EXCEVAL™ – Frequently asked questions

EXCEVAL™ should be gradually added to room-temperature water while stirring, then heated to dissolve. Heating methods include direct steam heating or indirect heating via a jacketed system. Since dissolution methods vary slightly depending on the grade, please refer to the following procedures:

1. Gradually add EXCEVAL™ while continually stirring room-temperature water.
2. Continue stirring and begin heating.
3. A. After reaching 95°C, maintain temperature and stir for 1–2 hours.
    B. After reaching 90°C, maintain temperature and stir for about 1 hour.
    C. After reaching 95°C, maintain temperature and stir for about 2 hours.
4. Turn off the heat source and reduce the stirring power. Stop stirring once the temperature drops to 40°C.

Note: Rapid cooling or continued stirring below 40°C may cause the solution to become cloudy.

1) Viscosity
Although the viscosity stability of aqueous solutions of EXCEVAL™ varies depending on the grade, it is recommended to use them as soon as possible.

2) Mold, Spoilage, and Rust
When storing EXCEVAL™ in aqueous form for extended periods, mold, spoilage, or rust may occur depending on the equipment specifications, materials, and storage conditions. It is recommended to add anti-mold, anti-corrosion, and anti-rust agents.

When dissolving EXCEVAL™ in water or using its aqueous solution, foaming may occur depending on viscosity and stirring speed. Foaming can be suppressed by adding defoamers (500–5000 ppm per EXCEVAL™). However, please note that the type and amount of defoamers may affect the original properties of EXCEVAL™.

Although it depends on the grade, a solid content of 10–15% is generally recommended.

Since the film-forming properties of EXCEVAL™ are not affected by drying temperature, it can be dried at any temperature suitable for your equipment. This is a significant advantage compared with PVDC, which requires heat to form a film.

A coating thickness of 1–2μm is sufficient to provide excellent gas barrier performance (permeation less than 1 cm³·m⁻²·day⁻¹·atm⁻¹).

The coating weight can be increased by raising the solid content of the coating solution, which also enables shorter drying times. Although the viscosity increases at higher solid content, it can be reduced by increasing the coating temperature.

Crystallisation is one of the main factors contributing to the gas barrier properties of EXCEVAL™. By applying heat treatment that promotes crystal formation, further performance improvement can be achieved. For example, storing the coated film at 50℃ for several days will enhance its gas barrier performance.

While crosslinking can enhance water resistance, it is known that gas barrier performance may decrease if crystallization is hindered. Crosslinking with metal complexes such as titanium makes it possible to achieve both high gas barrier performance and improved water resistance.

Yes, you can. EXCEVAL™ generally shows good compatibility with inks and can be printed.

Considering the flexibility required for packaging films, the barrier performance was evaluated after applying physical twisting (using a Gelbo Flex test). Even after more than 20 twisting cycles, no deterioration in gas barrier performance was observed.

EXCEVAL™ is a hydrophobically modified polyvinyl alcohol (PVOH, PVA, poval) developed through Kuraray’s proprietary technology. Compared to unmodified KURARAY POVAL™ (general grades), it exhibits significantly enhanced oxygen barrier properties and grease resistance under conditions of high humidity.

Yes, EXCEVAL™ is inherently biodegradable* in an aqueous solution form.

* Inherently biodegradable: The property by which the material itself is ultimately broken down into water and carbon dioxide by naturally occurring microorganisms, without the need for special conditions or additives.