Water-Absorbing Polymer Particles With Crosslink Spacing Control
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Solution Overview
Problem
Existing water-absorbing polymer particles face challenges in achieving a balance between high absorption capacity, permeability, and low extractables, which affect their performance in absorbent articles.
Innovation Solution
The method calculates the average closest distance between crosslinkers in water-absorbing polymer particles using a specific formula, incorporating inorganic solid particles to act as barriers, limiting extractables while maintaining fluid influx, resulting in improved permeability and capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If the level of internal crosslinking or surface crosslinking is increased, then permeability is improved and extractables are reduced, but absorption capacity decreases
Solution Approach 1:
The patent applies local quality by creating a surface-crosslinked layer with different crosslinking density than the internal core. The surface region has higher crosslinking to reduce extractables and improve permeability, while the internal core maintains lower crosslinking to preserve absorption capacity. This spatial differentiation of crosslinking properties resolves the contradiction between permeability and absorption capacity.
Solution Approach 2:
The patent creates a composite polymer particle structure with two distinct regions: an internal core region with lower crosslinking density and an external surface region with higher crosslinking density. This composite structure allows simultaneous optimization of absorption capacity (core function) and permeability/extractables reduction (surface function).
2Quantity of substance
If the level of internal crosslinking or surface crosslinking is decreased, then absorption capacity is improved, but extractables increase and permeability decreases
Solution Approach 1:
The patent applies local quality by creating a surface-crosslinked layer with different crosslinking density than the internal core. The surface region has higher crosslinking to reduce extractables and improve permeability, while the internal core maintains lower crosslinking to preserve absorption capacity. This spatial differentiation of crosslinking properties resolves the contradiction between permeability and absorption capacity.
Solution Approach 2:
The patent creates a composite polymer particle structure with two distinct regions: an internal core region with lower crosslinking density and an external surface region with higher crosslinking density. This composite structure allows simultaneous optimization of absorption capacity (core function) and permeability/extractables reduction (surface function).
Data Source
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AI summary
A method for making water-absorbing polymer particles is provided and consists of providing crosslinkers, polymerizable monomers and inorganic solid particles. The average closest distance between two neighboring crosslinkers (RXL) in a water-absorbing polymer particle for a specific X-load of the water-absorbing polymer particle is calculated via the formula (I) with x_L being the amount of liquid absorbed in the water-absorbing polymer particle in g liq/g water-absorbing polymer particle, rho_liq being the density at room temperature of the fluid that swells the water-absorbing polymer particle (generally saline of 0.9%w NaCl) in g/cm3, rho_dry being the true density of the dry water-absorbing polymer particle in g/cm3, Mr_CXL being the molar mass of the crosslinkers in g/mol, w_xl being the weight ratio of crosslinkers in dry water-absorbing polymer particle, NA being the Avogadro's number in mol-1.