PVC Recycling Process Using Density and Electrostatic Separation
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Solution Overview
Problem
Existing methods for recycling vinyl halide polymers, such as PVC, face challenges in purifying and reusing heterogeneous mixtures of ground particles, especially those containing fiber-reinforced articles, leading to complex separation processes with high energy consumption and potential environmental hazards.
Innovation Solution
A process involving the use of an aqueous phase with specific density to separate vinyl halide polymer pieces into intermediate phases based on density, followed by electrostatic separation to obtain high-purity recycled PVC without heating or organic solvents, preserving additives and avoiding hazardous waste generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thorough grinding is used to process vinyl halide polymer articles, then the material is converted into fine particles, but the resulting heterogeneous mixture is difficult to purify and reuse
Solution Approach 1:
The recycling process is divided into distinct stages: pre-treatment (removing contaminants), size reduction (grinding to specific particle sizes), and separation (using density and electrostatic properties). Each stage produces progressively purer PVC particles, transforming the heterogeneous ground mixture into homogeneous recycled material suitable for reuse.
2Productivity
If fiber-reinforced articles are ground, then the fibers are broken into small pieces, but they form wadding that complicates reuse
Solution Approach 1:
Instead of using complex mechanical separation systems to remove fiber wadding, the process employs density-based separation in liquid media and electrostatic separation. These non-mechanical methods effectively separate PVC particles from fiber contaminants without requiring complex mechanical sorting equipment.
3Manufacturing precision
If conventional recycling methods are used to separate PVC from other materials, then separation is achieved, but high energy consumption and environmental hazards occur
Solution Approach 1:
Liquid media with controlled density serve as intermediaries to separate PVC from other materials. By adjusting the liquid density to match non-PVC materials, PVC particles naturally separate through buoyancy differences. This eliminates the need for high-energy thermal or chemical separation processes.
Solution Approach 2:
The process changes physical parameters (density, electrostatic charge) rather than using high-energy thermal or chemical methods. Density separation uses controlled liquid media density, and electrostatic separation uses electric fields to charge and separate particles, both consuming significantly less energy than conventional high-temperature or solvent-based recycling.
4Manufacturing precision
If heating or organic solvents are used in recycling, then separation and purification are enhanced, but hazardous waste is generated and additives are lost
Solution Approach 1:
The process converts potentially harmful additives remaining in waste PVC into beneficial components of the recycled material. By using gentle density and electrostatic separation instead of harsh heating or solvents, original stabilizers and plasticizers are preserved, eliminating the need for additional additives in the recycled product.
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 effectively recycles PVC into high-purity, high-quality raw material for construction materials, reducing energy consumption and environmental impact while maintaining properties for reuse in articles.
Implementation Method 1
separating the first pieces from the first phase and vi) shredding them to particles
Implementation Method 2
dividing the common phase P into a first intermediate phase IPH and a second intermediate phase IPL, wherein the first intermediate phase IPH comprises first pieces of a density of more than D and the second intermediate phase IPL comprises pieces of a density of D at most
Implementation Method 3
dividing the particles into a first and a further fraction using at least one electrostatic plastic separation
Implementation Method 4
wherein the first fraction contains more particles of the vinyl halide polymer than the further fraction(s)
Data Source
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AI summary
The invention relates to a process of making a vinyl halide polymer comprising at least these steps: i) Providing a stream of pieces, wherein the pieces have a size of at most 120 mm and a density of 1.60 g/cm3at most, wherein the pieces comprise a plastic composition, which comprises at least 10 wt.% of the vinyl halide polymer, ii) adding an aqueous phase comprising at least one sort of powder particles, wherein the aqueous phase has a density of D in the range from 1.2 to 1.35 g/cm3; iii) forming a common phase of the stream of pieces and the aqueous phase; iv) dividing the common phase into a first intermediate phase and a second one, wherein the first intermediate phase comprises first pieces of a density of more than D and the second intermediate phase pieces of a density of D at most; v) separating the first pieces from the first phase and vi) shredding them to form a stream of particles of a particle size in the range from 3 to 15 mm; vii) dividing the particles into a first and a further fraction using electrostatic plastic separation, wherein the first fraction contains more particles of the vinyl halide polymer than the further fraction(s).