Innovating to launch customised surfactants

By Samir Rawal

The Huntsman Performance Products division has surfactants as a significant part of its portfolio with backwards integration in EO at USA and Australia manufacturing assets. This business focuses on diverse applications including but not limited to Agrochemicals, Home and Personal Care, Paints & Coatings, Oilfield Chemicals, Textiles, Metal Working etc.

At Huntsman, we constantly innovate to launch customised surfactants for our valued customer. Some of the themes are APE-free surfactants, polymeric dispersants, and surfactants for multi-active ingredients etc.

Some of the recent developments are shared here:

1. Novel dispersant for suspension concentrates

Patent Numbers: US8420573 & US8247353

TERSPERSE® 2612 dispersant is a novel polymeric dispersant for use in agrochemical suspension concentrates. It integrates Huntsman technology to create a dispersing agent that can provide improved formulation stability.

Introduction

Despite advances in formulation technology, there are several challenges still faced during the development and commercialization of Suspension Concentrates (SC).

These include:

• susceptibility to temperature
• unwanted rheological phenomena
•  particle size growth

All of these challenges can ultimately result in destabilisation of SC formulations.

Particle size growth

Particle size growth is one of the more common challenges faced in SC development. It can typically be well controlled by the use of dispersing agents, particularly those which are polymeric.

TERSPERSE® 2612 dispersant is beneficial in that it can offer improved suppression of particle size growth versus existing industry benchmark polymeric dispersants.

Ostwald ripening

Particle size growth typically occurs as a result of the spontaneous thermodynamic process known as Ostwald Ripening. In simple terms, the phenomena occur as a means of reducing surface energy. Larger particles will grow at the expense of smaller ones to minimise the exposed surface area.

In the case of agrochemical substrates, the phenomena can be accelerated by increased water solubility. This facilitates ‘easier’ detachment, diffusion and re-attachment of the energetically unfavourable surface molecules.

Dispersant synergy

TERSPERSE® 2612 dispersant achieves enhanced performance through improved synergy with agrochemical substrates. Its unique chemistry improves interfacial adsorption, increasing the energetic favorability of smaller particles and thus limiting Ostwald Ripening.

This is well highlighted by the microscopic comparison of two imidacloprid 600g/L SC formulations that have been subject to accelerated storage at 54° C.

2.Dispersants for high-electrolyte solutions

To overcome herbicide resistance (or tolerance) and meet the ever demanding needs of effective crop management, more advanced and often challenging multi-active ingredient formulations have become increasingly popular. A particularly desirable example is the dispersion of a water-insoluble active ingredient in a water soluble active ingredient; in other words, a finely divided solid suspended in a high-electrolyte solution (HES).

Introduction

A novel polyamide condensate that has demonstrated the ability to solve difficult high-electrolyte formulation problems. The attributes of TERSPERSE® 3030 dispersant include:

• Effectively disperses solid active ingredient in a salt or high-electrolyte solution
• Prevents agglomeration/flocculation of solid dispersed phase
• Low use-rate required for effective dispersion and typical SC preparative procedures can be employed

Problem

Traditional dispersants are typically antagonised by high electrolyte environments.

Challenge

To create stable, robust formulations where solid active ingredients are effectively dispersed in a high-electrolyte solution.

Particle size behaviour

The narrow particle size distribution offered by the use of TERSPERSE® 3030 dispersant both initially and following accelerated storage at 54°C shows its effectiveness in HES formulations. The use of a conventional polymeric dispersant will typically result in strong flocculation.

Rheological characteristics

Increasing the volume fraction of terbuthylazine (Φ) in an HES formulation using TERSPERSE® 3030 dispersant resulted in excellent viscoelastic behaviour (Delta >> 45°) and a low shear modulus over a wide temperature range. This behaviour is indicative of a dispersant which is working effectively even at such high active ingredient concentrations.

Example high-electrolyte systems

TERSPERSE® 3030 dispersant resulted in a phase stable solution with a lower viscosity than the standard polymeric dispersant. As expected, TERSPERSE® 2500 dispersant, unlike TERSPERSE® 3030 dispersant, showed strong shear thinning and a significant yield stress which are indicative of flocculation.

Particle size behaviour

TERSPERSE® 3030 dispersant is unique when compared to conventional dispersants in that it’s been shown to display adjuvancy toward at least one active ingredient.

3. APE-free surfactants

APE's (Alkyl Phenol Ethoxylates) are predominantly used in Textiles, and Industrial & Institutional cleaning industries.

Choice of alternatives is very dependent on end applications and formulation criteria. Finding a one-for-one replacement is not straightforward and we would strongly recommend our customers to work with our specialised technologists to enable us to find what might be the best fit for their needs.  Especially as application conditions can vary vastly - eg. pH, electrolyte levels, and temperatures.

Alcohol ethoxylates can be used as alternatives to APE’s. This class of surfactant is core to Huntsman's portfolio and we offer many varieties based on different hydrophobes with varying alkoxylation levels as befits the application.

Our series of HYDRAPOLTM RP nonionic surfactants are high-performance wetting and dispersing agents intended for general application as primary wetters, detergents, and scouring agents. They have a good biodegradability profile and are not identified as endocrine disruptors. As such they may be used as functional alternatives to APE's in most wetting and detergency applications.

Methyl ester ethoxylates (MEE’s) are a relatively new class of nonionic surfactants based on vegetable oils.  Huntsman’s series of SURFONIC® and TERIC® ME MEE’s are readily biodegradable with low aquatic toxicity profiles, and could be considered in some applications as APE alternatives. They have excellent emulsification properties and no appreciable gel phase in water compared to their AEO counterparts. They are most applicable under neutral pH conditions.

With R&D facilities in USA, Europe, China, Australia and India, we are continuously focusing on innovation in surfactants for our key markets.

Huntsman Corporation operates more than 100 manufacturing and R&D facilities in approximately 30 countries, within five distinct business divisions - namely Polyurethanes, Performance Products, Advanced Materials, Textile Effects and Pigments & Additives.

HYDRAPOLTM, SURFONIC®, TERIC® and TERSPERSE® are trademarks of Huntsman Corporation or an affiliate thereof.

Author: Samir Rawal is Country Manager, India Subcontinent, Huntsman Performance Products.

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