Water-absorbing agent with gradient crosslinking density
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional water-absorbing resins in absorbent articles like disposable diapers and sanitary napkins face challenges in achieving balanced performance across fluid retention capacity, water absorption speed, and liquid permeability, leading to issues such as urine leakage and discomfort due to inadequate liquid suction power, especially when used on curved surfaces like the human body.
Innovation Solution
A water-absorbing agent with a specific particle size distribution, centrifuge retention capacity (CRC), and absorption against pressure (AAP) is developed by controlling the average gap radius and surface area through gel-crushing and surface cross-linking, enhancing its ability to absorb and retain liquid under load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the amount of water-absorbing resin is increased to reduce thickness, then fluid retention capacity is improved, but water absorption speed and liquid permeability deteriorate
Solution Approach 1:
The water-absorbing resin particles are designed with non-uniform crosslinking density throughout their structure, with lower crosslinking density in the core region and higher crosslinking density in the outer layer. This local quality differentiation enables the core to rapidly absorb and retain large amounts of fluid while the outer layer maintains structural integrity and controls liquid permeation speed, thereby simultaneously improving fluid retention capacity and water absorption speed.
Solution Approach 2:
The invention changes the crosslinking density parameter within the resin particles by controlling the concentration and distribution of crosslinking agents during polymerization. By creating a gradient in crosslinking density (lower in core, higher in outer layer), the resin achieves optimized balance between fluid retention capacity and water absorption speed, resolving the contradiction between these two parameters.
2Reliability
If the amount of water-absorbing resin is increased to reduce thickness, then fluid retention capacity under pressure is improved, but liquid permeability deteriorates
Solution Approach 1:
The non-uniform crosslinking density structure allows the core region with lower crosslinking to expand and retain fluid under pressure, while the outer layer with higher crosslinking maintains structural stability and controls liquid permeation. This local quality differentiation enables the resin to achieve high fluid retention capacity under pressure while maintaining adequate liquid permeability.
3Ease of manufacture
If conventional water-absorbing resin is used, then production cost is reduced, but liquid suction power and comfort deteriorate
Solution Approach 1:
The invention modifies the crosslinking density parameter distribution within the resin particles by adjusting crosslinking agent concentration and polymerization conditions. This parameter change creates a gradient structure that significantly improves liquid suction power and comfort while maintaining compatibility with conventional production processes and cost structures.
4Ease of manufacture
If uniform crosslinking density is used in water-absorbing resin particles, then manufacturing simplicity is maintained, but balanced performance in fluid retention and liquid permeability deteriorates
Solution Approach 1:
The invention implements local quality differentiation by creating non-uniform crosslinking density within particles (lower in core, higher in outer layer). This is achieved through controlled polymerization processes where crosslinking agent concentration varies with radial position, enabling optimized balance between fluid retention and liquid permeability while maintaining manufacturing feasibility.
Solution Approach 2:
The crosslinking gradient structure is built into the resin particles during the polymerization process itself, before the particles are incorporated into the absorbent article. This preliminary action of creating the gradient structure during manufacturing enables the particles to automatically achieve optimized performance balance without requiring additional post-processing or complex assembly steps.
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 water-absorbing agent exhibits excellent liquid suction power and retention capacity, reducing urine leakage and improving comfort by effectively managing liquid absorption and diffusion in absorbent articles, even in inclined states.
Implementation Method 1
there has been a demand for water-absorbing resin to have many physical properties... capillary suction power
Implementation Method 2
Water-absorbing resin is a water-swellable, water-insoluble polymer gelling agent
Implementation Method 3
Water-absorbing resin is a water-swellable, water-insoluble polymer gelling agent
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(d)
AI summary
Provided is a water-absorbing agent which has an excellent ability to absorb water and hold the water and also has an excellent liquid-sucking ability. The water-absorbing agent contains a polyacrylic acid (salt)-type water-absorbable resin as the main component, and meets all of the following physical requirements (a) to (e): (a) the weight average particle diameter (D50) is 300 µm or more and less than 400 µm; (b) the content of particles each having a particle diameter of 600 µm or more and less than 850 µm is less than 10% by weight; (c) the average gap radius is 100 µm or more and less than 180 µm; (d) the CRC is 28 g/g or more and less than 34 g/g; and (e) the AAP is 24 g/g or more.