In my early years when I worked for my parental company Weldon Sales Corporation established in 1939, manufacturing stationary products like Weldon Fountain pen inks and office glues besides a range of stationary products, I remember that we used to affix paper labels on glass bottles using water-based adhesives. Initially these were solutions of gum Arabic and later we switched over to starch based adhesives produced by us captively. These worked well on glass bottles or paper-based packaging, the only challenge was that we had to wait for the adhesive to dry before putting these into secondary or tertiary packs as the labels would shift if packed wet compromising the appearance of the product. The same issue was encountered by the beer industry which continues to face it, at least for some brands that still rely on adhesives that do not address this problem. Since glass packaging was heavy and was susceptible to breakages in transit the introduction of plastic HDPE (High Density Polyethylene) bottles came as a big relief at that time. HDPE that was invented in 1953, started being initially imported and later produced in India by Polyolefin Industries Ltd. a Mafatlal Group Company under license from Hoechst Germany, in the late 1960s. HDPE plastic bottles came as a big innovative development for the liquid packaging industry. When we at Weldon started using outsourced Plastic bottles, later manufacturing them in-house, labeling them brought fresh problems.
The labels affixed with water-based adhesives, on drying would fall off in transit or get wrinkled. This was because of the reason that HDPE is a low-energy polymer and for normal water-based adhesives to form a permanent bond is a problem. For some round bottles, we started using wrap-around labels as then the label would come around and get pasted paper to paper. It was during this period after 1965 that the earliest self-adhesive labels started being produced in India and in the 1970s their usage in the packaging of products started to increase. These labels would bond instantly, would not need drying and would not shift in packaging , also aiding the aesthetics so their usage spread quickly and widely. It was that time we at Weldon also shifted to self-adhesive labels or pressure-sensitive labels. The rest of the evolution of Self-Adhesive labels is history and is still an ongoing process.
Adhesives: Pressure-sensitive adhesive(PSA) labels is now one of the fastest growing segments in a world of diverse labeling technologies. It provides accuracy of clean labeling and options to use a variety of adhesives for application on different surfaces in most environments, including temperature, humidity, exposure to UV, etc. Advancements in products and their packaging require labels to perform in extreme and demanding parameters.
Some food and pharma products require the labels to perform at very low temperatures, typical are for ice cream, pharma and vaccines that require extremely low temperature for storage. Synthetic adhesives that are in use nowadays harden at very low temperatures and tend to fall off so must be formulated to withstand the application and storage conditions. These adhesive soften at high temperatures therefore signages and labels that must be used for outdoor in diverse environments, withstand UV light and heat build up due continuous exposure to sun also need adhesives specially formulated to perform for the duration of their lifetime. Direct PSA labels application on food products like fresh fruits and vegetables is now in use and labels must be certified safe for direct food contact and that they should not have adhesive or inks from which plasticizer may migrate into the product. Coming to labeling on low energy surfaces like HDPE bottles mentioned above, though the label sticks well but in these days of increased incidence of anti-counterfeiting, pilferage and tampering, the label with standard general purpose adhesive can be pulled off cleanly by an experienced hacker or counterfeiter. So, the adhesives are an important and integral part of evolving trends in self-adhesive labels. A lot of development has been done on these lines and continue to be taken up to produce special formulations that conform to the specific requirements.
Substrates and embellishments: As customers grow in numbers, segments, literacy, urbanisation and geographical spread, the packaging development managers are attempting to create innovations in partnership with label printers to woo the consumers, increase the shelf appeal of products and increase brand recalls.
Moving from simple label substrates like uncoated maplitho or uncoated woodfree paper, now the selection of substrate is as per the imagination or creative ideas of the label developers. The label face materials can be selected from a wide range of options available like semigloss paper, metallised papers or films, textured paper, various clear or opaque films, fabric, cork, lenticular films, holographic paper or films and anything that emanates out of a creative designer’s mind. As for embellishments, there was a time when either using a cast coated paper or a good varnish were the only options, but now a whole world of new ways to embellish labels has erupted. Using multiple printing technologies to get the best of every printing process, adding value to win customers and beat competition is becoming a necessity for printers. Today we see labels being made in-line in a single pass employing a combination of flexographic printing for spot colours or pantones, offset to create vignettes or skin tones, screen for higher deposition of ink, rotogravure to get the best results of metallic inks, cold foil, hot foil, using a variety of varnishes to create effects like textures, high gloss, matt, silk finish or just spot varnish, embossing and debossing to bring amazing results in the finished labels. We see printers create labels with raised effects like dew drops, print that seems to give the look and feel of wood and fruits with pulp, giving a natural effect. Adding further to the capabilities, now printers are employing digital printing either in combination as mentioned or as repass to do variable printing and or personalization. The options are getting to be limitless.
Security Labelling: Increasing number of instances of duplication, counterfeiting and pilferage has created a need for security to be made an important part of labeling.
