Textile Bleaching Process
The whiteness of textile materials is liked by everybody. White fabric colored with dyes. Sometimes we want to get a white fabric; which is obtained by the bleaching process. After the scouring process bleaching is done to get white fabric. Bleaching is done for removing the natural color which is inherent in the fiber.
Bleaching is the second step of pretreatment of textile materials as well as wet processing technology. The bleaching process can be defined as; the destruction of natural coloring matter from the textile materials in order to achieve a clean white end product. Different types of bleaching agents are used during bleaching.
Objectives of Bleaching:
Different types of objectives are gained by the bleaching process. The followings are the objectives of bleaching. They are-
- The main objectives of bleaching are to get a sufficiently high and uniform degree of whiteness in the textile materials.
- To get a high and uniform absorptivity in the textile materials.
- Bleaching agent occur some damage to the textile materials. So bleaching must be accompanied with minimum fiber damage.
- To preserve a good user and technological properties of the textile materials.
- The process must be ecologically and financially sensible.
- To accelerate the next dyeing process.
The bleaching agent is alkaline in properties. Before using it one should have deep knowledge about different types of bleaching agents. Different types of bleaching agents are available in the market. Some are strong and some are weak in alkaline nature. So, we have to idea about which bleaching agent is suitable for which type of fabric.
Process Parameters of Bleaching
Following process parameters for bleaching must be considered. Points are as follows:
- Bleaching agents have a chemical construction. During bleaching; the chemistry of bleaching.
- The concentration of bleaching agents and other chemicals which use in the bleaching process.
- Bleaching is generally done in alkaline medium of the bath. Bath pH decides the performance of bleaching. So pH of the bath should be considered.
- Temperature of the bath should be considered during process of bleaching.
- Bleaching performance also affected by the duration of bleaching. So, time is an important factor.
- Materials and liquor ratio also considered during bleaching process.
- Scouring is done for removing impurities of fabric or fiber. If scouring process is not successfully done then presence impurities hamper the bleaching performance. So, presence of impurities in the materials is important point for bleaching operation.
- Bleaching agents are sensitive to atmospheric condition. So, storage condition of bleaching agent is important. The place of storage should be neat, clean and dry. Otherwise the working activities could be damaged.
Bleaching is done in different types of machines. Bleaching agents are manufactured by different types of chemical manufacturing companies. All of the bleaching agents do have not the same characteristics. In the bleaching process, H202 is used widely for bleaching.
So, bleaching should be perfect for getting a better dyeing performance. After bleaching, materials need to neutralize for the next process. After the neutralization process materials get ready for dyeing. It is also called scouring and bleaching is half of the dyeing.