The Complete Guide to Paper Sizing Agents for Specialty Paper

This guide explains what paper sizing agents are, why they matter, and how to choose the right specialty paper sizing additive for your production line. It covers the main types, application methods, and a product-level overview from JHDA, a papermaking chemical manufacturer.

What Is a Paper Sizing Agent?

A paper sizing agent is a chemical additive that reduces the ability of paper to absorb water or other liquids. Sizing can be carried out internally (wet-end) or on the surface (size press). The result is improved water resistance, reduced ink penetration, and better dimensional stability. Sizing agents are used in almost all paper grades, from packaging board to printing and writing paper.

According to Dataintelo, the global paper sizing agent market was valued at approximately USD 3.8 billion in 2025 and is projected to reach USD 5.9 billion by 2033, with a CAGR of 5.8%. Asia Pacific held the largest share of 42.3% in 2025. China's annual paper sizing agent consumption is estimated at 650,000 tons in 2025. According to SNS Insider, synthetic sizing agents including AKD and ASA held a 54.5% market share in 2024, and liquid sizing agents held a 57.8% market share in 2024. These figures show that sizing additives are a major input in the paper industry.

Why Sizing Agents Are Essential for Specialty Paper

Unsized paper behaves like a blotter. Moisture can penetrate quickly, causing loss of strength, curl, and surface defects. In packaging, water absorption can lead to carton softening and collapse during humid storage or cold-chain logistics. In printing, excessive moisture uptake can cause ink feathering, dot gain, and loss of print sharpness.

Sizing agents solve these problems by lowering the surface energy of cellulose fibers. AKD reacts with cellulose to form covalent bonds, creating a permanent hydrophobic barrier. Styrene-acrylic (SAE) sizing agents form a continuous polymer film on the paper surface, improving both water holdout and surface strength.

Internal Sizing vs. Surface Sizing

Internal Sizing

Internal sizing agents are added to the pulp before sheet formation. They become distributed throughout the sheet and provide bulk water resistance. AKD emulsion is one of the most common internal sizing chemistries. For example, JH-103 is an AKD internal sizing agent, also known as a neutral internal sizing agent. It is made of AKD wax and supports neutral and alkaline papermaking lines.

Surface Sizing

Surface sizing is applied to the dry or semi-dry paper web at the size press. This method concentrates the hydrophobic chemicals on the surface, where water and ink interact first. Surface sizing reduces chemical carryover into white water and allows faster response to machine changes. Many surface sizing agents are designed to be mixed with starch, which is a low-cost carrier.

How AKD and SAE Work

AKD molecules react with hydroxyl groups on cellulose, forming a chemical bond that is hydrophobic. SAE polymers, on the other hand, form a film by coalescing as the paper dries. The two mechanisms complement each other: AKD gives durable water repellency, while SAE adds film toughness and surface strength.

JHDA Sizing Additives for Specialty Paper

Qingzhou Jinhao New Material Co., Ltd. (branded as JHDA) is a manufacturer of professional papermaking fine chemicals. The company was founded in 2005 and is located in Qingzhou City, Shandong Province, China. Its product portfolio includes AKD sizing emulsions, cationic styrene-acrylic surface sizing agents, PAE wet strength resin, and other paper chemicals. JHDA has an annual production capacity of 100,000 tons and an overseas production entity in Long An Province, Vietnam, serving ASEAN clients.

The following sections describe six JHDA sizing additives that cover typical specialty paper needs.

JH-611 Cationic SAE Surface Sizing Agent

JH-611 is a cationic surface sizing agent based on styrene acrylic copolymer. It is a water-soluble liquid with a solid content of 30.0 ± 1.0%, pH of 2.0–5.0, and viscosity ≤50 cps at 25°C. It belongs to the starch-based surface sizing agent category and is compatible with ordinary raw starch. JH-611 can directly replace wet-end internal sizing agents; no curing time is required, and stable waterproof performance is obtained after drying. It is designed for corrugated paper and boxboard applications, helping to improve ring crush stiffness, surface hardness, and smoothness.

JH-600 Moisture-Resistant SAE Surface Sizing Agent

JH-600 is a moisture-resistant surface sizing agent classified under papermaking surface coating agents. It is made of styrene acrylic and supplied as a light brown to dark brown liquid, with a solid content of 30 ± 1% and viscosity less than 50 cps at 25°C. The product is cationic and water soluble. It forms a dense closed protective film that blocks continuous infiltration of ambient moisture. This is especially valuable for paper exposed to rainy seasons, cold storage, and long-distance maritime transport. JH-600 helps maintain ring crush strength and surface rigidity under high humidity, reducing softening and box collapse.

JH-325 Anionic SAE Surface Sizing Agent

JH-325 is an anionic surface sizing agent made of anionic styrene acrylic copolymer. It is primarily designed for cultural paper, including offset printing paper, copy paper, and book paper. It reacts and crosslinks rapidly with starch components to build a tight protective coating. JH-325 works in both acidic sizing processes with aluminum sulfate and modern neutral papermaking systems. It helps eliminate linting and picking during high-speed rotary printing, and it controls ink bleeding and penetration. Its solid content is 25.0 ± 1.0%, pH 2.0–5.0, and viscosity ≤50 cps at 25°C.

