The idea of converters making their own self adhesive labelstock to reduce costs and add value is slowly gaining ground throughout Europe.

Why should the average converter take a leap into the unknown by adding an in-house labelstock coating facility? After all, the major laminators have built-up considerable expertise in producing many combinations of paper and filmic laminates. Their efforts have played a key role in making the self adhesive industry the dynamic forced internationally-based manufacturers to shorten delivery times and give good technical back-up.

One good reason, say in-house coating equipment suppliers, is that label converters can produce the types of customised constructions that might otherwise be difficult, or too costly, to buy in normal off-the-shelf conditions. These reflect a greater diversification of end-user needs, particularly in niche non-retail markets. Besides certain prime labels, applications could additionally include form/label constructions, direct mail labelling and perhaps security labels and seals.

Equally important, modern in-house coating techniques can allow converters – and certain forms producers too – to cost-effectively produce commodity items. Volumes of plain or part-printed die-cut A4 sheets or continuous stock for imprinting uncoated VIP labels on thermal-transfer, laser and ink jet printers have grown dramatically. Production efficiencies and financial benefits gained through reduced stockholding represent are also important. Remember, however, that no single in-house coating method will necessarily address all of a converter’s labelstock needs. As discussed later, current in-line or off-line technology is based solely upon hot-melt adhesives. Larger off-line modules, as favoured in North America, use emulsion adhesives.

But a huge range of options remains. Introduce the cost element and you have a well proven ‘enabling’ technology that all forward-looking converters should consider, particularly since the laminate represents the most expensive part of a finished label. When setting out their stall, therefore, those with vested interests in the subject not surprisingly highlight the cost-saving element. They claim potential savings of eight to ten pence per square metre, giving overall estimated savings of some 30-35 per cent of total self adhesive material costs. It’s a potent argument at a time when many converters must adapt to the pressure of increased competition, rising production costs and reduced margins, particularly in prime-product labelling.

The financial aspects figured prominently in new techno-market review, called ‘In-house Coating and Laminating for Label and Forms printers’ (compiled by Phazer Technologies and published by Label & Labelling Consultancy). It quotes the Plimsoll Financial Analysis, which found that only 41 per cent of Britain’s 400 label firms are financially ‘good to strong’, set against long-term financial models. The rest range from mediocre to a ‘state of danger’. Arguably, other European countries show similar patterns of financial health, but concern about material costs is universal.

Around ten years ago, laminate costs typically accounted for around 40 per cent of the label selling price. Using the US market as a guide, laminate prices have since risen by an average 1.7 per cent each year, which most converters have had to absorb. Consequently, many converters’ material costs now account for 70 per cent of their selling price. Adding labour, ink, shipping, plant overhead, selling and administrative expenses results in depressed profit margins.

Depending on order size and specification, European
label printers pay cost corresponding to 35-38p per square metre for a typical self adhesive 80 gsm facestock on a 62-gsm glassine and/or supercalendered kraft (SCK) release liner. When handled in-house, laminate costs tumble to about 24p per square metre. A saving of around one third of the cost equals around £100,000 for every million square metres produced. Here are some representative in-house lamination costs:

Paper facestock and paper liner
78 gsm facestock 07.5p/sq.m
20 gsm adhesive 05.0p/sq.m
32 gsm glassine 11.5p/sq.m
Total 24.0p/sq.m

Paper facestock and OPP liner
78 gsm facestock 07.5p/sq.m
20 gsm adhesive 05.0p/sq.m
3 micron OPP 11.0p/sq.m
Total 23.5p/sq.m

The oriented polypropylene (OPP) example highlights its increasing usage as a lower-cost alternative to polyester liners, while retaining similar clarity and stiffness. Compared with conventional glassine paper liners – which account for two-thirds of demand – commercially-available OPP films offer superior technical performance and are now less expensive than people commonly perceive. By combining smoothness with high density and uniform calliper they contribute to the rising usage of filmic liners in general. This is generally growing at around 10-12 per cent annually in North America and around five per cent in European markets. The latest multi-layer coextruded OPP’s, so-called engineered films, have helped advance their cause.

Polyester also has excellent moisture resistance, but offers superior clarity and smoothness, which makes it ideal for high-quality ‘no label-look’ products. It also has the broadest low-to-high temperature range of any filmic, which makes it the best choice for demanding applications.

