Water-Absorbent Resin Particle Production via Reversed-Phase Suspension

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Solution Overview

Problem

Existing methods for producing water-absorbent resin particles struggle to achieve a suitable particle size and narrow particle size distribution while maintaining excellent water-absorption ability, which is crucial for their application in absorbent articles.

Innovation Solution

The use of a specific organic acid ester of monoglyceride as a dispersion stabilizer in reversed-phase suspension polymerization allows for the production of water-absorbent resin particles with suitable particle size and narrow distribution, enhancing their water-absorption capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If aqueous solution polymerization method is used, then the polymerization process is simple, but the resulting gel is viscous and block-shaped making milling complicated and generating fine particles

Engineering Contradiction:

Improvepolymerization process simplicityVSAvoidmilling process complexity

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent inverts the conventional polymerization approach by using reversed-phase suspension polymerization instead of aqueous solution polymerization. This inversion allows the polymerization to occur in a dispersion medium rather than aqueous solution, producing particles with controlled size and shape that eliminate the need for complicated milling processes.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the physical and chemical parameters of the polymerization system by selecting specific dispersion media (hydrocarbons with 6-8 carbon atoms) and controlling droplet size during polymerization. These parameter changes result in particles with suitable size distribution that do not require extensive milling, thus resolving the contradiction between manufacturing simplicity and process complexity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If particle size is increased, then water-absorption capacity is improved, but the absorbent material becomes hard when compressed

Engineering Contradiction:

Improvewater-absorption capacityVSAvoidmaterial hardness

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies local quality by creating particles with specific size ranges (0.1-1.0 mm median diameter) and controlled internal structure through reversed-phase suspension polymerization. This allows different regions of the absorbent material to have appropriate particle sizes that balance water-absorption capacity with compressibility, preventing excessive hardness while maintaining high absorption performance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent uses partial action by controlling the polymerization to produce particles with optimal size distribution rather than uniformly large particles. This selective size control ensures sufficient water-absorption capacity while avoiding the excessive hardness that would result from using only large particles, thus resolving the contradiction between absorption performance and material softness.

Inventive Principle:

Principle #16Partial or excessive action

3Ease of operation

If particle size is decreased, then the particles can pass through metallic mesh easily, but they are not preferable for absorbent material performance

Engineering Contradiction:

Improveparticle handlingVSAvoidabsorbent material performance

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent changes the particle size parameter to a specific range (0.1-1.0 mm median diameter) that is large enough to be retained by metallic mesh during absorbent material production, yet small enough to ensure good flowability and handling. This parameter optimization resolves the contradiction between ease of operation and material performance by finding the optimal size window that satisfies both requirements.

Inventive Principle:

Principle #35Parameter changes

4Manufacturing precision

If conventional dispersion stabilizers are used in reversed-phase suspension polymerization, then particle size can be controlled, but narrow particle size distribution and excellent water-absorption ability cannot be achieved simultaneously

Engineering Contradiction:

Improveparticle size controlVSAvoidwater-absorption ability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent introduces a specific dispersant (sorbitan fatty acid ester or polyglycerol fatty acid ester with particular HLB values) as an intermediary substance that mediates between the hydrophobic dispersion medium and the hydrophilic polymerizing monomer. This specialized dispersant enables precise control of particle size distribution while maintaining excellent water-absorption ability, resolving the contradiction between manufacturing precision and product performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent optimizes the HLB parameter of the dispersant (specific ranges for sorbitan and polyglycerol fatty acid esters) to achieve the desired balance between particle size control and water-absorption performance. By carefully selecting dispersants with specific HLB values, the patent simultaneously achieves narrow particle size distribution and high water-absorption capacity, resolving the contradiction between precision and performance.

Inventive Principle:

Principle #35Parameter changes

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 produces water-absorbent resin particles with improved water-retention capacity and suitable particle size distribution, making them suitable for use in absorbent articles such as disposable diapers and sanitary napkins.

Implementation Method 1

reversed-phase suspension polymerization method comprising dispersing a water-soluble ethylenically unsaturated monomer in the presence of a dispersion stabilizer in an organic dispersion medium

Methodology Applied

Scientific EffectDispersion: Dispersion (of waves)

Implementation Method 2

the use of a specific organic acid ester of monoglyceride as a dispersion stabilizer

Methodology Applied

Scientific EffectSurfactant action: Surfactant

Implementation Method 3

polymerization of a water-soluble ethylenically unsaturated monomer is the mainstream method for producing water-absorbent resin particles

Methodology Applied

Scientific EffectPolymerization:

Implementation Method 4

crosslinked products of partially neutralized polymers of acrylic acid

Methodology Applied

Scientific EffectCrosslinking:

Implementation Method 5

water-absorbent resin particles are required to exhibit not only an excellent water-absorption capacity and water-retention capacity

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Implementation Method 6

an absorbent material composed of water-absorbent resin particles and hydrophilic fibers

Methodology Applied

Scientific EffectCapillary action: Capillary Action

Data Source

PatentEP3124502B1Method for producing water-absorbent resin particle

Publication Date: 2019.05.01 SUMITOMO SEIKA CHEM CO LTD

AI summary

Provided is a method for producing water-absorbent resin particles suitable for use in absorbent article and the like, the water-absorbent resin particles having better water-absorbent performance, a suitable particle size, and a narrow particle-size distribution. A method for producing water-absorbent resin particles by reversed-phase suspension polymerization of a water-soluble ethylenic unsaturated monomer in a carrier fluid, wherein the method for producing water-absorbent resin particles comprises conducting the reversed-phase suspension polymerization reaction in the presence of an organic acid monoglyceride.