JH-200 AKD Surface Sizing Emulsion

JH-200 is a surface AKD sizing agent made from AKD wax powder. It is classified as an AKD surface sizing emulsion. The product is cationic and water soluble, with solid content available at 20.0 ± 1.0% or 30.0 ± 1.0%. It is suitable for neutral and alkaline papermaking environments. Unlike traditional pulp-added AKD, JH-200 can be added directly to the surface sizing tank without adjusting the pulp formula. It reacts with cellulose to form a waterproof barrier, and the sizing effect is finalized once the paper passes through the drying cylinder, eliminating the slow curing period. It also shows good mechanical shear stability and low foaming, making it suitable for high-speed sizing machines.

JH-103 AKD Internal Sizing Emulsion

JH-103 is an alkyl ketene dimer emulsion used as an internal sizing agent in papermaking. It is made of AKD wax and is cationic and soluble. The solid content ranges from 12.5% to 25.0% ± 1.0%, with pH 2.0–5.0 and viscosity ≤50 cps at 25°C. JH-103 functions as a neutral internal sizing agent and supports neutral and alkaline papermaking lines. It is designed as a pulp sizing additive that can be added continuously by metering pump. The product is compatible with common wet-end chemicals such as retention aids and defoamers.

JH-WH3364 Composite Surface Sizing Agent

JH-WH3364 is a dual-function composite sizing additive. It is made of weak anionic styrene acrylic and AKD, integrating the reactive waterproof advantage of AKD with the high film-forming toughness of SAE styrene-acrylic resin. The product is a milky white to pale yellow liquid with a solid content of 25.0 ± 1.0%, pH 2.0–5.0, and viscosity ≤50 cps at 25°C. It is designed for neutral papermaking systems and can replace separate purchases of AKD emulsion and SAE sizing agent. This simplifies dosing and can reduce overall sizing chemical procurement cost.

Step-by-Step: How to Select and Apply a Specialty Paper Sizing Additive

When selecting a sizing additive, paper mills evaluate a range of performance indicators. These include Cobb water absorption value, ring crush strength, bursting strength, paper brightness, fiber retention rate, and overall paper machine runnability. JHDA's technical team uses these indicators to optimize machine settings.

1. Define your target paper quality. List the required Cobb value, surface strength, printability, and moisture resistance for the finished paper.
2. Determine application method. If wet-end bulk resistance is needed, choose an internal sizing agent such as JH-103. If rapid surface response and lower dosage are preferred, choose a surface sizing agent.
3. Check system compatibility. Confirm pH, cationic demand, starch type, and machine speed. Most JHDA surface sizing agents work with oxidized starch, cationic starch, and ordinary raw starch.
4. Match ionic type. Cationic surface sizing agents such as JH-611 and JH-600 combine well with anionic starch. Anionic JH-325 fits both acid and neutral systems. Weak cationic JH-WH3364 works as a composite replacement.
5. Run a laboratory test. JHDA provides pre-shipment laboratory testing and complete TDS/MSDS documents. Lab results help predict dosage and final properties.
6. Scale to an on-machine trial. A field technical team can assist with machine debugging, adjusting the feeding point, concentration, and dosage to optimize Cobb values, ring crush, and runnability.
7. Monitor and optimize. Track water absorption, surface strength, and paper machine runnability. Because moisture resistance can change during storage, re-test after a few days to confirm stable sizing.

Use Cases by Paper Grade

JHDA additives are applicable to kraft linerboard, corrugated medium paper, printing and writing paper, household tissue paper, and food-grade cardboard. The following examples show how specific sizing products can be matched to paper grades.

Packaging Paper: Kraft Linerboard and Corrugated Medium

High-humidity environments are a common challenge for corrugated packaging. A moisture-resistant surface sizing agent such as JH-600 helps prevent damp collapse by maintaining ring crush strength under humid conditions. JH-611 can also improve surface rigidity and reduce cracking during creasing and die-cutting.

Printing and Writing Paper

Cultural paper requires balanced water resistance and ink affinity. JH-325 is formulated for this application: it reduces paper linting and picking during high-speed offset printing and prevents ink feathering, giving cleaner text and more uniform color. It also improves surface flatness and gloss, which can upgrade the paper grade.

Food-Grade Cardboard and Barrier Paper

For food contact packaging, compliance is critical. JHDA's product portfolio includes food-grade water vapor barrier coating and hydrophobic coating for food packaging paper. The company has ISO9001, ISO14001, and SGS food contact safety testing. Food-grade paper can be produced with these additives while maintaining regulatory documentation.

Comparison Table: JHDA Sizing Agents at a Glance

Frequently Asked Questions

Conclusion

Sizing agents play a key role in specialty paper production. They control water absorption, improve surface strength, and ensure reliable printability. The choice between internal and surface sizing depends on your product target, machine configuration, and raw material system. Products such as JH-611, JH-600, JH-325, JH-200, JH-103, and JH-WH3364 cover a wide range of applications, from corrugated packaging to printing and writing paper.

To evaluate a sizing additive for your mill, start with a laboratory test and then scale to a machine trial. Qingzhou Jinhao New Material Co., Ltd. offers sample trials, formula customization, and bulk export quotations. You can also download the JHDA company brochure for more details.

Contact JHDA
Email: info@sdqzjinhao.com
WhatsApp: +86 139 6468 8976
Phone: +86-536-3808962