Solvent-Free Polyurethane Thickener Process for Stable Rheology
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Solution Overview
Problem
Existing batch processes for producing polyurethane compositions as rheology modifiers in paint and coating formulations are inefficient, leading to high production costs, batch-to-batch variations, and mechanical/thermal destruction of polymers due to high shear rates, and require the use of toxic solvents.
Innovation Solution
A continuous process for preparing polyurethane compositions by mixing polyethylene glycol, C4 to C30 alcohols or alkoxylates, and polyisocyanate with a catalyst at controlled temperatures and residence times, without solvents, using static mixers to achieve a non-Newtonian rheology profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If batch processes are used to produce polyurethane compositions, then production flexibility is maintained, but production costs increase and batch-to-batch variations occur
Solution Approach 1:
The patent implements a continuous process where polyurethane composition is produced continuously through a reactor system with continuous feed of raw materials and continuous discharge of product. This eliminates batch-to-batch variations, reduces production costs, and maintains production flexibility through continuous operation.
2Productivity
If high mechanical energy input is used for mixing, then homogenization speed increases, but polymer melt destruction occurs due to high shear rates
Solution Approach 1:
The patent replaces high-energy mechanical mixing with a reaction-driven homogenization process. The polyurethane composition is formed through chemical reaction between isocyanate and hydroxyl components, which naturally homogenizes the mixture without requiring high-shear mechanical mixing. This substitution of mechanical mixing with chemical reaction prevents polymer destruction while achieving complete homogenization.
3Ease of operation
If solvent-based processes are used for high viscosity polyurethanes, then processability improves, but toxic solvent use and additional solvent exchange steps are required
Solution Approach 1:
The patent extracts and eliminates the solvent component from the process entirely. Instead of using organic solvents to improve processability, the invention achieves direct processing of high-viscosity polyurethane compositions through controlled continuous reaction and extrusion, removing the harmful solvent step and eliminating toxic waste.
4Reliability
If higher viscosity is used in surface coating compositions, then resistance to settling increases, but fluidity during application decreases
Solution Approach 1:
The patent produces polyurethane compositions with specifically controlled rheological parameters including viscosity and shear-thinning characteristics. By adjusting the molecular weight, composition ratios, and reaction conditions, the final product exhibits high viscosity for settling resistance while maintaining shear-thinning behavior for application fluidity.
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 efficiently homogenizes highly viscous polyurethane polymers, providing a non-Newtonian rheology profile suitable for water-borne coatings, reducing production costs and avoiding solvent use.
Implementation Method 1
mixing polyethylene glycol, C4 to C30 alcohols or alkoxylates, and polyisocyanate with a catalyst
Implementation Method 2
faster mixing on the macro-level can be achieved with a higher input of mechanical energy. The power introduced is dissipated and leads to heating. At a high power, a turbulent flow profile is produced. In a turbulent flow, chaotic eddies are formed.
Implementation Method 3
Mixing transverse to the flow direction is significantly higher due to this convective contribution than in the case of laminar flow in which transverse mixing is based on diffusion alone.
Implementation Method 4
The continuous process for preparing a polyurethane composition comprises the steps of (A) mixing... at a temperature in the range of ≥50° C. to ≤80° C. (B) reacting the reaction feed stream... at a temperature in the range of ≥80° C. to ≤150° C., wherein the difference between the temperature in step (B) and the temperature in step (A) is at least 10° C.
Data Source
AI summary
The presently claimed invention provides a continuous process for preparing a polyurethane composition which behaves as a rheology modifier upon addition to paint and coating formulations. The present process employs mixers for homogenization of highly viscous polyurethane polymers and by adjusting the process parameters and reactor conditions in specified ranges obtained a polyurethane composition. The polyurethane composition obtained from the process of the present invention is used as thickener in water-borne paint and coating formulations.