EVOH Aqueous Dispersion via Controlled Phase Transition
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Solution Overview
Problem
Current methods for producing ethylene/vinyl alcohol copolymer aqueous dispersions result in low concentration and poor storage stability, with large particle diameters and economic inefficiencies, particularly due to the use of organic solvents and complex processes.
Innovation Solution
A method involving dissolving ethylene/vinyl alcohol copolymers in a mixed solvent with heating, followed by cooling to precipitate the copolymer, reducing the organic solvent concentration, and distilling it off, using a water-soluble organic solvent and a dispersion stabilizer to achieve high concentration and small particle diameters with improved storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If EVOH is dissolved in a solvent to form a solution for coating, then the solution can be applied to form thin coat films, but the viscosity increases with concentration making it difficult to use, and organic solvents require recovery apparatus
Solution Approach 1:
The patent changes the dispersion medium from organic solvent to water, fundamentally altering the chemical parameter of the solvent system. This allows the formation of aqueous EVOH dispersions that maintain low viscosity even at high concentrations (5-50% by weight), eliminating the viscosity-concentration problem while removing organic solvent recovery requirements
Solution Approach 2:
The patent replaces expensive organic solvents that require recovery apparatus with water, which is inexpensive and does not require recovery equipment. This eliminates the need for complex solvent recovery systems and reduces operational costs
2Object-affected harmful factors
If known methods are used to produce aqueous EVOH dispersions, then water is used as dispersion medium improving working environment, but the dispersions are low in concentration and insufficient in storage stability
Solution Approach 1:
The patent performs preliminary dissolution of EVOH in water with heating to ensure complete dissolution before cooling. This preliminary action prevents aggregation during subsequent storage and handling, thereby improving storage stability while maintaining high concentration
Solution Approach 2:
The patent controls temperature parameters during dissolution (heating to dissolve, then cooling to precipitate) and maintains specific pH conditions using dispersants. These parameter controls enable the formation of stable, high-concentration aqueous dispersions that resist aggregation during storage
3Quantity of substance
If centrifugation is used to concentrate the resin component, then concentration is improved, but the process is complicated and uneconomical
Solution Approach 1:
The patent extracts the harmful centrifugation step from the process by directly forming high-concentration aqueous dispersions through controlled dissolution and precipitation. This eliminates the need for complex centrifugation equipment and multiple processing steps while achieving the desired concentration
4Ease of manufacture
If melt-mixing EVOH with dispersing agent is used, then dispersion is achieved, but the particles in the aqueous dispersion are great in particle diameter
Solution Approach 1:
The patent performs preliminary dissolution of EVOH in water with heating to ensure complete molecular-level dissolution before cooling. This preliminary dissolution prevents aggregation during precipitation, resulting in fine, uniform particles with small diameter rather than large aggregates
Solution Approach 2:
The patent utilizes phase transition by heating to dissolve EVOH and then cooling to precipitate it as fine particles. This controlled phase transition process produces uniform, small particle diameter dispersions compared to mechanical melt-mixing methods
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 produces ethylene/vinyl alcohol copolymer aqueous dispersions with high concentration and excellent long-term storage stability, featuring small particle diameters, which are industrially advantageous and suitable for various applications.
Implementation Method 1
dissolving ethylene/vinyl alcohol copolymers in a mixed solvent with heating
Implementation Method 2
cooling a solution obtained in said step to precipitate the ethylene/vinyl alcohol copolymer
Implementation Method 3
cooling a solution obtained in said step to precipitate the ethylene/vinyl alcohol copolymer
Implementation Method 4
a step of distilling off said water-soluble organic solvent
Data Source
AI summary
The present invention provides a method of producing, in an industrially advantageous manner, an ethylene/vinyl alcohol copolymer aqueous dispersion which has a high concentration and is excellent in long-term storage stability and in which the resin particles in the aqueous dispersion obtained are small in particle diameter. The method of the present invention relates to producing an ethylene/vinyl alcohol copolymer aqueous dispersion, which comprises: (1) a step of dissolving an ethylene/vinyl alcohol copolymer in a mixed solvent comprising 5 to 65% by weight of water and 35 to 95% by weight of a water-soluble organic solvent, with heating, (2) a step of cooling a solution obtained in step (1) to precipitate the ethylene/vinyl alcohol copolymer, (3) a step of reducing a concentration of the water-soluble organic solvent in the mixed solvent to a level lower than 35% by weight relative to the total amount of the water and water-soluble organic solvent by adding water, and (4) a step of distilling off the water-soluble organic solvent.