Powder Coating Extrusion Using Immiscible Process Liquid
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Solution Overview
Problem
Conventional powder coating processes generate waste due to the need for specific particle size distributions, which are difficult to achieve and result in energetic costs and inefficiencies, particularly when using supercritical or liquefied gases as process fluids.
Innovation Solution
A process involving a melt extruder where a process liquid, such as water or volatile silicone oils, is added to create nano-scale weaknesses in the extrudate, allowing for easier comminution into desired particle sizes with reduced energetic costs by evaporation and introduction of discontinuities during cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional melt-mixing and extrusion processes are used to produce powder coating, then the resin components are properly mixed and formed, but the resulting extrudate is difficult to comminute into desired particle sizes requiring excessive grinding energy and generating waste powder
Solution Approach 1:
The patent applies preliminary action by introducing process liquid into the extruder before the extrusion process completes. This liquid creates pre-formed weaknesses and discontinuities in the extrudate structure during the extrusion itself, preparing the material in advance for easier comminution. The liquid is injected at specific points along the extruder barrel, allowing it to mix with the molten resin and create a foamed or discontinuous structure that will break down more easily during subsequent grinding operations.
Solution Approach 2:
The patent utilizes phase transitions by introducing a process liquid (such as water or volatile silicone oils) that undergoes phase change from liquid to vapor within the extruder. This phase transition creates expansion and forms gas cells or foam structures within the extrudate, creating inherent weaknesses that facilitate easier comminution. The evaporating liquid leaves voids and discontinuities in the solidified extrudate structure, reducing the energy required for grinding.
2Ease of manufacture
If supercritical or liquefied gases are used as process fluids to reduce viscosity during extrusion, then the powder coating precursor can be processed, but the method incurs high energetic costs and complexity
Solution Approach 1:
The patent applies this principle by using inexpensive, readily available process liquids such as water or volatile silicone oils instead of expensive supercritical or liquefied gases. These simple liquids serve their purpose of reducing viscosity and creating weaknesses during extrusion, then evaporate or are removed, leaving no residual cost or complexity. The process liquid is consumed in the process (evaporating or being removed), similar to disposable objects, but at minimal cost compared to maintaining supercritical fluid systems.
Solution Approach 2:
The patent changes the physical parameters of the process fluid from supercritical or liquefied gas states to simple liquid states at atmospheric or near-atmospheric conditions. This parameter change dramatically reduces the energy requirements and system complexity while still achieving the desired viscosity reduction and weakness formation effects. The process liquid operates at temperatures and pressures comparable to normal extrusion conditions, eliminating the need for expensive high-pressure or low-temperature equipment.
3Manufacturing precision
If particle separation techniques are applied to achieve specific particle size distributions, then the desired powder coating quality is obtained, but waste powder is generated that must be downgraded or disposed of
Solution Approach 1:
The patent applies preliminary action by pre-forming the extrudate with built-in weaknesses and discontinuities during the extrusion process itself. This preliminary structuring allows the material to break down more uniformly and predictably during comminution, reducing the need for extensive separation operations. The pre-formed gas cells and voids create natural fracture points that guide the breaking process, yielding a more consistent particle size distribution with fewer outliers requiring rejection.
Solution Approach 2:
The patent creates a porous or foam-like structure within the extrudate by introducing process liquid that evaporates or leaves voids. This porous structure facilitates more uniform and controlled breakage during comminution, as the voids act as stress concentration points that guide fracture propagation. The resulting particle size distribution is more predictable and uniform, reducing the amount of powder that falls outside specification ranges and must be discarded.
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
This process enhances the grindability and reduces energetic costs by introducing nano-scale weaknesses and discontinuities, allowing for efficient production of powder coatings with desired particle sizes while minimizing waste and energetic expenses.
Implementation Method 1
wherein said process liquid evaporates when the premix leaves the extruder
Data Source
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AI summary
A process for the manufacture of a powder coating comprising the steps of: Preparing a powder coating premix comprising a resin and optionally a crosslinker therefor; Feeding the premix through a melt extruder; Cooling the extruded material; and Comminuting it to fine particles, wherein said process is characterized in that between 1 and 25 wt. % (based on the weight of said premix) of a process liquid is added to the melt extruder, wherein said process liquid is immiscible with at least said resin of the powder coating premix and wherein said process liquid evaporates when the premix leaves the extruder.