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Dyeing Process basically discusses what you do with the dyes. There are today available latest and state-of-the-art dyeing methods that effectively colour the various substrates. This is a very critical operation carried out in the Dye houses in a series of steps. The pages here gives precious information regarding the various dyeing processes in different industries.
Dyeing Process
Batch Dyeing Process Continuous Dyeing Process Semi-continuous Dyeing Pigment Dyeing

The dyeing process is used in a variety of industries. Though the most widely publicised dyeing process is in the context of textile dyeing but other popular dyeing processes are that in leather, plastics and host of others. Let us see the method of working in each of the processes.

Dyeing Process of Leather

Drum Dyeing process
Dyeing Leather substrate is an uphill task. As leather has myriad of structural differences, grooves, knurls, and folds along with other sorts of imperfections. Therefore for achieving the target of a level and uniform dyeing, the dyer needs to be an experienced, and have a thorough knowledge of the dyeing processes, properties and the auxiliaries that need to be used. Leather dyeing is generally done by two processes. Drum dyeing and Rub dyeing, with Drum dyeing being predominant. In the process of drum dyeing, the application of dyestuffs to the leather is done by immersing the leather in drums. The drum is then tumbled. This tumbling allows the leather to be fully penetrated by the dyes. The ultimate aim of drum dyeing is getting the desired color, that appears level and uniform throughout the skins. The leather colourants that are used is dominated by the Acid dyes which accounts for nearly 90% of the market, followed by metal complex dyes and, cationic dyes to some extent. The dyes are applied either on the grain or suede side.

Inkjet Manufacturing Process

A very stringent process control is needed in the manufacturing of inkjet process. It involves the following:

  • In the manufacturing process, only the best quality raw materials are acceptable.
  • A spanking clean room environment is a must.
  • In Filtration lies the key to a successfull ink making process - generally 0.2 to 0.4 micron filters reduce foreign material in ink.
Considerations in the manufacturing process
The following points are vital in the manufacuring of inkjet and needs to be particularly taken care of:
  • The ink ingredients must show stability this is important for avoiding separation or sedimentation.
  • Precaution must be taken to so that there is no incidence of a sudden burst of heat altering or even destroying chemicals and colorants in inks.
  • Retention of samples are vital as colour and purity of colourants along with other ingredients can vary with different batches.
  • Checking for any chemical reactions to cartridges is also essential.
  • Material safety data sheets(MSDS) are also needed.
  • "Receipe' needs to be followed according to the specifications.
The diagram illustrates a typical dye based ink formulation.

formulationformulation


Textile Dyeing Process

Dyeing is the process in which a dye molecule gets thoroughly dissolved and dispersed in the carrier. It can be in water or some other carrier also, but it must be able to penetrate and colour the textile materials in the process. In the textile dyeing process the dyeing is carried out at different stages like polymer, yarn, fabric and garment or even at the product stage.

Textile dyeing process

The following figures illustrate with process flow diagrams the whole operation of finishing processes and how the dyeing process is a part and parcel of the process of textile making.

Textile dyeing process


Knit Fabric Finishing


Materials used in the Textile Dyeing Process
The materials that are used as inputs in textile dyeing and finishing process may include water, fiber, yarn or cloth. Examples are of wool, cotton, polyester, and a host of process chemicals that includes:
  • Acids, e.g. acetic, formic.
  • Alkalis- NaOH, potassium hydroxide, sodium carbonate.
  • Bleaches- Hydrogen peroxide, sodium hypochlorite, sodium chlorite etc.
  • Dyes, for example direct, disperse, pigment, vat.
  • Salts, e.g. NaCl.
  • Size, e.g. PVA, starch.
  • Stabilisers from sodium silicate, sodium nitrate also organic stabilisers.
  • Surfactants
  • Auxiliary finishes, like fire retardant, softeners.
Methods of Textile Dyeing
In selecting the method of textile dyeing the type of process used depends on several factors that includes type of material like fiber, yarn, fabric, fabric construction, garment. Generic type of fibers, quality standards used in the dyed fabric, sizes of the dye lots etc.

The following chart gives a comparison between batch dyeing and continuous dyeing

Comparision
Comparision

Textile materials are generally dyed using two processes. They are the following:


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