Recycled Superabsorbent Polymer Degradation and Repolymerization

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

There is a need to recycle absorbent hygiene products (AHPs) and their major component, superabsorbent polymer (SAP), by degrading recycled SAP into poly(acrylic acid) (PAA) in a short time frame with low energy consumption at mild conditions, to support the circular economy and achieve properties comparable to virgin SAP.

Innovation Solution

A method involving the separation of recycled SAP from recycled AHPs, degradation to PAA, and subsequent polymerization of acrylic acid in the presence of PAA to form a superabsorbent polymer with specific absorption and conductivity properties, combined with other AHP components and packaged with an environmental message.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If recycled SAP is degraded into PAA to produce new SAP, then environmental sustainability and circular economy are improved, but the degradation process traditionally requires high energy consumption and harsh conditions

Engineering Contradiction:

Improveenvironmental impactVSAvoidenergy consumption

Core Design Contradiction:

Object-affected harmful factorsVSUse of energy by moving object

Solution Approach 1:

The patent changes the parameters of the degradation process by using mild conditions (pH 2-7, temperature 25-100°C) instead of traditional harsh conditions, thereby reducing energy consumption while maintaining effective degradation of recycled SAP to PAA

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces traditional mechanical/thermal degradation methods with a chemical degradation process using aqueous acid or base solutions, which operates under milder conditions and consumes less energy

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Productivity

If recycled SAP is degraded into PAA, then the material can be reused to make new SAP, but the process traditionally takes a long time

Engineering Contradiction:

Improverecycling efficiencyVSAvoiddegradation time

Core Design Contradiction:

ProductivityVSLoss of time

Solution Approach 1:

The patent employs periodic agitation or mixing during the degradation process to enhance mass transfer and accelerate the degradation rate, reducing the overall time required while maintaining completeness of the reaction

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent optimizes parameters such as pH, temperature, and concentration to achieve faster degradation kinetics, transforming the traditionally slow process into a more efficient operation

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If recycled SAP is used directly in applications, then energy consumption is reduced, but the properties are inferior compared to virgin SAP

Engineering Contradiction:

Improveenergy consumptionVSAvoidmaterial performance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent recovers the valuable PAA component from degraded recycled SAP and uses it as a feed material to synthesize new SAP with properties comparable to virgin SAP, rather than discarding the recycled material or using it directly in downcycled applications

Inventive Principle:

Principle #34Discarding and recovering

Solution Approach 2:

The patent controls the polymerization parameters when synthesizing new SAP from recycled PAA to achieve desired molecular weight, crosslinking density, and absorbency properties, ensuring the recycled SAP meets the performance requirements

Inventive Principle:

Principle #35Parameter changes

4Ease of manufacture

If harsh conditions are used to degrade recycled SAP, then degradation is more effective, but decarboxylation of PAA occurs

Engineering Contradiction:

Improvedegradation effectivenessVSAvoidPAA degradation

Core Design Contradiction:

Ease of manufactureVSLoss of substance

Solution Approach 1:

The patent carefully controls pH (2-7) and temperature (25-100°C) parameters to achieve effective degradation of recycled SAP while maintaining conditions that prevent decarboxylation of the resulting PAA, thus preserving the valuable carboxyl groups

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces harsh thermal or mechanical degradation methods with mild chemical degradation using aqueous acid or base, which effectively breaks down the crosslinked SAP structure without causing unwanted side reactions like decarboxylation

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

This approach enables the production of AHPs with SAP derived from recycled resources, achieving properties comparable to virgin SAP while reducing energy consumption and promoting environmental sustainability.

Implementation Method 1

degrading said rSAP to a material comprising poly(acrylic acid) (PAA)

Methodology Applied

Scientific EffectHydrolysis: Hydrolysis

Implementation Method 2

polymerizing an acrylic acid in the presence of said PAA to form said SAP

Methodology Applied

Scientific EffectPolymerization: Photopolymerisation

Implementation Method 3

SAP has an exceptionally high ability to absorb aqueous liquids, such as contaminated water or urine

Methodology Applied

Scientific EffectAbsorption: Absorption (physical)

Data Source

PatentEP4228577B1Method of producing absorbent hygiene product comprising superabsorbent polymer partly derived from a recycled resource

Publication Date: 2024.12.04 PROCTER & GAMBLE CO

Figure 1A
Figure 1B
Figure 2A~2B

AI summary

An AHP is disclosed having a topsheet, a backsheet joined with the topsheet, an absorbent core, disposed between the topsheet and the backsheet, and a poly(acrylic acid)-based superabsorbent polymer (SAP), partly derived from recycled resources. The SAP exhibits defined Saline Flow Conductivity and Absorption Against Pressure values. Methods for making the aforementioned AHP are also disclosed.