The Benefits of Lansperse BIO868 for Pigment Violet 23 in Water-Based Systems

Written by: Dr. Cathy Cooper, Technical Manager

Introduction to Pigment Violet 23

Pigment Violet 23 (PV23) is a vital material in the paint and coatings industry. Its vivid violet shade, strong resistance to fading, and versatility across various applications make it a popular choice. PV23 is widely used in automotive finishes, industrial coatings, and other high-performance systems. However, creating a stable aqueous dispersion of PV23 can be challenging.

The pigment is naturally hydrophobic and tends to agglomerate. This makes it difficult to disperse evenly in water-based formulations. Achieving appropriate millbase viscosity, storage stability, and colour development requires careful formulation. Overcoming these challenges often involves using specialized dispersants. In recent years, bio-based dispersants have gained attention as a sustainable and effective solution. These dispersants improve pigment stability in water and reduce environmental impact. This makes them a smart choice for manufacturers aiming to meet both performance and sustainability goals.

Figure 1: Structural representation of Lansperse BIO868

Lansperse BIO868: A Sustainable Solution

Lansperse BIO868 is an advanced bio-based dispersing agent developed using Lankem’s BioLoop technology. Its dual hydrophobic sections are derived from soybean feedstock, while the hydrophilic chain comes from molasses. This design enhances compatibility with aqueous systems and supports effective pigment dispersion.

The product promotes strong steric stabilisation and efficient processing. As a result, it is a valuable tool for formulators seeking high performance with a reduced environmental footprint. In this blog, we outline recent development work evaluating Lansperse BIO868 in comparison to a market-leading synthetic polyether-modified styrene-maleic anhydride copolymer.

Initial Screening Tests

Screening tests were developed using an ARE-310 THNIKY planetary mixer. The mixer operated at 2000rpm for 5 minutes with 3mm glass beads. This method was found to be fast and effective for predicting performance on larger bead mills, using only a sample size of 40g.

Initial testing was performed at a pigment loading of 30% w/w. The agent on weight of pigment (AOWP) was also set at 30% w/w. The formulation is outlined in Table 1, with the market standard dispersant supplied at 40% w/w actives in water. In contrast, Lansperse BIO868 has a higher actives content of 75% w/w.

Table 1: Screening aqueous formulations tested using a planetary mixer

After milling, both samples were fluid. However, after 24 hours at room temperature, the dispersion containing the market standard settled to form a compact layer of beads and pigment at the bottom of the pot. In contrast, the one with Lansperse BIO868 remained pourable. Figure 2 shows the difference in the number of beads remaining in the pots once the millbase was poured out without additional stirring or scraping.

Figure 2: Beads remaining in milling pots after the millbase was poured out

Dispersant Loading Optimisation

Given the low millbase viscosity of the 30% pigment violet dispersion using Lansperse BIO868, the pigment loading was raised to 35%. A dispersant loading ladder was performed using the planetary mixer. Figure 3 is a graph of the initial millbase viscosity of each dispersion at a shear rate of 37.5 s-1, along with the viscosity after one week of storage at 50 °C.

Figure 3: Initial and storage viscosity of millbase dispersions made with a pigment loading of 35 % w/w and increasing levels of Lansperse BIO868

The initial viscosity is low across the range of AOWP values tested. The values of < 0.5 Pa•s indicate a highly fluid millbase. The storage viscosity outlines the significant effect of under-dosing the dispersant at the 30% w/w level, with a jump up to 1.46 Pa•s. In this sample, the pigment lacks sufficient dispersant surface coverage to fully prevent particle interactions.

On storage at an elevated temperature of 50°C, increased molecular motion can accelerate particle collisions and aggregation. This leads to a rise in viscosity as the dispersion structure becomes more networked and less fluid.

Dispersion on Eiger Bead Mill

Pre-mixes were made using a high-speed mixer. Ingredients were added as specified in Table 2, with all liquid ingredients mixed prior to the addition of the pigment. The slurry was mixed at 1000rpm for 5 minutes, then transferred to an Eiger bead mill with 1.5mm zirconia beads.

Five full passes of the millbase through the chamber were performed, and viscosity was measured on a Haake Roto-Visco 1 instrument.

Table 2: Aqueous formulations tested using an Eiger bead mill with 37% pigment loading

A pigment loading ladder indicated that a good dispersion was possible at 37% w/w PV23. The optimal dispersant loading for Lansperse BIO868 on the Eiger milling was found to be 32% agent on weight pigment. The initial and storage viscosity is compared in Figure 4 with the market standard dispersant, at the same and slightly increased loading levels.

There is already an advantage in dispersant use as supplied due to the concentration of Lansperse BIO868, which is supplied at 75% w/w actives. However, the optimised performance is also at a lower agent on weight pigment than the market standard.

Figure 4: Initial and storage viscosity of millbase dispersions made on an Eiger bead mill with a pigment loading of 37 % w/w and varying levels of dispersant

Samples were taken after passes 1, 3, and 5 for let-down into a commercial white water-based paint at a ratio of 1:9. This gave a final PV23 loading of 37g/kg. The samples were drawn-down onto Leneta card at a wet film thickness of 50 µm. The colouristic properties were measured after overnight drying at room temperature.

Figure 5 shows the comparison in colour strength between the 5th pass of the market standard at 34% AOWP and the earlier samples. Lansperse BIO868 generates the equivalent colour strength more efficiently, with a relative strength of 99.2% after only one pass through the bead mill.

Figure 5: Colour strength of reduced-shade drawdowns from samples taken during the milling process, relative to that of the market standard dispersion after 5 passes

Conclusion

The results from this study show that Lansperse BIO868 performs exceptionally well as a bio-based dispersant for Pigment Violet 23 in water-based systems. It consistently produced low-viscosity millbases, remained stable during storage, and achieved strong colour development with fewer milling passes than the market standard.

Lansperse BIO868 worked effectively at a lower dosage than the market standard and has the added benefit of being more concentrated as supplied. Its bio-based composition also supports sustainability goals, making it a practical and efficient choice for formulators.

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All information, recommendations, and suggestions appearing in the literature concerning the use of the products are based upon tests and data believed to be reliable. However, it is the user's responsibility to determine the suitability for their own use of the products described here, and we recommend testing a range of dispersant loading levels.