Catalyst-Free Aromatic-Aliphatic Copolyester Synthesis
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Solution Overview
Problem
Existing methods for synthesizing aromatic-aliphatic copolyesters require catalysts, which lead to side reactions, accelerated aging, and environmental and health hazards due to toxic heavy metal residues, limiting their application in food and medical fields.
Innovation Solution
A method for synthesizing aromatic-aliphatic copolyesters without catalysts, involving a prepolymerization stage with aromatic and cyclic dicarboxylic acids followed by a polymerization stage under reduced pressure, where the cyclic dicarboxylic acid forms anhydrides and spontaneously adjusts the alcohol-acid ratio to produce high-molecular-weight copolyesters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If catalysts are used in the synthesis of aromatic-aliphatic copolyesters, then the polymerization reaction efficiency is improved, but toxic heavy metal residues remain in the product causing health and environmental hazards
Solution Approach 1:
The patent removes the catalyst component from the polymerization system entirely, extracting the harmful element while maintaining the core polymerization function through alternative mechanisms (direct esterification and transesterification without catalyst). This resolves the contradiction by eliminating toxic residues while preserving productivity through optimized reaction conditions.
Solution Approach 2:
The patent introduces an intermediary approach by using a two-stage process where the first stage produces prepolymers with controlled carboxyl termination, and the second stage completes polymerization. This intermediary step allows catalyst-free operation while maintaining efficient polymerization through controlled molecular weight buildup and end-group chemistry.
2Speed
If catalysts are used in the synthesis process, then the polymerization speed increases, but side reactions occur and product aging is accelerated
Solution Approach 1:
The patent segments the polymerization process into two distinct stages: prepolymerization to build initial chains with controlled end groups, and subsequent polymerization to increase molecular weight. This segmentation allows each stage to be optimized independently, achieving fast initial polymerization while maintaining long-term product stability through controlled chemistry at each stage.
Solution Approach 2:
The patent performs preliminary action by completing the esterification and establishing controlled end-group chemistry in the first stage before proceeding to the second stage. This preliminary establishment of molecular architecture prevents unwanted side reactions during the main polymerization, ensuring both speed and reliability.
3Ease of manufacture
If conventional catalysts are used for esterification and transesterification, then the copolyester synthesis is achieved, but the storage time and service life are shortened due to accelerated aging
Solution Approach 1:
The patent employs self-service by designing a system where the polymer chains themselves participate in the transesterification reactions without external catalysts. The terminal carboxyl and hydroxyl groups of prepolymers react with each other in a self-catalyzed manner, eliminating the need for harmful catalysts and thereby extending product lifespan and storage stability.
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 catalyst-free synthesis method results in high-purity, degradable copolyesters suitable for food and medical applications, reducing environmental impact and extending storage and service life by avoiding toxic residues and side reactions.
Implementation Method 1
the alcohol-acid ratio is spontaneously adjusted during polymerization by means of the properties of autocatalysis and anhydride formation of such monomer
Implementation Method 2
subjecting raw materials comprising an aromatic dicarboxylic acid, a dihydric alcohol and a cyclic dicarboxylic acid or a corresponding anhydride thereof to an esterification reaction
Implementation Method 3
Existing methods for synthesizing the copolyesters usually include a two-step melting and condensation polymerization method in the presence of a catalyst, and the method specifically includes two stages including esterification and transesterification
Data Source
AI summary
The present invention discloses a method for synthesizing an aromatic-aliphatic copolyester without a catalyst and a product thereof. The method includes: a prepolymerization stage: under the condition of not adding a catalyst, subjecting raw materials including an aromatic dicarboxylic acid, a dihydric alcohol and a cyclic dicarboxylic acid or a corresponding anhydride thereof to an esterification reaction to obtain a carboxyl-terminated prepolymer, where the total molar amount of the dicarboxylic acids is greater than the molar amount of the dihydric alcohol; and a polymerization stage: under the condition of reduced pressure, removing the anhydride corresponding to the cyclic dicarboxylic acid from the carboxyl-terminated prepolymer at a reaction temperature not lower than the boiling point of the anhydride corresponding to the cyclic dicarboxylic acid to obtain an aromatic-aliphatic copolyester. According to the method of the present invention, the aromatic-aliphatic copolyester without a catalyst can be prepared, so that the problems of biological toxicity, accelerated aging, shortened storage time and service life and the like caused by a catalyst residue can be avoided. Meanwhile, the aromatic-aliphatic copolyester has degradability, so that the current environmental protection pressure is reduced.