Dialkyl Phosphinate Synthesis via Continuous Addition
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Solution Overview
Problem
Existing methods for preparing dialkylphosphinate flame retardants face challenges in controlling the content of long chain alkyl phosphinates and monoalkyl phosphinates, often requiring high pressure, which is unsafe for industrial production and affects product quality and thermal stability.
Innovation Solution
A process involving the continuous addition of phosphinic acid and/or its salts into a reaction system with alkene and an initiator, controlling the total mole fractions of monoalkyl phosphinic acids/salts to ensure the formation of dialkylphosphinic acids/salts with reduced long chain alkyl phosphinate content, thereby shortening reaction time and improving yield and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phosphinic acid or its salts are fed into the reaction kettle at one time and reacted with alkenes in the presence of azo initiators, then dialkyl phosphinate can be prepared, but the long chain alkyl phosphinate content becomes high (7-12%) and unstable, affecting product quality
Solution Approach 1:
The patent divides the phosphinic acid addition process into two stages: first adding part of the phosphinic acid to start the reaction, then continuously adding the remaining phosphinic acid during the reaction process. This segmentation of the addition process allows better control over the reaction kinetics and product distribution, reducing long chain alkyl phosphinate content to below 10% while maintaining stable quality.
Solution Approach 2:
The patent performs preliminary action by adding a portion of phosphinic acid before the main reaction to establish the reaction system and control the initial formation of monoalkyl phosphinate. This preliminary addition sets the stage for controlling the overall product distribution during subsequent continuous addition.
2Manufacturing precision
If water is used as co-solvent and phosphinic acid is fed at one time to react with alkene in the presence of initiator, then long chain alkyl phosphinate content can be controlled below 6%, but high pressure (20 bar) must be used which increases reaction risk
Solution Approach 1:
The patent changes the reaction parameters by using continuous addition of phosphinic acid instead of one-time feeding, and by adjusting the addition rate to control the reaction exotherm and pressure buildup. This allows achieving good product quality (long chain alkyl phosphinate < 10%) without requiring excessive pressure, thereby improving reaction safety while maintaining manufacturing precision.
3Productivity
If sodium phosphinate is reacted with ethylene in the presence of photoinitiators, then sodium diethylphosphinate can be prepared, but sodium monoethylphosphinate content becomes high (≥2.5% mole), resulting in low thermal stability of the final product
Solution Approach 1:
The patent applies continuous addition of phosphinic acid during the reaction process, maintaining continuous useful action that controls the concentration of reactive intermediates. This continuous control prevents excessive accumulation of monoalkyl phosphinate and promotes complete conversion to dialkyl phosphinate, thereby improving thermal stability while maintaining preparation efficiency.
Solution Approach 2:
The patent implements feedback control by monitoring the reaction progress and adjusting the phosphinic acid addition rate accordingly. This feedback mechanism ensures that the reaction conditions are optimized to minimize monoalkyl phosphinate formation and maximize dialkyl phosphinate yield, thereby improving product thermal stability.
4Manufacturing precision
If metal complexes and initiators are used to prepare dialkylphosphinate by feeding sodium phosphinate at one time, then monoalkyl phosphinate production is avoided, but various organic solvents are required which adversely affect purification and environment
Solution Approach 1:
The patent uses water or alcohol as an intermediary solvent that facilitates the reaction between phosphinic acid and alkene while being easily separable from the final product. This intermediary solvent system allows good control over monoalkyl phosphinate content without creating purification difficulties, and is more environmentally friendly than traditional organic solvents.
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 effectively controls the content of long chain alkyl phosphinates and monoalkyl phosphinates, reduces reaction time, and enhances the yield and purity of dialkylphosphinate products, making it suitable for industrial production while maintaining thermal stability.
Implementation Method 1
reacting the phosphinic acid or alkali metal salts thereof with alkenes in the presence of azo initiators to prepare the intermediate dialkyl phosphinic acids or alkali metal salts
Implementation Method 2
reacting phosphinic acid with alkene in the presence of an initiator to prepare dialkylphosphinate
Data Source
Figure 1
AI summary
The present provides a process for preparing dialkyl phosphinate, comprising: (1) firstly adding 0-99% of the total weight of phosphinic acids and/or salts thereof and a solvent into a reaction kettle;(2) in the reaction kettle in the presence of alkene and initiator, continuously adding 1-100% of the total weight of the phosphinic acids and/or salts thereof into the reaction system, during the addition process, when the mole contents of monoalkyl phosphinic acids and/or salts thereof account for 10% or less of the total molar contents of phosphorus in the reaction system, stopping adding the phosphinic acids and/or salts thereof. Also providing a dialkyl phosphinate flame retardant prepared by above preparation process.