fibers exclusively containing polyolefins or polyesters being preferred nonwovens of which 100 by weight consists of polyolefin or polyester fibers are particularly suitable polyolefin fibers are among the most commonly used fibers for the production of nonwovens examples of suitable polyolefins are polypropylene polyethylene or copolymers of ethylene or propylene with butadiene polyester fibers mainly polyethylene terephthalate fibers are also used besides the fibers mentioned other synthetic fibers suitable for the production of nonwovens may also be used including for example fibers of nylon u00ae fibers consisting of two or more components for example polyester copolyester fibers or polypropylene polyethylene fibers are also particularly suitable the nonwovens used in the process according to the invention may be produced by any of the known processes for producing nonwovens which are described for example in ullmann 39 s encyclopedia of industrial chemistry vol a 17 vch weinheim 1994 pages 572 581 nonwovens produced either by the dry laid process or by the spunbonded process are preferred the dry laid process starts out from staple fibers which are normally separated by carding into individual fibers and are then laid together by an aerodynamic or hydrodynamic process to form the unbonded nonwoven the unbonded nonwoven thus produced is then made up into the final nonwoven by a heat treatment known as thermobonding to this end the synthetic fibers are either heated to such an extent that their surface melts and the individual fibers are joined together at their points of contact or the fibers are coated with an additive.