Microporous Polyurethane Fabric for Breathability and Waterproofing
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Solution Overview
Problem
Existing moisture-permeable waterproof fabrics face challenges in achieving a well-balanced combination of moisture permeability and waterproofing properties while maintaining excellent tensile strength, often requiring large amounts of inorganic materials that can deteriorate the fabric's strength and increase environmental burden.
Innovation Solution
A moisture-permeable waterproof fabric with a microporous layer of synthetic polymer, primarily composed of polyurethane resin, is produced using a process involving the application of a synthetic polymer solution with fine inorganic particles and a polar organic solvent, followed by exposure to a gas phase with uniformly dispersed water fog, and subsequent immersion in water for complete coagulation, resulting in a fabric with controlled pore size and distribution for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a porous film with large pores is formed to improve moisture permeability, then moisture permeability is improved, but waterproofing properties deteriorate
Solution Approach 1:
The porous film is segmented into two distinct layers: a skin layer with micropores (diameter ≤1 μm) for waterproofing and a honeycomb layer with larger pores for moisture permeability. This segmentation allows each layer to perform its specialized function, resolving the contradiction between waterproofing and moisture permeability.
Solution Approach 2:
Different regions of the film are given different pore structures tailored to their specific functions: the outer skin layer has fine micropores optimized for blocking water while allowing vapor transmission, while the inner honeycomb layer has larger pores optimized for high moisture vapor permeability. This local differentiation resolves the functional contradiction.
2Manufacturing precision
If inorganic particles are added to control pore size and distribution, then manufacturing precision is improved, but strength deteriorates
Solution Approach 1:
The patent optimizes the particle size parameter of inorganic additives to 1 μm or smaller, and controls their concentration within specific ranges (5-50 parts by mass per 100 parts resin). These parameter changes enable precise pore size control while minimizing the negative impact on tensile strength through careful optimization.
Solution Approach 2:
The patent uses composite materials combining organic polymer resin with inorganic particles (such as metal oxides or carbonates) to achieve both precise pore control and maintained strength. The composite structure allows the inorganic particles to define pore geometry while the polymer matrix provides structural integrity.
3Ease of manufacture
If conventional wet coagulation method is used to form porous film, then ease of manufacture is improved, but environmental burden increases
Solution Approach 1:
The patent changes the solvent parameter from conventional organic solvents to water as the continuous phase in the coagulation bath. This parameter change transforms the coagulation process into an environmentally friendly water-based system while maintaining the effective wet coagulation mechanism for pore formation, thus reducing environmental burden without sacrificing ease of manufacture.
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 fabric exhibits improved moisture permeability, waterproofing, and tensile strength, while minimizing the use of organic solvents and reducing environmental impact, thus achieving a balanced performance without compromising strength or increasing environmental burden.
Implementation Method 1
a solution wherein a synthetic polymer consisting mainly of a polyurethane resin is dissolved in an organic solvent compatible with water is applied on a fibrous fabric or a releasable base material to coagulate by immersing them into water, whereby the organic solvent in the resin solution is replaced by water to form a film having many pores
Implementation Method 2
bringing said synthetic polymer solution into contact with a gas phase in which water fog having an average particle diameter of 1-30 μm are uniformly dispersed to make the synthetic polymer into semi-coagulation
Data Source
AI summary
A moisture-permeable waterproof fabric which has a well-balanced combination of moisture permeability and waterproofing properties and has excellent strength, in particular, tensile strength, is provided without increasing environmental burden. A synthetic-polymer solution comprising a synthetic polymer consisting mainly of a polyurethane, fine inorganic particles, and a polar organic solvent is applied to one surface of a fibrous fabric and then brought into contact with a gaseous phase in which waterdrops having an average particle diameter of 1-30 μm have been evenly dispersed, thereby making the synthetic polymer semisolid. The fabric is then immersed in water to completely solidify the polymer and thereby obtain a moisture-permeable waterproof fabric comprising the fibrous fabric and, united to one surface thereof, a microporous film of a single-layer structure comprising the synthetic polymer consisting mainly of a polyurethane (the number of micropores having a pore diameter of 0.1-5 μm is (5-200)×104/mm2 in a vertical cross-section, and the film has a tensile strength of 3-80 MPa, a moisture permeability as measured by the calcium chloride method of 6,000 g/m2·24 hr or higher or a moisture permeability as measured by the potassium acetate method of 6,000 g/m2·24 hr or higher, and a water pressure resistance of 60 kPa or higher).