The use of digital inkjet as an application method for depositing chemicals on textile substrates is an area of significant development over the last few years, as it gives the opportunity to apply functional textile finishing and coating chemicals on to specific areas of textile substrates.
The development of new chemical functionalities opens a completely new route for functionalisation of personal protective equipment (PPE), such as workwear, enabling increased comfort and protection. Innovations in digital application also enable the production of new functional textile materials (smart textiles, innovative technical textiles) with functionalities and qualities that could not be produced in the traditional way, enabling the production of a completely new generation of smart textiles.
An interesting digital coating application, which could become significant in the future, is the use of digital technologies for the application of the pretreatment chemicals that are required for the subsequent fixation of the digital ink systems. This would enable the development of complete digital-textile printing systems, where the necessary pretreatment stage is incorporated ‘in-line’ into the digital textile production system, either as a ‘wet-on wet’ system or as a ‘wet-on-dry’ system that utilises an in-line dryer/ fixation unit prior to digital printing.
DTG (Direct-to-Garment) pigment-ink pretreatment systems are already available from various suppliers, and these use digitally controlled valves or print heads, followed by a separate fixation stage (to fix the pigment polymer pretreatment) before the subsequent digital garment printing. Kornit has developed the ‘PreT’ ‘wet-on-wet’ system, incorporated into some of its DTG printers (for example, the Storm and the Avalanche). This eliminates the requirement for an off-line pretreatment/fixation stage.
Kornit also recently announced, in June of this year, an interesting further development to this technology, with the new Allegro One-Step digital-textile pigment printing process, which incorporates the pretreatment technology, digital printing and heat fixation in a ‘roll-to-roll’ digital pigment-printing production process (Figure 1).
The concept of integrating the pretreatment (the pfdp stage - prepared for digital print) into the digital print production process could have huge impact in the printed-garment production industry, where digital pigment printers could be integrated into the manufacturing process and both shorten overall production and delivery times, and also reduce inventories and, at the same time, reduce energy and water usage.
The development of similar integrated pre-treatment systems for dye-based digital ink systems would be more challenging, as the dye pretreatment would have to be dried prior to digital printing, although – if the challenges could be overcome and a dye-based digitally controlled pretreatment system could be integrated into the digital print production process – similar huge production, inventory and energy reductions benefits might follow.
At the forefront of digital applications of functional finishing and coating was the major European project, Digitex, which was a part-funded European Brite project.
The project had 26 partners, with the Royal Ten Cate Group of the Netherlands acting as the project co-ordinator. Since the completion of the project a considerable number of published papers have been published and the Ten Cate Group has built up an interesting patent portfolio in the area, which points the way to the many finishing technologies that can be applied by inkjet applications.
The Royal Ten Cate Group has announced that it is developing the digital finishing and coating technology for its Fabric Protective Group; an interesting passage from its 2011 Annual Financial Report (English Edition), emphasises that it is envisaging a considerable future market advantage from this technology… “This represents a revolution for Ten Cate in the field of coatings and textile finishing, because functional characteristics can be applied to materials on a nano scale. This is an entirely new process in the treatment of technical textiles. This technology is therefore gradually being introduced into Ten Cate’s production process, initially in the Ten Cate Protective Fabrics market group”.
There are a number of other European funded and university projects examining digital printing of functionalised textiles – for example, the EU Brite project ‘Microflex’ and the research work carried out by Professor Marc Van Parys’s group at the University of Ghent in Belgium.
However, in the public domain, Royal Ten Cate Group appears to be the major player in the digital-finishing-technology area and the only major textile group with a large-scale digital-finishing project.
It will be interesting to now closely watch how inkjet technology and functionalised textile chemicals will be exploited in the future, not only by the Ten Cate Group but by other textile groups, who well might be developing digital functional technologies for their own production.
In conclusion, we are at a very early stage in actual production developments, both in the application of functional textile-finishing chemicals by digital inkjet and in the inkjet application of pretreatment technologies for digital textiles. However, I believe it to be an area that will offer both significant developments in production speeds, by shortening the overall production process, and significant environmental advantages, with less water and energy usage. Undoubtedly, the major chemical suppliers and digital textile-printing and finishing-machinery manufacturers are already studying and possibly developing systems to apply these technologies in the near future.