Powder Coating Flake Pigment Bonding
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Solution Overview
Problem
Powder coating compositions with flake-like pigments face challenges in achieving consistent, lustrous metallic finishes due to improper alignment and non-uniform distribution of pigments, leading to dull appearances and potential electrical discharges during electrostatic spraying.
Innovation Solution
A method involving a pigment composition with an initial particle size distribution that is heated to a temperature more than 2°F above the softening temperature of the polymeric binder, causing a shift to a second particle size distribution without fine particles, which enhances bonding and uniformity of flake-like pigments with the binder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If flake-like pigments are merely admixed with polymeric coating powder particulates, then the coating composition can be prepared, but the flakes are not charged to the same extent or deposited at the same rate as the polymeric coating powder particulates, resulting in inconsistent coatings and changing appearance over time
Solution Approach 1:
The patent bonds flake-like pigments to polymeric resin particles through controlled heating and mixing, merging them into a unified particulate structure. This ensures that both the polymer and flakes are charged and deposited together as a single unit, eliminating the inconsistency caused by separate charging behaviors.
Solution Approach 2:
The bonding of flakes to resin particles is performed in advance during the powder coating composition preparation stage. This preliminary action ensures uniform charge distribution and consistent deposition behavior before the electrostatic spraying process begins, preventing appearance changes over time.
2Manufacturing precision
If high shear mixing is used to bond flake-like pigments to resin particles, then bonding can be achieved, but many flake-like pigments are sensitive to fragmentation in high shear environments whereby the flake shape is damaged or destroyed
Solution Approach 1:
The patent changes the mixing parameters by using low shear mixing instead of high shear mixing, and controls the heating temperature to bond the flakes to resin particles. This parameter change achieves effective bonding while preserving the delicate flake shape that would be destroyed by high shear forces.
Solution Approach 2:
The patent creates a composite structure where flake-like pigments are bonded to polymeric resin particles to form a unified particulate material. This composite approach allows the flakes to be securely attached without requiring high shear mixing, thus maintaining their shape integrity.
3Ease of manufacture
If conventional bonding temperature (maximum 2°F higher than TG of base resin) is used to soften resin particles for flake adhesion, then bonding can occur, but the temperature may not be sufficient to achieve optimal bonding while maintaining particulate form
Solution Approach 1:
The patent increases the bonding temperature beyond the conventional limit of 2°F above the glass transition temperature (TG) of the base resin. This parameter change provides sufficient thermal energy to achieve optimal bonding of flakes to resin particles while still maintaining the particulate form necessary for powder coating applications.
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 produces a powder coating composition with improved uniformity and a lustrous metallic finish, reducing the risk of electrical discharges and maintaining consistency over time, even with reclaimed overspray particles.
Implementation Method 1
heating the pigment composition to a temperature to effect bonding of the flake-like, color effect pigments to the polymeric binder particles. In one embodiment, the pigment composition is heated to more than 2° F. greater than the TG of the polymeric binder
Implementation Method 2
The dispersed particles are subjected to a high voltage field in which the particles pick up an electrostatic charge. The charged particles are attracted to a charged substrate resulting in a fine layer of powder on the substrate.
Implementation Method 3
The charged particles are attracted to a charged substrate resulting in a fine layer of powder on the substrate.
Implementation Method 4
The coated substrate is heated to a temperature sufficient to melt the powder coating and to cause it to flow and provide a smooth, even finish.
Data Source
AI summary
A method of producing a coating composition containing flake-like, color effect pigment particles and polymeric binder. The pigment composition has an initial size with fine particles. Upon mixing and heating the pigment composition to a temperature to achieve a second particle size distribution, the fine particles in the initial particle size distribution are bound to the larger particles in the pigment composition. The time and temperature of bonding the pigment composition can be adjusted to account for the chemistry of the polymeric binder and the loading of the flake-like, color effect pigment.