Acrylamide Copolymer Stability via Polyvalent Cationic Ions
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Solution Overview
Problem
Existing processes for producing cationic or amphoteric acrylamide polymers through Hofmann degradation reaction result in unstable products with low molecular weight, limiting their effectiveness in applications like paper manufacturing due to instability and poor drainage performance.
Innovation Solution
Introducing a significant proportion of polyvalent cationic ions into the reaction medium before adding hypohalide and hydroxide, allowing the use of readily available and less impure sodium hypochlorite, which stabilizes the polymer chain and increases molecular weight, resulting in high viscosity and improved stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Hofmann degradation processes are used to produce cationic or amphoteric acrylamide polymers, then cationic charge density is achieved, but the resulting polymers have low molecular weight and poor stability
Solution Approach 1:
The patent applies preliminary action by adding polyvalent cationic ions to the reaction medium before initiating the Hofmann degradation reaction. This pre-treatment modifies the reaction environment to prevent polymer chain scission during degradation, thereby maintaining high molecular weight while achieving the desired cationic charge density. The polyvalent cationic ions act as protective agents that stabilize the polymer chains throughout the degradation process.
2Reliability
If calcium hypochlorite is used to improve stability, then polymer stability increases, but impurity levels increase and handling becomes more difficult
Solution Approach 1:
The patent applies parameter changes by switching from solid calcium hypochlorite to aqueous sodium hypochlorite solution as the hypohalide source. This change in physical state and chemical composition eliminates the handling difficulties associated with powdered calcium hypochlorite while maintaining the stability benefits. The aqueous sodium hypochlorite solution is easier to handle, store, and apply in industrial settings, and the patent further optimizes by adding polyvalent cationic ions to ensure polymer stability is maintained despite the reagent change.
3Quantity of substance
If high concentration of hypohalide is used to achieve high cationic charge density, then cationicity increases, but polymer stability decreases
Solution Approach 1:
The patent applies the intermediary principle by introducing polyvalent cationic ions as mediators between the hypohalide reagent and the polymer chains. These intermediary ions facilitate the Hofmann degradation reaction to proceed efficiently, achieving high cationic charge density, while simultaneously protecting the polymer chains from excessive degradation and maintaining stability. The polyvalent cationic ions mediate the interaction between the aggressive hypohalide and the polymer substrate, balancing reaction efficiency with polymer integrity.
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 achieves stable and high-molecular-weight cationic or amphoteric polymers with enhanced viscosity and cationic charge density, suitable for paper manufacturing and drainage applications, while simplifying handling and reducing impurity issues.
Implementation Method 1
Hofmann's degradation This reaction, discovered by Hofmann at the end of the nineteenth century, makes it possible to switch from an amide function to a primary amine function by elimination of a carbon atom.
Implementation Method 2
In the presence of a base (e.g.: NaOH), a proton is stripped from the amide.
Implementation Method 3
The amidate ion formed then reacts with the active chlorine (Cl2) of the hypochlorite (e.g.: NaClO) to give an N-chloramide.
Implementation Method 4
The base (NaOH) strips a proton from the chloramide to form an anion. The anion loses a chloride ion to form a nitrene
Implementation Method 5
The anion loses a chloride ion to form a nitrene which undergoes rearrangement to isocyanate.
Implementation Method 6
By reaction between the hydroxide ion and the isocyanate, a carbamate is formed.
Implementation Method 7
After decarboxylation (elimination of CO2 in the presence of acid, e.g.: HCl) from the carbamate, a primary amine is obtained in the form of an acid salt.
Data Source
AI summary
The invention relates to a method for preparing cationic or amphoteric (co)polymers derived from acrylamide by a Hofmann degradation reaction in an aqueous solution in the presence of an alkaline and/or alkaline-earth hydroxide and of an alkaline hypohalide on a base copolymer characterised in that the base solution on which the reaction is carried out contains a polyvalent cationic salt representing at least 0.5 wt % and preferably 2 to 10 wt % of the base copolymer.