Pleatable PTFE Filter Bag With Metallic Scrim
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Solution Overview
Problem
Certain filtration materials, such as PTFE, are traditionally unpleatable and thus not available in a pleated form, limiting their use in applications where increased surface area and filtration efficiency are needed, despite their exceptional thermal and chemical resistance characteristics.
Innovation Solution
PTFE fibers are felted onto a pleatable metallic scrim, which enhances the pleatability of the material, and an E-PTFE membrane is laminated onto the felted PTFE, creating a filtration material that can be pleated at room temperature and retains its shape, thereby overcoming the unpleatability of PTFE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTFE material is used for filtration, then thermal and chemical resistance is improved, but pleatability deteriorates (material becomes unpleatable)
Solution Approach 1:
The patent combines PTFE fibers with a thermoplastic polymer matrix to create a composite filtration material. The PTFE provides thermal and chemical resistance, while the thermoplastic component enables pleatability through heat activation. This composite structure resolves the contradiction by integrating materials with complementary properties.
Solution Approach 2:
The patent utilizes temperature as a parameter to change the properties of the filtration material. By heating the material above the glass transition temperature of the thermoplastic polymer, the material becomes soft and pleatable. Upon cooling, it retains the pleated shape. This parameter change enables pleatability in a material that would otherwise be unpleatable.
2Area of stationary object
If pleated bags are used, then surface area is increased, but manufacturing complexity increases
Solution Approach 1:
The patent incorporates a pleating aid layer during the manufacturing process that pre-determines the pleating pattern. This preliminary action simplifies the subsequent pleating operation, as the material is already prepared with guides and reinforcement structures that facilitate uniform pleating without requiring complex manufacturing equipment or procedures.
3Ease of manufacture
If thermosetting resin is added to enable pleating, then pleatability is improved, but process complexity increases (requires heating blades and cooling)
Solution Approach 1:
The patent uses a thermoplastic polymer as a disposable pleating aid that is integrated into the filtration material structure. This thermoplastic component performs the function of holding pleats during manufacturing but is not required to provide long-term structural support, as it is replaced by the permanent pleating structure after formation. This approach simplifies the overall process compared to using permanent thermosetting resins.
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 resulting pleatable filtration material offers improved filtration efficiency and resistance to harsh environments, extending the lifespan of filter bags in applications like waste incineration facilities by maintaining thermal and chemical resistance while increasing surface area without requiring heated pleating processes.
Implementation Method 1
Felting by hydro-entanglement (spunlacing) can be better suited than neddle-felting when using a metallic scrim.
Implementation Method 2
Some pleating machines operate at room temperature.
Implementation Method 3
an E-PTFE membrane is laminated onto the felted PTFE
Data Source
Figure 1
AI summary
The pleated filter bag, which can be used in a bag-house type dust collector, is elongated and has a longitudinal hollow center with an open end, and a pleated filter wall circumscribing the hollow center. The pleated filter wall has a felt such as PTFE fibers felted onto an apertured and pleatable scrim which can be made of metal, and having a permeability lower than a permeability of the scrim. A membrane of lower-permeability material, such as an E- PTFE membrane, covers the support felt on the outer side of the bag.