Other liner materials include clay-coated papers, which because of their good lay-flat and handling characteristics are widely used for the growing computer/EDP sector. While less expensive, their strength properties are lower than those of high-density glassines. Polyethylene extrusion coated papers, or polymer coateds, combine the strength of long-fibred papers, such as MG krafts, with the smooth, non-absorbent surface of a filmic liner. Bleached and unbleached MG krafts and MF uncoated woodfress are growing in usage, particularly in developing nations, because of their economic advantages, but tend to be used for speciality products.

Adhesive coatings
Self adhesive (PSAs) come in many forms, each with different properties. Collectively, they are unique among adhesives. PSAs are formulated to bond well to a paper or filmic substrate without adhesive transfer, while being permanently tacky for affixing to a wide range of surfaces for specific end-use applications. Furthermore, the adhesive must bond to the release liner, yet have a sufficiently low adhesion to allow easy peeling during dispensing. The current PSA technologies are:

Solvent-based acrylics
Water-based and hot-melt formulations have widely displaced acrylic solutions for both economic and ecological reasons. Solvent recovery and/or incineration is essential to meet clean air legislation requirements. Such equipment is expensive and can only be justified for large output operations. Their main usage is for speciality applications, such as ‘no-label-look’ PVC labels and where optimum water resistance is needed.

Rubber/resin solutions
These are less frequently used, but find usage for peelable labels and labelling motor oil containers where a high tack is needed. They offer the best performance for freezer labels.

Acrylic emulsion
Water-based acrylic PSAs (emulsion) now represent the dominant technology and offer a practical option for in-house coaters. The large labelstock suppliers formulate their own adhesives, but ready-to-use formulations are commercially available for small and medium-sized coaters. They offer good die cutting performance, but are unsuitable for labels that must withstand wet conditions. For ecological and cost reasons, emulsion types have become the dominant PSA technology. They are easy to coat in-house using a simple Mayer rod (the same coater can also coat silicone emulsions).

Hot-melt adhesives
Also free of solvents, hot-melt PSAs are growing in usage and, significantly, are easy to coat using compact units. Their performance has improved, especially for permanent has improved, especially for permanent paper labels that account for most of today’s self-adhesive labels. Like rubber adhesives, they quickly develop high peel or adhesive strength.

In-house converters can formulate their own emulsion adhesives, but specialist adhesive suppliers are the best source of HMPSA adhesives. They are supplied in blocks and tack-free slabs, while larger users specify drums for use with attendant holding tanks and metering pumps.

Radcure adhesives
These are types that can be cross-linked (cured) by electron-beam or ultra-violet radiation. This enhances some characteristics, such as the high temperature performance of hot-melt adhesives. Radcure adhesives are now used in some speciality tape applications, but do not yet offer a practical option for label or forms converters.

Equipment choices
The choice of adhesive determines the in-house coating method. Water-based emulsions require stand-alone equipment, usually in web widths of 1 to 1.5 metres, and sufficient space for hot-air ovens. These remove moisture from paper substrates, so a re-moisturising unit is essential. Therefore, equipment and energy costs are much higher compared with hot-melt coating, although production capacity is considerably higher.

Hot-melt coating/laminating does not need drying ovens, which means it is easily adapted to narrow-web production. Alternatively, wider-width stand-alone units supply customised labelstocks for several presses. The adhesives do not offer as broad a prime-product label range as water-based adhesives, but the coating technology itself offers much more flexibility. Instead of just continuous coating, hot-melt coaters offer the option of using specific slot-die coating heads. This allows users access to pattern and/or stripe coatings, high finishes for ‘no-label look’ products and coatings in specific shapes.

Depending upon the facestock and liner, they offer both label and form converters many potentially profitable business opportunities. These can include piggy-back coupons, form/label sets with permanent or peelable labels, self-adhesive pocket labels, or reverse-side printing of film followed by adhesive coating for full protection.

The two largest European suppliers of in-line and off-line hot-melt coater/laminators equipment for labelling (and many other applications) are Nordson and Mercer Adhesive Systems in Rugby. The former claims market leadership and works with Meltex, a wholly-owned subsidiary since 1989. Nordson (UK) Ltd in Thame, Oxfordshire, is among its key worldwide subsidiaries. Mercer in the UK is an independent distributor for ITW Dynatech INC, which makes hot and cold adhesive coating systems. It acquired the Mercer Corporation, the UK company’s former parent, around eight years ago. Besides labels, both companies have supplied customised turn-key systems for industrial applications over many years.

