Application Technology - Alkalinity in Cleaning Products
Typical soil today contains an extensive amount of acidic components whose removal is facilitated or made possible through alkalinity. The alkalinity in cleaning products is generated through ingredients commonly referred to as builders. Builders are substances that generate, enhance and maintain the efficiency of a cleaning product. Their working mechanism includes neutralisation of water hardness, generating alkalinity for cleaning effectiveness and buffering this alkalinity, that is maintaining it throughout the cleaning process. They prevent redeposition of soil by dispersing it in the solution and keeping it there, as well as emulsifying fatty and oily dirt. Common sources of alkalinity include sodium hydroxide, sodium metasilicate, sodium carbonate, sodium orthophosphate and their potassium analogs.
The different working mechanisms of alkalinity are:
Saponification: This is the process by which fat is converted into soap by way of reacting with an alkaline substance. A large share of fatty and oily dirt consist of saponifiable fats and fatty acids. The soap that is generated by saponification has the additional advantage of supporting the cleaning process. In addition the dirt that is trapped to the fibres through the sticky fats and oils is released during the process.
Emulsification: Paraffin and mineral oils are not saponifiable through alkalinity. However, they can be emulsified. Sodium hydroxide and sodium carbonate form good an stable emulsions with, for example, motor oils, but are difficult to rinse out. Silicates and phosphates not only form good emulsions, they are also easy to rinse out and are therefore preferred for this process.
Buffering: This describes the ability of the builder to stabilise and maintain the pH-value (in this case the alkalinity) of the cleaning solution. This ability is important on one hand for the saponification process and on the other for the stabilisation of softening the water.
Dispersion: The potential to disperse larger particles, that is they are distributed as smaller particles and held in solution. This ability is usually directly related to the soil carrying ability of the solution and at the same time keeping it in solution thereby preventing a redeposition on the fibres.
Sequestering of water hardening ions: This is the ability of the builder to keep ions in solution that directly determine the water hardness, since these can combine with soil and salts in order to form salts (calcium carbonate or scale, for example) that are insoluble and deposit on the fibres or the machinery. These can be extremely difficult to remove and may also cause damage to pumps, in-line heaters and other machine components.
The above summary lets the reader recognise that alkalinity plays an important role in determining the effectiveness of the cleaning product. Alkalinity in itself is no heal-all but it is an important factor which should be recognised by both manufacturer and user.
Since alkalinity is defined as the pH-realm from 8 to 14 the following question presents itself: how are the individual types of fibres suited for alkalinity in a cleaning product ?
As a rule of thumb, alkalinity generates the most effectiveness as of a pH-value of 9.5.
Synthetic fibres: In general alkalinity presents no danger for synthetic fibres.
Wool: This fibre is slowly degraded by alkalinity. The hydrolysis of the peptides caused by alkalinity slowly leads to a dissolution of the fibre. For this reason wool is usually cleaned with milder, fat-restoring or slightly acidic products.
Silk: Is a protein fibre just like wool and therefore endangered in a similar manner. In addition the effect of alkalinity is seen much more rapidly as the silk begins to lose its luster and therefore its appeal almost immediately.
Cellulose fibres: Cotton, hemp or linen are degraded slowly through alkalinity but in general resist cleaning with mildly alkaline cleaning products.
Stain resistant carpets: Carpets that have been equipped with stain resistant protection from the manufacturer are susceptible to alkalinity. This is due to the fact that the stain resistant protection is applied to the fibres in an acid bath. The protection adsorbs to the fibre, forming a relatively durable connection to them. An increased pH-value can lead to a reversal of this process. In general the pH-value should be below 10 when such a carpet is cleaned.
This discourse shows how important alkalinity can be in a cleaning product but also demonstrates that alkalinity can not always be used. It is up to the manufacturer of cleaning products to recognise this and take these factors into consideration when formulating a product for a specific use.
CEBE has a solution for all cases - the products are formulated in such a way, that they unfold maximum effectiveness for the purpose they were formulated for, if they are applied correctly.