Water-absorbing Polymer Redox Initiator Segmentation

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Solution Overview

Problem

Existing methods for producing water-absorbing polymers face challenges in optimizing the initiator system mixing, leading to premature polymerization and high uncrosslinked polymer content, which affects the efficiency and quality of the polymerization process.

Innovation Solution

A continuous process where a monomer solution is mixed with a redox initiator consisting of an oxidizing agent and a reducing agent, with the oxidizing agent being premixed and added before the polymerization reactor and the reducing agent metered into the reactor, using a Venturi tube for precise mixing to minimize premature polymerization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the redox initiator components are mixed together before entering the polymerization reactor, then the mixing is simple, but premature polymerization occurs

Engineering Contradiction:

Improvemixing simplicityVSAvoidpolymerization control

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The redox initiator system is segmented into two separate feeds: one containing the oxidizing agent (sodium persulfate) and the other containing the reducing agent (ascorbic acid). These segmented feeds are introduced at different locations - the oxidizing agent is premixed with monomer solution before the reactor, while the reducing agent is metered in immediately before the kneader, preventing premature contact and polymerization.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A Venturi tube is introduced as an intermediary mixing device that enables precise control of the redox initiator addition. The Venturi tube creates a controlled mixing zone where the oxidizing and reducing agents can be combined under specific flow conditions immediately before polymerization, acting as a mediator between separate feed systems.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the monomer solution is rapidly mixed with both initiator components, then the mixing efficiency is high, but uncrosslinked polymer content increases

Engineering Contradiction:

Improvemixing efficiencyVSAvoidcrosslinking quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The oxidizing agent (sodium persulfate) is preliminarily mixed with the monomer solution in a controlled manner before entering the polymerization reactor. This preliminary action allows the oxidizing agent to be uniformly distributed in the monomer phase without immediately reacting, setting the stage for controlled polymerization when the reducing agent is subsequently added.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The Venturi tube serves as an intermediary device that enables efficient mixing of the redox initiator components under controlled conditions. By utilizing the Venturi effect, the tube creates a controlled mixing zone where rapid mixing occurs only at the precise location and time needed for optimal crosslinking, preventing premature reaction while ensuring thorough mixing when required.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Stability of the object's composition

If the reducing agent is added earlier in the process, then the initiator system is more stable, but polymerization control is reduced

Engineering Contradiction:

Improveinitiator system stabilityVSAvoidpolymerization control

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The conventional approach of adding both initiator components to the monomer solution beforehand is inverted. Instead, the oxidizing agent is added first and premixed with the monomer solution, while the reducing agent is added later at the precise moment needed for polymerization initiation. This inversion of the addition sequence allows the oxidizing agent to remain stable in the monomer phase while maintaining polymerization control through timed reducing agent addition.

Inventive Principle:

Principle #13The other way round (Inversion)

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 approach reduces the risk of premature polymerization, maximizes monomer conversion, and minimizes uncrosslinked polymer content, resulting in high-quality water-absorbing polymer particles with low residual monomers and extractables.

Implementation Method 1

using a Venturi tube for precise mixing to minimize premature polymerization

Methodology Applied

Scientific EffectVenturi effect: Venturi Effect

Implementation Method 2

a monomer solution is mixed with a redox initiator consisting of at least one oxidizing agent and at least one reducing agent

Methodology Applied

Scientific EffectRedox reactions: Redox Reactions

Data Source

PatentEP1926758B1Polymerization method

Publication Date: 2018.02.28 BASF SE

Figure 1~2

AI summary

The invention relates to a method for continuously producing water-absorbing polymer particles, whereby a monomer solution is mixed and polymerized with a redox initiator, comprising at least one oxidant and at least one reducing agent. The invention is characterized in that the monomer solution, before being fed to the polymerization reactor, is mixed with at least one oxidant and the at least one reducing agent is metered into the polymerization reactor. The invention also relates to a method for carrying out said method.