Bleaching is the most important part of wet processing. Bleaching is done for removing natural color of the textile materials. During pre treatment of the textile materials different parameter is maintained strictly. Bleaching is done by different types of bleaching agents.
Bleaching agents are applied on different types of fiber. Textile fiber may be natural or synthetic. Depending on fiber types bleaching agents also differ. Bleaching agents mainly classified as the follows:
- Oxidizing Agents
- Ozone (O3)
- Bleaching Powder
- Hydrogen Per Oxide (H2O2)
- Sodium Hypochloride (NaOcl)
- Sodium Chlorite (NaclO2)
- Potassium Dichromate (K2Cr2O7)
- Potassium Permanganate (KmnO4)
- Per Acetic Acid (CH3COOH)
- Sodium Per Oxide (Na2O2)
It is mentioned that;
Above no. 1 and 2 agent uses for home purpose.
Above no.3, 4 and 5 agent uses for industrial purpose.
Above no. 6, 7, 8 and 9 agent uses for washing purpose.
- Reducing Agent
- Ferrose Sulphate (FeSO4)
- Zinc Dust (ZnO)
- Stannous Chloride (SnCl2)
- Sulpher Dioxide (SO2)
- Sodium Hypo Sulphite (Na2S2O2)
- Hydrogen Sulphide (H2S)
Bleaching agents have different applicability depending on fiber types.
Different types of bleaching agents use on different fibers. Among all of the bleaching agents hydrogen per oxide is called universal bleaching agent. There have some reasons behind this specialty. They are as follows:
- Hydrogen per oxide is a very gentle bleaching agent.
- It is very easy for application.
- Permanent treatment is possible with hydrogen per oxide.
- It is easy to apply with any types of fiber.
Bleaching agents are applying on fiber by two processes. They are:
- Discontinuous or Semi-continuous process: In this method bleaching agent apply on fiber discontinuously or semi continuously. Bleaching tank, Jigger, Padder, Kier and many others use for treatment with bleaching agent.
- Continuous process: In this process bleaching treatment is performed as per sequence of treatment. J-Box use for continuous process.
During bleaching; following points must be considered for get better performance:
- Bleaching Agent
- Wetting Agent
- Sequestering Agent
- Materials and Liquor ratio
- Application time
Different types of machine manufacturing company manufacture this type of machine. Machine should have enough properties which is required for performing the operation.
Anyhow, when we will select the chemicals we have to ensure the chemical properties, which is required. Well known chemical manufacturing companies also supply the guide line of chemical use. We will use right bleaching agent for right fiber.