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In an era in which packaging is becoming ever more sophisticated, it is salutary to reflect that some of our most traditional packs still find favour in many industries. What could be more omnipresent, reassuring and natural than the indispensable paper sack? Rodney Abbott reports

Every day more than 16M sacks are used by the industrial sector, the retail trade and general consumers. About 70 companies produce 6bn paper sacks from 140 European sites employing 7000 people, giving a total sales turnover of €1.2bn.

Well, that’s what Eurosac – which celebrated its 50th anniversary at its 2002 Congress, staged in Brussels last month – says. Eurosac has more than 60 active members from 22 countries representing about 80% of the industry. However, around 70% of the paper sack business has been cornered by just four companies – Frantschach Industrial Packaging, Korsnäs Packaging, Smurfit Paper Sack and Gascogne Emballage.

But even the humble paper sack has moved on to better things – quality and performance has improved in terms of weight, resistance, tightness and surface finish for any use.

The use of the paper sack is prolific in the building material, food product, animal feed, and chemical and fertiliser sectors.

Paper sacks have been used in the building sector for 70 years now because they are easy to transport and handle, even with long distance haulage. Building materials have traditionally been bagged in open mouth or valve paper sacks.

Open mouth sacks, formed as a tube, are sewn or glued before they are delivered to the customer where they are filled, then stitched or glued again.

The type of bag/sack used is governed by the size of the particulate. Cement is filled into bags or sacks by air or gravity.

High volume cement is filled on rotary machines with 16 heads at high speed. Valve sacks lend themselves to this type of application, bagging at up to 4000/hr [a 25-50kg sack is filled every second]!

Two things have happened in the last few years that put a slightly different complexion on the bagging of building materials. Firstly, the industry has become retail driven. Secondly, the Health & Safety Executive will no longer permit operatives to lift 50kg weights.

So the larger bag has become an anachronism. Over night, the shape of the industry has been turned on its head.

The industry is fortunate in that other material suppliers pose little threat. Plastics has never taken off in this market, primarily because it sweats and is difficult to palletise. Aerated plastics may solve the problem but it is not economically viable. Cement filling literally involves a considerable amount of hot air at temperatures ranging from 140-160 [deg]C.

A paper bag allows the product to breathe. In addition, smaller bag designs sit much more firmly on the pallet and are easily handled. The market has seen a lot of product and factory rationalisation.

Products end up in DIY stores, builders’ merchants and other factories for conversion to other products before they reach the consumer. Blue Circle’s main cement line produces 50M+ bags/yr.

But the drive to push the product through the retailer has resulted in other packs. Today block-bottomed and self-opening satchel bags allow the product to be stood up, so essential for shelf impact. Presentation is the name of the game to Homebase, B&Q and Wicks.

The market is going to see more of these smaller packs. There is a lot more money per kilo to be made in smaller packs alive with graphics. When shifting cement, the very volume restricts returns both to customer and packaging supplier.

A few years ago 25kg bags were standard. Increasingly, 10kg and even 5kg bags are becoming more popular, purely because of convenience. Who wants to buy 25 kilos of cement just to put in a new fence post? People will pay for convenience.

Just 50 years ago cement sacks used three or four plies of paper. Today, only two plies are required. And the grammage of each ply has dropped considerably. This has been achieved with new technology controlling the way the fibres are laid down and the speed at which the machines are run.

A decade ago a normal cement bag would comprise three 90g plies – the equivalent of 270g/m. Now those same bags use just two 70g plies – virtually half. This reduction in the use of the material is not only cost-effective but environmentally friendly.

While this technological progress has provided advan-tages for both the customer and user it has posed considerable production cha-llenges for the bag maker. 90g papers are a production man’s dream. This weight is consistent, especially where folding is concerned. On the other hand, 70g is thinner and more difficult to control.

A single ply at 110 or 120g would be even better but, before this is introduced, the industry has to convince the customer of its value and to encourage users to trust a product that has only one layer. It’s a question of perception. There is a need to convince people that it is as strong, as sound and as reliable as traditionally produced papers.

The paper bag has also become a major ally of the food sector. In the consumer food sector the demand for flexible paper packaging is growing due to the high performance it offers at a low material input. Kraft paper products enable safe and cost-effective packaging with good printability for product presentation.

By combining other materials – film or aluminium – the barrier effect has been further reinforced. Many different liners can be laminated to kraft or kraft can be coated to create such barriers.

There is intense ongoing research regarding develop-ment of barrier materials from renewable sources such as gluten, whey, chitosan and starch.

These materials have excellent gas barrier properties in dry conditions. By various techniques their sensitivity to humidity has been improved substantially.

In the future the industry can expect applications with composites of kraft paper and barriers from renewable resources, thus offering a completely compostable material. New technology, such as high temperature sealing, self-closing valve, ultrasound and mechanical closing, services quicker and more efficient packaging and product preservation. These techniques are especially suitable for dry pet food.

The industry has purposefully applied HACCP inspection rules. Moreover, manufacturers use water-based inks and corn- or starch-derived glues.

Whether in powder or pellet form, many chemical materials [sodium carbonate, acids, PVC and flammable products] are packed in paper sacks to ensure the best safety conditions for handling and transport.

Combining the use of other materials has reinforced the required barrier effect [insulation from external elements or from the packed products].

The main challenge facing this industry is one of greater sophistication to satisfy increasing retail demands for product variety, particularly where colour is concerned.

More and more bags will be SOS or block-bottomed and feature handles and windows. Production runs will get smaller and packs will carry more and more graphics for that vital shelf impact.

Frantschach stand-up pouches are made of plastics and plastics and aluminium laminates. These pre-made pouches are used in a wide range of applications such as food, pet food, liquid household products, personal care products, and chemicals.

Bags are durable, both chemically and physically, and can be sterilised in a further production process. A wealth of structural options, such as reclosable openings, spouts, laser perforations and a choice of different sizes and shapes and printing capabilities are available.

Flexibility, good palletisation and quick, low-cost filling are the distinguishing features of the Korsnäs valve sack which is suitable for packaging grain and feed, granulates, cement, flour and liquid products which are often produced in large volumes and require a large filling capacity.

For hygienic sack emptying Korsnäs Packaging also has a range of easy-open solutions.

Valve sacks can be filled under pressure and they meet the demands of a large filling plant capacity. Optimum filling speed is achieved using strong and porous ABC paper that allows excess air to escape easily from the sack.

Korsnäs valve sacks are available in sizes ranging from 3–150 litres, with a variety of valve types ranging from automatic closing to sealed closing systems. The sacks can be sealed to make them airtight to ensure that the product inside has a long lifetime.

Smurfit-Stone claims to be the world’s largest producer and mark-eter of bag packaging products. The company’s multiwall packag-ing is specifically designed to safely and effectively package and protect a wide range of industrial and com-mercial products for shipping includ-ing chemicals, pharmaceuticals, build-ing products, food, fertilizer, salt, feed and seed.

Multiwall bags can be customised with easy-open features, handles and resealable closures. A variety of liners, treatments and coatings can be incorporated into the bag to solve particular packaging challenges.

Smurfit-Stone multiwall packages can be printed with colour graphics to increase product identi-fication, differentiation, and marketability.

Gascogne Emballage produce bags for building materials, human and cattle food, petfood and chemicals. Products are designed to be durable, neat and well presented and can be tailored to suit use and climate, storage and distribution. All materials are recyclable. Other features include digital photoengraving, quality of flexo printing, varnish UV high brilliancy and non-skid properties.