Process for manufacturing a leather-like nonwoven fabric
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Solution Overview
Problem
Existing methods for producing leather-like nonwoven fabrics with microfibers using waterborne polyurethane result in hard textures due to strong adhesion of polyurethane to fibers, and the use of organic solvents poses environmental concerns.
Innovation Solution
A process involving the addition of an aqueous polyvinyl alcohol solution with specific saponification and polymerization degrees to a fibrous substrate, followed by the application of a waterborne polyurethane dispersion and subsequent removal of the polyvinyl alcohol, which reduces adhesion and allows for the formation of voids between fibers and polyurethane, resulting in a soft texture and reduced solvent use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If waterborne polyurethane is used to replace organic solvent-based polyurethane, then environmental harm is reduced, but the texture becomes hard due to strong adhesion to fibers
Solution Approach 1:
The patent introduces polyvinyl alcohol (PVA) as an intermediary substance between the fibrous substrate and waterborne polyurethane. The PVA forms a barrier layer that prevents direct contact and strong adhesion between the polyurethane and fibers, thereby maintaining texture softness while using environmentally friendly waterborne polyurethane instead of organic solvent-based alternatives.
Solution Approach 2:
The patent applies PVA to the fibrous substrate before adding the waterborne polyurethane. This preliminary action of coating the fibers with PVA creates a protective barrier in advance, preventing the polyurethane from directly adhering to the fibers and causing hardening, thus solving the texture problem while maintaining the environmental benefits of waterborne polyurethane.
2Loss of substance
If PVA with low degree of polymerization (500) is used, then it is water soluble and can be removed, but it dissolves in waterborne polyurethane dispersion causing unstable adhesion control
Solution Approach 1:
The patent specifies precise parameter ranges for PVA: degree of polymerization of 800-3,500 and viscosity of 10-50 mPa·s at 20°C. These parameter changes optimize the balance between water solubility (for removability) and stability in waterborne polyurethane dispersion. The controlled parameters ensure PVA remains stable during polyurethane application while still being removable later to achieve the desired texture.
3Strength
If PVA is added to suppress fiber-polyurethane adhesion, then voids are formed improving softness, but PVA dissolves in water during wetting steps causing loss of control
Solution Approach 1:
The patent specifies PVA with degree of polymerization of 800-3,500 and viscosity of 10-50 mPa·s at 20°C. These parameter changes ensure PVA remains stable during water-based processing steps while maintaining water solubility for eventual removal. The optimized parameters prevent premature dissolution during polyurethane application but allow controlled removal later to create voids for softness.
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 process produces a leather-like nonwoven fabric with a soft texture and elegant appearance while minimizing the use of organic solvents, achieving good abrasion resistance and environmental sustainability.
Implementation Method 1
strong adhesion of the polyurethane to the fibers in the fibrous substrate
Implementation Method 2
since PVA is water soluble, when the fibrous substrate with added PVA is wetted with water, the PVA is dissolved away and lost in the water
Implementation Method 3
waterborne polyurethane (polyurethane dispersed in water)
Data Source
AI summary
Provided is an environmentally friendly process for producing a sheet-shaped material having both an elegant, napped appearance and a soft texture, which qualities have not been achieved concurrently, and also exhibiting good abrasion resistance. The process of the present invention for producing a sheet-shaped material comprises the successive steps of: (a) adding a polyvinyl alcohol having a degree of saponification of 98% or more and a degree of polymerization of 800 to 3,500 to a fibrous substrate in an amount of 0.1 to 50% by mass relative to the total mass of fibers in the fibrous substrate; (b) adding a waterborne polyurethane to the fibrous substrate with the added polyvinyl alcohol; and (c) removing the polyvinyl alcohol from the fibrous substrate with the added waterborne polyurethane.