Waterborne Coating Composition for High-Transfer Multi-Color Application
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Solution Overview
Problem
Current automotive coating methods require multiple spray operations for multiple colors, leading to labor-intensive masking, significant waste, and inefficient droplet distribution, while conventional inkjet inks lack durability and sag resistance for vertical surfaces.
Innovation Solution
A one-component waterborne coating composition is applied using a high transfer efficiency applicator, comprising a resin dispersion, polyurethane, optional cross-linker, pigment, water, water-soluble solvent, and rheology control agents, with a pH >7 and viscosity of 20-100 cps, to form a uniform coating layer with minimal overspray and sag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional spray equipment is used to apply automotive coating, then a uniform high-quality coating can be produced in relatively short time, but significant overspray waste occurs and labor-intensive masking is required for multiple colors
Solution Approach 1:
The coating application is segmented into digitally controlled droplet ejection through multiple nozzles, allowing precise placement of paint only where needed on the substrate, eliminating the broad jet distribution that causes overspray waste
Solution Approach 2:
The conventional pneumatic spray system is replaced with a digital inkjet system that uses piezoelectric or thermal mechanisms to eject precisely controlled droplets, enabling pattern-based application without physical masking
2Ease of operation
If conventional inkjet inks are used for digital printing, then low viscosity enables easy ejection through nozzles, but the coating lacks durability and sag resistance for vertical surfaces
Solution Approach 1:
The viscosity parameter is dynamically controlled through shear-thinning rheology, where the coating maintains low apparent viscosity during high-shear ejection through nozzles but exhibits high viscosity at rest to prevent sagging and ensure durability on vertical surfaces
Solution Approach 2:
The coating formulation uses composite rheology control combining shear-thinning polymers with sag-resistance agents, creating a material that simultaneously achieves easy nozzle ejection and excellent durability for automotive applications
3Manufacturing precision
If multiple spray operations are used for multiple colors, then complete color coverage is achieved, but labor-intensive masking and multiple passes increase time and cost
Solution Approach 1:
Digital patterns and color designs are copied directly onto the substrate through programmable droplet ejection, eliminating the need for physical masking and enabling complex multi-color patterns in a single operation
Solution Approach 2:
The system uses periodic actuation of individual nozzles in a scanning pattern, selectively ejecting different colors at different positions and times to build up complete multi-color coverage without requiring multiple physical passes
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 method achieves nearly 100% transfer efficiency with minimal overspray and sag, enabling efficient application of multiple colors and patterns on automotive surfaces without labor-intensive masking, while ensuring durability and resistance to weathering.
Implementation Method 1
In drop-on-demand printing, the energy to eject a drop of ink can be from a thermal resistor, a piezoelectric crystal, acoustic or a solenoid valve.
Implementation Method 2
conventional ink jet inks are formulated to have a low and generally shear-rate independent, or Newtonian, viscosity... By contrast, an automotive coating typically has significant non-Newtonian shear behavior with extremely high viscosity at low-shear to help avoid pigment settling and to ensure rapid and even set-up of the coating immediately after application
Implementation Method 3
conventional ink jet inks have typically been formulated to print on porous substrates such as paper and textiles where the ink is rapidly absorbed into the substrate thus facilitating drying and handling of the substrate shortly after printing
Data Source
AI summary
A method includes applying a coating composition to a substrate through a high transfer efficiency applicator wherein the coating composition has a pH of greater than about 7 and comprises:A. a resin dispersion comprising a latex, a polyurethane, or combinations thereof;B. an optional cross-linker;C. an optional pigment;D. water;E. a water-soluble solvent; andF. at least one rheology control agent chosen from an alkali swellable emulsion, a layered silicate, and combinations thereof;wherein the coating composition has a viscosity of about 20 to about 100 cps as determined using ASTM 7867-13 with cone-and-plate or parallel plates at a shear rate of 1000 sec-1, andwherein the coating composition has a wet film thickness of at least 20 microns measured at about 45 degrees without visible sag.