Water-absorbent resin with hydrophobic coating for flowability
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Solution Overview
Problem
Conventional water-absorbent resins used in hygienic materials like sanitary articles and disposable diapers face issues with aggregation during storage, leading to reduced flowability and manufacturing challenges, such as blocking in piping and uneven dispersion, and also affect the appearance and quality of the absorbent articles due to coloration and increased resin proportion.
Innovation Solution
A water-absorbent resin is developed through reverse phase suspension polymerization using a water-soluble ethylenically unsaturated monomer in a hydrocarbon dispersion medium with an internal-crosslinking agent, azo-based compound, and peroxide, followed by post-crosslinking with specific agents, ensuring a yellow index of 5.0 or less, gel strength between 500 Pa and 1800 Pa, and a water-absorption capacity of 16 ml/g or more under a load of 4.14 kPa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the proportion of water-absorbent resin is increased to reduce thickness, then the absorbent article becomes thinner, but the resin aggregates during storage causing poor flowability and manufacturing issues
Solution Approach 1:
The patent applies preliminary action by conducting surface treatment on the water-absorbent resin particles before they are exposed to atmospheric moisture during storage. The hydrophobic coating is applied in advance to prevent hygroscopic aggregation, ensuring the resin maintains good flowability throughout storage and manufacturing processes.
Solution Approach 2:
The patent uses a hydrophobic substance as an intermediary layer between the hydrophilic water-absorbent resin and the atmospheric moisture. This intermediary coating prevents direct contact between moisture and the resin surface, eliminating the aggregation problem while allowing the resin to maintain its water-absorbent functionality.
2Reliability
If surface treatment is performed with surfactant to enhance moisture absorption resistance, then flowability improves, but the resin still aggregates and manufacturing issues persist
Solution Approach 1:
The patent changes the key parameter of surface hydrophobicity by using hydrophobic substances with specific contact angles (greater than 90 degrees). This parameter change provides superior moisture resistance compared to conventional surfactants, effectively preventing aggregation while maintaining flowability.
Solution Approach 2:
The patent creates a composite structure by combining the water-absorbent resin core with a hydrophobic surface coating. This composite material approach allows the inner resin to maintain its absorbent functionality while the outer coating provides protection against moisture-induced aggregation.
3Volume of moving object
If the proportion of water-absorbent resin is increased, then thickness is reduced, but the yellow coloration of resin lowers appearance cleanliness
Solution Approach 1:
The hydrophobic surface coating acts as an intermediary layer that masks the yellow coloration of the water-absorbent resin. This coating layer provides a clean, white appearance to the final product, hiding the inherent color of the resin while allowing the article to maintain high resin content for reduced thickness.
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 resin maintains satisfactory dispersion and flowability even in a moisture absorption state, preventing manufacturing issues like blocking and bridge formation, while enhancing the cleanliness and appearance of absorbent articles by maintaining a low yellow index and ensuring uniform distribution.
Implementation Method 1
a water-absorbent resin which is obtained by performing reverse phase suspension polymerization on a water-soluble ethylenically unsaturated monomer in a hydrocarbon dispersion medium in the presence of an internal-crosslinking agent and in the presence of an azo based compound and a peroxide
Implementation Method 2
a water-absorbent resin satisfying the followings: (A) a yellow index of 5.0 or less; (B) gel strength of 500 Pa or more and 1800 Pa or less; and (C) a water-absorption capacity of physiological saline under a load of 4.14 kPa of 16 ml/g or more
Data Source
Figure 1
AI summary
The following are provided: a water-absorbent resin in which, in the formation of an absorbent material forming an absorbent article, dispersion is satisfactory even in a moisture absorption state, which prevents the occurrence of troubles at the time of manufacturing of the absorbent article and which allows efficient manufacturing; and an absorbent article using an absorbent material containing the water-absorbent resin. The water-absorbent resin according to the present invention is obtained by polymerizing a water-soluble ethylenically unsaturated monomer and performing post-crosslinking thereon with a post-crosslinking agent, and the water-absorbent resin satisfies the requirements below: (A) yellow index is 5.0 or less; and (B) gel strength is 1800 Pa or less.