Sulfite Dissolving Pulp for High Tenacity Rayon
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Solution Overview
Problem
Sulfite dissolving pulps have been considered unsuitable for producing high tenacity rayon and technical filaments due to their broad molecular weight distribution and high hemicellulose content, which negatively impact the strength of regenerated cellulose fibers.
Innovation Solution
A novel sulfite dissolving pulp with specific properties, including a viscosity of 700-1000 ml/g, R18 value of 93-95.5%, R10 value of 92-94%, and a polydispersity of 9-15, is produced by adjusting the pulping process to achieve a high proportion of cellulose chains above 100 KDa and low chains below 25 KDa, enabling high tenacity applications without reducing hemicellulose content or polydispersity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If sulfite dissolving pulp is used for producing regenerated cellulose, then the production process can use wood as starting material, but the broad molecular weight distribution and high hemicellulose content result in low tenacity fibers
Solution Approach 1:
The patent applies parameter changes by modifying the pulping process parameters (sulfite cook conditions, temperature, time) to produce cellulose with controlled molecular weight distribution. This resolves the contradiction by maintaining wood as starting material while achieving narrow molecular weight distribution and high tenacity through optimized process parameters
2Productivity
If conventional sulfite pulping process is used, then production efficiency is maintained, but the pulp has broad molecular weight distribution unsuitable for high tenacity applications
Solution Approach 1:
The patent applies preliminary action by controlling the molecular weight distribution during the pulping process itself, rather than attempting to narrow the distribution after pulp production. The sulfite cook parameters are optimized in advance to produce cellulose with the desired narrow molecular weight distribution, achieving both high productivity and manufacturing precision
3Ease of manufacture
If sulfite dissolving pulp with high hemicellulose content is used, then the pulp production is simpler, but the hemicellulose negatively impacts fiber strength
Solution Approach 1:
The patent converts the typically harmful effect of hemicellulose into a benefit by selecting specific wood chips with appropriate hemicellulose characteristics and using sulfite cooking conditions that selectively remove harmful impurities while preserving beneficial hemicellulose. This approach maintains production simplicity while improving fiber tenacity
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 novel pulp results in regenerated cellulose fibers and filaments with remarkably high strength, matching or exceeding the performance of prehydrolyzed Kraft pulps, with wet tenacity of at least 1.9 cN/dtex and dry tenacity of at least 3.0 cN/dtex, suitable for high tenacity applications without significant process adaptations.
Implementation Method 1
In the pre-ripening step, the alkali-cellulose will be degraded into desired degree of polymerization through depolymerization reaction with the oxygen in the air
Implementation Method 2
the cellulose is dissolved in a solvent to form a cellulose dope
Implementation Method 3
In the regeneration process the cellulose xanthate is applied to a coagulation bath. Typically, this involves pumping of the cellulose xanthate through spinnerets, into an acid bath where cellulose is regenerated
Data Source
AI summary
The present invention relates to a novel sulfite dissolving pulp suitable for high tenacity applications having: a) a viscosity of 700-1000 ml/g; b) a R18 value of 93-95.5%; c) a R10 value in of 92-94%; d) a PD of 9-15; e) a proportion of cellulose chains having a molecular weight below 25 KDa of less than 8% (w/w); and f) a proportion of cellulose chains having a molecular weight above 100 KDa of above 75% (w/w).