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Capabilities Serving The Future Demands in Spunmelt Hygiene Nonwovens

November 30, -0001

Hygiene applications are nowadays the largest segment in spunmelt production. These commodity nonwovens are distinguished by high production volumes, standardized product specifications and high cost pressures thanks to a lack of differentiation. The end product is usually a disposable article. There is not only a series of different applications in the hygiene sector (diapers, fem pads, adult incontinence items), the nonwovens also have different purposes such as topsheet, backsheet or leg cuffs to be fulfilled.

The production capabilities of today's commodities have already been optimized to a great extent during the last several years and now only allow for limited development potential.

There are however new directions of development in spunmelt for the hygiene industry. These developments in the main have two targets: a further reduction of the costs of the nonwovens and the improvement of the properties of the end product.

The reduction of the costs of the nonwovens can be attained by decreasing the applied raw materials or by applying more economical raw materials while maintaining the quality characteristics of the nonwovens web.

A further approach for reducing costs can be achieved through nonwovens of improved properties. It is therefore conceivable that the function of certain nonwoven layers could be completely eliminated because their functions can be taken over by other, advanced nonwoven webs. Moreover, an improvement of the nonwovens characteristics leads to a higher efficiency in the further process steps, which in turn has a positive influence on the cost structure of the fabric.

Other developments are directed toward the improvement of the nonwovens' properties in the end product, such as, for example, a better wearing comfort through lighter materials, less skin irritations through softer nonwovens or better functions such as barrier characteristics or better liquid distribution.

Future oriented spunmelt technologies not only have to follow the most different development trends of the industry but must also have the potential to produce these economically when they have been certified for commercial production.

Two development directions are being stated here that have been under discussion for a longer time and are now slowly penetrating the market: microfilaments and bicomponent nonwoven materials. In both cases, Oerlikon Neumag today offers a technology platform for spunbond and meltblown supporting a multitude of new development opportunities as well as the production of today's commodity nonwovens in a highly efficient manner.

Microfilaments are normally defined as being lower than one denier. Nonwoven webs from microfilaments have a much higher opacity in comparison to filaments with higher titers. The effective filament surface is larger and more uniform. The distribution of the meltbown on a microfilament web is therefore much more even and the application of the meltblown much more efficient.

Trials have proven that, in connection with meltblown, the hydrohead of the nonwoven is positively influenced, respectively with the same hydrohead, the use of meltbown can be reduced. Based on this evenness, optimizations can also be attained during the further processing and/or confectioning.

A further effect is that with the reduction of the titer, the tenacity of the filaments increases. This is attained by the high drawing of the filaments in the draw slot. Last but not least, nonwovens out of microfilaments give a much more pleasant skin feeling compared to fibers of coarser denier.

With the spunbond technology of Oerlikon Neumag, microfilaments can be produced below one denier (down to 0.7 denier) with traditional standard polypropylene (Ziegler Natta) with an MFI of 25 or 35. Therefore no expensive polymers have to be used. Furthermore, the basis weight distribution in cross direction has been improved and is below 5% under production conditions.

The main advantages of Oerlikon Neumag can be seen at the beginning of the spunbond process, in the spinning section. Smallest melt temperature fluctuations would lead to process instabilities especially producing microfilaments. Oerlikon Neumag uses a segmented spinning beam. Over the entire spinning width, the melt flow is divided from the spinning pump onwards for each segment and separately guided to the spin pack. This ensures that the melt has exactly the same 'history', i.e. temperature and retention time are practically identical. The melt flows meet again in the spin pack, directly before the spinneret. This ensures an absolutely uniform titer distribution, a stable spinning process up to the last spinneret hole and a reduction/or elimination of the so-called "edge effect."

One key component during the production of microfibers is the draw slot, which is responsible for the titer. An innovative design ensures a constant air supply over the entire plant width and guarantees absolutely stable draw conditions.

Nonwovens from bicomponents are also increasingly catching on in various new applications in the hygiene industry e.g. to increase the quality of a product through softness or strength, or to reduce the product costs. In the spunbond hygiene sector, the current market demands are nearly exclusively for core-sheath fibers, i.e. core and sheath consist of different polymers such as PP/PE or the same polymers such as PP/PP.

EDANA and INDA both expect strong growth during the next five years in this area with a doubling of the output of polypropylene-based bicomponents to 126,000 tons by 2012, mainly focused on absorbent core markets. According to estimates, the total bicomponent production was between 160,000 and 170,000 tons in 2007, about 40% being polypropylene based.

Core-sheath fibers can be produced on Oerlikon Neumag plants with a sheath percentage below 10%. The material quantity of the core is thus optimized and the edge trim can also be guided to the spinning section again without causing irritations in the spinning process. A quality characteristic is that the sheath is also completely closed and remains closed (even with a percentage below 10%).

Other cross-sections such as islands-in-the-sea, segmented pie and side-by-side are also conceivable.

The Oerlikon Neumag bicomponent technology has been proven in fiber plants over decades, has been specially adapted to the spunbond process and is already applied in several spunbond plants.

One critical advantage of the bico equipment of Oerlikon Neumag is that nonwovens out of one polymer can be produced with almost the same cost structure and quality as on a sole homopolymer plant. The producers therefore have more flexibility and can also furthermore competitively produce nonwovens from homopolymer.

The bico spinning equipment needs the same maintenance as with the homopolymer spinning technology and no expensive wear parts are used that have to be regularly exchanged. However, the initially higher investment costs for the Oerlikon Neumag bicomponent equipment are amortized within a short time due to a longer operation life.

These examples only give a small insight into the development potential of commodity products in the hygiene sector. Many of the innovative ideas will never reach commercial production, but the best of them will promote the industry with better product characteristics and/or improved cost structures.
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