Polymer Film Casting Die Orientation and Chill Roll Gravity Support
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Solution Overview
Problem
Existing polymer film casting methods face issues with sagging and premature contact of molten polymer due to gravity, leading to inconsistent sizing and non-uniform cooling, particularly when manufacturing low melt strength polymers.
Innovation Solution
A casting apparatus with a die having a non-zero discharge angle and a chill roll configuration where the second chill roll is positioned to gravity support the polymer film, ensuring uniform cooling and sizing by maintaining equal contact lengths on both sides of the film, with additional polishing rolls for further cooling and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the die discharge angle is horizontal (zero degree), then the polymer film can be easily extruded, but the molten polymer sags and makes premature contact with chill rolls due to gravity
Solution Approach 1:
The die is oriented at a non-zero discharge angle (e.g., 5-15 degrees) relative to the horizontal plane, creating an asymmetric configuration that uses gravity to assist polymer delivery to the chill roll gap while preventing sagging and premature contact, thereby achieving both ease of extrusion and sizing consistency
Solution Approach 2:
The problem is solved by introducing a angular dimension (discharge angle) to the originally horizontal die configuration. This angular orientation creates a gravitational component that directs the polymer melt toward the chill roll gap, transforming the gravity force from a harmful sagging effect into a useful delivery mechanism
2Productivity
If chill rolls are positioned close together to reduce film contact length, then production speed can be increased, but uniform cooling and sizing become difficult to achieve
Solution Approach 1:
Different sections of the chill roll system are designed with different functions: the first chill roll gap is optimized for initial sizing and thickness control, while subsequent polishing rolls provide uniform cooling over extended contact lengths. This local differentiation allows high production speed while maintaining cooling uniformity in each specific zone
Solution Approach 2:
The cooling system is segmented into multiple independent chill roll stages rather than using a single long contact zone. This segmentation allows each stage to be optimized for its specific function (sizing vs. cooling) while working together to achieve both high productivity and uniform cooling across the entire film
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 solution effectively mitigates sagging and premature contact, achieving consistent and uniform polymer film sizing and cooling, improving the overall quality of the manufacturing process.
Implementation Method 1
The non-zero discharge angle of the discharge direction of the die is of a predetermined magnitude so as to gravity assist delivery of the molten polymer to the first gap
Implementation Method 2
The second chill roll is positioned to gravity support the polymer film exiting the first gap along a first length of a first side of the polymer film
Implementation Method 3
The molten polymer gradually solidifies as it passes over the chill rolls as heat is transferred from the polymer film to the chill rolls
Data Source
AI summary
A casting apparatus for manufacturing polymer film includes a die for discharging a molten polymer and having discharge direction oriented at a discharge angle offset from horizontal. The apparatus includes a first chill roll having a first diameter and a second chill roll having a second greater diameter. There is a first gap between the first chill roll and the second chill roll. The discharge angle is of a predetermined magnitude to gravity assist delivery of the molten polymer to the first gap. The second chill roll is positioned to gravity support the film exiting the first gap along a first length of a first side of the film. A first polishing roll is positioned downstream first and second chill rolls. The first polishing roll engages and cools a second length of a second opposite side of the film. The first length is substantially equal to the second length.