Presentation on theme: "5- WASHING CHEMICALS Chapter 5 summary Enter. Substances defined as detergents are those that have the property of removing dirt from an object without."— Presentation transcript:
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 Active oxygen Optical WHITENERS Neutralisers Disinfectants SOFTENERS Neutralisers Starch Fire retardants FINISHING PRODUCTS
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 waterZeolites They provide the bath with alkalinitySodium carbonate They prevent the dirt from re-depositingPolicarboxilates 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.
AUXILIARY AGENTS 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
Oxidising agents: These release active oxygen, which is ultimately responsible for bleaching out and removing coloured stains. In addition they possess disinfecting properties.
Whitening process: Effectiveness of whiteners vs temperature Each type of oxidising agent has a temperature of maximum effectiveness 80-85ºC60ºC55-60ºC 20-25ºC
Reducing agents: These are used in special processes. They are especially effective on synthetic colourants, and are widely used to remove colour bleeding on white articles. Their characteristic odour is due to their compounds with sulphur.
Softeners Washing processes end up reducing the softness and flexibility of fabrics. On washing the fibres become tangled, and on drying they do not return to their natural position, which reduces their resistance. SOFTENERS Their main component (cationic surfactant) provides lubrication to help the fibres return to their natural position In addition, softeners contain: Perfume Preservatives Additives: colourants, optical whitening agents, disinfectants, etc. Presentation aids
Improves water extraction during spinningMakes ironing easierGives garments a fluffy feelNeutralises residual alkalinityReduces or eliminates static electricityPerfumes the linen Properties:
Added to the end of the detergent process, this group of products restores the treated fabrics to their initial conditions. They help to neutralise, lighten, soften and condition the linen before it is dried and ironed. Finishing products: