Paper bio-sizing agents

Paper bio-sizing agents are wet-end and surface chemicals of biological origin — pine-gum rosin, fatty-acid-derived alkyl ketene dimer (AKD) and alkenyl succinic anhydride (ASA), plus high-biomass polymer and transparentizing agents — that orient a hydrophobic film around fibres so paper and board resist water, oil and print bleed. The renewable-carbon position differs sharply by chemistry, and the distinction matters commercially: rosin is a pine-tree exudate and therefore bio-based by nature, AKD is built from C16–C18 plant and tallow fatty acids, but standard ASA is made from fossil isomerised C16–C18 olefins and is bio-based only in the newer maleated-vegetable-oil grades now reaching commercial supply (Kemira’s Fennosize MO 30 is 30% renewable, the balance conventional ASA). Rosin and AKD are thus the segments where renewable carbon is the default feedstock rather than a retrofit; ASA is mid-transition. The global paper sizing agent market is about USD 1.2 billion in 2024 on track to roughly USD 1.8 billion by 2033–34 at near 5% CAGR, with AKD sizing alone growing about 2.8% a year through 2035 as packaging and paperboard premiumise and printing grades decline. The structural pull is plastic-free, recyclable fibre packaging: a well-sized AKD or rosin program lets a corrugated or folding-carton line meet both 2-minute and UN 30-minute Cobb water-resistance targets with a single product, while the neutral-to-alkaline pH (7.0–9.0) of AKD/ASA cuts machine corrosion and effluent load versus acidic rosin sizing (pH 4.5–6.0).

Key directions of paper bio-sizing agents:

1. Rosin sizing (Rosin Sizing): the original bio-based acidic size — pine-gum rosin saponified or fortified into a soap or cationic emulsion, dosed at acid pH; the chemistry China’s gum-rosin industry (Guangxi) supplies globally, and the FCN/FDA-listed food-contact rosin-size family.
2. AKD sizing (Alkyl Ketene Dimer): a neutral/alkaline reactive size synthesised from fatty-acid dimers, the dominant grade for packaging and board, with stronger and more stable water resistance than rosin and full compatibility with recycled fibre and calcium-carbonate fillers.
3. ASA sizing (Alkenyl Succinic Anhydride): a fast-curing neutral size from isomerised C16–C18 olefins and maleic anhydride, dosed as a cationic emulsion on high-speed packaging machines, where deposit control at the wet end is the key engineering problem. Conventionally fossil-based; the bio route maleates high-oleic sunflower or rapeseed oil in place of the olefin.
4. Biomass surface & transparentizing agents (Biomass Surface/Transparentizing): high-biomass surface sizes and transparentizing/barrier agents — pine-rosin and polymer-based, up to 85% biomass content and food-contact certified — that displace plastic films in fibre packaging and make selected paper areas transparent.

Sectoral value chain#

[rosin / fatty acid] ──> [synthesis] ──> [emulsification] ──> [wet-end / size press]
                              │                                       │
                    (AKD / ASA / rosin)                       (form + dry)
                              │                                       │
                              ▼                                       ▼
[Cobb-sized paper] <─── [sizing development] <────────── [recycle loop]

Value chain levels#

Cross-cutting technologies of the sector:

• Cationic rosin emulsion preparation (Cationic Rosin Emulsion): fine-particle cationic rosin sizes that run at near-neutral pH for food-contact grades.
• AKD wax emulsification & cationic stabilization (AKD Emulsification): starch-stabilized AKD dispersions tuned for alkaline high-speed machines.
• Size-press surface sizing (Size-Press Surface Sizing): polymer/rosin surface sizes (e.g. POLYMARON) applied at the size press for printability and surface strength.

The bio-sizing stack is built on rosin chemistry, fatty-acid-derived reactive sizing (AKD/ASA) and high-biomass surface and barrier agents.

1. Rosin sizing (Rosin Sizing):
   • pine-gum rosin saponified or fortified into a soap or cationic emulsion dosed at acidic pH 4.5–6.0.
   • case: Harima Chemicals’ biomass transparentizing and barrier agents built from pine-derived rosin; FDA FCN-listed rosin-size families for food contact.
2. AKD & ASA neutral sizing (AKD/ASA Neutral Sizing):
   • fatty-acid-derived AKD and (conventionally fossil) olefin-derived ASA reactive sizes run at neutral/alkaline pH 7.0–9.0 for stronger, more stable water resistance and lower corrosion; the renewable ASA route swaps the olefin for maleated high-oleic vegetable oil.
   • case: Kemira Fennosize MO 30 (30% renewable ASA from high-oleic sunflower oil) plus AKD wax and neutral-sizing emulsions for packaging; Solenis imPress SB-798 surface size eliminating surface ASA and its deposits, and Hercon 620 fine-paper surface sizing.
3. Biomass surface & transparentizing agents (Biomass Surface/Transparentizing):
   • polymer and rosin-based surface sizes and high-biomass barrier/transparentizing agents that displace plastic films and make selected paper areas transparent.
   • case: Harima water-based barrier-coating agents with up to 85% pine-based biomass, food-contact certified; Arakawa POLYMARON surface sizing agent for acid-to-neutral grades.