For in-line coating, Nordson uses Meltex coating heads of the type found in its range of stand-alone coaters. The EP 45 head is suitable for continuous, striped and intermittent applications. The EP 51 is mainly intended for continuous coating at 18 to 25gsm. Both types include an in-line filter with a high-volume filter cartridge. The replaceable coating heads are available in standard application widths of up to 500mm.

By inserting various shim plates, operators can change the application width and pattern as needed. Replacement nozzle tips are available. The air manifold and heated body are normally isolated, which allows continuous operation at temperatures up to 260ºC.

For high-gloss continuous coatings of clear filmic labels, Nordson supplies the Type BC 40. A rotating bar eliminates any streaks, while inserting Teflon profiles alters the coating width.

The Type CP 3000 rotary coatings drum selectively applies hot-melt points in varying sizes, patterns and pictures to the substrate. Pre-etched screens give the required pattern and repeat for each application. This method is a more expensive than using slot-die heads, but is useful for form.label constructions, multi-layer, piggy-back and tracking labels.

Flexo coating also offers adapted printing technology to obtain specific adhesive patterns of different densities. Nordson’s Flexo-O-Coat uses a steel hot-melt wheel, fed from a standard Meltex applicator and metering system. This applies the adhesive to a heated rubber-coated transfer roller with the required pattern and repeat etched on the surface. A reverse-side impression roller transfers the adhesive to the substrate. Multiple circumferences between 150 and 300mm allow a variety of repeat lengths, running up to 150 m/minute.

Nordson also supplies spray-slot heads for non-contact coating. Here, the adhesive and spray air are pre-mixed inside the spray nozzle. The finish is not as high as that of a contact method, but there is finer control over coating weights with better edge and cut-off definitions. While used extensively in the non-wovens industry, demand is picking up for label applications.

Among the stand-alone coaters, the CT 4000 series applies coatings up to 350mm with single-sided roller mounting. Coating widths of 400 to 800mm are handled on the CT 5000 series. A main frame holds the bearings for the unwind shaft, conditioning rollers, coating and laminating rolls, unwind and rewind. The coating head is mounted to give three-axis control and automatically swivels away from the substrate when the unit stops. The main coating roller is usually coated with silicon rubber, but Nordson recommends using a chromed roller for gloss finishes. Laminating rolls, mounted to the side of the coating roller, are either chilled or heated to ensure the stabilised application of the hot-melt. This maintains a high finish and accurate coat weight. Once the materials are combined, they are wound on to the rewind shaft.

The melt equipment (also used for in-line applications) stands alongside the unit. A drum melt system, incorporating the ‘melt on demand’ principle is usual for labelstock production. The bulk meter feeds the adhesive into a stabilising tank, metering pumps eliminate any air bubbles before supplying material to the application head.

Mercer Adhesive Systems retro-fitted units also produce coatings of permanent, pressure-sensitive or remoistenable adhesives that are full width, striped, beaded, spot, patterned or zoned. Again, intermittent or continuous operation is possible, as on its off-line systems. It also supplies the SP-117, a rotary screen hot-melt applicator for zone and/or pattern coating.

The in-line modules accept slot-die coating heads from 150 to 500mm wide. The heads are fitted with high-quality needle valves that, says Mercer, can run a minimum of 30 million cycles before servicing to reduce maintenance. The company also claims its latest coating module has a simple set-up system for controlling coating weights, stripe patterns and position.

Because lay down accuracy is vitally important, especially when printing at high speeds, the modules include air-activated bracketry for automatic accurate positioning, a silicone rubber back-up roll and web guide idlers as standard. A direct drive press interface is optional.

‘The heads that can be attached to the main coating station module will cover most of the process needs’, says Greg Taverner, Mercer Adhesive System’s managing director. ‘This includes dual-web laminations for speciality coupons and envelopes and many patterns, stripes and squares. The equipment is capable of precise registration for continuous, intermittent and multi-shot applications.’

Of course, the vital element is how much does an in-line retrofit cost? ‘How long is a piece of string? The price depends upon the type of press, the method of application and ancillary configurations. It can be as low as £20,000, or three times as much if the job involves a fitting frame. Any modifications to an unwind or special adhesive tanks would push the price up much higher.

The silicone equation
Even with in-house adhesive coating, the converter must still purchase the siliconised release liner. Including a non-stick silicone coating as part of an in-line process can introduce even greater in-house savings. However, its not a subject for the feint-hearted: it involves a complex chemistry and great precision in applying very low-weight coatings using gravure or flexo anilox rolls. So far, both Nordson and Mercer have kept out of this market.

