Invisible, but indispensable: geo-synthetics in ground works

Oerlikon Neumag has progressive technologies both for the production of fibers for geotextile carded nonwovens and for the manufacture of geotextile spunbonds.
Oerlikon Neumag has progressive technologies both for the production of fibers for geotextile carded nonwovens and for the manufacture of geotextile spunbonds.

Oerlikon Neumag has progressive technologies both for the production of fibers for geotextile carded nonwovens and for the manufacture of geotextile spunbonds.

The quality of nonwovens is determined by the stabilization, the application and the fiber quality. As a proven expert in spinning, Oerlikon Neumag beneficially deploys its many years of expertise here both for its spunbond and staple fiber technology. Hence, Oerlikon Neumag is able to offer solutions for processes and systems for manufacturing high-end spunbonds and fibers for carded nonwovens.

Since 2002, nonwovens have experienced a sharp rise, with 6 percent annual growth with regards to its use in geotextiles. This above average growth trend continues, as huge infrastructure programs are being implemented particularly in China and emerging countries, which require large volumes of geotextiles. Furthermore, many manufacturers are continually developing new, innovative applications in which nonwovens frequently replace classical materials. Here, nonwovens are often combined with other structures, such as geogrids, bubble films or geomembranes to create so-called geo-synthetics, with the aim of being used as composites for fulfilling several functions at the same time. And nonwoven products are also already providing various functions here: including drainage, separation, reinforcement and penetration protection. They increase the load-bearing capacity of the substrate in road, path and railroad construction and help secure dams and disposal sites. And, once installed, they are no longer visible!

Here, the diverse textile fabrics really showcase their special properties: geo-nonwovens are voluminous and also very easily absorb tension. In road construction, this can considerably reduce the required mineral substructure, for example. In addition to further factors, the tenacity of the nonwovens is hugely important in such industrial applications. They need to be extremely tear-resistant and often simultaneously very extensible. Here, the materials should behave isotropically, i.e., longitudinal and transversal direction show similar characteristics (MD/CD=1).

To achieve the greatest possible mechanical robustness and durability, the polymer raw materials used are either polypropylene (PP) or polyester (PET). PP is always used if the product has to be extremely durable – geotextiles frequently remain in the ground for more than 50 years and must still be able to provide their load-bearing function. Here, the chemical resistance and hydrolysis resistance of PP is more advantageous to those of PET. In contrast, PET is cheaper and is suitable for solutions requiring shorter lifetime tenacity in the ground or if the geo-nonwovens are installed close to the ground surface; in other words, they are exposed to solar UV radiation over longer periods of time. Here, the UV resistance of PET is superior to that of PP.

However, the quality of the nonwovens is decisively determined by the targeted transformation of the polymers into fibers and filaments with the application-appropriate properties. And this is where Oerlikon Neumag brings decades of experience into the equation. More than 4.3 million metric tons of fibers per year are today manufactured across the globe using systems from the Neumünster-based company. This spinning expertise has also been successfully transferred to spunbond technology. To this end, Oerlikon Neumag has progressive technologies both for the production of fibers for geotextile carded nonwovens and for the manufacture of geotextile spunbonds.

Examining the nonwoven during production: the required tenacities can be achieved with reduced base weights.

Carded nonwovens: high fiber quality in demand

Carded nonwovens are made from staple fibers, whereby the card web is generally doubled and flattened using a cross-lapper before it is subsequently needled. The staple fibers used for geo-nonwovens can be manufactured on single-stage staple fiber systems, with which the spinning and subsequent drawing are carried out in an in-line process. The capacities of these ‘small’ special systems generally lie between 40 and 80 metric tons a day. Most fibers are manufactured in white, although the extruder technology deployed also permits fibers that are spun-dyed and/or include additives – such as a UV stabilizer – to cater to the corresponding target applications. The systems offer superlative flexibility in terms of raw materials (PP, PET, recycled PET, PA6) and provide the highest product quality along with total reliability. This is essential, as the fiber quality requirements are very high.

Critical fiber characteristics for geotextiles include high tenacities with simultaneously high elongation – not only in terms of the resulting controllable nonwoven quality, but also particularly in terms of the processability on carding and needling machines. In addition to these internal fiber characteristics, reliable further processing also requires excellent, even spin-finish application and the crimping of the fibers. The better the crimping and the spin-finish application are, the faster and more even opening of the fibers in the carding system is. Geo-nonwovens production generally involves the use of fibers with a so-called 2D crimp, whereby the shape of the crimp is in 2 directions. The Oerlikon Neumag Baltic Crimper is excellently suited to this task, as it ensures homogeneous crimping and enables good opening of the fibers.

Spunbonds: high-tenacity with low material input

Spunbonds are on the rise in many industrial nonwovens applications, as the market is increasingly demanding more efficient processes and products; in other words, often the same or greater product requirements with lower raw material input. For this reason, spunbonds are – due to their technical and commercial benefits – progressively replacing classical carded nonwovens. And geotextile applications are on the rise. To this end, the current generation of Oerlikon Neumag spunbond systems have – particularly in the case of polyester – been able to achieve excellent nonwoven tenacities with low raw material input. Compared to the predecessor generation, the energy consumption has also been reduced by approx. 20 to 30 percent. General benchmark comparisons with standard products in Europe have shown that higher nonwoven tenacities can be achieved at comparable base weights. Conversely, the required tenacities can be achieved with reduced base weights and thus with lower raw material input: in corresponding trials, it has been shown that this alone allows raw materials savings of more than five percent.

For manufacturing needled spunbond for geotextiles, Oerlikon Neumag offers the entire process – from the polymer granulate all the way through to the rolled product. The single-phase spunbond technology combines efficiency and productivity and thus offers a potential reduction of production costs of up to 20 percent with low wastage and maximum nonwoven quality compared to conventional spunbond processes. Here, the production capacities range from 800 to 1,500 kg/h, depending on the product type and nonwoven weight. The unique Oerlikon Neumag spunbond technology enables extremely high spinning speeds, which are required for producing high-tenacity filaments. To this end, especially – but not exclusively – PET filament nonwovens that are extremely-strong and that have very low shrinkage can be manufactured. To set the isotropy, the spunbonds are traverse-drawn directly in-line following the needling. End products include geo-nonwovens with excellent properties and an outstanding price-performance ratio.