5- WASHING CHEMICALS Chapter 5 summary Enter
Substances defined as detergents are those that have the property of removing dirt from an object without damaging it. Detergents are combinations of chemical compounds which, associated with the factors of time, temperature and mechanical action, allow a surface to be freed of its dirt. DEFINITION:
Alkali Neutral Manuals, etc. DETERGENTS CHEMICALS WASHING Chlorine Activeoxygen Optical WHITENERS Neutralisers Disinfectants SOFTENERS Neutralisers Starch Fire retardants FINISHING PRODUCTS
DETERGENTS SURFACTANTS Anionic surfactants Non-ionic surfactants Cationic surfactants Amphoteric surfactants BUILDERS Sodium tripolyphosphate Zeolites Sodium carbonate Polycarboxylates WHITENING SYSTEM Chemical whiteners Whitening activators Optical whitener ADDITIVES Enzymes Anti-redepositing agents Corrosion inhibitors De-foaming angents Perfume AUXILIARY AGENTS Water Sodium sulphate Typical composition:
These are the constituents of detergents, and provide special wetting, foaming and detergent properties.They reduce the surface tension, causing water to behave in a particular fashion in the presence of solids and fats. Hydrophilic end: Lipophilic end Diagram of a surfactant molecule: SURFACTANTS
Types of surfactants: Depending on their Ionic behaviour in aqueous solution, they are classified into 4 groups: Anionic S. (-) Noionic S. (nil) Cationic S. (+) Anphoteric S. (depending on mean pH) Manual dishwasher Linen detergent for machines Softener for linen Creams, disinfectants, etc. Examples of use: SURFACTANTS
How do surfactants work? The soiled fabric comes into contact with the water SURFACTANTS The bath with detergent wets the fabrics and the dirt The surfactants separate the dirt from the substrate The dirt is stabilised. The hydrophilic part in contact with the bath. The lipophilic part in contact with the dirt.
They are added to detergents to protect or improve the detersive efficiency. They add detergent properties that improve the detergent process. They remove the hardness from the water Zeolites They provide the bath with alkalinity Sodium carbonate They prevent the dirt from re-depositing Policarboxilates They improve the emulsion and dispersion of the dirt Sodium tripolyphosphate…. BUILDERS
In laundering we use the term "whiteners" to refer to the chemicals that remove the colouring dirt and keep the fabrics white. In the composition of a detergent, we can find the following: Whitening activator:This enhance the whitener so that it acts at low temperature Chemical whiteners:For example: Perborate and percarbonate DO NOT attack the colours Optical whiteners:These reflect the light and give the sensation of greater whiteness WHITENING SYSTEM
Minority substances in the composition of a detergent. Their properties differ from one detergent to another: ADDITIVES ENZYMES: These are natural proteins that enhance detergents and allow them to work at a low temperature. Each type of enzyme degrades one type of substance. ANTI-REDEPOSITING AGENTS: These keep the dirt removed from the fabrics in suspension in the bath. CORROSION INHIBITORS: These are used to protect the substrates on which the detergent acts. DE-FOAMING AGENTS: These are needed to ensure that the detergent solution possesses an optimum level of foam. PERFUME: This is added to make the product pleasant to use and to leave a residual aroma.
AUXILIARYAGENTS Without a mission in the detergent process, they are necessary to ensure that detergents have a presence that aids their use and that allows their properties to be preserved. Water Auxiliary presentation agent in liquid detergents. Influences fluidity, viscosity, density, etc. Sodium sulphate A colourless and crystalline powder. It acts as an absorbent and helps to disperse all the compounds of a detergent powder evenly.
An oxidising agent is a chemical element that captures electrons, ending up with a positive charge. A reducing agent is a chemical element that cedes electrons, ending up with a less positive charge than it had. TYPES OXIDANTS Hydrogen peroxide Sodium perborate Sodium percarbonate Peracetic acid Sodium hypochlorite Chloroisocyanurates Ozone REDUCERS Sodium hydrosulphites Sodium bisulphites