Branched-Polymer Nonwoven Coating for Breathable Liquid Barriers
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Solution Overview
Problem
Current composite materials comprising nonwoven fabrics and coatings struggle to achieve a balance between breathability and liquid barrier properties, often requiring heavy films, costly production processes, and resulting in poor comfort in protective clothing due to limited breathability.
Innovation Solution
A composite is developed using a nonwoven fabric coated with a thin layer of branched-chain polymer, specifically polypropylene or polyethylene, which provides good breathability and barrier properties without the need for stretching, thereby reducing production costs and improving comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a laminate of breathable film and nonwoven fabric is used to achieve good liquid barrier properties, then barrier properties are improved, but weight increases and breathability is limited
Solution Approach 1:
The patent applies this principle by using an ultrathin polymer coating layer (gramage 1-20 g/m²) instead of heavy breathable films. The coating layer provides liquid barrier properties while maintaining low weight, directly resolving the contradiction between barrier performance and weight reduction.
Solution Approach 2:
The patent changes the gramma ge parameter of the coating layer from conventional thick films to ultrathin coatings (1-20 g/m²). This parameter change enables achieving barrier properties with minimal weight, resolving the technical contradiction between these two requirements.
2Ease of operation
If high amounts of filler material are used to obtain acceptable breathability, then breathability is improved, but production cost increases due to costly drying steps
Solution Approach 1:
The patent extracts the filler material from the coating composition, using a pure polymer coating without fillers. This eliminates the need for drying steps and associated production costs while maintaining breathability through the polymer's inherent microporous structure formed during extrusion coating.
Solution Approach 2:
The patent uses a simple polymer coating process without expensive filler materials and drying steps. The extrusion coating method creates a functional coating that provides both barrier and breathability properties without requiring costly additional processing steps.
3Ease of operation
If high amounts of filler material are used to obtain acceptable breathability, then breathability is improved, but liquid barrier quality deteriorates due to macro-pore formation in stretching
Solution Approach 1:
The patent removes filler materials from the coating composition, using only polymer. This eliminates macro-pore formation issues associated with filler particles during stretching, ensuring continuous liquid barrier properties while maintaining breathability through the polymer matrix structure.
Solution Approach 2:
The patent uses a homogeneous polymer coating without filler particles that could create heterogeneities and macro-pores. The uniform polymer structure ensures consistent liquid barrier properties across the coating layer while providing breathability through controlled microporosity.
4Reliability
If conventional coating methods are used to achieve good barrier properties, then barrier properties are improved, but device complexity increases due to complicated production process
Solution Approach 1:
The patent merges the coating application and barrier property formation into a single extrusion coating step. The polymer is extruded directly onto the nonwoven fabric in a molten state, forming a continuous coating that provides liquid barrier properties without requiring separate drying, stretching, or curing steps.
Solution Approach 2:
The patent implements continuous extrusion coating where the polymer is continuously applied to the nonwoven fabric in a single pass. This continuous process eliminates间断性 processing steps, reducing production complexity while ensuring consistent barrier properties across the entire coating layer.
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 composite achieves excellent breathability and barrier properties with a low coating weight, enhancing comfort and reducing production costs by eliminating the need for stretching and heavy films.
Implementation Method 1
Nonwoven fabrics typically have good moisture vapor permeability but moderate barrier properties
Implementation Method 2
a breathable material (good vapor permeability) having good liquid barrier properties is needed
Data Source
AI summary
Coated nonwoven fabric comprising a nonwoven fabric layer and a coating, said coating comprises a polymer having a branching index g′ of equal or below 0.9.