Reactive Diluent Polymerization for Low VOC Coatings
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Solution Overview
Problem
Conventional exterior coatings for automobiles and trucks face challenges in reducing volatile organic compound (VOC) emissions, with existing methods either increasing complexity, cost, or compromising on appearance and properties, and there is a need for a solvent-free solution that maintains low viscosity for easy application.
Innovation Solution
The process involves polymerizing ethylenically unsaturated monomers with a reactive diluent as a liquid carrier, which has at least two reactive sites, allowing for the production of high solids (low VOC) paints that can be applied easily without volatile organic solvents, using alkoxy silanes, alkoxy silicates, amide acetals, ketimines, cyclic carbonates, orthoesters, or spiro-orthoesters as reactive diluents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the solids content of solvent borne liquid coatings is increased to reduce VOC emissions, then the polymer solution becomes too viscous, but this causes major problems with handling during manufacturing and ability to spray or otherwise apply the coating
Solution Approach 1:
The patent changes the chemical nature of the liquid carrier from conventional non-reactive solvents to reactive diluents with at least two reactive sites. This parameter change allows the system to achieve both high solids content (reducing VOC) and low viscosity (maintaining ease of application) because the reactive diluents participate in the polymerization reaction, becoming part of the polymer structure rather than remaining as separate volatile components.
Solution Approach 2:
The reactive diluent acts as an intermediary substance that mediates between the conflicting requirements of high solids content and low viscosity. By having at least two reactive sites, the diluent can crosslink with polymer chains, effectively reducing the viscosity of the high-solids polymer solution while still allowing for easy handling and application. The reactive diluent intermediates the contradiction by transforming from a simple solvent to an active participant in the polymer network formation.
2Ease of operation
If reactive diluents are used in the final paint to keep spray viscosity within acceptable limits, then the film-forming polymer must be stripped of environmentally adverse hydrocarbon solvents that are used in the polymer synthesis, but the stripping step adds complexity, time and expense to the polymer synthesis
Solution Approach 1:
The patent applies preliminary action by conducting the polymerization reaction directly in the reactive diluent from the start, rather than first synthesizing the polymer in conventional solvents and then stripping them. This preliminary choice of reaction medium eliminates the need for subsequent stripping steps, reducing process complexity while maintaining the desired spray viscosity through the reactive diluent's participation in the polymerization.
Solution Approach 2:
The invention takes out the harmful hydrocarbon solvents from the process entirely by replacing them with reactive diluents in the polymerization step. Instead of adding solvents and then removing them (the conventional approach), the reactive diluent is used from the beginning and becomes incorporated into the polymer structure, eliminating the extraction/stripping step and its associated complexity.
3Quantity of substance
If conventional organic liquid carrier solutions are used to attain high solids paints, then VOC emissions increase, but the need to reduce these emissions conflicts with maintaining low viscosity for easy application
Solution Approach 1:
The patent changes the fundamental parameter of the liquid carrier from non-reactive conventional organic solvents to reactive diluents with polymerization-active groups. This parameter change enables the system to maintain high solids content (increased quantity of polymer) while the reactive diluent becomes part of the polymer structure through its reactive sites, thereby eliminating VOC emissions as the diluent no longer volatilizes separately.
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
This approach enables the production of high solids content paints with low VOC emissions, maintaining low viscosity for easy application and achieving durable, weatherable coatings without the need for volatile organic solvents, thus addressing the environmental and operational challenges of conventional coating methods.
Implementation Method 1
polymerizing at least one ethylenically unsaturated monomer in the presence of a catalyst and a liquid carrier
Implementation Method 2
polymerizing at least one ethylenically unsaturated monomer... wherein said liquid carrier is a reactive diluent
Data Source
AI summary
The present process is directed to preparation of addition polymers in diluents that are subsequently reactive in coatings during cure, instead of in traditional hydrocarbon solvents. The polymers so prepared can be used as the main film-forming polymer in high solids coating compositions, especially those useful for finishing automobiles and truck exteriors.