Breakthrough in the development of labelling adhesives

As a leading supplier of adhesive technologies, Henkel is dedicated to application-driven research and development of innovative solutions that respond to the growing needs of the market and the environment.
In the course of their life cycle, beverage bottles can encounter a whole range of conditions – in bottle cellars, in beverage retailing, during transportation, in refrigerators or during cleaning. The same applies to their labels that position the brand and also inform the consumer about the beverage’s composition and ingredients. The label is also exposed to a large variety of influences, eg fluctuating temperatures, changes of air, moisture and mechanical stress. The adhesives employed, therefore, have to do far more than just stick the label to the container. In fact, they have to feature a broad profile of processing and in-use properties. For instance, the label should not become detached from the bottle on exposure to condensation but still come off cleanly when the bottle is washed in preparation for re-use.

Sustainability as a market trend
Labelling adhesives have been consistently optimised over the past few years with the goal of leaving established processes at beverage bottling plants unchanged while offering extra functional advantages. The trend toward sustainability has been making a lasting impression on the market here, as well. The growing environmental awareness of consumers and also of beverage bottlers has stimulated further demand for environmentally compatible production processes and products. Demonstrating entrepreneurial responsibility in its bid to efficiently satisfy consumer needs, the industry is investing heavily in application-driven research and development. It aspires to continuous improvement and innovative, sustainable solutions that open up new opportunities. Many companies have a traditional commitment to products based on renewable raw materials like casein and special starches. The beverage industry, for instance, often uses water-based casein adhesives to label glass containers.

The rising cost of renewable resources
Despite their proven properties, such adhesives have their constraints. Renewable raw materials are subject to strong price fluctuations and manufacturers are often confronted with rising costs due to increasing demand coupled with supply volatility. For example, seasonal effects and climate changes can impact on the available quantities of the derived renewable raw materials. Markets also tend to respond in a volatile and speculative manner to fluctuations in the supply situation. The price of casein, for example, has soared in the last few years – and experts anticipate that this trend will continue. Constantly rising prices for casein – a raw material derived from cow’s milk – have also driven up the cost of conventional labelling adhesives.

Right product for trouble-free production processes
For many years now, both beverage manufacturers, such as breweries and mineral water bottlers, and adhesives manufacturers have, therefore, been looking into alternative substances that are less susceptible to price fluctuations, whose performance features contribute to environmentally compatible processes and whose low complexity facilitates ease of processing. Casein-free adhesives are, therefore, being increasingly used, as they offer not only a longer shelf life and temperature stability but also a whole series of further advantages over conventional labelling adhesives. These novel products, based on robust polymers, feature exceptionally good initial tack, for example, while supporting fast setting and drying, thus helping to reduce adhesive usage rates. They represent an effective alternative to products based on traditional resources and make it possible to save up to 30% on adhesives. For the industry, this expansion of the range of adhesives means greater production and budgeting security. This becomes all the more important when one considers that natural polymers may become scarce and the market situation can quickly change. With this extended range of options in adhesives, bottlers can thus make choices that cut their costs and ensure trouble-free production processes.

Tough requirements
However, anyone considering a switch to casein-free labelling adhesives should bear in mind a number of points when assessing the possible overall costs and the most suitable adhesive. These include the volume of waste and resource availability along with storage life and waste water treatment. The adhesive should be able to withstand wide-ranging conditions without showing any changes in its product characteristics. At the same time, it should be versatile in order to cover a broad range of labelling applications, have a neutral odour, ensure rapid drying and not disrupt the cleaning cycles of labelling machines. Furthermore, the adhesive should support the beverage bottler in his efforts to boost the efficiency of his plant by reducing the consumption of cleaning agents, additives, water and energy – and hence the production costs. These tough requirements are fully satisfied by Henkel’s improved generation of casein-free labelling adhesives.

Performance without constraints
A number of demanding challenges have to be mastered, particularly in the returnable bottle sector. For example, it has to be possible to wash off the label during the defined cleaning process. Foaming in bottle cleaning machines has to be restricted, which today still often means high levels of defoaming agents during the wash-off process. The adhesives industry has been investigating effective solutions to these problems for some time now. As a leading supplier of adhesives technologies, Henkel embarked on the development of casein-free adhesives with equivalent bonding and processing characteristics back in the late 1990s. With its second generation of casein-free adhesives, the company now has a product series for glass bottle labelling that has a broader and more comprehensive performance spectrum and can be termed a pioneering, landmark innovation.
Long-term tests have shown that the Optal XP product line meets customer expectations. In addition to their wet tack, the adhesives exhibit good adhesion even to chilled glass surfaces. The food and beverage industry can, therefore, turn to a powerful and efficient range of products that cover the entire spectrum of bottle labelling needs, including sophisticated adhesive solutions with high ice-water and condensation-water resistance.

Economic and ecological process benefits
Unlike their conventional counterparts, these adhesives are based on synthetic polymers and are hence independent of the dairy industry. The raw materials employed are thus subject to lower price volatility than casein. For bottling plants, greater price stability means improved cost estimation security in their budgeting. The elimination of casein also yields further benefits, as this resource then becomes available for food production instead of being processed for technical purposes.
The use of Optal XP adhesives yields economic and ecological process benefits in terms of mileage and their field-proven wash-off behaviour. Long-term use by various national and international beverage bottlers has shown that the labels can be detached with ease in bottle washing plants using standard cleaners and settings, as shown in the image on the left. In addition, these second-generation adhesives give no cause for concern during waste water treatment. The products also have FDA approval, are free of toxic ingredients and contain no alkylphenol ethoxylates, zinc or borax.
With their machinability properties and greater efficiency in production due to improved processes and reduced complexity, the adhesives contribute to environmentally compatible production and thus offer bottling plants an equivalent alternative adhesive that is not formulated with resources from the food sector.

Product design with added value
The new generation of casein-free adhesives thus eliminates existing familiar drawbacks and presents an excellent alternative for many different applications. Whatever the requirement – high-speed machines or slow labelling processes, cold or hot, dry or wet conditions, heavy labels or thin aluminium foils, condensation/water resistance or extreme resistance to ice water – the Optal XP product series includes a suitable adhesive. Key brewing customers are now employing these innovations for a range of labelling systems on returnable and disposable bottles.
Market testing was recently carried out for further Optal products that offer labelling solutions for PET returnable packages and even for containers with the up-and-coming no-label look. The printed, transparent labels stay firmly in place even after temperature changes and prolonged storage in ice water, for example.

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