Superabsorbent Mixture Segmentation for Absorption Speed and Retention

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Solution Overview

Problem

Existing superabsorbent mixtures face challenges in achieving rapid liquid absorption and high centrifuge retention capacity, with nonlinear behavior in liquid absorption and volumetric liquid absorption under pressure, and linear behavior in centrifuge retention capacity, making it difficult to optimize both properties simultaneously.

Innovation Solution

A superabsorbent mixture comprising at least 70% by weight of superabsorber A with rapid liquid absorption and/or volumetric liquid absorption, combined with at least 5% by weight of superabsorber B with high centrifuge retention capacity, where the properties are optimized by adjusting the amount of crosslinker, surface crosslinking, and production methods such as solution polymerization, droplet polymerization, or reverse suspension polymerization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If superabsorbent A with rapid liquid absorption is used, then liquid absorption speed is improved, but centrifuge retention capacity deteriorates

Engineering Contradiction:
Improveliquid absorption speedVSAvoidcentrifuge retention capacity
Core Design Contradiction:
SpeedVSReliability

Solution Approach 1:

The superabsorbent system is segmented into two distinct components: superabsorbent A (rapid absorption, low CRC) and superabsorbent B (slow absorption, high CRC). Each component is optimized for its specific function, with superabsorbent A providing rapid liquid uptake and superabsorbent B providing centrifuge retention. This segmentation allows the system to achieve both rapid absorption and high retention capacity simultaneously, resolving the contradiction between speed and reliability.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention creates a composite superabsorbent system by combining superabsorbent A and superabsorbent B in specific ratios (70:30 to 95:5 wt%). This composite approach leverages the complementary properties of both materials: the rapid absorption capability of superabsorbent A and the high centrifuge retention capacity of superabsorbent B. The composite structure enables the system to achieve performance levels that neither material could achieve alone, resolving the contradiction between absorption speed and retention capacity.

Inventive Principle:
Principle #40Composite materials

2Quantity of substance

If crosslinker amount is increased to improve liquid absorption, then liquid absorption is improved, but centrifuge retention capacity deteriorates

Engineering Contradiction:
Improveliquid absorptionVSAvoidcentrifuge retention capacity
Core Design Contradiction:
Quantity of substanceVSReliability

Solution Approach 1:

The crosslinking strategy is segmented into two separate superabsorbent materials with different crosslinking densities. Superabsorbent A contains a higher crosslinker concentration (0.5-2.0 wt%) to achieve rapid liquid absorption, while superabsorbent B contains a lower crosslinker concentration (0.1-0.5 wt%) to maintain high centrifuge retention capacity. This segmentation of crosslinking levels allows each material to be optimized for its specific function, resolving the contradiction between liquid absorption quantity and centrifuge retention capacity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Different regions of the superabsorbent system have different crosslinking densities tailored to their specific functions. Superabsorbent A (with higher crosslinking) is localized to provide rapid absorption, while superabsorbent B (with lower crosslinking) is localized to provide retention. This local differentiation of crosslinking quality allows the system to achieve both high liquid absorption and high centrifuge retention capacity simultaneously, resolving the contradiction between quantity and reliability.

Inventive Principle:
Principle #3Local quality

3Quantity of substance

If surface postcrosslinking is applied to improve liquid absorption, then liquid absorption is improved, but centrifuge retention capacity deteriorates

Engineering Contradiction:
Improveliquid absorptionVSAvoidcentrifuge retention capacity
Core Design Contradiction:
Quantity of substanceVSReliability

Solution Approach 1:

Surface postcrosslinking is segmented into selective application: superabsorbent A receives surface postcrosslinking treatment (with crosslinker concentrations of 0.01-0.5 wt%) to enhance liquid absorption, while superabsorbent B either receives no surface postcrosslinking or minimal treatment to preserve its high centrifuge retention capacity. This segmented approach to surface modification allows the system to achieve both improved liquid absorption and maintained centrifuge retention capacity, resolving the contradiction between quantity and reliability.

Inventive Principle:
Principle #1Segmentation

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 resulting superabsorbent mixture achieves comparable liquid absorption to pure superabsorber A and significantly enhanced centrifuge retention capacity, improving performance in applications like hygiene products and agricultural horticulture.

Implementation Method 1

The liquid absorption of 20 g/g (T20) of the superabsorbent A is preferably less than 240 s

Methodology Applied
Scientific EffectCapillary action: Capillary Action

Implementation Method 2

volumetric liquid absorption under 0.3 psi (2.07 kPa) pressure (VAUL) with a τ value of less than 400 s

Methodology Applied
Scientific EffectDiffusion: Diffusion

Implementation Method 3

at least 5 wt.% superabsorbent B with a centrifuge retention capacity (CRC) of at least 30 g/g

Methodology Applied
Scientific EffectCentrifugal separation: Centrifugal Separation

Implementation Method 4

The liquid absorption of 20 g/g (T20) and the volumetric liquid absorption under 0.3 psi (2.07 kPa) pressure (VAUL) of superabsorbent A can be improved by increasing the amount of crosslinker in the monomer solution

Methodology Applied
Scientific EffectChemical bonding: Chemical Bonding

Implementation Method 5

Superabsorbent A, for example, is produced by solution polymerization. The resulting polymer gel must be dried and comminuted

Methodology Applied
Scientific EffectPolymerization: Photopolymerisation

Data Source

PatentEP3737709B1Superabsorber mixtures
Publication Date: 2024.12.04 BASF SE
  • EP3737709B1 patent drawingFigure 1~2
  • EP3737709B1 patent drawingFigure 3~4
  • EP3737709B1 patent drawingFigure 5~6

AI summary

Disclosed are superabsorber mixtures M containing at least 70 wt% of superabsorber A, which has a 20 g/g liquid uptake (T20) of less than 300 s and/or volumetric absorption under load (VAUL) below 0.3 psi (2.07 kPa) with a τ value of less than 400 s, and at least 5 wt% of superabsorber B, which has a centrifugal retention capacity (CRC) of at least 30 g/g.