Stepan Company: Meeting the Agrichemical Market Demand for Sustainable Solutions in Oil Dispersion Formulations

Shrikant Aherkar
Lead Scientist, Stepan Agricultural Solutions - Singapore

Stepan Agricultural Solutions understands the needs of farmers and formulators by staying on the pulse of ever-changing market preferences. One such dynamic is the shift to using oil dispersion (OD) formulations.

In China, the market share of more environmentally friendly sustainable formulations such as soluble concentrates (SC), OD and water dispersible granules (WG) has increased from 14.9% in 2015 to 23.8% in 2020. Meanwhile, the market share of emulsion concentrate (EC) and wettable powder (WP) formulations has dropped from 53% in 2015 to 39.4% in 2020.¹ OD formulations have been favoured, with ICAMA data in 2021 showing an average annual registration growth rate of 17%.² India approved three OD registrations for import³ and six OD registrations for production⁴ as of July 1.

Farmers and formulators alike prefer OD products due to following reasons:
1.Safer compared to traditional EC and WP.
2.Better active stability than SC for water-sensitive actives.
3.Oil in OD potentially provides adjuvancy properties and improves product efficacy.
4.Oil also potentially reduces drift compared to other formulations, by drone or aerial application.
5.Solid and liquid actives can be combined to make a stable, synergistic formulation.

Stepan offers a wide range of solutions for most of the components used in OD that can help farmers and formulators address their challenges.

The typical components of an OD formulation are shown in Table 1 below.

Table 1. Typical Components of an OD Formulation

Dispersion Media

A formulator’s choice for the dispersion media includes vegetable oils, methylated seed oils, paraffinic mineral oils and aromatic hydrocarbons. The least preferred choice is aromatic hydrocarbons due to active ingredient solubility issues, as well as known hazards to human health and the environment. Similarly, paraffinic mineral oils are not preferred due to their source. Vegetable oils are the most preferred medium due to their natural origin and lower actives solubilization. However, there is always a concern on quality consistency, which may lead to poor emulsification from batch to batch. Methylated seed oils could be a better option as they provide good adjuvancy properties, have low actives solubility, while also being of natural origin.

Stepan Agricultural Solutions offers a wide range of sustainably advantaged methyl esters that are naturally derived from vegetable oil (see Table 2). These products are bio-based and are approved for use as inert ingredients under U.S. EPA 40 CFR 180.910 and are REACH registered. They also exhibit excellent freeze/thaw stability and are suitable for use as either solvents or co-solvents, crop oils or carrier oils in agricultural applications.

Table 2. Oils from Stepan for OD Formulation

Emulsifiers

Stepan offers a wide range of anionic and nonionic emulsifiers for OD formulations. For anionic emulsifiers, our NINATE^® Series of linear or branched calcium dodecyl benzene sulfonates are available in a 100% dry form or in liquid variants of various concentrations in different solvents. For nonionic emulsifiers, alkoxylates with varying moles of ethylene oxide are available. These alkoxylates use different hydrophobes including castor oil, synthetic alcohol, fatty acid, sorbitan esters and alkyl phenols. Apart from these, a range of ethylene oxide-propylene oxide block co-polymers of butanol, polypropylene glycol and trystyrenated phenols are also available.

Stepan has developed an optimized emulsifier blend, STEPGROW^® AB 1005, that is designed to work with various methyl esters and varying water hardness. The required dosage is only about 10% of oil loading in the formulation. Apart from Stepan’s methyl esters, it is expected to emulsify various C12-C18 methyl esters, derived from different feedstocks. The application data for emulsion stability is shown in Table 3.

Table 3. STEPGROW AB 1005 Emulsion Stability Results with Stepan Methyl Esters (ME)

Dispersants

STEPFAC™ 8181 PT3K is a ~100% actives phosphate ester with a defined mono- to di-ester ratio. This optimized ratio makes it a suitable oil dispersant in a formulation, then as an aqueous dispersant upon dilution in water. Without this optimized mono- to di-ester ratio, formulators may need to use separate oil and aqueous dispersants with different chemistries. This complicates the formulation development process especially with respect to formulation and dilution stability.

Figure 1. Emulsion performance of Nicosulfuron 40 OD with and without STEPFAC 8181 PT3K.

Rheology modifiers

Stepan also has a ready-to-use, self-emulsifying and easy-to-handle rheology modifier – STEPGROW^® RM-1002. It is a proprietary blend containing surfactants and other non-reactive ingredients. STEPGROW RM-1002 does not need any special activation process by longer mixing or heating for better dissolution. This provides an advantage over other rheology modifiers such as modified clays, fumed silica and polyamides. Formulators can simply add the STEPGROW RM-1002 in the high active loading formulations after milling, just like the xanthan gum in SC formulations. At low dosage levels of 1 to 5%, STEPGROW RM-1002 improves the formulation stability and thixotropic properties of high loading OD formulations. For low active or solid loading, there may be a need to combine with modified clay for better viscosity profile and the dosage requirement could be slightly higher, up to 10%.

Most of the OD formulations are either for water-sensitive actives like Nicosulfuron or a combination of multiple actives with higher loading. For example, a Atrazine 300 + Mesotrione 60 + Nicosulfuron 50 g/l OD formulation. The recipes and pictures of these formulations using above mentioned Stepan products and their stability after heating to 54°C for 14 days as shown below.

Table 4. Atrazine 300g/l + Mesotrione 60 g/l + Nicosulfuron 50 g/l OD Formulation

Figure 2. Pictures of Atrazine 300 + Mesotrione 60 + Nicosulfuron 50 g/l OD Formulation after 14 days.

Table 5. Nicosulfuron 80 OD Formulation Recipe

Figure 3. Nicosulfuron 80 OD Formulation after 14 days

Along with the technologies highlighted in this article, Stepan Agricultural Solutions is actively developing other dispersion media and more to help optimize agricultural formulations. We are here to help you grow through science.

For more information about Stepan Agricultural Solutions, visit www.stepan.com/agriculture.

References:
1. AgroPages, article in Chinese https://cn.agropages.com/News/NewsDetail---23886.htm
2. Formulation dynamic by number of registrations in China: Although the number of EC registrations has always been the largest, its ratio to the total product registrations of the year has been declining. It only increased in 2020, an increase of 26.2% compared with 2019, indicating that the production license and registration of EC appropriate control; the same WP ratio is also declining year by year, but it will also increase in 2020, an increase of 24.7% compared with 2019; while the ratio of SC, WG and OD continues to rise, the average annual growth rate is 9.1%, 6.7% and 17.0% respectively. (data source: ICAMA, 2021)
3. Source of import and list of indigenous manufacturers of insecticide as on 01.07.2021.pdf
4. Pesticides and formulations registered for use in the country under the insecticides act 1968 as on 01.07.2021.pdf