John Swazey, Ross Clark, Anju Bansal – CP Kelco, US SUSPENSION AIDS
Novel suspension aid derived from microbial fermentation
Two trends that continue to gain momentum in the personal care and household care markets are: The move to incorporating more biodegradable ingredients into new and existing formulations.
The move to more concentrated products.
In personal care, the emphasis is on the first trend, namely the desire to have naturally-derived, biodegradable ingredients that are made by sustainable processes. In household care, the emphasis is on the second trend, that being the desire to create more concentrated products in order to reduce package size and, hence, reduce the cost of packaging, shipping, and the amount of waste that eventually ends up in landfills. These ‘green’ trends are becoming evident throughout the world. Suspension-aids are often an important
ingredient in personal care and household care products. In personal care, suspension-aids have allowed manufacturers to differentiate their products in both an aesthetic and functional way. For example, the shelves of stores are now stocked with eye-catching bodywashes, shampoos, and liquid hand soaps that incorporate decorative beads, glitter, or pearlescents as well as the suspension of more functional ingredients like exfoliating or moisturising beads. In household care products suspension-aids are used to suspend abrasives, help stabilise emulsions, and improve cling.
1 µm ABSTRACT
This paper is intended to introduce a new type of biodegradable suspension-aid known as microfibrous cellulose or MFC. MFC is produced by the fermentation of the bacterium, Acetobacter xylinum. The organism is typically grown in glucose syrup- (eg corn-syrup) based media and produces cellulose that is chemically identical to plant-derived cellulose. However, though identical in chemical structure, MFC fibres are much smaller in diameter than plant-derived cellulose which leads to a far higher surface area by weight of the cellulose. This high surface area allows the MFC to create a three-dimensional network that produces a true yield value in solution at low use levels. Also, because the MFC is completely insoluble, it does not compete for water and, therefore, has a wide range of compatibility. Applications for MFC include adding suspension properties to surfactant-thickened bodywashes, shampoos, and liquid hand soaps, as well as to ‘ultra’ liquid dish soaps and concentrated liquid laundry detergents.
Suspension-aids that are naturally-
derived are present in the market and are being utilised more and more by both the personal care and home care formulators. Examples of these polymers include xanthan gum, carrageenan, various cellulose-ethers, as well as natural clays. Though the interest in using these ‘green’ ingredients is strong, it can be quite challenging to the formulator when you consider that synthetic, petroleum-derived suspension-aids like Carbopol thickeners and other polyacrylates are so widely used, particularly in the personal care market. These synthetic products are extremely useful to provide good suspension and viscosity in variety of formulations. In fact, these products are so versatile, that it is unlikely that any one type of naturally-
Figure 1: (left) An electron- microscope image of Microfibrous Cellulose (MFC) with its net-like structure.
Figure 2: (right) An electron- microscope comparison of MFC fibre size (at the end of the arrow) vs. other common fibres.
derived polymer could possibly mimic the entire performance range of these various synthetic polymers. In particular, it has been challenging to replace these synthetic suspension-aids in surfactant-thickened products like bodywash, shampoo, and liquid hand soaps. These polyacrylates- copolymers provide good suspension of insolubles while maintaining the ‘honey- like’ viscosity of typical surfactant-thickened formulations. Using alternative, naturally- derived suspension-aids like xanthan gum can provide sufficient suspension in these formulations but cannot recreate the honey-like surfactant rheology due to xanthan’s high pseudoplasticity. Further, the attempt to use surfactant-thickening in combination with xanthan gum or other biodegradable viscosifiers generally leads
Polyester fibre
Wood pulp fibre
March 2012 PERSONAL CARE
69
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