Recyclable Polyamide Coating Powder via Melt Mixing
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Solution Overview
Problem
Current methods for manufacturing pigmented polyamide powders for coating substrates face challenges in recyclability, as overspray powder does not maintain the same composition or properties as the original powder, leading to inconsistencies in appearance and performance after recycling.
Innovation Solution
Incorporating pigments into low-viscosity polyamide in the melted state, followed by extrusion, grinding, and heat treatment to achieve the target viscosity, ensuring uniform distribution and stability of pigments and additives, thereby maintaining color and mechanical properties during recycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pigments and additives are dry-mixed with polymer powder, then manufacturing is simple, but recyclability is poor because overspray powder does not maintain the same composition as original powder
Solution Approach 1:
The patent combines pigments and additives with the polymer matrix through melt mixing to create a homogeneous composite powder. This merging ensures that all components are uniformly distributed and remain together during spraying and recycling, preventing composition degradation of overspray powder while maintaining manufacturing efficiency through a single integrated process.
Solution Approach 2:
The patent performs preliminary mixing of pigments and additives with the polymer in the melt state before powder formation. This preliminary action ensures uniform distribution of all components throughout the powder particles, so that when overspray occurs during application, the recovered powder maintains the same composition and properties as the original formulation.
2Ease of operation
If pigments are incorporated by adding to solution, then mixing is easy, but pigment incorporation is limited and nucleating effects cause difficulties
Solution Approach 1:
The patent changes the physical state parameter of the polymer from solid or solution to melt state during pigment incorporation. By processing the polymer in its molten state, the system achieves both ease of mixing (like solution processing) and high pigment incorporation capacity (overcoming solution limitations), while avoiding nucleating effects because the polymer is already in a fluid state that accommodates pigments without crystallization interference.
3Use of energy by stationary object
If polyamide is ground at ambient temperature, then energy consumption is low, but ductile polyamide grades are too ductile to be amenable to grinding
Solution Approach 1:
The patent utilizes phase transition by cooling the molten polyamide-pigment mixture to below its glass transition temperature, transforming it from a ductile rubbery state to a brittle glassy state. This phase transition enables effective grinding at ambient temperature with low energy consumption, as the brittle particles fragment easily rather than deforming plastically as would occur with ductile material.
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 process results in a pigmented pulverulent composition that maintains consistent appearance and performance even after recycling, with improved film formation and mechanical properties, making it suitable for demanding applications like automotive parts and dishwasher baskets.
Implementation Method 1
incorporating the pigment or pigments into the polyamide of low viscosity in the melted state
Implementation Method 2
The melt mixture is then cooled, pelletized and ground
Implementation Method 3
The melt mixture is then cooled, pelletized and ground
Data Source
AI summary
A pigmented pulverulent composition based on polyamide for coating substrates, including: (a) 40% to 99% by weight of at least one polyamide, (b) 1% to 30% by weight of at least one pigment, and (c) 0% to 30% by weight of at least one additive, wherein the polyamide has an inherent viscosity, as measured using an Ubbelohde tube at 20° C. on a 0.5% by weight solution in m-cresol according to standard ISO 307 but with a measuring temperature of 20° C. rather than 25° C., of more than 0.7 (g/100 g)−1, and wherein the composition has a volume-median diameter Dv50, as measured according to standard ISO 9276—parts 1 to 6, of 10 to 200 μm. A process for manufacturing the composition, the use thereof for coating a—metallic—substrate, and an object comprising a metallic substrate coated with a coating obtained with the pigmented pulverulent composition based on polyamide.