Polyester Monomer Slurry Recycling Without Evaporation Blockage
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Solution Overview
Problem
Existing methods for recycling monomers from condensation polymers, such as polyesters, face challenges in efficiently preparing and using monomer products with residual liquid content, forming energy-intensive byproducts, and separating contaminants that solidify during cooling, which can lead to reactor blockages.
Innovation Solution
A method involving the preparation of a monomer slurry with a specific composition and conditions to maintain it in liquid form, optimizing solvent recovery, and controlled cooling to precipitate contaminants, thereby reducing byproduct formation and facilitating efficient recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If the recycled monomer product is added to the conventional polyester preparation process, then the monomer recycling is achieved, but the mole ratio of total A and B units shifts requiring increased evaporation energy and causing viscosity changes
Solution Approach 1:
The patent changes the physical state parameter of the recycled monomer product from solid to liquid by controlling temperature above the melting point (e.g., above 80°C for BHET). This parameter change allows the liquid monomer to be directly fed into the reactor without evaporation, eliminating the energy-intensive evaporation step while maintaining the desired mole ratio in the polymerization process
Solution Approach 2:
The patent performs preliminary melting of the recycled monomer product before feeding it to the reactor. By pre-heating the solid monomer to its liquid state in advance, the process avoids the need for high-energy evaporation during polymerization, thus resolving the contradiction between recycling efficiency and energy consumption
2Device complexity
If the recycled monomer product with residual liquid content is used directly, then the processing complexity is reduced, but contaminants that solidify during cooling can cause reactor blockages
Solution Approach 1:
The patent applies local quality control by heating the recycled monomer product to a temperature above its melting point specifically in the feeding zone and reactor inlet. This localized temperature control ensures the monomer remains in liquid form where it is fed, preventing solidification and blockages in the feeding system while allowing the rest of the process to proceed with reduced complexity
Solution Approach 2:
The patent employs beforehand cushioning by maintaining the recycled monomer product in a liquid state through temperature control before it enters the reactor. This preventive measure ensures that contaminants do not solidify and block the reactor, thus maintaining reliability without adding complex filtration or separation systems
3Manufacturing precision
If flash evaporation is used to reduce liquid content before particle forming, then the particle quality is improved, but the energy consumption increases significantly
Solution Approach 1:
The patent changes the temperature parameter to above the melting point of the monomer (e.g., above 80°C), transforming the monomer from solid to liquid state. This parameter change eliminates the need for flash evaporation to remove liquid content, as the residual liquid is now the desired state for direct polymerization feed, thus improving particle quality without the energy penalty of evaporation
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 method enables the efficient recycling of monomers into polyesters by minimizing energy consumption, reducing byproduct formation, and preventing reactor blockages, thus creating a sustainable recycling loop.
Implementation Method 1
providing a recycled monomer product obtained by depolymerization of a polyester, wherein said recycled monomer product comprises a condensation monomer and wherein the melting point of the condensation monomer is above ambient conditions... maintaining the recycled monomer product in liquid form
Implementation Method 2
controlled cooling to precipitate contaminants, thereby reducing byproduct formation and facilitating efficient recycling
Data Source
AI summary
The present invention is related to a method for the preparation of a polyester, comprising the steps of providing a monomer slurry from a recycled monomer product and at least one diacid monomer, where the monomer product contains 50% to 97% of a condensation monomer and 3% to 50% by weight of a substance which is liquid at ambient conditions, and using the monomer slurry for the polymerization of a polyester, wherein the step of preparing said monomer slurry is executed in a way that allows to maintain the monomer slurry in liquid form. The present invention is furthermore related to solid particles comprising a recycled monomer product and a diacid monomer B at a mole ratio of B″ units —OC—R2—CO— to diacid HOOC—R2—COOH in the range of 5:1 to 1:5. Further the present invention is related to a method for providing a recycled monomer product, where the monomer product contains 50% to 97% by weight of a condensation monomer and 3% to 50% by weight of a substance which is liquid at ambient conditions.