SAP Separation by Oxidative Solubilization in Sanitary Waste Recycling

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Solution Overview

Problem

Existing methods struggle to effectively separate super-absorbent polymers (SAP) from cellulose and plastic fractions in post-consumer absorbent sanitary products, leading to impurities that affect the purity and quality of recycled materials.

Innovation Solution

A method involving sterilization, immersion in an aqueous solution with oxidizing compounds like hydrogen peroxide to cleave cross-links and solubilize SAP, followed by separation and purification steps to obtain high-purity cellulose and plastic fractions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If mechanical separation or enzymatic action is used to separate cellulose from SAP, then the cellulose fraction can be separated, but SAP residues remain in the cellulose causing impurity

Engineering Contradiction:

Improvepurity of separated componentsVSAvoidSAP residues in cellulose fraction

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent changes the chemical state of SAP from cross-linked insoluble form to non-cross-linked soluble form by controlling the oxidation process. This parameter change allows SAP to be solubilized and separated from cellulose, achieving high purity in both fractions without leaving residues

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent uses strong oxidizing agents (sodium persulfate, potassium persulfate, or hydrogen peroxide) to accelerate the cleavage of cross-links in SAP. This strong oxidation process effectively breaks down the cross-linked structure, enabling complete solubilization and separation of SAP from cellulose, thereby eliminating SAP residues in the cellulose fraction

Inventive Principle:

Principle #38Strong oxidants (Accelerated oxidation)

2Manufacturing precision

If SAP is deactivated with calcium chloride or aluminum ions before separation, then plastic can be separated from SAP, but the process becomes complex and SAP purity is compromised

Engineering Contradiction:

Improvepurity of plastic and SAP fractionsVSAvoidcomplexity of separation process

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent extracts SAP from the mixed fraction by solubilizing it through oxidation. By taking out SAP in its solubilized form before plastic separation, the process simplifies the separation sequence and achieves high purity in both plastic and SAP fractions without requiring deactivation steps

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of the conventional approach of deactivating SAP first then separating, the patent inverts the sequence by solubilizing SAP first through oxidation, then separating it from both cellulose and plastic. This inverted approach simplifies the overall process and achieves superior purity

Inventive Principle:

Principle #13The other way round (Inversion)

3Manufacturing precision

If supercritical phase extraction is used to separate SAP from cellulose, then separation can be achieved, but the process requires complex equipment and high energy input

Engineering Contradiction:

Improveseparation efficiency of SAP and celluloseVSAvoidenergy consumption for supercritical extraction

Core Design Contradiction:

Manufacturing precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces the mechanical/physical supercritical extraction system with a chemical oxidation system. By using oxidizing agents to solubilize SAP, the process achieves effective separation without requiring high-pressure equipment or excessive energy input, thereby reducing both equipment complexity and energy consumption

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 achieves a significant reduction in SAP content to less than 1% by weight in cellulose and 3-9% by weight in plastic, ensuring high purity for reuse and recycling.

Implementation Method 1

treating said post-consumer absorbent sanitary products by immersion in a bath with an aqueous solution containing at least one oxidizing compound, preferably selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, potassium monopersulfate, and hydrogen peroxide; preferably hydrogen peroxide, to cleave the cross-links and solubilize the SAP

Methodology Applied

Scientific EffectOxidation: Oxidation

Data Source

PatentUS12605752B2Method for separating and recovering super-absorbent polymers (SAP) from post-consumer absorbent sanitary products

Publication Date: 2026.04.21 PROCTER & GAMBLE CO

AI summary

A method for separating a fraction of super-absorbent polymers (SAP) from post-consumer absorbent sanitary products, said post-consumer absorbent sanitary products further including at least one cellulose fraction and one plastic fraction. The method includes the steps of sterilizing the post-consumer absorbent sanitary products and treating said post-consumer absorbent sanitary products by immersion in a bath with an aqueous solution containing at least one oxidizing compound. The oxidizing compound is preferably selected from the group consisting of sodium persulfate, potassium persulfate, ammonium persulfate, potassium monopersulfate, and hydrogen peroxide; preferably hydrogen peroxide. The treatment by immersion allows cross-link cleavage and solubilizing of the SAP contained in said post-consumer absorbent sanitary products, and obtaining a suspension comprising i) a solid fraction and ii) a liquid fraction, wherein the liquid fraction comprises linear polyacrylate derived from the cross-link cleavage and solubilization of SAP.