Cellulose Substrate ePTFE Membrane Thermal Lamination
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Solution Overview
Problem
Existing filter media technologies face challenges in achieving high efficiency ratings while maintaining cost-effectiveness, pleatability, and air permeability, particularly in applications requiring HEPA-grade filtration.
Innovation Solution
A filter media comprising a substrate layer with a fibrous polyester and cellulose blend, thermally laminated with an ePTFE membrane layer, which allows for increased pleatability and air permeability, while maintaining high filtration efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PTFE laminated spunbond polyester is used to achieve high efficiency rating (MERV 16-17), then filtration efficiency is improved, but cost increases and pleat performance decreases (only five pleats per inch)
Solution Approach 1:
The patent uses a composite structure combining cellulose substrate with ePTFE membrane layer. The cellulose provides pleatability (12 pleats per inch) while the ePTFE layer provides high efficiency filtration (MERV 15-17), resolving the contradiction between filtration efficiency and pleat performance.
Solution Approach 2:
The patent changes the material parameters by using ePTFE (expanded PTFE) instead of conventional PTFE membrane, and optimizing the cellulose-to-polyester ratio in the substrate to less than 80% polyester by weight, enabling both high efficiency filtration and improved pleat performance.
2Reliability
If ePTFE membrane layer is thermally laminated to cellulose substrate, then filtration efficiency is improved, but air permeability may be reduced
Solution Approach 1:
The patent uses ePTFE membrane with controlled porosity that allows high air permeability while maintaining HEPA-grade filtration efficiency. The expanded PTFE structure provides interconnected pores that facilitate airflow while trapping particles.
Solution Approach 2:
The patent applies the ePTFE membrane layer only on one side of the cellulose substrate, optimizing the balance between filtration efficiency and air permeability by concentrating the filtration function where needed while maintaining breathability.
3Strength
If binder layer is used to laminate filter media layers, then structural integrity is improved, but pores are closed off reducing air permeability
Solution Approach 1:
The patent replaces mechanical bonding (binder layers) with thermal lamination, where heat and pressure bond the ePTFE membrane to the cellulose substrate without requiring additional adhesive materials that would block pores.
Solution Approach 2:
The patent removes the binder layer from the conventional three-layer structure, using direct thermal lamination between the cellulose substrate and ePTFE membrane, eliminating the harmful binder that closes pores while maintaining structural integrity.
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 proposed filter media achieves HEPA-grade filtration efficiency with increased pleatability and air permeability, reducing pressure drop and operational costs, making it suitable for various industrial applications.
Implementation Method 1
a membrane layer made from ePTFE that is thermally laminated to the one side of the substrate layer
Implementation Method 2
HEPA filters remove at least 99.97% of aerosols 0.3 micrometers (μm) in diameter
Data Source
AI summary
A filter media that includes a substrate layer, which includes a sheet having a fibrous polyester and cellulose blend with less than 80% polyester fibers by weight. The sheet further includes a membrane layer that is made from ePTFE. The membrane layer is thermally laminated to the one side of the substrate layer. In particular embodiments, the filter media can be pleated into a filter element that has more than five pleats per inch.