Enhancing Whiteness Development in White Papers: Synergy Between Optical Brighteners and Strength Aids

The pursuit of higher whiteness levels remains a continuous challenge for the white paper industry, whether for printing and writing grades or packaging. Beyond aesthetics, whiteness is directly linked to the perception of quality, influencing the market value of graphic, tissue, and specialty papers.

Ecosign Technologies, a reference in sustainable solutions for the pulp and paper sector, has been developing technologies that not only enhance whiteness but also improve the mechanical properties of paper sheets — generating performance and cost benefits.

Whiteness vs. Brightness: Understanding Optical Parameters

In the context of white papers, it is essential to distinguish between brightness and whiteness:

• Brightness: measured at 457 nm, it reflects the paper’s ability to reflect blue light and is primarily associated with pulp evaluation.

• Whiteness: evaluated across the entire visible spectrum, it represents the overall visual perception of the paper’s color.

While brightness is a prerequisite for pulp quality, whiteness results from the combination of pulp treatment and chemical additives — including Optical Brightening Agents (OBAs) and shading dyes.

Factors Influencing Optical Properties

Several parameters directly impact the development of paper whiteness:

• Optically active materials: optical brighteners and shading dyes (violet, blue, red);

• Pulp quality: uniformity and purity of the cellulose base;

• Presence of oxidants: agents such as hydrogen peroxide, chlorine dioxide, and peracetic acid may degrade or alter OBA structures;

• Metals: elements like aluminum, iron, and manganese can positively or negatively affect additive fixation;

• Pulp refining degree: influences optical characteristics, typically causing a slight reduction in brightness.

Optical Brighteners: Beyond the Visual Effect

Traditionally, OBAs are applied to increase whiteness through fluorescence, converting ultraviolet radiation into visible light. However, studies conducted by Ecosign have shown that when combined with chemicals typically used as strength aids, OBAs can achieve better fiber fixation — thereby improving both brightness and whiteness efficiency.

Surprising Synergy: OBAs and Strength Aids

Laboratory trials demonstrated that the application of a cationic strength aid resulted in significant gains not only in sheet strength but also in optical properties. Industrial-scale applications confirmed the increase in brightness and whiteness, while the total consumption impact of OBAs (in mass and surface applications) is still being evaluated.

The results indicated:

• A synergistic effect between the anionic brightener and the cationic strength aid, likely due to charge balance that favors cellulose/OBA interaction;

• Increased mechanical strength in unrefined sheets, even with increasing OBA dosages;

• Simultaneous improvement in both brightness and whiteness, enhancing overall paper quality.

Interestingly, excessive product dosages were not required to achieve these effects: applications between 200 and 300 g/t were sufficient to demonstrate improvements in both physical and optical properties of the pulp. However, in printing and writing paper production, only optical properties were notably enhanced.

Industrial Benefits

The combination of optical brighteners and strength aids opens new perspectives for white paper production:

• Cost reduction: improved OBA efficiency allows for lower total product consumption;

• Higher filler loading: when mechanical strength increases, mineral content can be raised, reducing fiber usage;

• Process optimization: potential for higher machine speeds and productivity if mechanical resistance is appropriately leveraged;

• Sustainability: improved chemical efficiency reduces environmental impact, aligning with circular economy principles.

The development of solutions that integrate optical performance with mechanical resistance represents a strategic advancement for the pulp and paper industry.

Ecosign Technologies, with its commitment to delivering biodegradable products and innovative technologies, reinforces its position as a key partner for manufacturers seeking high-performance white papers with lower environmental impact.

Author: Paulo R. B. Pelissari – New Business Manager

References

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2. Li, J., et al. (2025). Evaluating Alkali Pre-impregnation for Enhancing Pulp & Bleaching Processes. Industrial Crops & Products, 215, 117329. https://www.sciencedirect.com/science/article/pii/S0926669025003759

3. Shi, H., Liu, Y., Ni, Y., et al. (2023). Review: Use of Optical Brightening Agents (OBAs) in the Production of Paper Containing High-Yield Pulps. BioResources, 18(3), 5123–5145. https://bioresources.cnr.ncsu.edu/resources/review-use-of-optical-brightening-agents-obas-in-the-production-of-paper-containing-high-yield-pulps/

4. Fortune Business Insights. (2024). Optical Brighteners Market Size, Share & Trends, 2024–2032. https://www.fortunebusinessinsights.com/optical-brighteners-market-112407