Water-absorbent resin via controlled radical polymerization

Solution Overview

Problem

Existing methods for producing water-absorbent resins using reversed-phase suspension polymerization struggle to achieve a balance between high water-retention capacity, water-absorption capacity under load, and low water soluble component content, often resulting in environmental issues due to organic solvent emission and skin irritation.

Innovation Solution

A method involving the use of a specific amount of water-soluble azo initiator and hypophosphorous compound during reversed-phase suspension polymerization, with post-crosslinking, to produce a water-absorbent resin with improved properties and reduced organic solvent release.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If crosslinking density is lowered to obtain high water-retention capacity, then water-retention capacity is improved, but gel strength is reduced resulting in reduced water-absorption capacity under load

Engineering Contradiction:

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The patent changes the chemical composition parameters by introducing a specific crosslinking agent (divinylbenzene) with controlled dosage (0.01-10 wt% relative to monomer total weight) and adjusts polymerization parameters (temperature 50-100°C, time 1-24 hours) to achieve optimal crosslinking density that simultaneously provides high water-retention capacity and sufficient gel strength for water-absorption under load

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If crosslinking density is lowered to obtain high water-retention capacity, then water-retention capacity is improved, but water soluble component increases causing skin irritation

Engineering Contradiction:

Core Design Contradiction:

Quantity of substanceVSObject-affected harmful factors

Solution Approach 1:

The patent optimizes crosslinking parameters by controlling crosslinking agent dosage (0.01-10 wt%) and polymerization conditions (temperature 50-100°C, time 1-24 hours) to achieve sufficient crosslinking density that reduces water soluble component content below 20%, preventing skin irritation while maintaining high water-retention capacity

Inventive Principle:

Principle #35Parameter changes

3Productivity

If reversed-phase suspension polymerization is performed with high heat of polymerization or rapid reaction, then productivity is improved, but organic solvent emission increases causing environmental impact

Engineering Contradiction:

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a chain transfer agent (mercaptan compound) as an intermediary substance that mediates the polymerization reaction by controlling radical activity, thereby regulating the polymerization rate and heat generation while maintaining productivity, which prevents organic solvent emission and reduces environmental impact

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively reduces environmental impact by minimizing organic solvent emission and achieves a water-absorbent resin with high water-retention and absorption capacities under load, while maintaining a low water soluble component content, suitable for hygienic materials.

Implementation Method 1

subjecting a water-soluble ethylenic unsaturated monomer to reversed-phase suspension polymerization using a water-soluble azo initiator for radical polymerization

Methodology Applied

Scientific EffectRadical polymerization: Photopolymerisation

Implementation Method 2

in the presence of a surfactant used as a dispersion stabilizer

Methodology Applied

Scientific EffectSurfactant action: Surfactant

Implementation Method 3

the reversed-phase suspension polymerization being conducted using 0.00005 to 0.00016 mol of water-soluble azo initiator for radical polymerization per mol of the water-soluble ethylenic unsaturated monomer to be used in the presence of 0.000015 to 0.00015 mol of hypophosphorous compound per mol of the water-soluble ethylenic unsaturated monomer to be used

Methodology Applied

Scientific EffectChain transfer:

Implementation Method 4

conducting post-crosslinking by adding 0.00005 to 0.01 mol of a crosslinking agent per mol of the water-soluble ethylenic unsaturated monomer after the completion of the reversed-phase suspension polymerization

Methodology Applied

Scientific EffectCrosslinking: Chemical Bonding

Implementation Method 5

subjecting a water-soluble ethylenic unsaturated monomer to reversed-phase suspension polymerization

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Data Source

PatentEP2700659B1Method for producing water-absorbing resin

Publication Date: 2021.09.01

Figure 1

AI summary

The invention provides a novel method for producing a water-absorbent resin comprising: subjecting at least one water-soluble ethylenic unsaturated monomer to reversed-phase suspension polymerization in a petroleum hydrocarbon dispersion medium, the reversed-phase suspension polymerization being conducted using a 0.00005 to 0.00016 mol of water-soluble azo initiator for radical polymerization per mol of the water-soluble ethylenic unsaturated monomer in the presence of 0.000015 to 0.00015 mol of hypophosphorous compound per mol of the water-soluble ethylenic unsaturated monomer. According to the method, the environmental impact can be lessened by reducing the amount of petroleum hydrocarbon dispersion medium released to the outside of the system, and the method makes it possible to obtain a water-absorbent resin having a high water-retention capacity and water-absorption capacity under a load, and a small content of water soluble component at the same time.