Foaming and grease cutting are just a few requirements for detergents.
The most economical way to add sodium alkyl benzene sulfonate is to neutralize the DDBSA while making the batch. Make sure your mixing tank and agitator are constructed of a material that can take pH extremes. The preferred procedure for neutralization of DDBSA is to add the formula amount of water into the mixing tank and start mixing. Add the formula amount of sodium hydroxide 50% solution and then slowly add the DDBSA. Adjust the mixer speed so that it will mix the contents well but at the same time will not generate excessive foaming. Remember, you are handling strong alkali and strong acid, so be careful as these are corrosive material, read MSDS and take appropriate precautions. Also, this neutralization reaction is exothermic. It generates a considerable amount of heat. So also take precautions to accommodate the heat generation, particularly if you are manufacturing a large batch with big amounts of DDBSA and sodium hydroxide. Alternatively, you can buy pre-neutralized material as well. It will probably cost more but may be worthwhile in some instances. Pre-neutralized materials or the sodium salts of DDBSA, also called sodium linear alkyl benzene sulfonate or sodium LAS, are available in 30-, 40-, 50- and 60% active varieties. Some of these materials may contain a hydrotrope (sodium xylene sulfonate) to reduce the viscosity and make the product easier to handle. Others that do not contain a hydrotrope, may come in a paste or gel form. These high viscosity versions need special handling and storage.
The foam height data listed in Table 1 shows that the national brand commercial product has better foam stability than the premium formula made with LAS and alkanolamide. So, the obvious question is, how to increase the foam stability? We tried adding lauramine oxide and cocamidopropyl betaine to the medium formula. First we added 3% active lauramine oxide to the “medium” formula. The initial foam height increased to 130mm but it dropped 120mm after five minutes. When 3% active cocamidopropyl betaine was added to the “medium formula” the initial foam height increased to 135mm and after five minutes it dropped to 130mm. This shows that in LAS-based formulas, the cocamidopropyl betaine may be a better choice as a secondary surfactant than lauramine oxide. Polymers like cellulose ethers (hydroxypropyl methylcellulose, for example) can also be used as foam stabilizers although they may not be as economical as amine oxides and betaines, will take longer to process and will not add to the foam volume in any considerable quantity.
We then tried using sodium lauryl sulfate and sodium laureth-2 sulfate as primary surfactants in dishwash formulas. We chose the medium formula and replaced the LAS with equal amount of active SLS. The initial foam height, as well as the height after five minutes, was the same as those listed for the LAS based formula (initial, 120mm and after 5 min., 105mm).
Next we made a modification to the medium formula by replacing LAS with an equal active amount of SLES (2 mole EO). This formula showed a slight reduction in initial foam height compared to the LAS formula but an improvement in the foam stability (foam height after five minutes). The initial foam height was 115mm and after five minutes it dropped to 110mm.
In light of these experiments and their results, an optimum hand dishwash liquid formula can be developed by using LAS, SLES, and cocamidopropyl betaine and perhaps some cocamide DEA. Let us develop a 15% active formula using these surfactants. A starting formula can be made using 6% active LAS, 4% active SLES, 3% active cocamidopropyl betaine and 2% cocamide DEA. This formula, when diluted 0.1% with deionized water, gave an initial foam height of 135mm and five minutes later the foam went down to 133mm (Ross Miles foam test). In contrast, when lauramine oxide was substituted for cocamidopropyl betaine in the above-mentioned formula, the initial foam height was 120mm and after five minutes it went down to 115mm. That means cocamidopropyl betaine is a better secondary surfactant in an LAS/SLES formula than lauramine oxide.
One or two percent of tetrasodium EDTA or sodium citrate can be added to this formula as a builder; viscosity can be reduced by adding SXS, propylene glycol or denatured ethyl alcohol. A naturally-derived product can be formulated using SLES, cocamide DEA and cocamidopropyl betaine. SLES will give better foam stability than LAS, particularly in hard water. A DEA-free formula can be developed by using LAS, SLES and cocamidopropyl betaine. A sulfate-free and DEA-free formula can be developed using LAS and cocamidopropyl betaine. Both surfactants are listed on the Cleangredients’ database used by EPA’s Design for Environment.
Alkyl diphenyloxide disulsonates (ADPODS), such as Calfax DB-45 from Pilot Chemical Co., is an
Some formulations feature essential oils such as lavender or rosemary for a green way to clean.
To create mild and skin friendly dishwashing liquids, use SLES with three moles of EO like Pilot’s Calfoam ES-303. Cocamidopropyl betaine can be added for improved mildness. Other amphoterics like sodium lauroamphoacetate can also be used for mildness. Aloe vera, vitamin E, panthenol, glycerin and other herbal extracts can be added to the formula for skin care benefits in premium products. Essential oils, such as lavender and rosemary, can be used for aromatherapy benefits. Triclosan is commonly used as an antibacterial agent. To claim antibacterial/antimicrobial efficacy, the product must be registered with appropriate regulatory agencies such as FDA and EPA.
About the Author
Shoab Arif is manager, applications & tech service, at Pilot Chemical Company.
Tel: 513-326-0618; Email: firstname.lastname@example.org