Single Layer White Kraftliner Surface and Strength Optimization
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Solution Overview
Problem
Existing kraftliners for corrugated fiberboard often have issues with surface roughness, specific formation, compressive strength, and tensile stiffness, which affect their performance and printing quality.
Innovation Solution
A single layer white kraftliner is developed with a grammage of 120 to 185 g/m2, composed of bleached hardwood and softwood fibers in a specific dry weight ratio, coated with starch and pigment on both surfaces, and processed to achieve improved roughness, formation, compressive strength, and tensile stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single layer white kraftliner is produced with bleached hardwood and softwood fibers in a specific ratio, then surface roughness and specific formation are improved, but manufacturing complexity increases due to precise fiber ratio control
Solution Approach 1:
The patent applies parameter changes by precisely controlling the dry weight ratio of bleached hardwood to softwood fibers within the range of 95:5 to 82:18. This parameter optimization resolves the contradiction by achieving superior surface roughness (Bendtsen roughness < 300 ml/min) and specific formation (< 0.7 √g/m) through controlled fiber composition, while the coating process with starch and pigment further refines surface properties without significantly increasing manufacturing complexity
2Manufacturing precision
If the kraftliner is coated with starch and pigment on both surfaces, then surface finish and printing quality are improved, but manufacturing steps and complexity increase
Solution Approach 1:
The patent applies preliminary action by applying coating compositions containing starch and pigment to both surfaces of the kraftliner before final product completion. This preliminary coating step achieves superior surface finish and printing quality (with the coating providing a smooth, uniform surface) while the coating itself becomes an integral part of the product structure, justifying the additional manufacturing step
3Strength
If the grammage is optimized to 120-185 g/m2, then compressive strength and tensile stiffness are improved, but production flexibility decreases
Solution Approach 1:
The patent applies parameter changes by optimizing the grammage to the specific range of 120-185 g/m2, which resolves the contradiction by achieving superior compressive strength index (≥ 21 Nm/g) and geometric tensile stiffness index (≥ 5.2 kNm/g). This parameter optimization balances strength requirements with production flexibility, as the range allows for some variation in production conditions while maintaining performance standards
Data Source
AI summary
There is provided a single layer white kraftliner having a grammage from 120 to 185 g/m2 when measured according to ISO 536:2019, wherein the kraftliner: comprises bleached hardwood fibers and bleached softwood fibers in a dry weight ratio from 95:5 to 82:18; comprises a first surface that is coated with a first coating composition comprising starch and pigment; comprises a second surface that is coated with a second coating composition comprising starch and pigment; has a Bendtsen roughness of less than 300 ml/min on at least one of the surfaces when measured according to ISO 8791-2:2013; has a specific formation of less than 0.7 √g/m when measured according to SCAN-P 92:09; has a compressive strength index in the cross direction (CD) of at least 21 Nm/g when measured using a short-span compressive tester according to ISO 9895:2008; and has a geometric tensile stiffness index of at least 5.2 kNm/g when measured according to ISO 1924-3:2005. There is also provided a method of producing a single layer white kraftliner.