Volatile Amine-Free Polyurethane Dispersions via Alkaline Neutralization
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Solution Overview
Problem
Existing aqueous dispersions of anionic polyurethanes contain volatile amines, which cause toxicological and ecological issues, and the use of alkaline metal cations for neutralization leads to instability and reduced water resistance in films.
Innovation Solution
A procedure for preparing stable aqueous dispersions of anionic polyurethanes without polyoxyethylene or polyoxypropylene side chains, using alkaline metal hydroxide for neutralization, eliminating the need for volatile amines and ensuring high chemical and mechanical resistance of the resulting films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If volatile tertiary organic amines are used as neutralizing agents, then dispersibility and stability in water are improved, but toxicological and ecological problems arise and bad smell is generated
Solution Approach 1:
The patent changes the chemical nature of the neutralizing agent from volatile organic amines to non-volatile alkaline metal hydroxides, fundamentally altering the volatility parameter while maintaining the neutralization function. This substitution eliminates toxic emissions and bad smell while preserving dispersibility through the carboxylic acid groups.
Solution Approach 2:
The patent employs common, inexpensive alkaline metal hydroxides (sodium hydroxide, potassium hydroxide) as neutralizing agents, replacing expensive and hazardous volatile organic amines. These simple inorganic bases provide effective neutralization without the need for complex purification or handling procedures.
2Object-affected harmful factors
If alkaline metal cations are used as neutralizing agents, then volatile amines are eliminated, but film instability and reduced water resistance occur
Solution Approach 1:
The patent optimizes the neutralization degree parameter by controlling the molar ratio of alkaline metal hydroxide to carboxylic acid groups, achieving complete neutralization without excessive base addition. This precise parameter control prevents film instability while eliminating volatile amines.
Solution Approach 2:
The patent creates a composite polyurethane structure containing both carboxylic acid groups (for stability and water resistance) and the introduced side chains (for dispersibility). This composite structure reconciles the conflicting requirements of film stability and water resistance with dispersibility in aqueous media.
3Reliability
If polyoxyethylene or polyoxypropylene side chains are introduced, then dispersibility and stability in water are improved, but chemical and mechanical resistance of the film decreases and swelling in water increases
Solution Approach 1:
The patent changes the chemical nature of the side chains from polyoxyethylene/polyoxypropylene to alternative structures that provide dispersibility through different mechanisms. The introduced side chains maintain water compatibility without the severe compromise to film strength and chemical resistance observed with conventional polyoxyalkylene chains.
Solution Approach 2:
The patent develops a composite polyurethane system where the main chain provides mechanical strength and chemical resistance, while the introduced side chains provide dispersibility. This composite approach allows optimization of each component's function without the trade-offs inherent in using polyoxyethylene/polyoxypropylene side chains.
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 stable, volatile amine-free aqueous dispersions that form films with excellent chemical and mechanical resistance, suitable for various applications including leather and paper, without the drawbacks of traditional neutralization methods.
Implementation Method 1
dispersing the pre-polymer in an aqueous solution containing an alkaline metal hydroxide, at temperature between 5° and 30°C, the amount of alkaline metal hydroxide being enough to neutralize at least 60% of the carboxylic groups of the pre-polymer
Implementation Method 2
extending the pre-polymer by addition of a polyamine, maintaining the temperature between 5 and 40°C, and obtaining a 20 to 50% by weight aqueous dispersion of anionic polyurethane
Implementation Method 3
Aqueous dispersions of anionic polyurethanes have been known for a long time and used in various fields, due to the high chemical and mechanical resistance of films which are obtained by evaporation of their liquid phase
Data Source
AI summary
Process for the preparation of aqueous dispersions of carboxylated anionic polyurethanes free from volatile amines, useful for the preparation of coatings for leather, paper, metals, textiles and plastics.