Polymodal Polyurethane Coating for Spatter-Free Application
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Solution Overview
Problem
Existing methods for applying protective films to painted motor vehicle parts suffer from issues such as overspray, spatter, frayed edges, and the need for manual removal, which are inefficient and costly, particularly due to the use of solvents or labor-intensive foil applications.
Innovation Solution
A coating composition comprising an aqueous polyurethane dispersion with specific rheological properties, obtained by polymerizing NCO prepolymers and neutralizing agents, allowing for precise, spatter-free application and easy removal, characterized by a degree of neutralization, solids content, pH, and polymodal particle size distribution, which enables viscoelastic behavior and controlled viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional aqueous dispersions are used for coating, then the coating can be applied to painted surfaces, but the liquid cannot be applied with precise edges and without overspray
Solution Approach 1:
The patent applies parameter changes by carefully controlling the degree of neutralization (30-70%) and adjusting the pH value (6.5-8.5) of the coating composition. These parameter adjustments modify the rheological properties and surface tension of the liquid, enabling precise application edges and preventing overspray while maintaining complete area coverage
2Manufacturing precision
If multi-jet nozzle is used to achieve overspray-free application, then precise edges can be obtained, but spatter occurs when switching the nozzle on and off
Solution Approach 1:
The patent modifies the rheological parameters of the coating composition, specifically optimizing viscosity and shear thinning behavior. This allows the coating to be discharged at controlled speeds from the nozzle, preventing spatter when switching on and off while maintaining precise edge definition during application
3Productivity
If coating material is discharged at high speed to maintain application efficiency, then productivity is improved, but pressure surges cause material to splash back and contaminate the surface
Solution Approach 1:
The patent optimizes the viscosity parameters and shear thinning characteristics of the coating composition. This allows the material to be discharged at high speeds for productive application while the controlled rheological behavior prevents pressure surges and splash-back, eliminating spatter contamination
4Reliability
If conventional coatings are applied to achieve complete coverage, then the film can protect the surface, but frayed edges make it difficult to peel off the film
Solution Approach 1:
The patent applies parameter changes by controlling the degree of neutralization (30-70%) and pH value (6.5-8.5), which creates a balanced film structure. This results in frayed-free edges that maintain film coherence for reliable protection while enabling easy peeling off without manual intervention
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 composition allows for efficient, spatter-free application and complete removal of films without the need for follow-up treatments, ensuring uniformity and coherence, reducing labor and material waste.
Implementation Method 1
obtained from the polymerization of NCO prepolymers containing reaction products of aliphatic and/or cycloaliphatic diisocyanates
Implementation Method 2
The coating composition according to the invention has viscoelastic behavior, with the material functions of the modulus of elasticity G′ and the loss modulus G′′ having a substantially constant slope in the deformation range between γ=0.05 and γ=1
Implementation Method 3
After the film has dried or hardened
Implementation Method 4
applying an aqueous dispersion to the painted parts and solidifying the dispersion to form a peelable film
Data Source
Figure 1a
Figure 1b
Figure 2a
AI summary
The invention relates to a coating composition, a method for the production thereof, and the use thereof for producing liquid films, wherein the coating composition can be produced from one or more polyurethane dispersions, which are obtained from the polymerization of NCO prepolymers made of aliphatic and/or cycloaliphatic diisocyanates, macrodiols, 2,2-bis-(hydroxymethyl)-monocarboxylic acids and short-chained diols, by adding a neutralizing agent and subsequent slow stirring, wherein at least one polyurethane dispersion has a polymodal particle size distribution having at least one part in the range from 50 to 150 nm, at least one part in the range from 250 to 600 nm and/or at least one part in the range from 1000 to 3000 nm.