Low Primary Amine Polyaspartic Esters for Extended Pot Life
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Solution Overview
Problem
The rapid reactivity of primary amines in polyaspartic esters leads to short pot life and increased viscosity in polyurea coatings, especially in high humidity and temperature conditions, making it difficult to apply coatings effectively.
Innovation Solution
A method for producing low primary amine polyaspartic esters by reacting an aliphatic diamine with an excess of a Michael addition receptor in the presence of a C1-C10 alcohol, resulting in a product with a monoaspartate content of less than 10%, which slows down the reaction and extends the working time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If standard polyaspartic amines are used with high primary amine content, then the crosslinking reaction with polyisocyanate is rapid and highly crosslinked polyurea coatings are formed, but the pot life is very short (seconds to minutes) and viscosity increases rapidly
Solution Approach 1:
The patent changes the chemical composition parameters of the polyaspartic ester by controlling the ratio of diamine to Michael addition receptor to be less than 0.5:1, and controlling the primary amine value to be less than 35 mg KOH/g. This parameter change transforms the highly reactive primary amine groups into less reactive secondary amine groups, thereby reducing the reaction rate with polyisocyanate while maintaining crosslinking density
Solution Approach 2:
The patent uses an excess of Michael addition receptor (more than 1 equivalent relative to diamine) to ensure complete consumption of primary amine groups. This excessive action of the Michael addition receptor converts more primary amines to secondary amines, further controlling the reactivity and extending pot life
2Adaptability or versatility
If the reaction is conducted in high humidity and high temperature environments, then the coating can be applied in challenging conditions, but the working time is decreased and application issues occur
Solution Approach 1:
The patent changes the chemical structure parameters by creating polyaspartic esters with low primary amine content and controlled molecular weight distribution. This structural modification makes the system less sensitive to temperature and humidity variations, allowing application in broader environmental conditions while maintaining adequate working time
3Strength
If standard polyaspartic esters with high primary amine content are used, then the reaction with polyisocyanate is fast and highly crosslinked coatings are formed, but heat is generated and viscosity increases rapidly
Solution Approach 1:
The patent changes the functional group composition by controlling the primary amine value to be less than 35 mg KOH/g. This parameter change reduces the number of highly exothermic primary amine-isocyanate reactions, thereby reducing heat generation while still achieving sufficient crosslinking through secondary amine reactions
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 polyaspartic esters with a lower monoaspartate content, leading to slower reactivity and increased working time, allowing for more effective application of polyurea coatings in challenging environmental conditions without compromising productivity.
Implementation Method 1
reacting an aliphatic diamine with a Michael addition receptor in the presence of a C1-C10 alcohol to produce a polyaspartic ester
Implementation Method 2
Reaction of polyisocyanates with an amine as the isocyanate-reactive component produces highly crosslinked polyurea coatings
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Low primary amine (LPA) polyaspartic esters are provided which comprise a reaction product of an aliphatic diamine and an excess of a Michael addition receptor optionally, in the presence of a C1-C10 alcohol, wherein the low primary amine (LPA) polyaspartic ester has a monoaspartate content of less than 10%. The low primary amine (LPA) polyaspartic esters of the invention may find use in slow reactivity polyurea systems and react with polyisocyanates to produce polyurea coatings, adhesives, sealants, films, composites, castings, and paints.