Counterfeiting products is a problem not only limited to pharmaceuticals industry, but it also affects 5 to 7 percent of global trade. It has impacted other industries as well, such as electronics, automotive parts, spirits, consumer products and high-end cosmetics. Earlier security labels were only with security cuts incorporated at the time of die cutting, then specialized stocks with overt and covert features like the Void labels started being used followed by destructible labels. Holograms also have been largely employed and is now hologram production is a large segment of label industry. With development in pre-press and printing technologies printers use micro printing which is not visible to naked human eyes and other such printing methods used in printing currency to inbuild security in labels. Barcodes are also being largely employed to play an important role in security in labels besides aiding variable statutory information, track n trace information, inventory and logistical data. A very important development in recent times has been Intelligent labels that include near field communication (NFC) or radio frequency identification (RFID) to perform a wide variety of tasks. Integrating these capabilities with traditional labels is one of the most dramatic development in labeling.
Printing Equipment: The narrow web self-adhesive label manufacturing commenced in India in the first half of 1970s on small, about 4-5inches label presses imported from far eastern countries mostly from Japan at that time. These small narrow web presses that did block printing were extremely slow about 5 meters per minute but still did the printing and die cutting inline in a single pass, that was its USP.
It may appear strange to the younger printers of today that there were no drying arrangements in these presses. Printers would print and then hang the printed rolls of labels on a clothesline for drying before rerolling them on a core and sending to customers. Shop floors of narrow web label printers would look like washing yards referred to in India as “Dhobhi ghat”. The printing technologies with time went through continuous changes. The flatbed block printing made way for semi-rotary intermittent letterpress using polymer plates. With improvement in Flexo ink and plate technology, rotary label presses with central impression drum (CI Label Presses) found their way into print shops. These provided faster speeds at increased widths of 7 inches(180mm)-10inches(250mm) and as the buyers became more demanding on colours, speeds and performance, together with further evolution of prepress, advancements in plate making and registration controls, the CI narrow web label presses moved out making way for modular presses using water-based inks with hot air dryers. However, CI presses continued to be used for other applications like lami-tubes and mid-web flexible packaging. Label presses have over the years evolved to print wider web widths of 330mm, 430mm, 530mm and at last Labelexpo presses over 650mm were displayed. Printing speeds have also escalated to over 200meters per minute. In an evolving scenario of rising demands for perfection in print and printers facing challenges in reproducibility, colour variations due to viscosity changes in ink trays and set up wastage, were releived when UV inks, UV lamps for drying and short web path became a standard part of presses. The UV printing also enabled printing and converting filmic labels after addition of corona treaters inline to enhance print adhesion. Some label companies have of now reverted to include a combination of hot air and UV as some food products have witnessed migration of photo initiators in UV inks migrating into the food causing contamination, so the option to print with water-based inks comes in handy to service such requirements. LED UV also is being seen as replacement as there is energy cost saving and better as regards migration issues. Ideal solution maybe Electron Beam curing which is costly but that has still to be accepted by Indian label industry. There is hardly any installation with EB curing for production of narrow web labels in India.
Other evolutions that happened include label presses designed for quick change overs to enable a large number of jobs per day, servo drives to eliminate gears coupled with advanced vision camera systems to achieve perfect registrations in both machine and cross direction without human intervention, better matrix removal, web cleaners to eliminate pinholes and print aberrations, web turn bars to print both sides of the web along with the delam-relam function for enabling printing on back or the adhesive coated side of the web. Movable lamination stations and embellishing stations like foiling add value to the printed labels. Multiple die-stations to enable functions like embossing, debossing, slitting besides simple die cutting or sheeting have become a standard function demanded by high-end printing companies. Change of heavy magnetic cylinders was a cumbersome and time-consuming job requiring manpower and lifting arrangements. Now in a couple of minutes one can slide-out and slide-in a magnetic cylinder.
The pandemic that surfaced in end of 2019 and drastically impacted the whole world and made businesses suffer for all of 2020 and when we are hoping for it to taper off in 2021 providing relief to mankind, it has started to resurface. It has prompted the industry to re-engineer their working. The aim now is to work with less. Workflow management, increased automation, clean room manufacturing, inventory controls, effective management systems, etc. are the buzzwords that even smaller entrepreneurs understand and are making efforts to implement them. Automatic butt slicers/reel changing systems to achieve continuous 24X7 production when needed, waste management equipment sucking waste matrix right from the die cutting stage and shredding and inline inspection/colour management systems to reduce rejections which were earlier a preference of only a selected few, but these are now a part of standard equipment configurations envisaged commonly by Label printing companies planning expansion or planning new setup. The evolution and shifting of trends in self-adhesive labels have been an ongoing process and printers need to adapt the changes as they originate to stay fit, competitive and innovative.
Author’s footnote: Each parameter listed above and many other parameter’s like inks, special adhesives, coatings and machine design are subjects that are to lengthy to be accommodated into one article and need separate coverage.
Written by Harveer Sahni, Chairman Weldon Celloplast Limited, New Delhi-India April 2021