Method for producing recycled polyester chips from recycled polyester fabric
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Solution Overview
Problem
Conventional chemical recycling methods for PET fabric require complicated purification procedures, leading to low recovery rates and high material recovery costs due to the presence of impurities like dyes and coating glue, resulting in poor quality recycled polyester chips.
Innovation Solution
A method involving a color removal process to partially remove dyes and coating glue, followed by chemical depolymerization using ethylene glycol to form BHET, simplified purification with activated carbon and crystallization, and granulation to produce recycled polyester chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional chemical de-polymerization is performed directly on PET fabric with impurities, then the de-polymerization product contains BHET, but the purification procedures become extremely complicated and the recovery rate becomes extremely low
Solution Approach 1:
The patent applies preliminary action by performing a color removal process on the PET fabric before chemical de-polymerization. This pre-treatment step removes dyes and coating glue from the fabric, so that when de-polymerization occurs, the resulting BHET requires minimal purification (only filtration and crystallization), thereby dramatically improving recovery rate and simplifying the overall purification procedure
Solution Approach 2:
The patent segments the recycling process into distinct stages: (1) color removal process to eliminate dyes and coating glue, (2) chemical de-polymerization to produce BHET, and (3) simplified purification through filtration and crystallization. This segmentation allows each stage to be optimized independently, preventing impurity carryover that would complicate purification
2Manufacturing precision
If complicated purification procedures are used to remove impurities, then the purity of BHET is improved, but the material recovery cost becomes excessively high
Solution Approach 1:
By performing color removal as a preliminary action before de-polymerization, the patent eliminates the need for expensive multiple purification steps. The pre-removed impurities prevent contamination of BHET, allowing purification to be achieved through simple filtration and crystallization, thereby dramatically reducing material recovery cost while maintaining high purity
Solution Approach 2:
The patent employs inexpensive purification methods (filtration through filter screen and crystallization) instead of expensive purification techniques. The preliminary color removal enables these simple, low-cost purification steps to achieve the required BHET purity, making the overall process economically viable
3Ease of operation
If direct chemical de-polymerization is performed on PET fabric with dyes and coating glue, then the process is simple, but the de-polymerization product contains impurities requiring over-complicated purification
Solution Approach 1:
The patent performs color removal as a preliminary action before de-polymerization. This pre-treatment step removes dyes and coating glue, enabling the subsequent de-polymerization and purification processes to be simple and straightforward, thereby resolving the contradiction between operational simplicity and purification complexity
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
Reduces the complexity of BHET purification procedures, improves recovery rate to at least 80%, and enhances the quality of recycled polyester chips with a whiteness index of not less than 55, while lowering material recovery costs.
Implementation Method 1
using a chemical de-polymerization liquid to chemically depolymerize the recycled polyester fabric, so as to form a de-polymerization product containing bis(2-hydroxyethyl) terephthalate (BHET) and oligomers
Implementation Method 2
performing a purification process, so as to enhance a purity of the BHET in the de-polymerization product
Implementation Method 3
performing a purification process, so as to enhance a purity of the BHET in the de-polymerization product
Data Source
AI summary
A method for producing recycled polyester chips from a recycled polyester fabric is provided. The method includes: providing the recycled polyester fabric attached with dyes and/or coating glue; performing a color removal process to at least partially remove the dyes and/or the coating glue attached to the polyester fabric; performing a de-polymerization process which includes: using a chemical de-polymerization liquid to chemically depolymerize the recycled polyester fabric, so as to form a de-polymerization product containing bis(2-hydroxyethyl) terephthalate (BHET) and oligomers; performing a purification process, so as to enhance a purity of the BHET in the de-polymerization product; and performing a granulation process, so as to re-polymerize the purified BHET and form the recycled polyester chips (r-PET).