultaneously depolymerized, then the capability to recycle complex polymer compositions is achieved, but the reaction conditions become more complex to control
Solution Approach 1:
The patent develops a universal depolymerization system using alkaline water that can simultaneously process multiple polymer types (polyester, polyamide, polycarbonate, polyurethane) through a single reaction mechanism. The alkaline water acts as a universal solvent and catalyst that effectively breaks down different polymer bonds, enabling one system to perform multiple functions without requiring separate processes for each polymer type.
3Ease of manufacture
If conventional depolymerization methods are used, then the process is simpler, but the energy consumption is high and the efficiency is low
Solution Approach 1:
The patent introduces alkali (sodium hydroxide, potassium hydroxide, sodium carbonate, or potassium carbonate) as an intermediary substance that mediates the depolymerization reaction between water and polymers. This intermediary enhances the reactivity of water, enabling efficient depolymerization at lower temperatures and shorter times while maintaining process simplicity, thus resolving the contradiction between ease of manufacture and productivity.
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 enables the efficient recycling of thermoplastic polyesters with high yields of pure dicarboxylic acids and diols, reducing energy costs and facilitating the recycling of complex polymer compositions.
Implementation Method 1
a thermoplastic polyester is depolymerized without use of an organic solvent such as methanol or ethylene glycol... bringing a polyester into contact with high-temperature and high-pressure water
Implementation Method 2
X and X·Y·Z which is the product of X, Y, and Z satisfy the following (I) and (II) simultaneously, assuming that the melting point of the polymer in the composition is Mp°C, as measured using a differential scanning calorimeter, that a reaction temperature is X°C
Data Source
Figure 1~2
AI summary
An object of a recycled monomer and a method of producing the same according to the present invention is to provide a method that can make use of the advantages of high-temperature and high-pressure water, inhibit the overreaction of a product obtained through depolymerization, and generate a recycled monomer such as a dicarboxylic acid or a diol with a high yield. In one preferable aspect of the method of producing a recycled monomer according to the present invention, i.e., the method intended to achieve the object, a polymer is a thermoplastic polyester (A), and X and X·Y·Z which is the product of X, Y, and Z satisfy the following (I) and (II) simultaneously, assuming that the melting point of the thermoplastic polyester (A) is Mp°C, as measured using a differential scanning calorimeter, that a reaction temperature is X°C, that a reaction time is Y minute(s), and that the mass ratio of water to the thermoplastic polyester (A) is Z:1. Mp≤X<300 2000≤X⋅Y⋅Z≤20000