Method for preparing novel waterborne polyurethane foam layer for synthetic leather
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Solution Overview
Problem
Traditional solvent-based polyurethane synthetic leather manufacturing processes face environmental pollution, high costs, and regulatory challenges due to the use of organic solvents, and existing waterborne polyurethane foaming methods lack stability and uniformity in foam structure, making it difficult to achieve the desired properties of real leather.
Innovation Solution
A method involving the preparation of charged cellulose nanofibers and ionic waterborne polyurethane dispersions, which self-assemble to form a stable Pickering foam, used as a template to create a waterborne polyurethane foam layer for synthetic leather, eliminating the need for additional stabilizers and allowing ambient temperature curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If solvent-based polyurethane is used for synthetic leather manufacturing, then the foam structure and leather-like properties can be achieved, but environmental pollution and solvent discharge problems occur
Solution Approach 1:
The patent changes the fundamental parameter of the dispersion medium from organic solvent to water, creating waterborne polyurethane. This substitution maintains the foam structure stability needed for synthetic leather while eliminating the harmful environmental effects of organic solvent discharge, directly resolving the contradiction between reliability and environmental harm.
Solution Approach 2:
The patent converts the challenge of water-based system foaming (which traditionally lacks stability) into an advantage by using Pickering foam stabilization with cellulose nanofibers. This approach transforms the potential harm of water displacement into a beneficial stable foam structure, achieving both environmental friendliness and foam stability.
2Object-affected harmful factors
If waterborne polyurethane is used instead of solvent-based polyurethane, then environmental pollution is reduced, but foam stability and uniformity deteriorate
Solution Approach 1:
The patent introduces cellulose nanofibers as an intermediary substance that stabilizes the waterborne polyurethane foam. These nanofibers act as Pickering stabilizers at the gas-liquid interface, preventing foam collapse and ensuring uniform structure, thereby resolving the stability issue while maintaining the environmental benefits of water-based systems.
Solution Approach 2:
The patent creates a composite foam system combining waterborne polyurethane with cellulose nanofiber stabilizers. This composite approach leverages the environmental advantages of water-based polyurethane while incorporating the stabilizing properties of cellulose nanofibers, achieving both reduced pollution and improved foam stability.
3Productivity
If chemical foaming method is used with waterborne polyurethane, then foaming can be achieved, but high temperature requirements and incompatibility with water-based system occur
Solution Approach 1:
The patent replaces the thermal/chemical foaming mechanism with a mechanical/Pickering stabilization approach. Instead of using high temperature to drive chemical foaming reactions, the system uses cellulose nanofibers to mechanically stabilize the foam structure at ambient temperatures, making it compatible with waterborne polyurethane while maintaining foaming capability.
4Productivity
If physical foaming method is used with waterborne polyurethane, then foam can be obtained, but process requirements are high and costs increase
Solution Approach 1:
The patent enables the waterborne polyurethane system to self-stabilize foam through the inherent properties of cellulose nanofibers as Pickering stabilizers. This self-service approach eliminates the need for complex external foaming equipment and stringent process controls, reducing both device complexity and production costs while maintaining foam production capability.
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 method achieves a stable, uniformly structured waterborne polyurethane foam layer with controllable pore size, reducing energy consumption and production costs while meeting environmental and regulatory standards.
Implementation Method 1
forming a bimolecular layer at the gas/liquid interface by a self-assembly of the cellulose nanofiber and waterborne polyurethane nanoparticles through electrostatic interactions
Implementation Method 2
forming a bimolecular layer at the gas/liquid interface by a self-assembly of the cellulose nanofiber and waterborne polyurethane nanoparticles
Implementation Method 3
The stable Pickering foam is used as a template, and dried and solidified to obtain the waterborne polyurethane foam layer for synthetic leather
Data Source
AI summary
A method for preparing a novel waterborne polyurethane foam layer for synthetic leather is disclosed. The method includes first preparing a charged cellulose nanofiber by using a wood pulp as a raw material; meanwhile, subjecting a polyisocyanate, a macromolecular diol, a hydrophilic chain extender and a small molecular chain extender to a polyaddition reaction and an acid-base neutralization reaction in sequence, to obtain a cationic or anionic waterborne polyurethane; adding the charged cellulose nanofiber and a certain amount of a crosslinking agent to the oppositely charged ionic waterborne polyurethane emulsion, stirring the resulting mixture, forming a bimolecular layer at the gas/liquid interface by a self-assembly of the cellulose nanofiber and waterborne polyurethane nanoparticles through electrostatic interactions to obtain a stable Pickering foam; using the stable Pickering foam as a template, drying and solidifying to obtain the waterborne polyurethane foam layer for synthetic leather.