Rethinking the Box Klabin’s Short-Fibre Kraftliner Paper

Brazilian paper and packaging giant Klabin S/A has filed a patent for a kraftliner paper produced using a high proportion of short chemical fibres – specifically eucalyptus pulp – rather than the long softwood fibres traditionally considered essential for strong, durable packaging board. The invention challenges a long-held assumption in the paper industry and could offer significant cost and sustainability advantages.

The Problem

Kraftliner is the heavy-duty outer facing layer of corrugated cardboard boxes – the material that gives cardboard packaging its characteristic strength, stiffness and printability. The global corrugated packaging market is enormous, driven by the growth of e-commerce, food and beverage logistics and industrial goods distribution. The performance requirements of kraftliner – particularly its burst strength, tensile strength and ring crush strength – have historically been met using long-fibre chemical pulp, predominantly from softwood species such as pine and spruce.

Long fibres create a strong, well-bonded paper network because their greater length allows more inter-fibre bonding points and better stress distribution across the sheet. Short fibres, derived from hardwood species such as eucalyptus, have typically been considered inferior for high-strength paper applications because their shorter length limits bonding efficiency and tensile performance. As a result, short-fibre pulps have generally been relegated to internal layers or lower-grade packaging applications rather than used as the primary material in high-performance kraftliner.

The problem for the industry is that eucalyptus and other short-fibre hardwood species are faster-growing, more widely planted and in many cases cheaper to produce than the slow-growing softwood species that dominate long-fibre pulp production. If short-fibre pulps could be used effectively in kraftliner production without sacrificing the required performance characteristics, the cost and supply chain advantages would be substantial – and the environmental footprint of packaging board production could be reduced in regions where eucalyptus plantations are already established.

What This Invention Does

Klabin’s invention demonstrates that kraftliner paper can be produced with a short chemical fibre composition ranging from 70 to 100 per cent, with the remaining fraction composed of long chemical fibres. The preferred formulation uses 100 per cent eucalyptus short chemical fibre, with surface application of zero to 30 kilograms of starch per tonne of paper to enhance surface properties and interply bonding.

The paper is produced on a machine with a one- to three-ply construction, reflecting the typical multi-layer architecture of kraftliner grades that balance surface quality with structural performance. The starch surface treatment compensates for the reduced inter-fibre bonding that would otherwise result from the shorter fibre length, building up surface strength and improving the interaction between plies in a multi-layer construction.

The invention also covers the corrugated boxes made using this paper, acknowledging that the ultimate test of a kraftliner formulation is not the sheet itself but the performance of the finished packaging under real distribution and storage conditions. By specifying the composition ranges and processing parameters that make high-short-fibre kraftliner viable, the patent establishes a clear framework for industrial implementation.

Key Features

High short-fibre composition. Kraftliner paper is produced with 70 to 100 per cent short chemical fibres – far higher than conventional practice – with eucalyptus pulp as the preferred raw material, enabling use of faster-growing, more widely available fibre sources.

100 per cent eucalyptus preference. The invention identifies production using 100 per cent eucalyptus short chemical fibre as the preferred embodiment, maximising the cost and sustainability advantages of this abundant South American plantation resource.

Starch surface treatment. Surface application of up to 30 kilograms of starch per tonne of paper provides the additional inter-fibre and inter-ply bonding strength needed to compensate for the shorter fibre length and achieve required kraftliner performance characteristics.

One- to three-ply construction. The paper is manufactured in multi-ply configurations that allow different formulations or basis weights to be combined across layers, offering flexibility in balancing cost, strength and printability.

Box application coverage. The patent extends to corrugated boxes manufactured using the new kraftliner, establishing protection across the full value chain from raw material to finished packaging product.

Who Is Behind It?

Klabin S/A is Brazil’s largest paper and packaging company, with operations spanning pulp production, kraft paper and board manufacturing, and corrugated packaging. The company is a major eucalyptus plantation owner and pulp producer, giving it a strong strategic interest in demonstrating the viability of eucalyptus short-fibre pulp in premium packaging applications. The inventors – Juliana Cristina da Silva, Osvaldo Vieira, Fernando Inacio Torres and Ricardo Silva Franco da Quinta – represent Klabin’s research and development capability in paper science and process engineering. This application is a divisional of an earlier filing (AU 2023247465) and is filed through Pearce IP.

Why It Matters

The global corrugated packaging market is worth hundreds of billions of dollars annually and is growing rapidly, driven by the continued rise of e-commerce and the shift away from single-use plastics. Kraftliner is a fundamental material in this supply chain. Any innovation that reduces the raw material cost of kraftliner, diversifies the fibre supply base away from constrained softwood resources, or improves the environmental profile of packaging board production has potentially enormous economic and environmental significance.

For Brazil specifically – where eucalyptus plantations are among the most productive and sustainably managed in the world – the ability to use eucalyptus short-fibre pulp as the primary raw material in high-performance kraftliner would represent a major competitive advantage. Klabin is well positioned to exploit this if the technology proves commercially robust. More broadly, the invention challenges a fundamental assumption of paper manufacturing that has persisted for decades, and if the performance claims hold up at industrial scale, it could trigger a significant shift in how the global packaging industry sources and specifies its primary raw materials.

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AU 2026201574 was published in the Australian Official Journal of Patents on 19 March 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.