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= Batch Dyeing = From Wikipedia, the free encyclopedia

Batch Dyeing (Exhaust Dyeing) is a method of dyeing a textile material. The method involves the gradual transfer of dye from a dye bath to the textile material in the same piece of equipment. Methods of batch dyeing come from the different machines used in the dyeing process. Machinery used commonly in the batch dyeing process include jigger dyeing machine, winch dyeing machine, jet dyeing machine and beam dyeing machine.

Principles of Batch Dyeing
The principle of batch dyeing is the migration of dye molecules from the dye solution into the piece of fabric until the fabric reaches full exhaustion, all within the same 'batch'. The time taken and the depth of colour achieved in the batch dyeing process is dependent of the different control factors. These include the temperature of the dye liquor, the specific liquor ratio and the method of agitation. The specific liquor ratio is the ratio between the weight of the fabric being dyed and the volume of the dye solution. The methods of agitation depend on the batch dyeing machine being used. There are three different forms of agitation that can be used. Method one is when there is circulation of the fabric only. Method two is when the dye solution gets circulated but the piece of fabric remains stationary. Finally method three is when both the fabric and the dye solution are both circulated to create agitation.

Jigger Dyeing Machine
The Jigger Dyeing Machine is a large closed dye vat with two main rollers located in the top half of the machine. The fabric is wound onto one roller and then fed onto the other. The dye liquor is located at the bottom of the dye vat below the two main rollers, it is specially designed to require a low specific liquor ratio. A number of smaller rollers are located through the dye liquor to guide the fabric through the solution. These are referred to as guide rollers. A steam heating coil is located at the base of the dye vat, this is used to control the heating of the dye liquor. Having the dye vat closed also controls the temperature of the dye solution keeping it a constant temperature at the top and bottom of the vat because no heat is lost to the atmosphere. To prevent the dripping of condensation created from the trapped steam, there are special steam coils located at the hood of the machine.

Winch Dyeing Machine
The Winch Dyeing Machine is a large dye vat that has a winch reel and a jockey reel located above the dye liquor in the top of the machine, that aid the movement of the fabric loop through the dye liquor. The winch reel controls how fast the fabric moves through the solution, helping with the circulation of the loop through the dye liquor by hauling it out of the solution and over the roller. The jockey roller acts as a guide for the fabric, helping it move through the width of the solution. The jockey roller is free moving. . The winch machine also has a front compartment, that is seperate from the main dye vat. The front compartment is separated by a perforated partition. The front compartment is where the dyestuff and dye auxiliaries are added. Heating coils along the side of the front compartment are used to control the heat of the dye liquor.

Jet Dyeing Machine
The Jet Dyeing Machine is a large vat that has a closed tubular system called a venturi that guides the fabric instead of a reel system. The venturi is also where the jet of dye is supplied. the machine consists of a large dye tank that is connected to a heat chamber through pumps that filter and control the temperature of the dye solution. Another pressurised pump moves the dye from the heat chamber to the venturi. The fabric is formed into a loop and moves through the dye chamber into the venturi, the fabric is moved around the venturi and the dye chamber by the pressurised dye solution. It is also aided by a reel that helps guide the fabric into the venturi, however the main form of movement is created through the jet system.

Beam Dyeing Machine
The Beam Dyeing Machine is a large dye vat that consists of a perforated beam that an open width of fabric is wound around. The perforated beam sits within the dye beam carrier. The machine consists of a number of high pressure pumps that transfer the dye liquor in and out of the machine. The dye liquor moves through the perforated holes in the beam into the high pressure beam carrier and then out through pumps located on the edge of the beam carrier.

Jigger Dyeing Process
The jigger dyeing machine is optimally used for the dyeing of woven fabrics. The jigger dyeing process involves the movement of fabric, while the dye liquor remains stationary. The dye bath is heated to boiling temperature through the steam heating coil with a atmosphere temperature of 98 degrees celsius. The jigger dye machine has a short specific liquor ratio due to step less speed and tension monitoring that allows optimal exhaustion with less dye solution. Around 4-5 meters of fabric are wound onto a roller. Fabric pieces can be sewn together 'head to tail' to reach the 4-5 meter length. The fabric piece is moved down from the wound roller through the dye solution and then would back onto the other roll. The rollers can be reversed so that the process of unwinding and winding can be done multiple times until the dyeing process is complete. Once the process has finished the dye bath is cooled and the fabric is taken out and dried.

Winch Dyeing Process
The winch dyeing machine is optimally used for the dyeing of woollen fabrics. The winch dyeing process involves the movement of fabric, while the dye liquor remains stationary. The dye bath is heated through the heating coils within the front compartment to a maximum temperature of 95-98 degrees celsius. The winch dyeing process has a high specific liquor ratio of around 1:20 to 1:40. Once the dye liquor has been made in the front compartment, the dye solution will gradually move from the front compartment into the main dye vat. The fabric is made into a number of loops by sewing the ends together. The loops are equal in length. The fabric is looped over the two wheels that are located at the top of the dye vat. The fabric has very little tension and most of the loop is immersed in the dye solution. The loop of fabric is rotated through the solution by the pull of the winch roller. The winch roller controls the rate of transport of the fabric loop through the solution. The jockey roller is free moving and acts as a guide to move the fabric loop around the entire dye vat. The fabric continues to rotate through the dye solution until the full exhaustion has been achieved, the winch dyeing process can be lengthy in time. Once the process is finished the dye bath is cooled and the fabric is taken out and dried.

Jet Dyeing Process
The jet dyeing machine is optimally used for the dyeing of knit fabrics. The jet dyeing process involves the movement of fabric, as well as the movement of dye liquid. The dye bath is heated to extremely high temperatures with its maximum ranging around 135 to 140 degrees celsius. The jet dyeing machine use a low specific liquor ratio ranging from 1:5 to 1:15. The jet dyeing process involves making the fabric into a loop. this is done by sewing the ends together. The fabric is then moved slowly through the autoclave, which is inside the dye vat. Here the fabric is immersed in the dye solution which fills the vat. The fabric is then lifted out of the vat by a free moving reel which guides the fabric into a jet which moves the fabric through the venturi. The jets push the fabric back through the tube systems and back into the other end of the dye vat. The jet creates turbulence within the dye liquor, this helps with the exhaustion process. The fabric is exposed to a high concentration of dye liquor when it runs through the venturi tube systems. Therefore the main dye vat is usually only partially filled. The fabric repeats this loop until the fabric reaches full exhaustion and the colour is achieved, the speed of each circulation is around 1 to 2 minutes and the entire process will continue for around 20 to 30 minutes. Once the process has been completed the dye solution is cooled and the fabric is taken out and dried.