PVB Extrusion Plate-Out Suppression via Organic Acid Addition
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Solution Overview
Problem
The extrusion process of PVB sheets containing Mg-salts as an adhesion control agent is hindered by the formation of a whitish layer inside the extruder and die due to hydrolysis, leading to production interruptions and difficulties in maintaining sheet thickness.
Innovation Solution
Adding weak organic acids to the extrusion mixture to increase acidity, thereby suppressing the hydrolysis of Mg-salts and preventing the formation of Mg-rich deposits, allowing for uninterrupted production and improved thickness control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Mg-salts are added as adhesion control agent to improve adhesion characteristics, then adhesion control is enhanced, but hydrolysis occurs leading to whitish layer formation inside extruder and die
Solution Approach 1:
Silica gel is introduced as an intermediary substance that selectively absorbs water from the extrusion mixture. The silica gel acts as a mediator between the Mg-salts and water, preventing direct contact and hydrolysis while allowing the extrusion process to continue normally. The silica gel particles circulate with the melt and continuously remove water, thereby preventing the formation of Mg(OH)2 deposits on the die and extruder walls.
Solution Approach 2:
Water is extracted from the extrusion mixture by silica gel through adsorption. The silica gel selectively removes water molecules from the melt, concentrating the adhesion control agent and preventing the water-induced hydrolysis reaction. This extraction of the harmful substance (water) eliminates the cause of whitish layer formation while preserving the functional Mg-salts in the mixture.
2Productivity
If production continues without interruption to maintain productivity, then output is maximized, but sheet thickness control becomes difficult due to deposit buildup
Solution Approach 1:
Silica gel serves as a mediator that prevents direct interaction between water and Mg-salts, thereby preventing deposit formation on the die. By eliminating the root cause of thickness control problems (whitish layer buildup), the extrusion process can continue uninterrupted while maintaining consistent sheet thickness. The silica gel particles remain suspended in the melt and continuously scavenge water, ensuring stable extrusion conditions throughout production.
3Manufacturing precision
If cleaning is performed frequently to remove deposits, then manufacturing precision is maintained, but production time is lost and productivity decreases
Solution Approach 1:
The silica gel continuously performs the useful action of water removal throughout the entire extrusion process. Instead of periodic cleaning interruptions, the water absorption function operates continuously as the silica gel circulates with the melt. This continuous action prevents deposit formation altogether, eliminating the need for cleaning stoppages and maintaining both precision and productivity throughout extended production runs.
Solution Approach 2:
The silica gel self-regenerates its water-absorbing capacity by being regenerated in situ within the extrusion system. The silica gel particles continuously adsorb water as they circulate through the melt, and their capacity is restored by desorption in the high-temperature extrusion zone. This self-service mechanism eliminates the need for external cleaning operations while maintaining precise thickness control throughout production.
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 addition of weak organic acids effectively reduces the formation of Mg-rich deposits, enabling longer production runs and maintaining adhesion characteristics of the finished PVB film without negatively affecting its properties.
Implementation Method 1
the formation of a whitish layer inside the extruder and die due to hydrolysis
Implementation Method 2
Adding weak organic acids to the extrusion mixture to increase acidity, thereby suppressing the hydrolysis of Mg-salts
Data Source
AI summary
The invention is directed to a process for extrusion of mixtures comprising at least one polyvinyl acetal, at least one plasticizer and least one earth alkaline salt of a carboxylic acid, wherein 0.001%-1 wt. % (based on the combined weight of PVB resin and plasticizer) of at least one organic acid having 4 to 30 carbon atoms is added to the mixture.