Polyurethane Foam Sheet Water Foaming Without Organic Solvents
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Solution Overview
Problem
Conventional methods for producing polyurethane foam sheets and laminated sheets face challenges such as the use of toxic organic solvents, environmental concerns, and difficulties in achieving uniform foam shape and mechanical strength, especially with thin sheets, due to the need for solvent-based processes and inadequate cross-linking reactions.
Innovation Solution
A method involving a solvent-free hot melt urethane prepolymer with isocyanate groups, mixed with a compound containing active hydrogen atoms, is used to create a liquid mixture that is water-foamed, allowing for controlled foam shape and increased viscosity, resulting in a polyurethane foam sheet with uniform shape, soft texture, and excellent mechanical strength and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If organic solvent-based polyurethane resin is used for producing artificial leather and synthetic leather, then the foam layer can be formed with good texture and flexibility, but the production process requires organic solvent drying or extraction which causes environmental contamination and high energy consumption
Solution Approach 1:
The invention changes the fundamental parameter of the resin system from organic solvent-based to water-based polyurethane resin. This parameter change eliminates the need for organic solvent drying or extraction processes, thereby removing environmental contamination and high energy consumption associated with solvent evaporation, while maintaining foam layer formation through water evaporation and cross-linking reactions
Solution Approach 2:
The invention replaces the mechanical/thermal process of organic solvent evaporation with a chemical cross-linking process. Instead of relying on heat-driven solvent evaporation, the foam layer is formed and stabilized through cross-linking reactions between isocyanate groups and water or active hydrogen-containing compounds, substituting a chemical mechanism for a thermal-mechanical one
2Object-generated harmful factors
If water-based polyurethane resin is used instead of organic solvent-based resin, then environmental impact is reduced, but the resulting polyurethane foam sheets exhibit inferior water resistance and durability
Solution Approach 1:
The invention creates a composite material system by combining water-based polyurethane resin with cross-linking agents (isocyanate groups). This composite approach allows the base resin to remain environmentally friendly (water-based) while the cross-linking network provides the necessary durability and water resistance, achieving both environmental benefits and performance requirements
Solution Approach 2:
The invention extracts and separates the harmful organic solvent component from the polyurethane resin system, replacing it with water as the carrier. The essential performance characteristics (durability and water resistance) are then achieved through the addition of cross-linking chemistry, effectively removing the harmful element while preserving necessary functional properties
3Productivity
If conventional mechanical foaming method is used for thin foam sheets, then production efficiency is maintained, but the foam shape becomes non-uniform and difficult to control
Solution Approach 1:
The invention applies preliminary action by pre-heating the water-based polyurethane resin composition to a specific temperature range (20-80°C) before foaming. This preliminary heating action increases the fluidity of the composition, allowing bubbles to form and distribute more uniformly throughout the material, thereby achieving both high production efficiency and uniform foam shape in thin sheets
Solution Approach 2:
The invention changes the temperature parameter of the resin composition from ambient to an elevated range (20-80°C) during the foaming process. This parameter change affects the viscosity and fluidity of the composition, enabling better bubble distribution and foam shape control while maintaining production efficiency through the enhanced flow characteristics
4Adaptability or versatility
If foam sheet is produced with high fluidity for easy processing, then applicability is improved, but the foam shape becomes difficult to control and uniformity is reduced
Solution Approach 1:
The invention applies dynamics by controlling the fluidity of the resin composition as a dynamic property that changes with temperature. The composition is heated to achieve high fluidity for easy application and coating, then the temperature is controlled during foaming to maintain appropriate viscosity for bubble uniformity. This dynamic control of fluidity through temperature manipulation allows both high applicability and precise foam shape control
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
This method enables the production of polyurethane foam sheets and laminated sheets with improved uniformity, flexibility, and durability, while eliminating the need for organic solvents, reducing environmental impact and energy consumption, and preventing foam deformation under stress.
Implementation Method 1
a method involving a solvent-free hot melt urethane prepolymer with isocyanate groups, mixed with a compound containing active hydrogen atoms, is used to create a liquid mixture that is water-foamed
Implementation Method 2
increased viscosity, resulting in a polyurethane foam sheet with uniform shape, soft texture, and excellent mechanical strength and durability
Implementation Method 3
water-foamed, allowing for controlled foam shape and increased viscosity, resulting in a polyurethane foam sheet
Data Source
AI summary
A method of producing a polyurethane foam sheet, and a laminated sheet that uses such a foam sheet, that can be applied to artificial leather, synthetic leather, and cushioning materials used in all manner of applications. A polyurethane foam sheet is produced by applying a liquid mixture, obtained by mixing together a heated and melted hot melt urethane prepolymer (A) containing isocyanate groups at molecular terminals, and a compound (B) containing at least 2 active hydrogen atom-containing groups, onto a substrate in a sheet-like manner, and then water foaming the liquid mixture by bringing the sheet-like liquid mixture into contact with water vapor or moisture (water). A laminated sheet is produced by bonding a third substrate to the polyurethane foam sheet.