High Curl Index Cellulosic Fiber via Steam-Plug Screw and Crosslinking
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Solution Overview
Problem
Current methods for producing high curl kraft fibers, such as those used in absorbent materials, do not effectively achieve the desired level of curl index enhancement, which is crucial for bulk and absorbency, as they rely on thermo-mechanical treatments that are limited in effectiveness.
Innovation Solution
A process involving mechanical treatment of chemical pulp using a plug screw and steam tube under elevated pressure and temperature, followed by treatment with a crosslinking agent like citric acid or glutaraldehyde, and subsequent curing at high temperatures to significantly increase the curl index of the fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If thermo-mechanical treatment is used to convolve fiber and produce higher curl index, then curl index is improved, but the effectiveness is limited and cannot achieve desired level of enhancement
Solution Approach 1:
The patent applies chemical crosslinking agents (such as glutaraldehyde or citric acid) to fundamentally change the chemical parameters of the pulp, creating covalent bonds between cellulose chains. This chemical modification works in conjunction with mechanical refining to lock in curled configurations, achieving curl index enhancements of 100% or more compared to the limited effectiveness of thermo-mechanical treatment alone.
Solution Approach 2:
The patent creates a composite structure by combining mechanically refined pulp with chemically crosslinked networks. The mechanical refining provides physical convolution and curl, while the chemical crosslinking agent forms a molecular network that locks these shapes in place, creating a synergistic effect that achieves the desired high curl index enhancement.
2Shape
If mechanical treatment and chemical crosslinking are combined to achieve high curl index, then curl index is significantly improved, but process complexity increases
Solution Approach 1:
The patent performs mechanical refining of the pulp before applying the chemical crosslinking agent. This preliminary mechanical treatment pre-convolves the fibers and creates the desired curled configurations, which are then locked in place by the subsequent chemical crosslinking. This sequence simplifies the overall process by preparing the pulp in advance for the chemical treatment.
Solution Approach 2:
The patent uses chemical crosslinking agents (glutaraldehyde or citric acid) as intermediaries that bridge the mechanical and chemical domains. These agents mediate between the physical convolution achieved by mechanical refining and the molecular structure of cellulose, creating covalent bonds that lock the curled shapes without requiring complex equipment.
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 process achieves a substantial increase in curl index, often exceeding 100% to 200% of the initial value, resulting in high curl kraft pulp suitable for absorbent materials that maintain loft under both wet and dry conditions.
Implementation Method 1
pressurizing the pulp while in the plug screw with steam at a temperature above 100°C and a pressure greater than 2 bar
Implementation Method 2
pressurizing the pulp while in the plug screw with steam at a temperature above 100°C
Implementation Method 3
The mechanically processed pulp can be treated with a crosslinking agent, dried at a temperature above 100 °C; and cured at a temperature of at least about 140°C to produce the high-curl pulp
Data Source
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AI summary
A process for producing cellulosic fiber with a high curl index is disclosed. The process can include mechanically treating and chemically crosslinking kraft pulp. The mechanical treatment of the pulp can include convolving and mechanically treating a pulp at in a plug screw and steam tube at temperatures above 100 °C and pressures above 3 bar. The mechanically treated pulp can be crosslinked with a crosslinking agent. The product fiber can exhibit a curl index of greater than 0.35, and can be at least 50% higher than the initial curl of the starting pulp material.