SELVOL Polyvinyl Alcohol ULTALUX FA

SELVOL Polyvinyl Alcohol ULTALUX FA is a polyvinyl alcohol product supplied for aqueous papermaking and paperboard operations in which retention of optical brightening agents, film continuity, and high-brightness surface uniformity are controlled in the same application. The grade is available as a free-flowing granular solid and is converted into an aqueous solution before use in size-press formulations, pigmented coating colours, or carrier systems for brightened top coatings. The model designation ULTALUX FA distinguishes the material from ordinary binder-grade Selvol PVOH; it is positioned for brightened paper and board where conventional PVOH can contribute to optical brightener mottling or quench. Because grade-specific numerical values are limited in public technical literature, all incoming lots should be verified against the supplier’s certificate of analysis before make-down. Generic PVOH test methodology and supplier-specific CoA entries remain the controlling specification reference.

The grade code ULTALUX FA does not follow the numeric viscosity/hydrolysis shorthand used in the standard Selvol range. In the standard range, the first digits indicate approximate viscosity and the trailing digits indicate hydrolysis. ULTALUX FA is instead identified by application-specific branding, which means the certificate of analysis is particularly important for lot release. Operators should not assume that the grade has the same viscosity or hydrolysis as any numeric Selvol grade. Typical packaging for specialty Selvol grades includes multi-wall paper sacks with polyethylene liners; the exact pack size should be confirmed with the supplier.

How Does ULTALUX FA Function in Size-Press and Coating-Color Applications?

In polyvinyl alcohol film formation, polymer chains align as water is removed, producing a continuous, low-porosity layer. The ULTALUX FA designation is used when that layer must also retain optical brightening agents at the surface rather than allowing them to migrate or undergo photofading. Mill trials generally begin with size-press solids in the range of 5 to 12 wt% and coating-color addition levels between 0.5 and 2.0 wt% of total colour solids. These figures are starting points only; the required addition is governed by base-stock cationic demand, starch type, wet-end ionic load, and the target CIE whiteness measured according to ISO 11475:2017 or diffuse blue reflectance measured according to ISO 2470-1:2016. On a rod-metering size press, wet film thickness is typically metered to 4–8 μm, and dry pick-up is normally 0.5–1.5 g/m² for paperboard. The grade is not a direct replacement for starch; it functions as a minority film-forming component that binds starch and optical brightener into a coherent surface film.

A recurring production-scale failure mode is the appearance of gel specks in return size-press circulation. This occurs when poorly dissolved PVOH particles pass through filters and re-deposit on the sheet. Filtration through 100–150 μm bag or self-cleaning filters is therefore applied to size-press formulations. The severity of mottling is assessed by measuring CIE whiteness across the web and recording the range; a variation greater than 1.0 CIE whiteness unit across the sheet is a common trigger for mill adjustment, although the acceptable range is product-specific.

Introduction before the metering size press requires high-shear resistance. The polymer solution is sensitive to borate ions; addition of borate-containing starch or borax can create a thermoreversible gel network at borax levels as low as 0.1 wt% on solution solids. Production vessels with residual borate from other products must be rinsed before preparing ULTALUX FA solutions. Anionic direct dyes and some aluminium-based sizing agents can also reduce optical brightener effectiveness, so addition sequences should be checked in bench-top jar tests before committing to production.

Solubility and Rheological Boundaries in Heated Make-Down Systems

The dissolution sequence is the most critical control point. The granular solid is dispersed in cold water at 20–25 °C under agitation, then heated to 88–93 °C and held for 30–45 minutes to complete chain hydration. Direct steam injection can create local hot spots above 95 °C that cause surface skinning and gel specks; indirect heating or jacketed vessels with low-shear impellers at 400–600 rpm are preferred. Solution viscosity rises with concentration and molecular weight; the grade-specific viscosity should be read from the certificate of analysis. The final solution should be filtered through a 100 μm bag or 150 μm self-cleaning filter before storage. Storage tanks should be maintained at 60–70 °C to prevent gelation, but holding beyond 8 hours may increase yellowing or microbial activity. Thermal degradation of PVOH begins near 200 °C under air; solution hold temperatures above 95 °C accelerate discoloration, so avoid long residence times above this threshold.

At the application unit, the wet film must not dry before metering. Premature drying produces film split patterns that appear as orange peel or streaks. On high-speed lines above 800 m/min, misting increases with low pH and high viscosity; misting is reduced by maintaining solution temperature at 50–65 °C, limiting solids to 10 wt% or lower, and keeping viscosity at the lower end of the supplier range. The first dryer section should use air temperatures of 140–180 °C and web surface temperatures below 90 °C for the initial 2–4 seconds to avoid rapid skinning. Final sheet moisture should return to 6–8 % before reel-up to prevent blocking in the roll.

Unopened product should be stored in a dry area at or below 40 °C and below 50% relative humidity. Open bags should be resealed because PVOH is hygroscopic. Moisture ingress can cause caking and shifts in apparent viscosity; clumping does not necessarily indicate chemical degradation but complicates make-down. If moisture exceeds the CoA limit, drying is not recommended on site.

When Optical Brightener Migration Limits Suitability for Food-Contact Paperboard

In food-contact applications, retained optical brightener and PVOH must not migrate into packaged food above regulatory limits. The final paperboard should be specified only after evaluation under EU Regulation EC 1935/2004, FDA 21 CFR 176.170, and FDA 21 CFR 176.180, along with applicable national recommendations. Migration testing is conducted with food simulants using EN 1186-1 to EN 1186-15 methods; the specific simulant and time–temperature conditions depend on food type and storage. PVOH is generally considered insoluble in cold water after film drying, but dried films can redisperse in hot aqueous or acidic foods, which changes migration behaviour. This boundary is a known limitation and must be addressed through barrier coatings or extrusion lamination if direct food contact is required.

For non-food graphic papers, the main limitation is optical brightener photofading. The product should be assessed for lightfastness under accelerated exposure according to ISO 12040 or a comparable xenon-arc test. If the final sheet is not lightfast, a change in optical brightener concentration rather than PVOH addition may be required.

Relative to conventional Selvol PVOH grades, ULTALUX FA is differentiated by its intended function as an optical brightener retention component rather than a simple surface-strength binder. A mill evaluation should compare CIE whiteness, D65 fluorescence component, print mottle, and dry pick resistance against the incumbent PVOH at equal film strength. If the only required function is surface strength, standard PVOH grades are more likely to be cost-efficient; ULTALUX FA is justified when brightness retention or optical brightener retention is the measured response variable. The product is not recommended where high water resistance is required without further crosslinking; PVOH alone remains water-sensitive. Mechanical film properties are not the primary release specification. If film strength is relevant, cast-film tensile testing can be performed according to ISO 527-3, but such data are not reliable predictors of size-press performance.

On a 3000 m/min paper machine with a film press, return solids can increase by 0.5–1.0 wt% over 8 hours due to evaporation; this raises viscosity and alters film split. Operators should control solids by online refractometer or gravimetric sample every hour. When viscosity drift exceeds the supplier window, dilution water should be added under controlled agitation rather than by direct batch addition, because rapid local dilution can produce gel specks.