Auto Care Products Formulation (part 1)

Manual Car Wash

Liquid manual car wash products are a blend of surfactants, builders, and solvents dissolved in water. The economical versions of car wash soaps are made with anionic and nonionic surfactants and some contain carbonates and/or chelating agents dissolved in water.

The cleaning performance of the main anionics linear alkylbenzene sulfonate (LAS), sodium lauryl ether sulfate (SLES), and sodium alkyl sulfate (SAS) can be enhanced by adding co-surfactants. Typical, easy-to-use, co-surfactants are Cocamidopropyl betaines, amine oxides, hydroxysultaines, and amphopropionates. Mostly they reduce the irritation level on the skin of the most aggressive anionics. These co-surfactants also minimize the influence of water hardeners.

The amphoterics in the formulations stabilize the foam and enhance the corrosion inhibition of the formulation. They will be cost-effective formulations when prices per weight are calculated.

The various builder systems depend on each locality’s different legal requirements. Phosphates showed the best results, but have some environmental disadvantages.

Automatic Prewash/Main Wash

Automatic car wash is divided into two categories.

a) Portal car wash

b) Tunnel car wash

In general, the cleaning process uses the same chemistry and the same steps of technology: Presoaker—Car Shampoo—Rim and Underfloor cleaning—Blower drying.

Presoaks

A good presoak will loosen the dirt, grease and traffic film from the car surface and make the car ready for the car washing soap. The presoak is applied to the car and allowed to work for a short time. It may or may not be rinsed before applying the car wash soap to remove the traffic film prior to the remainder of the cleaning process.

A standard presoak formula will contain good builders, surfactants with excellent wetting and penetrating properties and perhaps some solvents like glycol ethers. The pH value is adjusted at pH 9 to 12. Most presoak formulas are high pH and contain fair amounts of electrolytes such as phosphates, carbonates, silicates etc.

The surfactants suitable for this application must meet two important requirements. They must be stable at high pH values as well as in high electrolyte environments. Most amphoterics are good in alkali stability. In fact, amphoterics are stable in alkaline as well as acidic solutions.

Ethoxylated amines, amine oxides, or hydroxy sultaines are also good examples of the surfactants that can be used in the presence of electrolytes as well as in high and low pH applications

Main Car Wash (Brush Wash or Touchless)

Car wash soaps are designed for:

• High initial foam, reduced foam after usage
• Cutting through the traffic film on the car
• Removing dirt, grease, and grime
• Easy rinse ability
• No damage to paint or car surface
• Biodegradable components

Car wash soaps can be formulated as powders or liquids. Powders are a mixture of builders like phosphates, carbonates, silicates, etc. blended in a ribbon blender, and surfactants like dodecyl benzenesulfonic acid (DDBSA) and nonylphenol ethoxylate 9EO (NP-9) adsorbed onto the powder.

Liquid car wash soaps are a blend of surfactants, builders and solvents dissolved in water. If a creamy, dense foam is desired then amphoterics like Cocamidopropyl betaine can be added. For foam stability and viscosity building, an amide or amine oxide can be used. Low foaming surfactants derived from short-alkyl chain materials of the above listed products have shown interesting results. These low foaming surfactant systems show a high initial foam which will be reduced after a few seconds. The cleaning effect on the car is comparable to common systems while decreasing the foam formation after usage making rinsing easier.

Rinse/Drying Aids

The mode of action of drying aids is that they form a thin, almost invisible, layer of quat and mineral seal oil or ester oil on the car surface. When water comes in contact with this layer, it immediately gets repelled and forced to stick together rather than sticking to the car surface. That is what makes water bead off.

Nonionic surfactants are sometimes used along with the quat to form a microemulsion. The test results point to the fact that ethoxylated amines work much better than other nonionics in this application.

The use of a cationic surfactant after an anionic cleaning process is standard through the whole spectrum of the car care industry. For very quick processes, where the rinse aid has to work within a few seconds, this is a major problem. This fact leads to the application of cationic surfactants as a rinse aid and additive in car cleaning.

Different regulations create the basis of the rinse aid formulations. Typical formulations for the European Union (EU) market are ester oil or glycol based systems. Here esterquats and imidazolinium compounds are used to enhance in the first step of activity the penetration onto the surface. Additional beading and sheeting can be enhanced by usage of amides, silicones, or waxes.

On large surfaces found on vans, buses or trains, blowers are usually not used to speed drying. A drying aid for these surfaces could be a hydrophile or hydrophobe. Both effects can be used to shorten the drying time on vehicles. The hydrophilic effect uses the good spreading ability of surfactants. Only a thin layer of water will be left on the surface that dries very fast, leaving a non-streaky surface. This prevents the formation of stains caused by the drying of the drops from the last rinse water.

The hydrophobe effect uses the same system that is used in the blower drying operation. When the vehicle is moved, the airstream will dry the vehicle automatically. This procedure creates more gloss than the hydrophilic system. If the remaining water dries unevenly on the surface, it could create white visible spots. Therefore, exacting formulation work has to be carried out to avoid this. Acidic systems are easier to rinse than neutral systems.

In the United States, rinse aids are based on dicocoquats. The dicocoquat forms a crystal clear microemulsion of the mineral seal oil in water. For the ester oil based systems esterquats or imidazolinium quats are used. Both form microemulsions which can be diluted indefinitely without losing the clarity. Transparency of the product is a very important property, not only in appealing to the eye, but also in relation to the performance of the product. In order for the product to work its best, the microemulsion must have a certain particle size. If the product is hazy or cloudy, the particle size is not optimum and thus the performance will not be the best. If a mixture of coconut and soya or other product with higher alkyl chain is used, when making the quat, the performance will not be optimum. Most rinse aids are formulated at slightly acidic pH values, therefore non-corrosive materials or corrosion inhibitors should be used. With the imidazolines we can enhance the rinsing properties and the corrosion inhibition on the surfaces and equipment used in automatic car washes. If better shine and more protection are required, addition of real wax could help to enhance this effect.

Sources:

• F Müller, J Peggau, Low-foaming Surfactants in Ternary Blends, Jorn Com Esp Deterg 28:1998, 127–136.
• F Müller, J Peggau, Ternary Surfactants in Synergistic Blends, 4th World Conference on Detergents, Montreux 1998, Proceedings of the 4th World Conference on Detergents, A. Cahn ed., Champaign, 1999, pp. 234–237.
• F Müller, J Peggau, Low-Foaming Surfactants in Synergistic Ternary Blends, SÖFW-Journal 125: 1999 5, 2–10.
• J Henning, F Müller, J Peggau, Novel Applications of Silicone Surfactants in Cleaners and Polishes, Jorn Com Esp Deterg 29:1999, 235–246.
• J Henning, F Müller, J Peggau, Novel Applications of Silicone Surfactants in Cleaners and Polishes, SÖFW-Journal 127: 2001 1–2, 38–43.
• I Eissmann, J Henning, F Müller, S Stadtmüller, W/O-Emulsionen, enthaltend aminofunktionelle Organopolysiloxane, German Patent Application (DE) 198 56 930.0, 1998.
• Handbook of detergents, Michael S. Showell, Auto Care and Industrial/Institutional Products, Felix Mueller, Jörg Peggau, and Shoaib Arif.