Spiral Agitating Belt for Polylactic Acid Devolatilization
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Solution Overview
Problem
Existing polylactic acid devolatilization apparatuses face challenges with non-uniform heating of materials and low devolatilization efficiency, leading to yellowish products and inadequate removal of volatile components due to uneven heating and slow escape of volatile components from the liquid phase.
Innovation Solution
A polylactic acid devolatilization evaporator featuring a circular pipe-shaped cylinder with a spiral agitating belt and agitating shaft, ensuring uniform material distribution and heating, along with a spiral agitating belt to prevent material sticking and facilitate downward flow, enhancing volatile component escape and devolatilization efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the liquid membrane is made thinner to shorten diffusion distance, then the transfer rate of volatile components is improved, but the heating uniformity deteriorates due to material accumulation and sticking
Solution Approach 1:
The patent employs a spiral agitating belt that continuously moves and repositions the polymer melt on the heating surface. This dynamic action prevents the melt from sticking and accumulating in one location, maintaining a relatively thin and uniform liquid membrane layer while ensuring continuous exposure to heat, thereby resolving the contradiction between achieving thin film for fast volatilization and maintaining heating uniformity.
2Speed
If the turbulent intensity of the liquid is increased to refresh the gas-liquid interface continuously, then the transfer rate of volatile components is improved, but the material sticking and accumulation worsens
Solution Approach 1:
The spiral agitating belt acts as an intermediary mechanical element that provides controlled movement and interface renewal. Instead of relying on high turbulent intensity that causes sticking, the belt gently scrapes and redistributes the polymer melt, refreshing the gas-liquid interface continuously while maintaining controlled, uniform material distribution and preventing accumulation.
3Manufacturing precision
If the devolatilization time is extended to improve volatile component removal, then the purity is improved, but the productivity deteriorates due to long processing time
Solution Approach 1:
The patent changes the physical parameters of the devolatilization process by maintaining a thin, uniformly distributed liquid membrane through the spiral agitating belt. This parameter change (thin film thickness) dramatically increases the surface area to volume ratio and reduces diffusion distance, enabling rapid volatile component removal in a short time, thus achieving both high purity and high productivity simultaneously.
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 achieves uniform heating and high devolatilization efficiency, preventing material accumulation and ensuring the quality of the polylactic acid product by allowing volatile components to escape quickly, resulting in a significant reduction of residual monomer content.
Implementation Method 1
the materials to be devolatilized are not heated uniformly in the devolatilization process
Implementation Method 2
the devolatilization process utilizes the decrease of equilibrium concentration of volatilization at the gas-liquid interface to drive the volatile components in the liquid phase to transfer to the gas phase quickly
Data Source
AI summary
The present invention relates to the field of devolatilization, and discloses a polylactic acid devolatilization evaporator, which comprises: a container comprising a cylinder; an agitating shaft coaxial with the cylinder; an agitating belt connected to the agitating shaft and arranged in a spiral shape around the central axis of the cylinder, comprising an outer belt surface facing the inner circumferential surface of the cylinder and spaced apart from the inner circumferential surface of the cylinder. With the above technical scheme, the agitating belt makes the materials distributed more uniformly on the inner circumferential surface of the cylinder and form a thin layer in uniform thickness, thereby avoids agglomeration of the materials, facilitates uniform heating of the materials, avoids deterioration (e.g., darkened color) of the materials owing to non-uniform heating of the materials and excessive retention time in a high-temperature environment, and improves product quality.