EVOH Paste Washing for High-Purity Copolymer Production
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Solution Overview
Problem
Conventional processes for producing ethylene/vinyl alcohol copolymers face challenges in removing impurities like catalyst residues and solvent from the polymerization and saponification process, leading to incomplete purification and potential coloring issues in final products, while also being costly and energy-intensive due to the need for intermediate drying steps.
Innovation Solution
A process involving a horizontal washing tank where a high-viscosity ethylene/vinyl alcohol copolymer paste is kneaded with a shear force, allowing thorough contact with washing water to remove impurities, reducing the alcohol content significantly and eliminating the need for intermediate drying steps, thereby improving product quality and simplifying the production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the conventional washing process is used where washing is performed after pelletization in solid state, then the process is simple, but it is difficult to completely remove impurities from the inner part of the pellet
Solution Approach 1:
The invention performs washing before pelletization, rather than after. The paste is washed in a liquid state while it is still pliable and can be thoroughly contacted with washing water, enabling complete impurity removal from both surface and inner parts. After washing, the paste is then pelletized to produce the final product.
Solution Approach 2:
The invention changes the physical state parameter of the EVOH from solid (pellet) to semi-liquid (paste) during the washing step. This parameter change allows the washing water to penetrate and contact the inner parts of the material effectively, significantly improving impurity removal efficiency compared to washing solid pellets.
2Manufacturing precision
If intermediate pellet production and drying steps are added, then impurity removal is improved, but production cost increases due to additional apparatus and energy consumption
Solution Approach 1:
The invention merges the washing step with the pre-pelletization process. By washing the paste before pelletization in the same continuous process flow, there is no need for separate intermediate pellet production and drying steps, thereby reducing equipment requirements and energy consumption while maintaining high product quality.
Solution Approach 2:
The invention extracts the washing step from the conventional sequence and positions it before pelletization rather than after. This repositioning eliminates the need for subsequent drying steps and intermediate handling, simplifying the overall process while achieving superior impurity removal.
3Quantity of substance
If intermediate pellet is dried for a long period, then water content is reduced, but thermal deterioration occurs and foreign matter may be included in the final product
Solution Approach 1:
The invention performs washing before pelletization when the material is in a paste state that allows thorough water contact and impurity removal. This preliminary washing action reduces the need for extended drying later, minimizing thermal exposure time and preventing deterioration of the EVOH.
Solution Approach 2:
The invention skips the intermediate pellet drying step entirely by washing the paste before pelletization. The washing is so effective in the liquid state that minimal or no subsequent drying is needed, allowing the process to rush through to pelletization without prolonged thermal exposure that would cause deterioration.
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 process achieves high-efficiency removal of impurities, resulting in a high-quality, homogeneous ethylene/vinyl alcohol copolymer with reduced production costs and energy consumption, as well as improved product quality by eliminating the need for intermediate drying steps.
Implementation Method 1
applying a shear force to the paste to knead the paste while bringing the paste into contact with washing water
Implementation Method 2
bringing the paste into contact with washing water in the horizontal washing tank so that a surface of the paste is repeatedly displaced by an inner part thereof
Implementation Method 3
discharging at least some of the alcohol to an outside of the tank together with the washing water
Data Source
AI summary
A process is provided for producing an ethylene/vinyl alcohol copolymer by which impurities such as catalyst residue and by-products and solvent are removed to a high degree. A high-quality, homogeneous product can be efficiently produced by including a washing step including: introducing a paste containing an ethylene/vinyl alcohol copolymer and an alcohol into a washing tank; applying a shear force to the paste to knead the paste while contacting the paste with washing water so that a surface of the paste is repeatedly displaced by an inner part thereof; and discharging the alcohol to an outside of the tank together with the washing water to obtain a water-containing ethylene/vinyl alcohol copolymer composition having a small alcohol content.