Spunbond lines

Spunbond processes and fabrics have been commercial for over 40 years. The processes, fabrics, and markets are quite varied. The best known spunbond fabrics and markets are cover stock for diapers and feminine hygiene products. However, spunbond fabrics are also found in carpet backing, geotextiles, furniture dust covers, carriers for fabric softeners, and a host of other industrial and consumer applications. The key to most of these markets has been a low cost covering material with sufficient tensile and opacity properties to fit the application. The latest market trend is towards pre-wetted wipes for cleaning and similar uses. The product needs for this fabric include short term abrasion resistance and ability to hold solvents. 

As the new century began, we saw new beginnings in spunbond processes and products. New techniques are being developed to improve uniformity and barrier properties of spunbond fabrics to allow spunbond to compete successfully with carded thermal bonded nonwovens. Fabrics from new polymers and polymer combinations are poised to enter the market. Tactile as well as tensile properties are being improved to the point where even apparel applications may be considered as a future market (Anon., 2011). Several of these trends are described in the following paragraphs. 

The activity level to develop new polymers for fiber spinning is at an all-time high. This seems incompatible with the present low selling price of polyester and polypropylene, but many major chemical companies continue to look for polymers for special niche markets. Among these polymers are 

The other approach is to use a closed slot draw system. The best example of this is in Reifenhauser lines. In this approach the system is essentially sealed or closed from the spinneret to the laydown table. Flow through the slot comes from the quench above and the low pressure created by the vacuum box below the belt. This system generally results in fabrics with excellent uniformity once the air flows are balanced correctly. However, the filament velocities that can be obtained are much less than with the open system. 

A new Reicofil 4 spunbond line was introduced at Index 2002 in Geneva (Fi-Tech, Inc., 2011).The Reicofil 4 machine is a closed system however, the obtainable velocities were increased to approach those of a closed system (Reifenhauser GMBH and CO., 2011). The hole density in the spinneret was also increased and bicomponent capabilities were added. The results of the higher hole density and higher filament speeds was a 50% increase in throughput per meter of beam length. Alternately, the fabric producer can keep the throughput the same and go to lower filament tex to produce softer and more uniform fabrics. 

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Figure 3 Spunbond line 1, extruder 2, spinning head 3, cooling air 4, web-formation chamber 5, suction blower 6, conveyor screen 7, nonwoven material 8, calander, winder.

The uses of spunbonded fabrics as coverstock in diapers and other personal absorbent devices will most likely remain unchallenged for the near term. Virtually any other nonwoven production method appears to be at a cost disadvantage opposite spunbonded polypropylene. There have been composite products developed from meltblown and spunbonded combinations, where areas of either improved hydrophobicity or hydrophilicity are desired. These products can be produced on-line at relatively low additional cost and offer high value to diaper manufacturers. Any competitive threat is likely to come from advances in film technology such as large improvements in perforated film used in segments of absorbent product appHcations, particularly sanitary napkins. 

Spunbond and Melting Blown Process Charts, KASEN Corporation Japan. http //www.kasetL co.jp/English/product/line/work.html... 

The physical properties of flashspun fabrics are unique and not attainable via the melt-spun spunbond process. Even bicomponent melt spinning cannot produce similar structures. As a result the profitability of a fiashspun operation is very high when the capacity of a line is fully utilized. 

Extrusion coating and laminating are ways to add value to the existing product line of spunbonded PP [165]. 

Bonding temperature has a minimal effect on the final erystallinity of the webs, but it has a noticeable influenee on their thermomeehanieal behavior. Localization of crystallization during spunbonding of PP sets in along the spin line. In contrast to conventional melt blowing, the drawing force on the extruded... 

By far, the largest and fastest growing capacity for bicomponent fibers is in the area of spunbonds. There are approximately 50 such lines worldwide. About a third of these are pilot lines for product development, a third is older lines, and a third is modem curtain spinning lines with draw aspirators. It is estimated that 15-20% of all spunbond capacity worldwide has bicomponent capability. Much of this capability is not presently being used to make bicomponent products however, intense activity to develop new bicomponent products is reported and is reflected in patent applications. The increase in bicomponent spunbond capacity is continuing at a rate of over 10% per year. This increase is fueled by both new lines and retrofitting of older lines. As new bicomponent products are developed, this activity is expected to increase rather than decrease or stay level. It is estimated that within a few years over half of all new spunbond machines installed will have bicomponent capabilities (Wilkie, August 2009). 

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