Its biggest champion, at least in Europe, is Phazer Technologies, a developer of silicone releases and consultancy. It is currently working with Printing Specialities of Leek in Staffordshire, which has designed and manufactured several label presses with hot-melt coating installations for UK and overseas users. Both in turn have collaborated with Timsons, a narrow-web press manufacturer. The result is an in-line coater/laminator and converting press for self-adhesive labels and form/label combinations.

Outside industrial and label laminating, combining adhesive and silicone coating technology is not new. Stampiton, for example, uses such a facility for its trade stock label business. Several similar set-ups are also in use by continental label converters. One interesting point is that while liners are considered a wasteful, yet necessary, evil, in-house lamination can extend their usage. Converters can add promotional messages, or add security features, such as fluorescent, luminescent or biocode compounds, behind or above the silicone coating.

Peter Greenway, Phazer’s managing director, points out that there is plenty of information on the subject, including the techno-market review mentioned earlier. Nevertheless, tapping into the experience of companies like his is essential for new entrants. ‘There is a steep learning curve involved. Applying a thin, clear silicone coating means you cannot see any problem evolving before your eyes. So it’s still a black art. While the cost input may be low relative to the total PSA technology, siliconising can prove a very expensive element if things go wrong.’

While several silicone systems exist, the in-house choice is usually between solventless (emulsion) thermal cure and UV-curable silicones. The latter cost more (about £12-£20/kg), but use commercially-available UV curing systems. This feature allows either compact in-line or stand-alone applications, which large curing ovens prohibit. The coating, typically 1 gsm, must remain on the substrate’s surface. It must be free of pinholes: a point to consider when using any paper-based liner.

Where filmic liners are concerned, there are now fewer problems associated with processing heat-sensitive polyolefin films, such as OPP and LDPE and HDPE (mainly used for tapes, linings and self-seal pouches). This point does not apply to polyester. The introduction of low-temperature thermal cure silicones, also room-temperature UV and electron-beam cure systems for in-house coating, represent major advances. The following example relates to OPP:

Paper facestock and OPP liner
78 gsm facestock 07.5p/sq.m
20 gsm adhesive 05.0p/sq.m
30 micron OPP 05.6p/sq.m
2 gsm silicone 03.0p/sq.m
Total 21.1p/sq.m

These comparative figures will vary with market trends, volumes and the specific grades chosen. However, they show that label converters can achieve major cost savings by making the complete laminate in-house. One good example is that of blank labels. Craig Daniell, president of the Primadore Group of Companis, emphasised this point at a Cowise conference on PSA coatings in 1996. (His Canadian-based company operates both as an integrated label converter and a leading manufacturer of emulsion-based coating equipment with plants throughout North America.)

‘A substantial amount of the growth in the label industry has come from blank labels or near blank labels. As more printing is done at the point of packaging, the entry fee to enter the label industry decreases.’

‘Converters must find ways to differentiate themselves from their competitors. The skill-set required to run a business that converts purchased laminates into blank labels is not very large. The result is diminished margins and laminate costs that often approach 75 to 80 per cent of selling price.’

‘Today’s label industry players have vanilla presses, vanilla tooling, vanilla inks, vanilla labour rates and, to complicate the matter, have vanilla laminate prices. It has become a matter of who can run faster. No larger opportunity exists for taking costs out of the manufacture of pressure-sensitive adhesive labels than that afforded by manufacturing one’s own base laminate materials.’

Certainly, he and other experts consider that producing laminate on relatively slow, narrow-web equipment is not necessarily less efficient than making it on high speed, wide-width equipment. The in-house coating review maintains that small coaters can do the following:

- Eliminate all selling and marketing costs paid out of the selling price of laminate purchased from large suppliers.
- Eliminate all wrapping, packaging and shipping costs, which are also paid out of the selling price of bought-in laminate.
- Converters can buy-in their base paper and/or film substrate direct from manufacturers to eliminate double freight and handling costs.
- Add the value of laminating to their own operating profits.
- Generate more sales per unit of currency of investment than is possible on large laminators.

To a lesser extent these points also apply to operations involving just the adhesive coating element. What is certain is that we are sure to see a wider application of these techniques during the next five years, boosted by a new generation of UV-curable adhesives and silicones. Greater pressure on the need to reduce costs and develop added-value products will see to that. While it is unlikely to reach large-scale proportions and so affect the commercial activities of the major laminators – it still represents a major step in pressure-sensitive labelling technology.

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