Method for producing synthetic leather having air permeability
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Solution Overview
Problem
Conventional methods for producing synthetic leather lack air permeability, generate harmful volatile organic compounds (VOCs), and use environmentally unfriendly solvents, while also failing to provide the necessary hydrolysis resistance and chemical resistance similar to genuine leather.
Innovation Solution
A method involving a brushing process to raise the nap on the fabric, followed by a back reinforcing process with a hydrolysis-resistant and flame-retardant resin solution, and a film forming process using a water-soluble polyurethane resin solution to create a film with air permeability, while avoiding the use of VOCs and solvents, and enhancing chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a film is formed by coating a solvent-based polyurethane solution on release paper and bonding it to fabric using adhesive, then the synthetic leather has improved film formation and adhesion, but it loses air permeability and generates harmful VOCs
Solution Approach 1:
The invention extracts and removes the harmful solvent component from the polyurethane coating system. By using water as the solvent instead of organic solvents, the process eliminates VOC emissions while maintaining the film-forming and adhesion properties of the polyurethane resin on the fabric surface.
Solution Approach 2:
The invention changes the solvent parameter from organic solvents (toluene, MEK) to water. This parameter change transforms the coating system from solvent-based to water-based, eliminating harmful VOCs while preserving the functional properties of the polyurethane film.
2Strength
If the fabric surface is completely covered by the film to improve durability, then the synthetic leather has improved strength and texture, but it loses air permeability similar to genuine leather
Solution Approach 1:
The invention applies local quality by creating different film densities in different regions. The polyurethane film is formed with varying thickness and porosity - denser in some areas for durability and protection, while maintaining porous or gap regions in other areas to preserve air permeability, mimicking the structure of genuine leather.
Solution Approach 2:
The invention uses porous material structure in the polyurethane film. By controlling the film formation process, the film contains pores and gaps that allow air to pass through, maintaining breathability while still providing the protective and durable surface characteristics of synthetic leather.
3Shape
If solvent-based PU resin is used for film formation, then the film has improved flexibility and texture, but it causes environmental pollution and health hazards
Solution Approach 1:
The invention changes the solvent parameter from organic solvents to water, transforming the system from polluting to environmentally friendly. This parameter change maintains the film-forming capability and texture quality while eliminating environmental pollution and health hazards associated with organic solvents.
Solution Approach 2:
The invention converts the potential harm of water (which can cause hydrolysis of polyurethane) into a benefit by carefully controlling the drying and curing process. The water-based system provides environmental benefits while the process control prevents hydrolysis, ultimately producing a durable film.
4Strength
If adhesive is used to bond the film to fabric, then the bonding strength is improved, but it introduces additional VOCs and odors
Solution Approach 1:
The invention merges the coating and bonding functions into a single integrated process. The water-based polyurethane resin serves both as the film-forming coating and as the bonding agent, eliminating the need for separate adhesive application and reducing harmful emissions.
Solution Approach 2:
The invention extracts and removes the separate adhesive component from the process. By using the polyurethane resin itself as the bonding agent, the system eliminates additional adhesive-related VOCs and odors while maintaining strong bonding between film and fabric.
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 produces synthetic leather with air permeability similar to genuine leather, improved hydrolysis resistance, and chemical resistance, along with enhanced durability and texture, while being environmentally friendly by eliminating VOCs and solvents.
Implementation Method 1
a film is formed by applying a water-soluble polyurethane resin solution to the nap of the surface of the fabric
Implementation Method 2
a brushing process for brushing the surface of a fabric using a brushing machine to raise a nap
Implementation Method 3
a back reinforcing process for coating a hydrolysis-resistant and flame-retardant resin solution on the back of the fabric
Data Source
AI summary
Disclosed is a synthetic leather produced by directly coating a water-soluble synthetic resin solution on the surface of a fabric to form a film thereon such that fine gaps formed on the fabric are partially left open to have a certain degree of air permeability. In particular, a brushing process is used for brushing the surface of a fabric using a brushing machine to raise a nap. Next, a hydrolysis-resistant and flame-retardant resin solution is coated on the back of the fabric, which is opposite to the surface on which the nap is raised, to reinforce the back of the fabric. A film forming process then applies a water-soluble polyurethane resin solution to the nap raised on the surface of the fabric to form a film on the surface of the fabric thereby producing a synthetic leather product that has air permeability properties that are superior to genuine leather.