Man-made cellulosic fibre and nonwoven product or fabric comprising the cellulosic fibre
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Solution Overview
Problem
Existing modified cellulosic fibers, particularly anionic viscose fibers, lack sufficient binding strength when used alone to produce commercial-quality papers or nonwoven products, and the addition of cationic polymers like PAM-DADMAC can negatively impact tensile strength due to reduced fiber contact area and de-swelling effects.
Innovation Solution
A modified cellulosic fiber with anionic moieties exceeding 0.25 mol/kg and treated with a polymeric modifying agent containing cationic moieties, such as polydiallyldimethylammonium chloride (poly-DADMAC) or poly(acrylamide-co-diallyldimethylammonium chloride) (PAM-DADMAC), in amounts from 0.5 wt.% to 5.0 wt.% based on dry fiber, achieving a molar ratio of anionic to cationic moieties between 1:1 and 25:1, which are incorporated within the fiber matrix without surface derivatization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If anionic viscose fibres are used alone to produce papers or nonwoven products, then the fibre structure is simple and manufacturing is easy, but the binding strength between fibres is insufficient
Solution Approach 1:
A cationic polyelectrolyte is introduced as an intermediary substance between anionic fibres to mediate fibre-fibre bonding. The polyelectrolyte adsorbs onto the anionic fibre surfaces through electrostatic attraction, forming cationic bridges that connect adjacent fibres. This mediator enables strong binding without requiring complex fibre modification while maintaining ease of manufacture through simple addition to the fibre mixture.
Solution Approach 2:
The invention creates a composite system combining anionic fibres with cationic polyelectrolyte. The composite structure consists of fibres modified by adsorbed polyelectrolyte layers, forming a new material system where the polyelectrolyte-fibre composite provides both the structural properties of the fibre and the bonding functionality of the cationic polymer.
2Strength
If higher amounts of cationic polyelectrolyte are used to enhance binding strength, then fibre bonding is improved, but the amount of substance required increases and cost rises
Solution Approach 1:
The invention optimizes the polyelectrolyte dosage parameter to achieve maximum bonding efficiency at minimal effective concentration. By adjusting the dosage to the optimal range where charge neutralization is sufficient but not excessive, the system achieves strong fibre bonding while minimizing the quantity of polyelectrolyte required, thereby reducing material costs.
Solution Approach 2:
The anionic fibres themselves provide the binding function through their inherent negative charges, requiring only minimal cationic polyelectrolyte addition to activate and enhance this self-bonding capability. The fibres essentially serve their own binding function with the polyelectrolyte acting as a catalyst or activator rather than the primary binding agent, reducing overall substance requirements.
3Strength
If cationic polyelectrolyte is added to improve fibre bonding, then binding strength increases, but the product loses washproof properties and durability
Solution Approach 1:
The cationic polyelectrolyte serves as a washable intermediary that provides temporary bonding during processing and initial use. The system accepts that the polyelectrolyte-mediated bonds are designed to be reversible and washable, which is actually a functional advantage for certain applications where re-dispersibility and re-bonding capability are desired properties rather than deficiencies.
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
This approach enables reversible fiber-fiber bonding and redispersibility in aqueous fluids without significant strength deterioration, allowing for enhanced porosity and strength improvements in paper and nonwoven products, enabling higher anionic charge and lower cationic polyelectrolyte content for optimal results.
Implementation Method 1
a modified cellulosic fibre which comprises anionic moieties in an amount of more than 0.25mol/kg of dry fibre and has applied thereon a polymeric modifying agent in an amount of from 0.5 wt.% to 5.0 wt.%, based on dry fibre, the polymeric modifying agent comprising cationic moieties with a charge of at least 1.5meq per gram of polymer and the molar ratio of anionic moieties to cationic moieties contained in the fibre being in the range of from 1:1 to 25:1
Data Source
Figure 1
AI summary
The present invention relates to a modified cellulosic fibre that comprises anionic moieties in an amount of more than 0.25mol/kg of dry fibre and has applied theron a polymeric modifying agent in an amount of from 0.5 wt.% to 5.0 wt.%, based on dry fibre, the polymeric modifying agent comprising cationic moieties with a charge of at least 1.5meq per gram of polymer and the molar ratio of anionic moieties to cationic moieties contained in the fibre is in the range of from 1:1 to 25:1. The fibre according to the present invention is characterized in that the anionic moieties are incorporated in the fibre and are from carboxymethylcellulose, and that the polymeric modifying agent comprising cationic moieties is selected from the group consisting of polydiallyldimethylammonium chloride (poly-DADMAC), poly(acrylamide-co- diallyldimethylammonium chloride) (PAM-DADMAC) and mixtures thereof. The invention furthermore relates to a nonwoven product or fabric comprising the modified cellulosic fibre.