Soft PVB Recycling by Plasticizer Adjustment and Pelletizing
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Solution Overview
Problem
The recycling of poly(vinyl butyral) from multilayer sheets is challenging due to the compositional differences between the stiff and soft layers, leading to visual defects and inferior product quality when re-extruded, and the handling of highly viscous varnish containing soft poly(vinyl butyral) is difficult.
Innovation Solution
A process is developed to convert the viscous varnish into a more workable product by adding under-plasticized soft poly(vinyl butyral) to reduce plasticizer content, enabling the production of pellets suitable for extrusion and reuse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If multi-layer poly(vinyl butyral) sheets with different composition layers are recycled through conventional re-extrusion, then recycling is achieved, but visual defects and inferior product quality occur due to compositional differences between layers
Solution Approach 1:
The multilayer sheet is separated into individual layers through grinding and flotation processes, allowing each layer to be recovered independently based on its composition. This segmentation enables selective recycling of stiff and soft layers without the visual defects caused by conventional re-extrusion of mixed layers.
Solution Approach 2:
The flotation process extracts and separates the soft poly(vinyl butyral) layer from the stiff layer by exploiting differences in density and composition. The soft layer is removed as a distinct fraction, preventing the mixing that causes hazing in conventional recycling methods.
2Manufacturing precision
If plasticizer is added to remove soft poly(vinyl butyral) from granulate, then separation is achieved, but highly viscous varnish is produced that is difficult to handle
Solution Approach 1:
The viscosity of the varnish is reduced by adjusting process parameters such as temperature and plasticizer content. By controlling these parameters, the varnish transitions from a highly viscous,难以处理的 state to a more fluid state that can be easily handled and re-extruded.
Solution Approach 2:
Additional plasticizer acts as an intermediary substance that modifies the physical properties of the varnish. The plasticizer reduces intermolecular forces between polymer chains, lowering viscosity and improving flow characteristics for easier handling.
3Ease of operation
If under-plasticized soft poly(vinyl butyral) is added to reduce plasticizer concentration, then workable pellets are produced, but additional processing steps are required
Solution Approach 1:
Under-plasticized soft poly(vinyl butyral) is prepared in advance as a separate material component. This preliminary preparation allows the plasticizer concentration to be precisely controlled during the blending stage, producing pellets with optimal processability without requiring complex in-process adjustments.
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 process facilitates the recycling of soft poly(vinyl butyral) by transforming the viscous varnish into pellets with a lower plasticizer concentration, improving handling and enabling the production of high-quality poly(vinyl butyral) sheets.
Implementation Method 1
adding plasticizer to remove the soft poly(vinyl butyral) from the granulate to obtain a granulate enriched in the stiff poly(vinyl butyral) and a varnish of the soft poly(vinyl butyral) and the plasticizer
Implementation Method 2
adding under-plasticized soft poly(vinyl butyral) to the varnish, to provide a soft poly(vinyl butyral) composition having a lower concentration of plasticizer than the first concentration
Data Source
AI summary
A process is disclosed for recovering soft poly(vinyl butyral) from a plasticized poly(vinyl butyral) multilayer sheet comprising stiff poly(vinyl butyral) and soft poly(vinyl butyral). The multilayer sheet. which may be scrap or recycled material. is first converted to a granulate form and then treated with plasticizer. This plasticizer treatment serves to remove the soft poly(vinyl butyral) component from the granulate. but thereby provides a varnish comprising the soft poly(vinyl butyral) mixed with excess plasticizer. This varnish is however highly viscous and thus difficult to handle or mechanically process. The present disclosure provides a solution to this handling problem by the addition of soft poly(vinyl butyral) having a lower concentration of plasticizer to the varnish. until a product is obtained having a sufficiently low concentration of plasticizer to render the product capable of mechanical processing. for example pelletizing. The resulting product can then be utilized to form soft poly(vinyl butyral) sheets, thereby improving the recyclability of scrap multilayer poly(vinyl butyral) materials.