Water-absorbing Polymer Particles Coated with Metal Salt Complex
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Solution Overview
Problem
Existing water-absorbing polymer particles for hygiene articles face challenges in achieving high centrifuge retention capacity (CRC) and gel bed permeability (GBP) while avoiding dust and stickiness issues, and requiring coatings that are easy to apply and do not lead to corrosion or excessive insolubility.
Innovation Solution
The use of water-absorbing polymer particles coated with a complex consisting of a polyvalent metal salt and a 2-hydroxycarboxamide, specifically aluminum hydroxide and lactic acid amide, which are applied before, during, or after thermal surface post-crosslinking, to enhance CRC and GBP without causing dust or stickiness problems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If water-absorbing polymer particles are coated with polyvalent metal cations and fatty acids to improve liquid transfer and centrifuge retention capacity, then CRC and SFC are improved, but surface tension is lowered and diaper leakage risk increases
Solution Approach 1:
The patent introduces a specific complex consisting of polyvalent metal cations (Al³⁺, Fe³⁺, Zr⁴⁺) and 2-hydroxycarboxamides as an intermediary coating substance. This complex acts as a mediator that improves CRC and SFC without the harmful side effects of fatty acid coatings. The 2-hydroxycarboxamide component modifies the interaction between metal cations and polymer particles, achieving the desired performance while maintaining appropriate surface tension properties.
Solution Approach 2:
The patent changes the chemical parameters of the coating by specifying precise compositional ratios (0.1-3.0 mol of 2-hydroxycarboxamide per mol of polyvalent metal cation) and using specific metal cations with defined valences. This parameter optimization allows achieving high CRC and SFC while avoiding the surface tension reduction problem associated with fatty acid coatings.
2Reliability
If basic salts of polyvalent metal cations are used to improve gel bed permeability and absorption under pressure, then GBP and absorption capacity are improved, but dust and stickiness issues occur
Solution Approach 1:
The 2-hydroxycarboxamide acts as an intermediary that modifies the properties of polyvalent metal cation coatings. This intermediary substance enables the use of basic salts for improving GBP and absorption capacity while preventing the dust and stickiness problems that would otherwise occur with conventional coatings.
Solution Approach 2:
The patent creates a composite coating material combining polyvalent metal cations with 2-hydroxycarboxamides. This composite structure integrates the beneficial properties of basic salts (high GBP and absorption) with the dust-reducing and non-sticky characteristics of the 2-hydroxycarboxamide component.
3Reliability
If water-insoluble phosphates of polyvalent metal cations are used as coatings, then CRC and GBP are improved, but application difficulty increases due to insolubility
Solution Approach 1:
The patent changes the solubility parameters of the coating by using soluble polyvalent metal salts (such as aluminum sulfate, ferric chloride, zirconium chloride) combined with 2-hydroxycarboxamides. This parameter modification maintains the performance benefits of insoluble phosphate coatings while enabling easy application through soluble formulations.
Solution Approach 2:
The 2-hydroxycarboxamide serves as an intermediary that allows soluble metal salts to achieve the performance of insoluble phosphates. The complex formed between the soluble salt and 2-hydroxycarboxamide provides ease of application while delivering the required CRC and GBP performance.
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 coated particles exhibit improved CRC and GBP, maintaining optimal absorption capacity and liquid conductivity while preventing dust and corrosion, thus addressing the challenges of particle size distribution and application issues.
Implementation Method 1
coated with at least one complex consisting of a polyvalent metal salt and a 2-hydroxycarboxamide
Implementation Method 2
water-absorbing polymer particles which have, at least in places in the absorbent core or in the entire absorbent core, a concentration of water-absorbing polymer particles
Implementation Method 3
which at the same time have a strong wicking effect, i.e. which can absorb aqueous liquids against gravity
Implementation Method 4
thermally post-crosslinked on the surface. Crosslinkers suitable for this are compounds that contain at least two groups that can form covalent bonds with the carboxylate groups
Data Source
AI summary
Method for producing thermally surface crosslinked water-absorbent polymer particles, wherein the water-absorbent polymer particles are coated before, during or after the thermal surface crosslinking with at least one complex consisting of a multivalent metal salt and a 2-hydroxycarboxylic acid amide.