Pentaerythritol Mercaptocarboxylic Ester Purification for Optical Resins
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Solution Overview
Problem
The production of pentaerythritol mercaptocarboxylic esters often results in color deterioration, increased viscosity of polymerizable compositions, and whitening issues in polyurethane-based lenses due to impurities and poor storage stability of 3-mercaptopropionic acid, making it difficult to handle and polymerize effectively.
Innovation Solution
Purifying 3-mercaptopropionic acid to reduce thioester content to less than 5% and controlling bispentaerythritol content in pentaerythritol to less than 7 wt%, ensuring the reaction conditions produce a colorless and transparent pentaerythritol mercaptocarboxylic ester with low viscosity, which when mixed with a polyiso(thio)cyanate, yields a transparent and colorless polyurethane resin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If 3-mercaptopropionic acid is heated to maintain liquid state for handling, then ease of operation is improved, but purity decreases due to excessive heating
Solution Approach 1:
The patent controls the heating temperature parameter within a specific range (not exceeding the melting point of 16.8°C by more than necessary) to maintain the acid in liquid state for easy handling while preventing excessive heating that would degrade purity. This parameter optimization resolves the contradiction between operational ease and manufacturing precision.
2Loss of substance
If impure 3-mercaptopropionic acid is used to reduce production cost, then loss of substance is reduced, but color deterioration and viscosity increase occur
Solution Approach 1:
The patent performs preliminary purification of 3-mercaptopropionic acid before the esterification reaction to remove impurities that would cause color deterioration and viscosity increase. By conducting purification in advance, the process ensures high quality ester product while minimizing material waste through efficient purification methods.
3Ease of manufacture
If bispentaerythritol content is not controlled, then ease of manufacture is improved, but reliability decreases due to mold release issues and bubble formation
Solution Approach 1:
The patent specifies controlling the bispentaerythritol content within a defined range (not more than 7 wt% based on total pentaerythritol weight) to prevent mold release difficulties and bubble formation during polymerization. This parameter control maintains manufacturing simplicity while ensuring polymerization reliability.
4Productivity
If thioester content in mercaptocarboxylic acid is high, then productivity is improved, but manufacturing precision decreases due to color deterioration
Solution Approach 1:
The patent controls the thioester content in the mercaptocarboxylic acid to not more than 5% by area ratio in the HPLC chromatogram to prevent color deterioration while maintaining adequate reaction productivity. This parameter optimization balances manufacturing precision with production efficiency.
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 process ensures the production of high-quality, transparent, and colorless polyurethane-based resins with improved optical properties and heat resistance, reducing whitening and viscosity issues, making them suitable for optical materials like spectacle and camera lenses.
Implementation Method 1
thioester formed by intermolecular condensation of the acid
Implementation Method 2
reacting a usual polyhydric alcohol with a mercaptocarboxylic acid in the presence of an esterifying catalyst
Implementation Method 3
while removing by-produced water out of the system
Implementation Method 4
polymerizing pentaerythritol mercaptocarboxylic ester with a polyiso(thio)cyanate compound
Data Source
AI summary
A process for producing pentaerythritol mercaptocarboxylic ester by reacting pentaerythritol with a mercaptocarboxylic acid having a content of thioester formed by condensation of two molecules of the acid of 5% or below (in terms of area percentage) as determined by the high-performance liquid chromatography in the case of the total area of the mercaptocarboxylic acid and thioester formed by intermolecular condensation of the acid is taken as 100%.