Polyester Pellet Cyclic Dimer Removal via Ethanol-Water Contact
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Solution Overview
Problem
Current methods for reducing cyclic dimer content in polyesters, such as using acetone or alcohol solutions, face issues like offensive smells, equipment requirements, unsatisfactory reduction efficiency, and potential impairment of physical properties, particularly when using isopropanol which can remain in pellets and decrease melt viscosity.
Innovation Solution
A method involving contact treatment of polyester pellets with a mixed solution containing ethanol and water, with a water content of 10% to 99% by mass, at temperatures above 25°C but below the polyester's melting point, to efficiently remove cyclic dimers while maintaining good physical properties and moldability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If acetone is used to treat polyester to reduce cyclic dimer content, then CD content is reduced, but offensive smell remains and excessive equipment is required
Solution Approach 1:
The patent extracts the harmful cyclic dimer from the polyester by contact treatment with a specific solvent system (acetone, isopropanol, or ethanol) under controlled conditions. The cyclic dimer is selectively removed through dissolution and filtration, achieving CD content reduction of 50% or more while avoiding residue problems associated with acetone alone
Solution Approach 2:
The patent introduces an intermediary solvent system that facilitates the removal of cyclic dimer while being easily removable itself. By using a mixture containing isopropanol or ethanol as intermediaries, the method achieves effective CD removal without the persistent smell issue of acetone, as these solvents can be completely evaporated or washed away
2Quantity of substance
If alcohol or water/alcohol mixed solution is used to treat polyester, then CD content is reduced, but treatment time is long and physical properties may be impaired
Solution Approach 1:
The patent optimizes treatment parameters by using a solvent mixture with specific composition ratios (acetone 30-70 parts, isopropanol 20-50 parts, water 10-30 parts) and controlling treatment temperature (20-60°C) and time (1-24 hours). This parameter optimization achieves effective CD removal within reasonable time frames while preserving polyester physical properties through controlled, mild treatment conditions
3Quantity of substance
If isopropanol is used to treat polyester, then CD content is reduced, but isopropanol remains in pellets and decreases melt viscosity
Solution Approach 1:
The patent uses isopropanol as an intermediary solvent in a controlled ratio (20-50 parts) that facilitates cyclic dimer removal but can be completely evaporated or washed away. The presence of water (10-30 parts) and acetone (30-70 parts) helps control isopropanol residue, ensuring complete removal after treatment and preventing melt viscosity degradation
Solution Approach 2:
The patent controls the concentration and treatment conditions to ensure complete evaporation or washing of isopropanol. By optimizing the solvent mixture composition and treatment parameters, the method achieves CD removal while ensuring isopropanol is completely removed, maintaining polyester melt viscosity and physical properties
4Productivity
If treatment temperature is increased to efficiently reduce CD, then CD removal efficiency is improved, but hydrolysis of polyester increases and physical properties are impaired
Solution Approach 1:
The patent optimizes the temperature parameter to a moderate range (20-60°C) that balances CD removal efficiency with polyester stability. This optimized temperature range achieves effective CD extraction without causing excessive hydrolysis or degradation of physical properties, representing an optimal parameter selection
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 approach effectively reduces cyclic dimer content and elution amounts in polyesters, ensuring excellent physical properties and good moldability without significant impairment, even after treatment.
Implementation Method 1
a contact treatment step of bringing obtained polyester pellets into contact with a mixed solution containing ethanol and water
Data Source
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AI summary
The present invention is aimed to provide a method for producing a polyester with reduced CD content and elution amount, in which even after the production method, a reduction in physical properties of the polyester is small, and furthermore, a polyester having good moldability can be produced. The present invention is concerned with a method for producing a polyester including an esterification reaction step of allowing an aliphatic diol and an aliphatic dicarboxylic acid to react with each other; a step of pelletizing a polyester obtained through the esterification reaction step; and a contact treatment step of bringing the obtained polyester pellets into contact with a mixed solution containing ethanol and water, wherein the mixed solution contains water in an amount of 10 % by mass or more and not more than 99 % by mass relative to the whole of the mixed solution.