Stretchable Paper via Low Consistency Refining and Clupak Compaction
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Solution Overview
Problem
Current methods for producing highly stretchable paper often result in porous materials that are not suitable for applications requiring low porosity and improved printing properties, and existing technologies struggle to achieve high stretchability in the cross direction without compromising other properties.
Innovation Solution
A method involving sulphate pulp refinement, low consistency refining, controlled pulp dilution and discharge, pressing, and drying in a Clupak unit to achieve high stretchability in both machine and cross directions while maintaining low porosity and improved printing properties, with specific parameters for grammage, Gurley value, and surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional methods are used to produce highly stretchable paper, then stretchability is improved, but porosity increases and printing properties deteriorate
Solution Approach 1:
The patent applies parameter changes by controlling the consistency of pulp during refining (maintaining 2-6% consistency) and adjusting refining intensity to achieve optimal fiber modification. This resolves the contradiction by finding specific parameter ranges that provide high stretchability while maintaining low porosity and good printing properties
Solution Approach 2:
The patent strategically manages porosity by using controlled low consistency refining that modifies fiber structure without creating excessive porosity. The resulting paper has controlled porosity that allows stretchability while maintaining sufficient density for printing applications
2Use of energy by moving object
If pulp consistency is increased during refining, then energy efficiency improves, but fiber damage increases and stretchability decreases
Solution Approach 1:
The patent optimizes the consistency parameter during refining, maintaining it within 2-6% to achieve the best balance between energy efficiency and fiber integrity. This specific parameter range allows effective fiber modification for stretchability without excessive energy consumption or fiber damage
Solution Approach 2:
The patent applies partial action by using moderate refining intensity rather than excessive refining. This approach provides sufficient fiber modification for the desired stretchability while avoiding over-refining that would damage fibers and reduce stretchability
3Volume of stationary object
If Clupak unit compaction is increased, then paper density improves, but stretchability in cross direction decreases
Solution Approach 1:
The patent applies preliminary action by preparing the pulp with specific consistency (2-6%) and refining characteristics before it enters the Clupak unit. This preliminary preparation ensures that the fibers are optimally conditioned to maintain stretchability even under the compaction forces in the Clupak unit, achieving both density and cross-direction stretchability
Data Source
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AI summary
There is provided a method of producing a paper having a grammage according to ISO 536 of 50-250 g/m2, a Gurley value according to ISO 5636-5 of above 15 s and a stretchability according to ISO 1924-3 in the cross direction of at least 8 %, said method comprising the steps of:a) providing a pulp, preferably sulphate pulp; b) subjecting the pulp to refining; c) diluting the pulp from step b) and discharging the diluted pulp at a discharge rate to a forming wire to form a paper web, wherein the speed of the forming wire is at least 7 m/min higher or at least 7 m/min lower than the discharge rate; d) pressing the paper web from step c); e) drying the paper web from step d), which drying comprises a step of compacting the paper web in a Clupak unit.