Process for producing porous polyurethane coatings using polyol ester additives
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Solution Overview
Problem
The use of ammonium stearate in producing porous polyurethane coatings for synthetic leathers is problematic due to its susceptibility to hard water, leading to flocculation, gelation, and the formation of undesirable calcium soaps, as well as high migration capacity and the need for additional surfactants to achieve foam stability, increasing complexity and resulting in unsatisfactory tactile and mechanical properties.
Innovation Solution
The use of polyol esters as additives in aqueous polymer dispersions for producing porous polymer coatings, which enables efficient foaming, stabilizes foams, and prevents migration, thereby improving mechanical and tactile properties and breathability without the need for additional surfactants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ammonium stearate is used as surfactant, then foam stability is improved, but susceptibility to hard water increases leading to flocculation and gelation
Solution Approach 1:
The patent changes the chemical parameters of the surfactant system by replacing ammonium stearate with polyol esters having specific molecular weights (500-5000 g/mol) and hydroxyl numbers (50-200 mg KOH/g). This parameter change eliminates hard water susceptibility while maintaining foam stability, as polyol esters do not form insoluble calcium soaps like ammonium stearate does.
Solution Approach 2:
The patent employs a simple, straightforward surfactant system using only polyol esters without requiring complex combinations of multiple surfactants. This simplifies the formulation and eliminates the need to manage interactions between different surfactant components, making the system more reliable and easier to control.
2Reliability
If ammonium stearate is used, then foam stability is improved, but migration capacity increases leading to lubrication film formation
Solution Approach 1:
The patent uses a simple polyol ester surfactant system that provides adequate foam stability without the migration problems of ammonium stearate. The polyol esters remain in place and do not migrate to form unwanted lubrication films, eliminating this harmful effect while keeping the surfactant system simple and straightforward.
3Reliability
If multiple surfactants are combined to achieve foam stability, then foam stability is improved, but device complexity increases
Solution Approach 1:
The patent employs a simple, straightforward surfactant system using only polyol esters without requiring complex combinations of multiple surfactants. This simplifies the formulation and eliminates the need to manage interactions between different surfactant components, making the system more reliable and easier to control.
Solution Approach 2:
The polyol esters perform multiple functions simultaneously: they act as surfactants for foam stabilization, provide water resistance, and eliminate the need for additional surfactants. This multi-functionality reduces the overall complexity of the surfactant system while maintaining adequate foam stability.
4Quantity of substance
If ammonium stearate is used, then calcium soap formation occurs, but this leads to flocculation and gelation reducing manufacturing quality
Solution Approach 1:
The patent eliminates the harmful reaction between ammonium stearate and calcium ions that causes flocculation and gelation. By using polyol esters instead, the system avoids this harmful interaction entirely, maintaining dispersion homogeneity and preventing defects in the synthetic leather coating.
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
Polyol esters facilitate the production of coatings with a fine, homogeneous cell structure, enhanced air permeability, and improved processing characteristics, including quicker drying and reduced risk of drying defects, while eliminating surfactant-related issues such as migration and gelation.
Implementation Method 1
efficient foaming, stabilizes foams
Implementation Method 2
stabilizes foams, prevents migration
Implementation Method 3
there is evaporation of the water present in the PUD system, which results in formation of a film of the polyurethane particles
Implementation Method 4
hydrophilic (poly)isocyanates can react with free OH radicals present on the surface of the polyurethane particles during the drying step, thus leading to additional crosslinking of the polyurethane film
Implementation Method 5
it has quite a high migration capacity in the dried polyurethane film... polyol esters... preventing migration
Data Source
AI summary
The invention relates to a process for producing a porous polyurethane coatings, using a polyol ester as additives in an aqueous polymer dispersion, the process comprising the steps of a) providing a mixture comprising an aqueous polymer dispersion, a polyol ester, and an additive, b) foaming the mixture to give a homogeneous, fine-cell foam, c) adding at least one thickener to establish the desired viscosity of the wet foam, d) applying a coating of the foamed polymer dispersion to a suitable carrier, e) drying the coating. The invention further relates to a phosphorylated polyol ester.