Further progress in the evolution of industrial paper bags

Conventional industrial bags made of paper tend to be vulnerable to rain and moisture. When exposed to direct rain on an unprotected pallet, a standard paper bag absorbs water and may weaken as a result. Handling may then become awkward, and the shelf life of the contents may be affected. In some cases, a switch to plastic bags is the answer. But this may not be the optimum approach, as the cost of investing in form-fill-seal (FFS) machinery tends to be high. Mondi, from Vienna/Austria, has come up with a hybrid solution to the dilemma: the H­ybrid^PRO bag, offering the advantages of a plastic bag, yet fillable on conventional paper bag filling systems.

With the new bag material, paper combined with plastic really can provide the best of both worlds: uncompromising weather protection thanks to the bag’s outer PE barrier layer, allowing genuine outdoor storage for lengthy periods and extended storage stability, without the need to invest in expensive FFS filling systems.

The Hybrid^PRO bag, which will be marketed under the slogan “Made of PaPEr – combining the best of both worlds”, represents a whole new concept in industrial bag design. Like a hybrid drive in a car, the new bag material is an excellent combination of the available options: the inner ply is made of 120 g/m² Mondi A­dvantage One sack kraft paper; the outer ply is a 40 μm-thick layer of high-density polyethylene (HDPE). The innovative step here is that the HDPE forms a protective layer on the outside of the paper. Other bags also use a combination of paper and plastic, but not in this way. This is a considerable technical achievement that brings a new dimension to industrial bag design.

The bag is particularly suitable for building materials, including gypsum and cement, as well as many other moisture-sensitive products. It is suitable for filling contents at temperatures of up to 90 °C. The Hybrid^PRO enjoys excellent protection against direct rain during shipping or on site and as well as against gradual moisture ingress during outdoor storage, thanks to the 40 μm thickness of the unperforated HDPE film. This means shelf life is longer than with standard paper bags. For example, according to building materials producer Knauf, who collaborated in developing the new bag, gypsum packaged in the Hybrid^PRO enjoys an eight-month shelf life when stored outdoors with no further protective layer – twice as long as if packaged in a standard paper bag.

This impressive performance outdoors makes the bag very user-friendly and has benefits when it comes to streamlining the supply chain of fillers and end-consumers: with longer shelf life, order sizes can be larger, for potential reductions in shipping costs.

The Hybrid^PRO allows high-speed filling, with de-aeration twice as fast as with a standard three-ply bag (35 m³/h versus 18 m³/h tested on Mega Gurley equipment at Mondi’s R&D centre BAC in Austria). Since the bag’s HDPE film has anti-slip properties, there is no need to apply anti-slip substances during production. The anti-slip properties ensure safe handling during shipping. Workplaces, such as construction sites, are cleaner with the Hybrid^PRO, as less of the contents adhere to the outer layer – a benefit sure to appeal to end users.

The Hybrid^PRO is an eco-friendly solution: the total grammage of material used is less than with standard three-ply designs used for the same purpose. In addition, the plastic and paper components are easy to separate, for optimum re­cyclability.

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