Solid Gas Diamine Salt Formation Prevents Fouling
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Solution Overview
Problem
Existing processes for producing polyamides from diamine and dicarboxylic acid often require solvents or suspensions, leading to inefficiencies and challenges in isolating and recovering salts, and do not effectively prevent particle sticking and fouling during the reaction.
Innovation Solution
A process involving contacting diamine gas with dicarboxylic acid at a temperature below the melting points of both, resulting in a solid/gas reaction that forms discrete salt particles without the need for solvents, and subsequent solid-state polymerization to produce semi-crystalline polyamides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If salts are prepared in solution or suspension from aqueous solutions, then the reaction can proceed, but the salt must be isolated and recovered from the media, increasing process complexity
Solution Approach 1:
The patent extracts the salt formation process from the aqueous solution/suspension medium entirely. By using gaseous diamine reacting with solid dicarboxylic acid particles, the salt forms directly as discrete solid particles without dissolving in or dispersing within a liquid medium, eliminating the need for subsequent isolation and recovery operations.
Solution Approach 2:
The patent uses gaseous diamine as an intermediary reactant that delivers ammonia molecules to the solid acid particles without requiring a liquid medium. The gas phase serves as the intermediary transport medium, allowing salt formation to occur directly on the acid particles without dissolution.
2Productivity
If conventional salt preparation methods are used, then salts can be formed, but particle sticking and fouling occur during the reaction
Solution Approach 1:
The patent applies pneumatic principles by using gaseous diamine flow to deliver reactants to the solid acid particles. The gas flow prevents particle sticking by continuously moving over the particle surfaces and preventing localized accumulation of reactive material, while the discrete particle formation avoids fouling of reaction equipment.
Solution Approach 2:
The patent changes the physical state of the diamine reactant from liquid or dissolved to gaseous phase, and maintains the acid and salt in solid phase. This parameter change (phase state) fundamentally alters the reaction mechanism to prevent particle sticking and fouling while maintaining high productivity.
3Productivity
If diamine is provided as gas, then the reaction is fast and leads to high conversion, but the diamine must be heated to gas temperature
Solution Approach 1:
The patent performs the heating of diamine to gaseous state as a preliminary action before the actual salt formation reaction. By pre-heating the diamine to its gas temperature in a separate zone or step, the subsequent reaction with the solid acid proceeds rapidly at the gas-solid interface without requiring continuous energy input during the reaction itself.
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 method achieves high conversion rates and prevents particle sticking and fouling, allowing for efficient production of semi-crystalline polyamides with reduced energy costs and handling complexities.
Implementation Method 1
The reaction is a solid/gas reaction, due the fact that the diamine is provided as a gas; however the reaction mixture remains in the solid state
Implementation Method 2
The lower pressure leads to lower temperatures to convert diamine into a diamine gas
Data Source
AI summary
The invention relates to a process for preparing a salt from diamine and dicarboxylic acid, the process comprising contacting a diamine gas, having a gas temperature T-gas, with a dicarboxylic acid, thereby forming a reaction mixture comprising diamine/dicarboxylic acid salt, wherein the dicarboxylic acid and the reaction mixture are kept at a temperature T-mixture of at least 10° C. below the lowest of the melting temperature of the dicarboxylic acid (Tm-acid) and the melting temperature of the resulting diamine/dicarboxylic acid salt (Tm-salt). The invention also relates to a process for preparing a polyamide comprising preparing a salt from diamine and dicarboxylic acid.