Polyurethane Foam Block Production Using Low-Shear Graphite Injection
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Solution Overview
Problem
The processing of shear-sensitive fillers like expanded graphite in polyurethane foam production is hindered by mechanical stress, particularly in pumps and nozzles, leading to impaired flame-retardant properties and disruptions in the foam structure due to shear-induced acid release.
Innovation Solution
The filler is added directly to the metered polyol stream using a nozzle element that creates a local negative pressure, allowing the filler to be mixed with minimal shear stress and conveyed without additional pumping, utilizing the Venturi effect to draw the filler into the stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If expanded graphite is mixed in a container and pumped in a circuit to prevent settling, then the filler remains suspended, but the mechanical stress from pumping and stirring destroys the graphite particles and releases acid
Solution Approach 1:
The invention extracts the harmful mechanical stress elements (stirrers and pumping circuits) from the filler handling system. Instead of keeping filler in suspension through mechanical agitation, the filler is added directly to the moving polyol stream where it is carried along by the flow without subjected to damaging mechanical forces.
Solution Approach 2:
The polyol stream itself serves the dual function of both transporting the filler and providing the medium for filler distribution. The flowing polyol naturally carries the filler particles to the mixing chamber without requiring separate pumping or stirring mechanisms, making the system self-sufficient for filler handling.
2Device complexity
If filler is added directly to the metered polyol stream, then no additional pumping is needed, but the polyol-filler mixture must be pumped which causes shear stress to the filler particles
Solution Approach 1:
The invention removes the need for an additional pump for the polyol-filler mixture by designing the system so that the filler is introduced into the already-moving polyol stream. The polyol's own flow carries the filler through the system to the mixing chamber, eliminating the harmful pumping step.
3Ease of operation
If overflow valve is used to regulate pressure and create negative pressure for filler intake, then filler can be drawn into the stream, but the system complexity increases
Solution Approach 1:
The overflow valve acts as an intermediary pressure control element that automatically regulates the pressure differential needed for filler intake. By maintaining a defined pressure upstream of the nozzle, it creates the necessary negative pressure zone that draws filler into the polyol stream without requiring complex active control systems.
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 method minimizes shear-induced damage to expanded graphite particles, maintaining flame-retardant properties and improving foam structure by reducing mechanical stress and acid release during processing.
Implementation Method 1
the chemical component is guided through a nozzle element arranged in the line, thereby increasing the flow rate of the chemical component and thus creating a local negative pressure in the chemical component and the filler is supplied in the flow direction behind the nozzle element in the area of the local negative pressure
Data Source
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AI summary
The invention relates to a method for the continuous production of polyurethane block foam (1) in which several different chemical components (2, 3, 4) are supplied to a mixing chamber (5), wherein a filler (8), in particular expandable graphite, is added in the area of a line (7) for one of the chemical components (2) before the chemical component (2) enters the mixing chamber (5).To introduce filler particles, and in particular expandable graphite particles, into the metered polyol stream in such a way that they can be mixed into the metered polyol stream with the lowest possible shear stress, the invention provides that the filler (8) is added by means of a nozzle element (9) arranged in the line (7), wherein the filler (8) is supplied downstream of the nozzle element (9) in the flow direction (F), wherein the pressure of the chemical component (2) upstream of the nozzle element (9) is maintained at a defined value in the flow direction (F), wherein an overflow valve (12) is actuated to regulate the pressure, wherein a portion of the mass flow of the chemical component (2) is directed into a bypass line (13) by means of the overflow valve (12), and wherein the bypass line (13) opens directly or indirectly into the mixing chamber (5). Furthermore, the invention relates to a device for the continuous production of polyurethane block foam.