Polyurethane Adhesion Layer Composition to Suppress Phenolic Yellowing
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Solution Overview
Problem
Existing methods struggle to effectively suppress phenolic yellowing in aqueous polyurethane products used for coatings and laminate adhesives, as direct acid addition can lead to precipitation and loss of adhesion.
Innovation Solution
A grain-finished leather-like sheet is created with a polyurethane adhesion layer containing an aqueous polyurethane as the main component, which includes 0.01 to 0.45 mass % sulfate or alkyl sulfate content and exhibits acidity equivalent to pH 4.8 or less, thereby suppressing phenolic yellowing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an acid is directly added to an aqueous polyurethane liquid to suppress phenolic yellowing, then the pH is reduced to acidic range (pH 4.8 or less), but the polyurethane precipitates due to breakage of the emulsion
Solution Approach 1:
The patent uses a water-soluble polymer as an intermediary substance to mediate between the acid and the polyurethane emulsion. The polymer protects the emulsion structure while allowing acid to be introduced, preventing direct acid-polyurethane interaction that causes precipitation. This enables pH reduction to suppress phenolic yellowing without breaking the emulsion.
Solution Approach 2:
The patent changes the parameter of pH by introducing acid through a water-soluble polymer system. This allows the pH to be adjusted to the acidic range (4.8 or less) needed to suppress phenolic yellowing, while the polymer system maintains emulsion stability throughout the parameter change process.
2Object-affected harmful factors
If acid treatment is applied to solid polyurethane to suppress phenolic yellowing, then the pH is adjusted to acidic range, but the method cannot be directly applied to aqueous polyurethane liquids used for coating
Solution Approach 1:
The patent adapts the acid treatment method by changing the delivery system from direct acid addition to acid introduction through a water-soluble polymer. This parameter change in the treatment approach enables the method to be applied to aqueous polyurethane liquids while maintaining the beneficial pH reduction effect.
Solution Approach 2:
The water-soluble polymer serves as an intermediary that makes the acid treatment compatible with aqueous polyurethane liquid systems. This intermediary enables the transfer of the solid polyurethane acid treatment concept to liquid emulsion systems without causing the precipitation problems that would occur with direct acid addition.
3Object-affected harmful factors
If sulfate or alkyl sulfate is added to aqueous polyurethane to achieve acidic pH, then phenolic yellowing is suppressed, but the adhesion and water resistance must be maintained
Solution Approach 1:
The water-soluble polymer acts as an intermediary that enables sulfate or alkyl sulfate addition to achieve acidic pH while protecting the adhesion and water resistance properties. The polymer system allows these additives to function for pH control without compromising the reliability of the polyurethane coating.
Solution Approach 2:
The patent uses parameter changes in the form of adding sulfate or alkyl sulfate compounds to achieve the desired acidic pH range. This parameter change approach suppresses phenolic yellowing while the water-soluble polymer system ensures that adhesion and water resistance are maintained.
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 proposed solution effectively suppresses phenolic yellowing in the polyurethane adhesion layer while maintaining high water resistance and adhesion properties.
Implementation Method 1
the polyurethane adhesion layer includes an aqueous polyurethane as a main component, contains 0.01 to 0.45 mass %, in sulfur atoms content, in total of at least one selected from a sulfate and an alkyl sulfate, and exhibits coloration equivalent to pH 4.8 or less that is caused by a BCG (bromocresol green) solution
Implementation Method 2
a polyurethane adhesion layer that bonds the fiber base material and the polyurethane skin layer to each other
Data Source
AI summary
A grain-finished leather-like sheet includes: a fiber base material; a polyurethane skin layer bonded to one surface of the fiber base material; and a polyurethane adhesion layer that bonds the fiber base material and the polyurethane skin layer to each other. The polyurethane adhesion layer includes an aqueous polyurethane as a main component and contains 0.01 to 0.45 mass % in sulfur atoms content, of a sulfate or an alkyl sulfate. The polyurethane adhesion layer exhibits coloration equivalent to pH 4.8 or less that is caused by a BCG (bromocresol green) solution.