Oct. 19, 2017
Formulation technology plays a critical role in the agrochemical industry to enable high product stability and quality, convenience for application, satisfied drug efficacy and low environmental influence.
Regulatory pressures and a new generation of crop protection practices steer formulation technology transformation and new formulation development for adjuvants. High R&D investment is commonly needed to meet the new development trend.
Moreover, today’s formulation composition becomes more and more complex, including: combination of two or more active ingredients to address more serious drug resistance issue; diversified adjuvants to improve field performance; a multiple adjuvants system to adapt for different active ingredient sourcing or quality. These challenges bring difficulties for formulation development by using traditional manual operation method, and a high efficiency scientific study method becomes urgent.
Dow pioneers applying High-Throughput Research (HTR) R&D platform to the screening of pesticide formulations. As shown in Figure 1, it combines statistic experimental designs, automated robots to prepare formulations in parallel, collect data and conduct real-time analyses on a massive scale. The HTR platform greatly improves research efficiency and effectively eliminates human errors. At the same time, the generated massive data helps to build up predicting models and database, which are useful to better understand the mechanism of different formulation technology.
The HTR platform is capable of conducting many tests, such as solubility/compatibility, viscosity, solubilization, suspension stability, emulsion stability, surface tension/CMC, rheology, foam generation and stability, freeze-thaw stability, wetting performance, optical clarity and colors. After a few years’ investigation, HTR workflows have been explored for most of liquid formulation types, including Emulsifiable Concentrate (EC), Emulsion-in-Water (EW), Microemulsion (ME) and Suspension Concentrate (SC).
The development of SC, a stable suspension of the solid active ingredient in a fluid prior to dilution with water before use, is a key environmental friendly formulation type. The formulation stability for SCs is affected by many factors, such as the active ingredient chemical properties, impurities, and crystalline type. It is challenging to develop SC formulations with high active loading, high water solubility, low melting point and high electrolyte concentration.
To speed up formulation screening, a new efficient workflow was developed using high-speed dispersing instead of the traditional grinding process, as shown in Figure 2. Wetting agent and dispersant are screened based on flowability and powder dispersing performance. Experimental results indicate a good correlation between HTR and manual grinding operation. By using the new workflow, the sample preparation efficiency can be improved by 4~6 times, while the sample consumption is only 1/10 of manual grinding process.
A wetting agent and dispersant database is built up, based on the massive experimental data. The database indicates that Dow’s TERGITOL™ W-600 Surfactant, DOWFAX™ D-800 Surfactant and POWERBLOX™ D-305 Dispersant are a general-purpose adjuvant package for SC formulation.
At the same time, based on the database analysis and mechanism study, it has been found that EO/PO copolymer D-800 plays a critical role for low melting point active ingredients due to its emulsification and dispersion performance; POWERBLOX™ D-305 and D-205 Dispersant are helpful in to stabilizing high water soluble active ingredients by offering strong steric and electrostatic repulsion effect; and hydrotropes TRITON™ H-66 Surfactant and DOWFAX™ anionic series. Surfactants are very useful to solubilize other wetting and dispersing agents in high electrolyte SC system.
SC is a suspension system, and there is another big formulation group related to liquid droplet emulsification, e.g. EC, EW and ME. Solvent and emulsifier are the key factors in formulation stability. The big regulation pressure and people’s strong environmental protection consciousness facilitates green solvents’ development in replacing traditional high toxic solvents.
A molecular simulation method was utilized to identify solvent replacement candidates by calculating solubility, polarity and hydrophobicity parameters, as shown in Figure 3. The simulation method has closely matched experimental results and has been an attractive tool to serve Dow customers.
After identification of solvents, emulsifiers screening could also be done by HTR platform. Several complex solvent systems were developed for Indoxacarb EC, Imidacloprid EC, glufosinate based formulated ME etc. A solubility database is also available, and based on the database, two solvents were screened out as new generation solvents as aromatic solvent and polar solvent candidates: POWERBLOX™ SV-33 and SV-92. As shown in Figure 4, the two solvents showed comparable solvency to traditional aromatic and polar solvent, but a much better EH&S profile.
Formulation stability is the base of a pesticide product, and drug efficacy improvement is always pursued by pesticide producers. Traditional adjuvants such as tallow amine ethoxylates and alkyl phenol ethoxylates are under regulation pressure, and environmental-friendly adjuvants are the trend, which offer ready biodegradability, low aquatic toxicity, multifunctional performance and applicator convenience.
HTR platform offers on-site tools to quickly evaluate basic physiochemical properties of an adjuvant, such as wetting and spreading, sticking, solubility, foaming etc. It was found that ECOSURF™ EH Surfactant, when be formulated in pesticide and adjuvant formulations, provides benefits such as wetting, rapid dissolution, rapid foam collapse and low odor. These benefits coupled with low aquatic toxicity and ready biodegradability position it for widespread adjuvant use. Field tests were also done, and drug efficacy improvement was found on some herbicide, e.g. glyphosate, glufosiante etc.
Technology is one of key advantages of Dow, both in terms of product portfolios and R&D capabilities. The HTR platform is a good example of Dow’s R&D capability that is applied to serve the agrochemical industry. We will continue to offer technical solutions that would meet the development trend and lead the technology transformation, as a preferred solution provider for pesticide formulators globally.
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