Condensation Polyurethane Membrane for Waterproof Breathability
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Solution Overview
Problem
Conventional polyurethane membranes face challenges in achieving both moisture permeability and waterproof performance while being environmentally friendly, with existing non-isocyanate polyurethane (NIPU) processes requiring solvents, generating waste, and resulting in films with inadequate strength and tactile feel.
Innovation Solution
A condensation type polyurethane resin comprising urea, carbamate, and ethylene glycol units, formulated to have specific hydrogen atom ratios and amine values, is used to create a waterproof and moisture-permeable membrane through solvent-free processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyhydroxyurethane (PHU) is synthesized by addition polymerization of cyclic carbonate and polyamine, then the PHU contains abundant hydrogen bonding forces, but the fluidity of PHU is poor and solvent addition is required for membrane formation
Solution Approach 1:
The patent changes the chemical structure parameters by introducing ethylene glycol units with specific hydrogen atom ratios (A1/(A1+A2) from 0.10 to 0.30, A3/(A1+A2) from 3 to 21) to modify the balance between hydrogen bonding strength and fluidity, enabling solvent-free processing while maintaining membrane performance
Solution Approach 2:
The patent creates a composite polyurethane structure combining urea units, carbamate units, and ethylene glycol units in specific proportions to achieve both strong hydrogen bonding for waterproofness and adequate fluidity for processing without solvents
2Ease of manufacture
If dicarbamate monomer is prepared by polymerization of carbonate and diamine, then NIPU can be obtained suitable for direct melt processing, but organic solvents are required for purification by recrystallization generating large amount of liquid waste
Solution Approach 1:
The patent converts the harmful effect of requiring solvent purification into a benefit by designing a condensation polymerization process that inherently produces water as the only byproduct, eliminating organic solvent waste while maintaining melt processing capability through specific molecular structure design
Solution Approach 2:
The patent changes the polymerization method from addition polymerization to condensation polymerization, fundamentally altering the process to eliminate solvent requirements and reduce waste generation while maintaining the desired melt processing properties
3Reliability
If polyurea is synthesized by reacting carbonate and diamine in 1:1 molar ratio, then the film has strong hydrogen bonding forces, but the film feels overly hard
Solution Approach 1:
The patent adjusts the compositional parameters by controlling the ratio of urea units to carbamate units (A1/(A1+A2) from 0.10 to 0.30) and incorporating ethylene glycol units (A3/(A1+A2) from 3 to 21) to optimize the balance between hydrogen bonding strength for waterproofness and softness for tactile feel
Solution Approach 2:
The patent creates a composite structure combining urea units, carbamate units, and ethylene glycol units in specific proportions to achieve both strong hydrogen bonding for waterproofness and adequate softness for tactile feel, avoiding the overly hard characteristic of pure polyurea
4Reliability
If conventional polyurethane is prepared using isocyanate and phosgene, then high performance membrane can be produced, but the process is toxic and environmentally harmful
Solution Approach 1:
The patent converts the harmful toxic chemicals (isocyanate and phosgene) into a beneficial condensation polymerization process using only diamine and carbonate, where water is the only byproduct, thereby eliminating toxicity while maintaining membrane performance through alternative chemical pathways
Solution Approach 2:
The patent replaces the conventional chemical mechanism involving toxic isocyanate and phosgene with a condensation polymerization mechanism using diamine and carbonate, substituting the harmful chemical system with a cleaner alternative that achieves similar or superior membrane properties
5Object-affected harmful factors
If NIPU is made by poly-addition process, then green manufacturing is achieved, but the resulting film has inadequate strength and moisture permeability
Solution Approach 1:
The patent optimizes the molecular structure parameters by controlling the hydrogen atom ratios in urea and carbamate units and the amount of ethylene glycol units to enhance both the strength and moisture permeability of the film while maintaining the green manufacturing approach
Solution Approach 2:
The patent creates a composite polyurethane structure combining urea units, carbamate units, and ethylene glycol units in specific proportions to simultaneously achieve green manufacturing, high film strength, and good moisture permeability that were not obtainable with single-component 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
The membrane exhibits high moisture permeability, moderate elasticity, and resistance to water pressure, providing a dry and non-sticky tactile feel, overcoming the limitations of previous NIPU technologies.
Implementation Method 1
a condensation polymerization process generally involves reacting diamine and carbonate, followed by a transesterification reaction with polyol so as to obtain NIPU
Implementation Method 2
the membrane exhibits high moisture permeability, moderate elasticity, and resistance to water pressure
Data Source
AI summary
A waterproof and moisture-permeable membrane is prepared by subjecting a mixture including a condensation type polyurethane resin to a film-forming process. The condensation type polyurethane resin includes a urea unit represented by Formula (I), a carbamate unit represented by Formula (II), an ethylene glycol unit represented by Formula (III), and a terminal amine unit. In the condensation type polyurethane resin, a number of hydrogen atoms belonging to the urea unit is defined as A1, a number of hydrogen atoms belonging to the carbamate unit is defined as A2, and a number of hydrogen atoms belonging to the ethylene glycol unit is defined as A3. A1/(A1+A2) ranges from 0.10 to 0.30, and A3/(A1+A2) ranges from 3 to 21. The condensation type polyurethane resin has an amine value of at least 10 meq/kg.