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Latex-Free Tufted Carpets

Fleissner's AquaJet spunlace system may be used in a new process to bond carpet backings.

Alfred Watzl

C arpet tufting and the respective production processes are well known. A pile layer is attached, usually by insertion of yarn loops, to a carrier material - for example, spunbonded or woven fabric (primary backing). The surface may consist of velours or loops.

The tufts must be bonded in the primary backing by means of an adhesive coating to impart the required properties of utility and mechanical stress resistance to the tufted carpet. Anchoring tufts in position in the carrier layer is crucial for optimizing loop tearing resistance and behavior during roller chair testing.

In most cases, a so-called secondary backing then is added to improve walking comfort. This may be  a textile backing (web or fabric) or a foamed latex backing, although the latter is used less and less.

  The AquaJet spunlace system is used to bond primary and secondary backings to this tufted carpet, eliminating the need for a latex precoat.

Latex Precoat

The use of a latex precoat has disadvantages both during production and when recycling tufted carpets. Processing results in excessive waste water and unpleasant odor. Because laminating of secondary backings to tufted carpets still requires increased latex precoating, the cost for producing such carpets is correspondingly high. In some cases, the latex binder is spun out with calcium carbonate to reduce cost, which causes problems during waste disposal by incineration because of noncombustible filling material.

Using AquaJet spunlace technology, the web of this tufted carpet has been entangled with the primary backing.

Polyethylene Powder

Another possibility for bonding tufted carpet to a textile backing consists of the use of polyethylene powder. In this case, latex precoating also is required before applying the textile secondary backing. To avoid these disadvantages, the tufted carpet/primary backing is bonded to the secondary backing by mechanical needling. However, this causes severe damage to carpet surfaces.

Avoiding Latex

The ecologically harmful processes used in latex precoating and the problems associated with recycling the latex layer can be avoided when instead a nonwovens web is applied  to the tufted carpet backing using spunlace technology. This technology makes it possible to bond the web fibers in or on the primary backing and the retained pile layer without any web fibers appearing on the carpet face.

The nonwoven material used for stabilization of tufts should be a carding web that is either unbonded or slightly pre-bonded, which can be done by spunlacing as well. Possible fiber types include polyester, polypropylene and polyamide, among others. It has been shown that spunlacing allows the fibers of the stabilizing web to be injected only so far into the backing of the primary carrier material and into the tufts retained by it so that components of the nonwoven material on the reverse are not visible on the pile side or at the roots of the pile of the fabric length. This process is controlled by water-jet pressure and nozzle geometry, among other spunlacing instruments.

Beyond Tufted Carpet

Apart from tufted carpets, other pile goods such as plush can be stabilized in the same manner. The process of bonding carpet backings using spunlace technology was developed with Germany-based Fleissner GmbH's AquaJet spunlace system and is covered by a patent worldwide. This patent describes a process for continuous stabilization of pile goods such as pile carpets, tufted carpets, plush and similar goods - namely fabric lengths with a face that must not be changed in structure and quality and a reverse that is not stable at the beginning, so the pile layer must still be anchored in the backing. This is done by inserting (tufting) the pile layer into a primary carrier material made, for example, from spunbonded polyester fiber, or into a woven or knit fabric.

The reverse of the fabric length is then provided with a backing layer that secures the pile layer, thus anchoring the pile layer that is only loosely retained in the primary carrier material and the respective pile fibers. A nonwoven web is attached to the reverse of the primary carrier retaining the pile fibers by means of hydrodynamic needling.

In a second step, a secondary backing can be needled onto the nonwoven web by another jet head, which considerably improves the walking comfort of the carpet. This provides the carpet not only with a bonded pile permanently fixed in the backing, but also with the desired bulk and dimensional stability. Such a stabilized backing can have a weight of up to 600 grams per square meter.

It is also possible to use spunlace technology to needle the intermediate web, which bonds the tufting yarns into the primary backing, with the textile secondary backing.

Suitability of these last two possibilities depends on the weight of the secondary backing. If a certain weight is exceeded, the process must be undertaken in two stages.

The Fiber Mix

For optimum bonding of the carpet pile in the primary carrier, as well as for increased loop tearing resistance, a mixture of thermoplastic and non-thermoplastic fibers, or a mixture of standard fibers and bicomponent fibers may be used. After the carpet is dried, these melt fibers or bicomponent fibers are then activated in the same dryer, preferably a perforated drum dryer operating on the flow-through principle. For example, the fibers are melted or partially melted and then shrunk.

The textile backing also can consist of a mixture of standard fibers and melt fibers or bicomponent fibers, with the fibers of the textile secondary backing having much coarser titers than the fibers of the textile intermediate web, so the textile backing is provided with a higher bulk.

Editor’s Note: Alfred Watzl is senior vice president of Fleissner GmbH.