Wet Transfer Printing Process:
Transfer printing in the textile industry usually means the sublimation of thermally stable dyes from a colored design on paper at high temperature followed by absorption of the dye vapors by synthetic fibers in the fabric. In this water soluble dyes printed on paper migrate to fabric having fixing chemicals. The principle behind wet transfer printing processes is the use of water as the medium through which dye diffuses in passing from the paper to the fabric. Thus it resembles sublimation transfer printing in that it is a diffusion-controlled system, but since water is used instead of vapor it is not restricted to the use of dyes that can sublime. The first commercial exploitation of this approach dates from the introduction of the Fastran process in 1971. This involves padding wool garments with stabilized thickeners to obtain an expression of the order of 1:1 and then bringing the wet garment into contact with a transfer paper printed with acid or reactive dyes. The composite is then heated in a press for several minutes during which time the dye migrates to the fabric and becomes attached in the usual manner. The method is not highly productive but is quite suited for the printing of high-value articles such as knitted woollen garments, especially when novel design effects are obtained at the same time.
The general principles of the wet transfer printing process are:
- The use of Lanasol reactive dyes in the form of Aquatran W papers.
- Continuous prepadding of the goods with a thickened liquor.
- Contact between goods and paper for 30–60 seconds at 1060C, with the application of pressure.
- Washing-off to remove unfixed dye.
Several attempts have been made to devise continuous wet transfer systems. The DewPrint machine introduced in the late 1970s (shown schematically in Figure) offered an ingenious solution to the problems posed.
The major difficulty to be overcome in a system of this kind is how to maintain the contact pressure holding the paper to the fabric continuously at the required level over a period of time. This cannot be achieved simply by using a stretched blanket as in sublimation transfer. Consequently the DewPrint machine was fitted with a series of pressure rollers around the heated transfer cylinder, which exert a steadily increasing pressure up to but not exceeding the pressure of the mangle used initially to impregnate the fabric. The major drawback of this solution to the problems was the capital cost involved, which seriously affected adoption of the approach.
Continuous wet transfer continues to be of interest, and new equipment has been recently introduced by Küsters in association with the Cotton Art process developed by Dansk Tranfertryk for transfer printing reactive dyes using their specially developed transfer paper .
Steps of Wet Transfer Printing Process:
1. A wet transfer printing process for fabrics is known which comprises the following three stages.
2. Printing the required design on a selected grade of paper, using specially chosen dyes dispersed in a suitable paper printing medium.
3. Impregnating the fabric (nylon, wool, acrylic or the like) with an aqueous solution which may, for example, contain a dye fixation catalyst and a thickener, the latter to act as a dye migration controller and film-stabiliser.
4. Bringing the printed paper and the impregnated fabric into close conformity, by applying pressure, and maintaining this conformity under pressure for a period which may vary from a few seconds to several minutes, while maintaining the paper and fabric in a moist condition at a temperature of at least 100 on the printed paper are almost completely transferred to the fabric and, provided sufficient contact time is allowed, are fixed in the same operation.
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.