Polyester Resin Production via Transesterification and Distillation
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Solution Overview
Problem
The direct esterification method for producing polyester resins with a cyclic acetal skeleton results in wide molecular weight distribution and gelled forms due to decomposition by carboxyl groups and water, leading to inferior moldability and mechanical performance, and existing methods lack efficient purification and recycling of distillates, resulting in low recycling efficiency and reduced resin properties.
Innovation Solution
A method involving a transesterification reaction followed by polycondensation, where a dihydroxyester is formed from a dicarboxylic acid, a polyester resin, and a dicarboxylic acid dialkyl ester with a diol having no cyclic acetal skeleton, and then subjected to distillation under specific conditions to obtain a purified diol unit, which is recycled as a starting material, thereby improving the properties of the polyester resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If direct esterification method is used with a diol having a cyclic acetal skeleton, then polyester resin can be produced, but the cyclic acetal skeleton is decomposed by carboxyl groups and water resulting in wide molecular weight distribution and gelled form
Solution Approach 1:
The patent applies preliminary action by conducting transesterification reaction before polycondensation to pre-form esters with controlled molecular weight. This preliminary step allows the cyclic acetal skeleton to be incorporated into the polymer structure before exposure to conditions that would cause decomposition, thereby preventing wide molecular weight distribution and gelation while maintaining ease of manufacture
Solution Approach 2:
The patent uses transesterification as an intermediary step between direct esterification and polycondensation. This intermediary process allows controlled introduction of the diol with cyclic acetal skeleton into the polyester structure under milder conditions, avoiding direct exposure to harsh carboxyl groups and water that cause decomposition, thus resolving the contradiction between ease of manufacture and manufacturing precision
2Ease of manufacture
If direct esterification method is used with a diol having a cyclic acetal skeleton, then polyester resin can be produced, but the resin has inferior moldability and mechanical performance
Solution Approach 1:
The patent applies preliminary action by conducting transesterification reaction before polycondensation to pre-form esters with controlled molecular weight. This preliminary step allows the cyclic acetal skeleton to be incorporated into the polymer structure before exposure to conditions that would cause decomposition, thereby preventing wide molecular weight distribution and gelation while maintaining ease of manufacture
Solution Approach 2:
The patent uses transesterification as an intermediary step between direct esterification and polycondensation. This intermediary process allows controlled introduction of the diol with cyclic acetal skeleton into the polyester structure under milder conditions, avoiding direct exposure to harsh carboxyl groups and water that cause decomposition, thus resolving the contradiction between ease of manufacture and manufacturing precision
3Productivity
If distillates are not purified and recycled, then production efficiency is low, but purifying and recycling distillates requires additional processing steps
Solution Approach 1:
The patent applies self-service by designing a purification system that automatically removes decomposition products and impurities from distillates during the production process. The system uses selective dissolution and filtration mechanisms that operate continuously without requiring separate manual purification steps, thereby improving recycling efficiency while avoiding additional processing complexity
Solution Approach 2:
The patent introduces an intermediary purification step that selectively removes decomposition products from distillates before recycling. This intermediary process uses specific solvents and filtration mechanisms that target only the harmful impurities, allowing efficient recycling without requiring complex multi-step purification procedures, thus resolving the contradiction between productivity and device 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
This method efficiently purifies diols in the reaction system, producing polyester resins with improved properties, such as enhanced mechanical performance and moldability, by effectively recycling and purifying the diol units, thus overcoming the limitations of existing methods.
Implementation Method 1
decomposing a distilled-off diol mixture (C) comprising the component (B) and/or the component (A) under a pH condition of 10 or lower such that a concentration of the component (A) in the component (C) is 0.5% by mass or lower
Implementation Method 2
distilling the decomposed component (C) to obtain a purified diol (B1) comprising the component (B)
Data Source
AI summary
The present invention provides a method for producing a polyester resin comprising dicarboxylic acid units and diol units, wherein at least a portion of the diol units is a diol unit having a cyclic acetal skeleton, the method comprising specific steps (1) to (4-2).