Grafted Crosslinked Cellulose for Absorbent Articles
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Solution Overview
Problem
Cellulosic fibers used in absorbent articles tend to lose bulk and liquid retention capacity upon wetting, limiting their ability to acquire and distribute additional liquid, and existing crosslinking methods face challenges in enhancing both wet bulk and liquid permeability without compromising other performance properties.
Innovation Solution
The development of grafted crosslinked cellulose materials, where polymer chains composed of monoethylenically unsaturated acid group-containing monomers, such as acrylic acid, are crosslinked using agents like pentaerythritol or hyperbranched polymers, resulting in improved wet bulk, absorbent capacity, and permeability, while maintaining or exceeding the performance of non-grafted crosslinked cellulose fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of stationary object
If cellulosic fluff pulp is used to provide high bulk liquid absorbent fiber structure, then dry bulk and initial liquid acquisition are improved, but wet bulk and liquid retention capacity deteriorate due to structure collapse upon wetting
Solution Approach 1:
The cellulose fibers are pre-crosslinked before being incorporated into the absorbent article. This preliminary crosslinking action modifies the fiber structure in advance to resist collapse upon wetting, thereby maintaining both dry bulk and wet bulk properties simultaneously
Solution Approach 2:
The crosslinking degree and molecular weight of crosslinked products are controlled to optimize the balance between dry bulk and wet bulk. By adjusting these parameters, the fiber structure maintains its integrity upon wetting while preserving high liquid acquisition and retention capabilities
2Volume of stationary object
If crosslinked cellulose fibers are used to enhance wet bulk, then liquid retention capacity is improved, but liquid permeability deteriorates
Solution Approach 1:
The molecular weight of crosslinked products is precisely controlled within a specific range to achieve optimal balance between wet bulk and liquid permeability. Lower molecular weight crosslinked products maintain better permeability while still providing enhanced wet bulk compared to non-crosslinked fibers
Solution Approach 2:
Partial crosslinking is applied to achieve sufficient wet bulk enhancement without excessive crosslinking that would block liquid permeability. The crosslinking density is optimized to provide just enough structural support while maintaining open pore structure for liquid flow
3Duration of action of stationary object
If polymeric polycarboxylic acid crosslinking agents are used to resist aging and reversion, then shelf-life is improved, but production cost and material complexity increase
Solution Approach 1:
The molecular weight of polycarboxylic acid crosslinking agents is optimized to achieve the minimum required complexity for aging resistance. By selecting specific molecular weight ranges, sufficient crosslinking stability is achieved without unnecessary material complexity
Solution Approach 2:
Polycarboxylic acid crosslinking agents serve as intermediaries that form stable crosslinks between cellulose chains. These agents provide both crosslinking function and aging resistance, reducing the need for additional stabilizing agents or complex processing 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 grafted crosslinked cellulose materials exhibit enhanced wet bulk, absorbent capacity, and in-plane radial permeability, with improved trade-off relationships between these properties, allowing for better liquid retention and distribution, comparable to or exceeding those of non-grafted crosslinked cellulose fibers.
Implementation Method 1
crosslinked using agents like pentaerythritol or hyperbranched polymers
Implementation Method 2
the ability of an absorbent article containing cellulosic fibers to initially acquire and distribute liquid (such as from an initial liquid insult) relates to the article's dry bulk and capillary structure
Data Source
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AI summary
Grafted, crosslinked cellulosic materials used in absorbent articles, the grafted crosslinked cellulosic materials including cellulose fibers and polymer chains composed of at least one monoethylenically unsaturated acid group-containing monomer (such as acrylic acid) grafted thereto, in which one or more of the cellulose fibers and the polymer chains are crosslinked (such as by intra-fiber chain-to-chain crosslinks). Some of such materials are characterized by a wet bulk of about 10.0-17.0 cm3/g, an IPRP value of about 1000 to 7700 cm2/MPa•sec, and/or a MAP of about 7.0 to 38 cm H2O. Methods for producing such materials may include grafting polymer chains from a cellulosic substrate, followed by treating the grafted material with a crosslinking agent adapted to effect crosslinking of one or more of the cellulosic substrate or the polymer chains.