Clupak Creping for High-Stretch Sack Paper
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Solution Overview
Problem
Existing sack papers face challenges in balancing high tensile strength with sufficient air permeability to prevent sack rupture and ensure efficient filling, as increased porosity for air venting compromises strength.
Innovation Solution
A sack paper production process using a Clupak device for creping and compacting, which maintains high stretchability, tensile strength, and porosity, achieved by optimizing grammage, Gurley value, and tensile energy absorption through controlled moisture content, nip bar line load, and paper web speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the porosity of the paper is increased to achieve air permeability for efficient venting, then the air venting capability is improved, but the overall strength of the paper is significantly reduced
Solution Approach 1:
The patent applies local quality by creating micropores through controlled mechanical deformation during the creping process. These micropores are localized features within the paper structure that provide air permeability without compromising the overall integrity and strength of the paper. The micropores are formed in a controlled manner during creping, creating local void spaces that allow air to pass through while the surrounding paper matrix maintains its strength.
Solution Approach 2:
The patent utilizes porous materials by incorporating micropores into the paper structure through the creping process. These micropores create a controlled porous network that enables air permeability for efficient venting during filling operations. The porous structure is achieved not by increasing overall porosity through traditional means, but by creating specific micropore pathways that allow air flow while maintaining paper strength.
2Productivity
If the paper is mechanically perforated to achieve sufficient air permeability, then the venting capability is improved, but the strength is significantly reduced
Solution Approach 1:
Instead of mechanical perforation that creates large holes, the patent uses local quality by forming micropores through controlled mechanical deformation during creping. These micropores are subtle local modifications that provide air permeability without creating the large defects that would compromise strength. The local deformation creates microscopic pathways for air flow while preserving the overall paper structure.
Solution Approach 2:
The patent replaces the traditional mechanical perforation system with a creping-based micropore formation system. Instead of using perforating devices that physically punch holes through the paper, the invention uses the creping process to create micropores through controlled deformation and relaxation of the paper fibers. This substitution achieves air permeability without the strength-penalizing effect of mechanical perforation.
3Strength
If high tensile strength is achieved to prevent sack rupture, then the strength is improved, but the stretchability is compromised
Solution Approach 1:
The patent applies parameter changes by controlling the moisture content and processing conditions during creping to achieve optimal fiber-to-fiber bonding. By adjusting parameters such as moisture content, creping speed, and nip pressure, the paper achieves both high tensile strength and high stretchability. The controlled mechanical deformation during creping, combined with appropriate moisture levels, allows fibers to bond strongly while maintaining the ability to stretch and elongate without breaking.
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 results in sack paper with exceptional stretchability, maintaining strength and porosity, preventing rupture and ensuring efficient filling, with Gurley values below 15 seconds and tensile energy absorption above 300 J/m², enhancing handling and transportation capabilities.
Implementation Method 1
A sack paper production process using a Clupak device for creping and compacting
Implementation Method 2
drying a paper web in a drying section comprising a Clupak unit
Implementation Method 3
the present inventors have managed to produce a sack paper that exhibits exceptional stretchability
Data Source
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AI summary
There is provided a sack paper, wherein: the grammage according to ISO 536 is 50-140 g/m2, such as 70-130 g/m2; the Gurley value according to ISO 5636-5 is 15 s or lower, such as 13 s or lower; and the stretchability according to ISO 1924-3 in the machine direction is above 10 %, such as above 11 %, such as above 12 %. A method for producing the sack paper is also provided.