Stepan Company: Leveraging Rheology Modifiers to Stabilize OD Formulations

Shrikant Aherkar, Lead Scientist, Stepan Agricultural Solutions APAC

Stepan Agricultural Solutions continues to develop innovative products that address current and anticipated market needs. A key focus area is targeted towards providing solutions for sustainable, but potentially challenging, delivery systems like oil dispersions (OD). ¹

The rheology modifier is a critical component in any OD formulation based on its ability to adjust the viscosity and stabilize the formulation by reducing separation and sedimentation. Commonly used rheology modifiers include fumed silica, treated clays and polymerics. As formulations become more complex due to different components and processing conditions, there is a need for novel rheology modifiers capable of maintaining formulation stability.

Frequently encountered challenges associated with traditional rheology modifiers include:

• Storage instability
  

• Interference with emulsion properties, if not self-emulsifying
  

• Requirement for prolonged stirring or heating process for activation
  

• Difficulty in building viscosity in low active loading formulations
  

• Difficulty maintaining flowability of the formulation at low temperature
  

• Potential for incompatibility with the oil carrier in the system

Stepan Agricultural Solutions has developed the STEPGROW^® RM Series, a range of rheology modifiers for OD formulations that can help formulators address the stability concerns. Key features include:

• The ability to act as anti-settling agents that minimize formulation separation and sedimentation
  

• Ready-to-use and can be added after the milling process
  

• Self-emulsifying and do not interfere with formulation emulsion properties
  

• Also has strong anti-separation performance in concentrated emulsion (EW) and capsule suspension (CS) applications
  

The each of the products in the series offers tailored characteristics to meet diverse formulation needs — whether they be for high-active loading formulations, low pour point variant, or an alternative formulation type — making them valuable additions to a formulator's toolbox.

STEPGROW RM 1002 is suitable for vegetable oil and methyl ester-based systems. As a flowable liquid, it is easy to handle at room temperature. Formulators can add STEPGROW RM 1002 into high-active loading formulations (>30%) after milling, similar to adding xanthan gum in suspension concentrate (SC) formulations. At low dosage levels between 1% and 5%, STEPGROW RM 1002 improves formulation stability and thixotropic properties of high-loading OD formulations. For low-active or solid loading, STEPGROW RM 1002 in combination with a modified clay has been demonstrated to provide an improved viscosity profile as well.

For low-active loading formulations (<30%), formulators can count on STEPGROW RM 1003. It is a viscous liquid at room temperature, giving users the advantage of being able to add to the rheology modifier into the formulation after milling. Additionally, the product is also suitable for vegetable oil- and methyl ester-based systems.

STEPGROW 1004 is a lower pour point variant and was specially designed to meet formulation demands in cooler temperature regions. The product demonstrates excellent performance when used in low- and high-active loading formulations. It is compatible in systems using sustainable oil carriers such as vegetable oils and methyl esters. The recommended dosage typically varies from 3% to 15% depending on the active ingredient and overall active loading.

STEPGROW RM 1005 is developed for OD formulations that utilize paraffinic mineral oils. As mineral oils are one of the preferred dispersion media. A rheology modifier that is compatible with mineral oils while also providing strong performance is crucial for successful formulation development. STEPGROW RM 1005 can be used in low- and high-active loading formulations with the recommended dosage from 1% to 5%, depending on the active loading. The product offers high viscosity and low pour point, making it easy to handle at low temperatures.

Stepan Agricultural Solutions is continuously looking to generate formulation technology and solutions that are capable of addressing current and potential future market needs. Provided below in Table 1 are some of the available starting formulations from Stepan that incorporate our rheology modifier solutions.

Table 1. Starter formulations from Stepan

Formulations are measured based on percentage weight in volume.

In addition to the STEPGROW RM Series, Stepan offers a diverse portfolio of agricultural coformulants including emulsifiers, dispersants, solvents and adjuvants. Application data and formulation examples provided were in combination with additional products from the Stepan portfolio.

Dispersion Media

Stepan Agricultural Solutions offers a broad portfolio 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. EPA² 40 CFR 180.910 and are REACH³ registered. They 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 Agricultural Solutions also offers a range of anionic and nonionic emulsifiers for OD formulations. Stepan has developed an optimized emulsifier blend, STEPGROW AB 1005, that is designed to work across various methyl esters and varying levels of water hardness. The typical required dosage is only about 10% of oil loading in the formulation. The strong performance of the blend is demonstrated in the ability to emulsify various C12-C18 methyl esters derived from different feedstocks.

Dispersants

STEPFAC™ 8181 PT3K is a 100% actives phosphate ester with a defined mono- to diester ratio. This optimized ratio allows it to function as a suitable oil dispersant, and 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 and creates unnecessary challenges with respect to formulation and dilution stability.

Stepan Agricultural Solutions continues to actively cultivate innovation by developing solutions to help optimize agricultural formulations. We walk alongside partners to leverage science to not only keep pace with new technologies but to elevate customer aspirations and fuel future growth.

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

Reference:

¹Meeting the Agrichemical Market Demand for Sustainable Solutions in Oil Dispersion Formulations, AgroPages (2021)
²U.S. EPA = United States Environmental Protection Agency
³REACH = Registration, Evaluation, Authorisation and Restriction of Chemicals under European Union Regulation