Nitroxyl-Mediated Levelling Agents for Powder Coatings
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Solution Overview
Problem
Conventional levelling agents in high viscosity coatings and powder coatings, particularly thermally or radiation curable powder coatings, face challenges in achieving smooth surfaces and controlling yellowing tendencies, with existing solutions not providing an optimal balance of levelling performance and handling characteristics.
Innovation Solution
The use of nitroxyl-mediated controlled free radical polymerization to synthesize levelling agents with well-defined molecular weights and narrow distributions, allowing for the creation of solid levelling agents that can be used directly in powder coatings without the need for formulation into a liquid form, and reducing yellowing in coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional levelling agents are used in high viscosity coatings and powder coatings, then levelling performance deteriorates, but using liquid levelling agents requires formulation into master batches which increases production costs and handling complexity
Solution Approach 1:
The invention changes the physical state parameter of levelling agents from liquid to solid form through controlled polymerization. Solid levelling agents can be directly incorporated into powder coating formulations without requiring liquid carrier systems or master batch preparation, thereby simplifying the formulation process while maintaining or improving levelling performance in high viscosity and powder coatings.
2Reliability
If liquid levelling agents are formulated into master batches for powder coatings, then levelling performance can be maintained, but production costs increase and stock keeping becomes more difficult
Solution Approach 1:
The invention extracts the levelling function from liquid carrier systems and master batch formulations, delivering it in pure solid form. This eliminates the need for additional formulation steps and reduces the amount of material required, as solid levelling agents are 100% active material without liquid carriers, thereby reducing production costs and simplifying stock keeping.
3Ease of operation
If poly-tert.-butyl acrylate or poly-tert.-butyl methacrylate are used as levelling agents in powder coatings, then handling characteristics improve, but yellowing tendency increases
Solution Approach 1:
The invention creates composite polymer structures by copolymerizing tert.-butyl acrylate or tert.-butyl methacrylate with other monomers that have different yellowing characteristics. This composite approach allows the formulation to maintain the desirable handling characteristics of tert.-butyl-based polymers (solid state, high Tg) while mitigating the yellowing tendency through the presence of other monomer units in the copolymer chain.
4Manufacturing precision
If narrow molecular weight distribution is achieved through nitroxyl-mediated polymerization, then levelling performance improves, but polymer synthesis complexity increases
Solution Approach 1:
The invention employs nitroxyl mediators (such as TEMPO or other stable free radicals) as intermediaries in the polymerization process. These mediators enable controlled radical polymerization that produces polymers with narrow molecular weight distributions. The nitroxyl mediator acts as a reversible terminator, controlling chain growth and preventing uncontrolled branching and crosslinking, thereby achieving precise molecular weight control while using a well-established chemical mechanism.
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 nitroxyl-mediated polymerization process produces levelling agents that enhance the smoothness and reduce yellowing of coatings, improving handling characteristics and reducing production costs by eliminating the need for master batches, while maintaining high levelling performance in powder coatings.
Implementation Method 1
nitroxyl mediated free radical polymerisation (NOR)
Data Source
AI summary
The present invention relates to coating compositions containing a polymeric or copolymeric levelling agent, which has been prepared by nitroxyl-mediated polymerisation. Further aspects are a process for the preparation of smooth surface coatings and the use of said polymer or copolymer as levelling agent in coating compositions. Yet another aspect are specific ethylenically unsaturated monomer compositions from which copolymers can be obtained by atom transfer radical polymerisation or nitroxyl mediated polymerisation, which copolymers are useful as levelling agents in coating compositions. Still another aspect is the use of poly-tert.-butyl acrylate or poly-tert.butylmethacrylate as a levelling agent in powder coating compositions.