Aqueous Polyurethane-Polyurea Dispersions for Leather Coating
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Solution Overview
Problem
Existing coatings for flexible sheetlike substrates, particularly leather, do not effectively improve soiling characteristics and cleanability.
Innovation Solution
Aqueous polyurethane-polyurea dispersions are prepared by reacting polyisocyanates with isocyanate-reactive compounds containing polysiloxane groups, along with other reactants, to create a finish that enhances soil repellency and ease of cleaning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional coatings are applied to flexible sheetlike substrates, then the substrate is protected, but the soiling characteristics and cleanability are not improved
Solution Approach 1:
The patent applies composite materials by combining polyurethane and polyurea in a single coating system. The polyurethane provides flexibility and adhesion to the substrate, while the polyurea contributes hardness and chemical resistance. This composite structure creates a coating that simultaneously achieves protective functions and improved soiling/cleanability characteristics that neither material could provide alone.
Solution Approach 2:
The patent utilizes parameter changes by controlling the isocyanate index (NCO content) within a specific range of 80-150%. By optimizing this chemical parameter, the coating achieves the right balance between flexibility and hardness, hydrophobicity and adhesion, thereby improving both soiling resistance and cleanability without compromising protective functions.
2Duration of action of stationary object
If a coating provides protection, then durability is improved, but soil repellency and cleanability are compromised
Solution Approach 1:
The patent applies local quality by creating a coating with differentiated properties at different levels. The coating provides strong adhesion and flexibility at the substrate interface (local property 1), while simultaneously creating a hard, chemically resistant, and hydrophobic surface layer (local property 2). This spatial differentiation of properties enables the coating to be durable yet possess excellent soil repellency and cleanability.
Solution Approach 2:
The patent utilizes parameter changes by optimizing the isocyanate index to 80-150%, which transforms the chemical composition and physical properties of the coating. This parameter adjustment creates a crosslinked network structure that provides both long-term durability and surface properties that repel soil and facilitate easy cleaning.
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 polyurethane-polyurea dispersions significantly improve the soiling resistance and cleanability of leather substrates, providing a durable and effective coating solution.
Implementation Method 1
the reaction of isocyanates with isocyanate-reactive compounds comprising at least one polysiloxane group
Data Source
AI summary
The invention relates to a method for producing aqueous polyurethane-polyurea dispersions, where A) first a polyurethane prepolymer containing NCO groups is produced by reacting A1) polyisocyanates with A2) polymeric polyols and/or polyamines having number-average molecular weights of more than 400 to 8,000 g/mol, A3) possibly low-molecular-weight compounds having number-average molecular weights of 17-400 g/mol selected from the group comprising mono- and polyalcohols, mono- and polyamines, and amino alcohols, A4) isocyanate-reactive, ionically or potentially ionically hydrophilic compounds and/or isocyanate-reactive non-ionically hydrophilic compounds, A5) isocyanate-reactive compounds, which contain at least one C7 to C24 alkyl group or C7 to C24 alkenyl group, and A6) isocyanate-reactive compounds, which contain at least one polysiloxane group, and B); the NCO groups of the prepolymer that are not yet free are reacted with isocyanate-reactive monoamines, polyamines, hydrazine, and/or hydrazides, dimensioned in such a way that a calculated ratio of the isocyanate-reactive NH groups to the NCO groups of 0.7 to 1.2 is achieved.