COSMETICS & PERSONAL CARE
Current technology
Current shampoo bars are typically variations on syndet ( synthetic detergent ) bars . The availability of suitable ‘ dry ’ surfactants is limited , due to the manufacturing process and ultimate dry form of most commonly used surfactants . Many liquid surfactants are unusable in their water-free form .
A handful of dry surfactants are currently available to formulators . Most common is sodium cocoyl isethionate ( SCI ), plus sodium lauryl sulfate ( SLS ), sodium cocosulfate ( SCS ), sodium lauryl sulfoacetate ( SLSA ) and disodium lauryl sulfosuccinate ( SUS ). Whilst these materials are perfectly acceptable cleansing agents , they all have at least one limitation : skin feel , foaming , mildness , natural credentials , etc .
More telling , maybe , they rarely appear in classic liquid shampoo formulations . Whilst shampoo bars are increasing in popularity , consumers generally buy them for ethical reasons and make a compromise on performance . The market is likely to plateau without any real advances in the formulations themselves .
Consumers are also becoming more reticent about ingredients with perceived issues , including sulfates , palm , synthetics , ethoxylates , etc . Some of these perceptions are not based on sound scientific arguments , but it is the nature of our industry that many brands will adopt ingredient selection policies that prohibit some useful surfactants . This is problematic with such a limited number of available and suitable surfactants for shampoo bar formulation .
A new technology
JRS has a long history of working with cellulose and microcrystalline cellulose fibres . Their use as pharmaceutical excipients in tableting due to their binding properties is well documented . These fibres have another useful property : oil and water absorption . The fibre structure is perfect for absorbing liquids up to four times the fibre weight . This property has been used successfully in many applications across a wide range of industrial sectors .
Utilising the fibre ’ s binding and absorption characteristics JRS has looked at their ability to absorb liquid surfactants to create dry powders that can then be pressed into solid bars . Two were chosen initially .
Sodium laureth sulfate ( SLES ) was selected for its prevalence in shampoo formulations , which is due to a number of reasons , including cost , foaming , performance and salt-thickening ability . Additionally the low water content and paste-like consistency of SLES 70 % was seen as a good test of the fibres ’ absorption properties .
Cocoglucoside was evaluated due to its excellent performance in sulfatefree shampoo formulations . It is a widely used mild non-ionic surfactant with good foam and cleansing properties . The grade used was a 52 % active material with low viscosity .
Both were blended in the laboratory with various levels of fibre to optimise the surfactant-fibre ratio . The resultant slurry was transferred to aluminium foil trays and dried at 60 ° C to a water content of < 1 %. The dried blend was milled to produce a granular powder . Finally the powder was stamped on a tablet press to produce a 5g tablet . Figure 2 illustrates the process . Further trials were carried out to identify the most appropriate fibre and optimum surfactant-fibre ratios ( Figure 3 ).
The initial success of these trials suggested a more adventurous approach . Two basic liquid shampoo formulations were developed with a view to create a liquid and solid version of the same shampoo . A classic lowcost SLES shampoo and a sulfatefree version were both evaluated . Rather than create individual dried surfactants , as with the initial trials , each individual shampoo ingredient was added to the fibre one by one . The resultant slurry was dried and processed as with the previous surfactant samples .
Stamp & press pressures
This time , however , much larger tablets were stamped on a tablet press . The 30g tablets were more representative of shampoo bars . Pressures of 50- 300 bar were applied to optimise bar integrity .
Lower pressures resulted in a lower density bar , which felt lighter and less solid . These bars were also more likely to disintegrate quickly when used . They did , however , foam very quickly , with copious foam levels . Higher pressures ,
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