In the laundry industry (being On-Premise Laundry or Commercial laundry) bleaches are normally used to decolor and remove stains. In order to achieve the best performance, soil needs to be removed first by using appropriate detergent then the bleaching step takes place to decolor the stains.
While bleaching is an important step to remove stains, one has to note that it could be harmful to fabric if it is not used in an appropriate condition. Also it is to be made clear that bleach will not remove the bulk/gross soiling. Therefore bleaching agents are used only to decolor stains which are not removed during a good wash process and never to be considered as a substitute for adequate detergency.
Bleaching agents generally fall into two categories - oxidizing and reducing agents, and most commonly in an industrial laundry application oxidizing bleaching agents are being used. Two types of oxidizing bleaches are commonly used in laundry: i.e. chlorine based bleach and the oxygen based bleach. Both chlorine and oxygen bleaches are available in liquid and powder form.
The action of bleach is due to the fact that many colored substances become colorless or soluble in water during the oxidation process, and the reaction are catalyzed by temperature, pH and the presence of metal ions. Bleaching agents could be dangerous to fabric if it is used incorrectly and it will not only oxidizes the stain it will also oxidize the cotton fabric and make it much weaker and it is to be considered as chemical damage.
The speed of oxidation of stains and the degree of chemical damage caused to the fabric depends on a various factors i.e. the concentration of the bleach and its contact time together with the temperature and pH of the wash liquor, indeed higher concentrations of bleach and longer contact times have a greater effect on the fabric.
The energy required to oxidize cotton is much greater than that required to oxidize soil and so it is absolutely essential that the optimum temperature must be designed at which all the soil is oxidized with a negligible chemical damage.
Considering the above reason Sodium Hypochlorite (chlorine bleach) are preferably used at low temperature, and while using at higher temperature, dosage should be much lower keeping in mind about the desired active chlorine concentration and the pH of the wash liquor. Therefore Sodium Hypochlorite to be used at a temperature of 30°C pH of 9.5 or at 50-55°C with a pH of 10.5.
In contrast Hydrogen peroxide (oxygen based bleach) is totally inactive at pH 7 and is very effective at high pH of 11 and higher temperature, and therefore to be used during the main-wash where the pH and temperature are high enough to allow it to work most effectively. Hydrogen peroxide works best at temperatures at or above 80°C at the pH 11.
How one should determine when to use Hypochlorite and Peroxide bleach?
Each bleach has various advantages and disadvantages which are highlighted below:
Hypochlorite used in healthcare laundries will react with chlorhexidine leading to brown stains which can’t be removed
Hydrogen peroxide and even more peracetic acid may cause blood to set onto the fabric if it is present too early in the wash cycle.
If hypochlorite is used and then not neutralized effectively, chlorine can be retained on the fabric causing yellowing and chemical damage during drying at elevated temperatures.
Hypochlorite is a strong disinfectant whereas hydrogen peroxide has no disinfection properties at the normal usage concentrations. While using hydrogen peroxide desired hygiene levels are maintained by attaining desired temperature.
Hydrogen peroxide and even peracetic acid (PAA) based products can be used on colored linen, wherein Hypochlorite fade the color linen.
At Diversey we have various fabric care solution like Clax Xcellence and Clax Advanced, Clax Polar where we design wash program depending on the type of fabric and the soil by using different bleaching agent which are oxygen or chlorine based.
Please reach out to our expert team for more details or tailor the wash program to satisfy our customers need.