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Introduction |
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Why be concerned? |
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Supplier progress |
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Potential impacts |
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Functional groups |
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Substance list |
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Legislation / REACH |
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FAQs |
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Related Links |
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Wash with care |
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Environmental assessment of laundry detergents |
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Bleaching agents |
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General info The purpose of bleaching agents is to bleach the natural substances in cotton fibres and cellulose fibres that make the fabric yellowish and to bleach spots that are not removed by the laundering process. Bleaching agents also bleach textile colours and hence should be avoided for coloured textiles. Bleaching also impacts on the fibre structure and in that way reduces the lifetimes of textiles. Hence textile service companies naturally will be very concerned to not over-use bleaching. No general remark on the health and environmental effects can be given since the nature of different bleaching substances used varies greatly. Specific substances Sodium hypochlorite Sodium hypochlorite has a wide application as a bleaching agent for textiles and textile laundering. It also acts as a powerful disinfectant. Scientific evidence shows that slowly degradable organic substances which degrade slowly may be produced as reactants from the use of hypochlorite – the so-called ‘organo-chlorides’. These substances are measured by the analytical method of ‘absorbable organic halogens’ (AOX). In Germany the use of hypochlorite in laundries is regulated and the maximum amount of AOX allowed in the waste water from the laundries is fixed. Sodium hypochlorite is very hazardous to human health due to the etching effect that may cause skin damage and damage to the lungs. In its compound form it is very toxic to aquatic organisms and bacteria. However the toxic hypochlorite form will never reach the waste water treatment plants or the aquatic environment due to its highly active properties causing it to react with the organic substances in the waste water in the sewer. Storage of sodium hypochlorite should be undertaken very carefully since the substance is very corrosive and may lead to evaporation of chloride, which causes skin damage and damage to the lungs. In particular the substance should be kept away from acids since it reacts very rapidly with acids and creates a mixture of hydrochloric acid and chloride. Per-borates Per-borates has been widely used for bleaching purposes in the past but is now phased out due to its toxicity and potential mutagenic effects. Bleaching takes place through the use of active oxygen and per-borates are normally only active at temperatures above 60C. To make per-borates active at lower temperatures, it may be necessary to add an ‘activator’ like TAED which reduces the point of activity to around 40C and a stabiliser is also normally added. An example of a stabiliser could be phosphonates in very small amounts. The per-borates are skin irritatants in their pure form. Borates are created during the laundering process. Borates will remain stable in the wastewater treatment plants and may to some extent pass through the treatment plants. Borates have limited acute toxic effects. Per-carbonates Per-carbonates have increased in use as bleaching agents due to their ‘kind nature’. Per-carbonate behave quite similar to the per-borates by creating active oxygen and they also needs stabilisers for storage, but the active effects starts at 40C and hence no activator is needed. The reaction products – carbonates – are substances naturally found in the environment. Per-acetic acid Per-acetic acid reacts by creating active oxygen and acetic acid. Acetic acid is considered harmless in lower concentrations. Per-acetic acid is created by a reaction of hydrogen peroxide with acetic acid. To keep per-acetic acid stable during storage a stabilizer is needed. Per-acetic acid has to be stored and handled with care due to strong corrosive and etching effects. Hydrogen peroxide The use of hydrogen peroxide has also gained prominence over the recent years as a substitute for hypochlorite and other bleaching agents. Hydrogen peroxide acts by creating active oxygen. Hydrogen peroxide needs higher temperatures and high pH levers to oxidise. Hydrogen reacts very willingly with many chemical substances but creates no harmful by-products. Hence it can be considered harmless with respect to the environment. Hydrogen peroxide is a corrosive liquid that should be handled with care due to its high reactivity. TAED tetra-acetyl-ethylene-diamine This substance has the purpose of activating the bleaching agents, in particular percarbonates, and is active at lower temperature. Since the industrial laundries generally operate with high temperature processes TEAD is rarely found in the detergents for industrial laundries. TEAD is readily degradable and has very limited toxic effects on aquatic organisms. |
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Function: Bleaching or removal of difficult spots. |
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Examples: Per carbonates, Per-oxy-acetic acid and Hypochlorite |
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Synonyms: None |
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Environmental impacts: Differ greatly between the different chemicals groups used. See below. |
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The functional groups:
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Hypochlorite in professional laundries: Many laundries have substituted the use of hypochlorite due to the above problems described and the fact that it reduces the lifetime of the textiles. In most cases it is used for ‘re-wash’ only – that is when some spots on the textiles have not been removed sufficiently in the normal wash. In particular for the spots caused by storage of humid textiles in hot places (the black damp stain spots) no other alternative has been found so far. |