Drying, Curing & UV
THE ROLE DRYING TECH WILL PLAY By Tom Kerchiss of RK Print Coat Instruments
W
hile many of the processing issues and problems that print/ converting and other segments
of industry are likely to come up against in the next few years may be taxing: difficulties are not insurmountable. Especially if we consider how far we have
come. Take drying and curing as an example. Today, drying and curing technology provides converters with more options than at any previous time, and that’s a good thing. Choosing a suitable drying/curing technology is not necessarily as clear-cut as it was in the past. The need to differentiate an item from other competitive items is far from easy, especially with so many new products being launched all the time. The ‘brown box’ days are gone as bill- boarding opportunities abound; premium quality items may incorporate neck wrap around labels, decorative foils or marketers may specify a no-label look. Not only are those engaged in product
packaging manufacture and conversion tasked with adding value, they are faced with developing and producing new materials and techniques for industrial sectors such as electronics, electrical, security and medical devices, all of which require different approaches to printing, coating, laminating – and of course drying. Designed and developed by RK Print
Coat Instruments, the Rotary Koater and its high tech bespoke counterpart the VCM offer users a choice of hot air, infrared and UV curing in order that products can be developed, trialled and performance monitored. In the early days of converting, a typical
dryer oven was relatively unsophisticated. Typically they had a small fan and relied almost solely on heat, there was little in the way of air velocity and no finesse of control. The impetus to redefine and improve
drying techniques was due in part to the move away from solvent to water based coatings and adhesive systems.
spot drying applications where coatings and adhesives are applied selectively to precise and masked areas. In general and due to the space saving IR configuration, most IR systems can be fitted in with existing process line in order that they can be used in conjunction with or as a replacement to other drying methods.
DRYING TECHNOLOGY When drying a coating it is critical that the drying technology is optimised for the substrate and associated consumable elements. For instance some coatings do not react well when hit with a lot of heat and if a substrate was a lightweight gauge substrate the coating when hit by heat when being dried could pucker or dimple. Converters have witnessed a number of changes with regard to hot air drying over the years. Impingement systems generate controlled turbulence in the dryer. Air hits the substrate and breaks through the laminar zone of the boundary layer of air and efficiently heat dries an appropriate substrate. Infrared (IR) unlike conductive and convective heat transfer methods is regarded as a surface energy technology. Energy is transferred not heat. The material converts the radiated energy to heat by adsorption. IR provides for a calculated and defined depth of drying, which is critical for translucent plastics, some grades of paper and for textiles. Infrared is often selected for
ULTRAVIOLET Ultraviolet of UV curing is often thought of as a new technology but in actual fact has been around for almost 70 years. In contrast to convection type ovens, which are used to drive off solvents or water by applying heat to dry the coating, UV energy cures by polymerisation rather than evaporation, therefore VOCs and HAP emissions are virtually limited. Though not suited to every application, LED lamp technology and other methods of heat management minimises many of the difficulties associated with curing heat sensitive materials, broadening the range of products that can be subject to UV curing. Early commercial applications for LED UV
were for small area adhesive bonding application of medical devices, thermal ink jet coding and marking and for the curing of heat sensitive fibreglass composites. LED UV has found its way into niches areas associated with electronic production, wood coating flooring and digital printing. LED UV is also gaining traction in labelling and packaging conversion. One of the drawbacks in the past was the lack of suitable inks formulated to react to the output from the LED UV light source but this has changed.
LED UV lamps do not require a warm up time and are fully operational at the flick of a switch. LED UV is amongst a range of technology being utilised by ink and coating manufacturers as it is a safe product, one that will not pose a health and environmental problem.
rkprint.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
