Low-Basis-Weight SCK Paper Using BCTMP Fiber Furnish Balance
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Solution Overview
Problem
The challenge in producing supercalendered kraft paper for industrial release liners is maintaining quality characteristics such as transparency, density, and mechanical strength while reducing the basis weight to meet the demands of high-speed labeling processes, particularly when using bleached chemithermomechanical pulp (BCTMP), which complicates the production process and may lead to adverse effects on paper properties.
Innovation Solution
A method involving a specific combination of bleached softwood kraft pulp, bleached hardwood kraft pulp, and bleached chemithermomechanical pulp in controlled proportions to adjust the fiber furnish, allowing for the production of supercalendered kraft paper with a basis weight of less than 50 g/m², ensuring sufficient transparency, density, and mechanical strength suitable for industrial release liners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the basis weight of the paper is reduced to meet high-speed labeling process demands, then productivity is improved, but the mechanical strength and quality characteristics of the paper deteriorate
Solution Approach 1:
The patent changes the physical and chemical parameters of the pulp mixture by incorporating BCTMP with specific characteristics (bulk density, fiber length distribution, water retention value) to enable low basis weight paper production while maintaining mechanical strength. The optimized fiber furnish composition allows the paper to achieve required strength at lower basis weights suitable for high-speed labeling.
Solution Approach 2:
The patent uses a composite pulp mixture consisting of bleached softwood kraft pulp, bleached hardwood kraft pulp, and bleached chemithermomechanical pulp in specific proportions. This composite material approach combines the advantages of different pulps to achieve both low basis weight and high mechanical strength, resolving the contradiction between productivity and strength.
2Quantity of substance
If bleached chemithermomechanical pulp is used to reduce basis weight, then the quantity of substance is reduced, but the manufacturing complexity increases and adverse effects on paper properties occur
Solution Approach 1:
The patent specifies precise parameter ranges for BCTMP inclusion (10-30 wt.%) and optimizes fiber furnish composition parameters to control the adverse effects. By maintaining BCTMP within this optimized range and adjusting other pulp components accordingly, the manufacturing process achieves reduced pulp consumption while controlling complexity and quality issues.
Solution Approach 2:
The patent applies different quality characteristics to different pulp components in the mixture. BCTMP is used specifically for bulk and basis weight reduction, while bleached softwood and hardwood kraft pulps are used for strength and transparency. This localized functional assignment optimizes the mixture to achieve reduced substance quantity without excessive complexity.
3Quantity of substance
If the basis weight is reduced below 50 g/m², then the quantity of substance is reduced, but the transparency and density characteristics deteriorate
Solution Approach 1:
The patent creates a composite pulp mixture where BCTMP provides bulk and light scattering properties that enhance transparency. The combination of BCTMP with bleached softwood and hardwood kraft pulps in optimized proportions maintains density characteristics even at basis weights below 50 g/m², preventing transparency deterioration while reducing substance quantity.
Solution Approach 2:
The patent optimizes parameters including BCTMP content (10-30 wt.%), fiber length distribution, bulk density, and water retention value to maintain transparency and density at low basis weights. These parameter adjustments ensure that reducing pulp consumption does not compromise optical properties.
Data Source
AI summary
The invention relates to a method for manufacturing SCK paper having a basis weight of less than 50 g/m2, wherein an optimal combination of BSKP, BHKP and BCTMP is used to adjust the properties of the fiber furnish. In SCK papers with very low basis weight the formation of the paper web upon paper manufacturing may be controlled by means of the fiber furnish optimization, which can be used to produce exceptionally thin SCK paper without downgauging and without adverse effects to other paper properties, which would prevent the use of the SCK paper as substrate layer in a release liner. Thus SCK paper with a moderate share of BCTMP in the fiber furnish may be produced, that has quality characteristics of the paper sufficient for use as a substrate layer of an industrial release liner.