Anionic Polyurethane Dispersion for High Opacity Soft-Touch Coatings
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Solution Overview
Problem
Existing polyurethane dispersions for surface coating often require opacifying additives like silica, which destabilize polymer compositions, increase brittleness, and pose health risks, while also failing to achieve high opacity and soft-touch surfaces simultaneously without sedimentation issues.
Innovation Solution
An aqueous anionic polyurethane dispersion is developed, free from solvents and opacifying additives, using a prepolymer formed from aliphatic or cycloaliphatic diisocyanates, polytetramethylene glycol, and anionic or potentially anionic polyols, with a chain extender, resulting in films with high opacity and soft touch without sedimentation, achieved through a specific reaction and dispersion process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If opacifying particles (silica, silicates, or polymeric particles) are added to polyurethane dispersions to increase opacity, then the opacity of the coating is improved, but the polymer composition becomes destabilized and the film becomes more brittle
Solution Approach 1:
The patent removes opacifying particles (silica, silicates, or polymeric particles) from the polyurethane dispersion formulation entirely. Instead of adding heterogeneous particles to achieve opacity, the invention uses a purely organic solvent-based polyurethane system where opacity is achieved through the polyurethane matrix itself, thereby eliminating the destabilizing effect of particles on the polymer composition.
Solution Approach 2:
The patent changes the fundamental parameters of the dispersion system by using organic solvents instead of water, and by adjusting the molecular weight and composition of the polyurethane itself to achieve opacity through the matrix rather than through added particles. This parameter change eliminates the need for heterogeneous particles and maintains composition stability.
2Illumination intensity
If opacifying particles are added to polyurethane dispersions to increase opacity, then the opacity of the coating is improved, but the film becomes more brittle
Solution Approach 1:
The patent removes opacifying particles from the formulation, eliminating the source of brittleness. The opacity is achieved through the polyurethane matrix composition and molecular weight selection, which allows the film to remain flexible and elastic without the reinforcing but brittle particles.
Solution Approach 2:
The patent uses a composite polyurethane system with specific molecular weight ranges and compositions (including polyols and isocyanates in controlled ratios) to achieve both opacity and flexibility. The polyurethane matrix itself is designed as a composite of functional groups that provide both optical properties and mechanical flexibility.
3Illumination intensity
If heterogeneous particles are added to achieve high opacity, then the opacity is improved, but separation of materials occurs during application resulting in heterogeneity of optical effect
Solution Approach 1:
The patent removes heterogeneous particles from the system, eliminating the cause of separation and optical heterogeneity. The polyurethane dispersion remains homogeneous throughout application, and opacity is achieved uniformly through the molecular composition of the polyurethane matrix rather than through distributed particles that would separate.
4Illumination intensity
If amorphous or crystalline silica is used to increase opacity, then the opacity is improved, but health risks are created for operators
Solution Approach 1:
The patent removes silica and other opacifying particles from the formulation, eliminating the health hazards associated with handling and inhaling fine siliceous particles. The opacity is achieved through the organic polyurethane matrix, which poses no respiratory or health risks to operators during application.
Solution Approach 2:
The patent converts the harmful effect of requiring opacity-enhancing additives into a beneficial formulation by using the polyurethane matrix itself to provide opacity. This approach eliminates the need for separate opacifying agents and their associated health risks, turning a potentially harmful requirement into a safe solution.
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 solution produces stable, high-opacity films with a gloss below 10 and a soft-touch effect, maintaining homogeneity and re-dispersibility, thus overcoming the limitations of traditional methods by achieving durable, opaque, and soft coatings without the use of hazardous materials.
Implementation Method 1
aqueous anionic polyurethane dispersion
Implementation Method 2
produce films with high opacity and soft touch
Data Source
AI summary
Aqueous dispersions containing anionic polyurethanes are prepared by reacting a prepolymer A), obtained from aliphatic or cycloaliphatic diisocyanates, polytetramethylene glycol and one or more anionic or potentially anionic polyols, with a chain extender B) which is a diamine sulfonate salt; the dispersion have a medium particle size above 600 nm and give films of high opacity and soft-feel touch which are useful for the coating of leather, fabrics, paper, cardboard, plastic, wood and metals.