Soluble packaging is being used more and more for personal care products. So why use soluble packaging, and what challenges does it present to personal care formulators?
Why use soluble packaging?
There are many advantages to using soluble packaging. It allows for unit dosing, reducing overdosing and therefore resulting in less waste. Soluble packaging also allows for no contact with people, minimising any risk of skin irritation.
In terms of energy savings, soluble packaging allows for products to be transported easily within a concentrated format. In fact, one pallet of powdered concentrated pod is equivalent to a 20 tonne truck of TRU cleaners! So that’s a whole lot less energy used in storing and transporting these products.
The biggest ecological advantage, however, is a huge reduction in single use plastics compared to traditional packaging. While plastic will not disappear from use overnight, products in soluble film are one significant step towards reducing single use plastics.
How is soluble packaging made?
The predominant material used for water soluble packs is Polyvinyl Alcohol (PVOH), which is very water soluble and ‘readily biodegradable’ (leaving no waste). Polyvinyl Alcohol is however a petrochemical derived product. For the moment, PVOH is the most practical product, but natural based films have been produced and are being refined, so the future may well be in these types of film.
What are the challenges for the personal care industry?
Even though soluble pods have been hugely successful within the detergent industry, they have been relatively slow to appear within the personal care industry. So what are the problems for formulators?
The first universal problem with soluble film is water content. In general terms, we aim for a maximum of 5% water in the system, but this can give a lot of formulation headaches when it comes to personal care products because they tend to require a much higher water content.
With wash-off products, aesthetics provide a real challenge. Standard products such as shampoo are viscous liquids with a 10-20% level of actives, high foaming and with a strictly controlled preservative function and level. So formulators need to create a fairly low viscosity concentrate for filling into the soluble film. This concentrate needs to include:
- the correct level of fragrance, colour and preservative
- less than 5% water content
- the same rheological aesthetics in its diluted form as a standard product
It is difficult to use the surfactants normally used in personal care products (usually with at least 70% water content) in concentrates therefore, as formulators simply cannot get enough into a concentrate to give any performance on dilution.
In some cases, formulators have used glycolic solvents to replace water or much more concentrated rheology modifiers. However, this means compromises have to be made and the formulations look decidedly different to ready to use products on the market.
For leave-on applications, water content isn’t such an issue as the raw materials in products like skin creams (emulsifiers, emollient oils and esters, for example) are for the most post high active and low/no water containing ingredients. However, there is still the difficulty of thickening on dilution. The ingredients normally used to formulate a hot blended cream cannot be used, nor can normal polymer powders for cold blended creams as they’re not soluble in oils or low water systems. It’s possible to create powder systems for leave-on applications but these present more problems than they solve… so what’s the solution?
The technical team at Chemlink Specialities have found a few ways of producing a fully formulated cream on dilution from a water soluble pod, where the concentrated base is also compatible with PVOH film.
We showcased this new creation at the Laura Marshall Awards at SCS 2019. Each 5g pod dilutes into 50ml water with a 30 second shake to produce a stable, fully formulated emollient cream.
Other challenges for formulators to consider are:
- Film stability and pack labelling: concentrated products for soluble pods are at least 95% active which means that a large percentage in most cases of a water free preservative is contained in the concentrate. This has effects on film stability and may also affect pack labelling for the concentrate.
- Fragrance: As the fragrance also needs to be concentrated, this can cause damage to the film too and needs to be carefully chosen. The fragrance also needs to solubilise in the dilution with simple shaking.
- Dye stuffs: concentrated surfactants can cause instability of the dyes, and again they have to be soluble in the concentrate and dilution.
- Oversall stability: Stability testing of the products is doubled (stability within the pod and stability upon dilution) but there is also an open question yet to be answered about preservation. As the diluted product is not sitting on supermarket shelves for months on end, does it need the same level of preservation as ready to use products in personal care?
What’s next for formulators?
Formulating personal care products into water soluble film is not easy – there are many pitfalls, and requires bringing together experts in PVOH film with surfactant formulators. We would love to see surfactant producers looking at more concentrated versions of some of their surfactants where physically possible, as this would make future formulating much easier.
If you are thinking of formulating personal care products into water soluble film, talk to the technical team at Chemlink Specialities.
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