Apparatus and method for producing a web of thermoplastic filaments

An apparatus for producing a web of spunbonded thermoplastic filaments comprising:

• a) means for extruding filaments of a thermoplastic polymer;
• b) a slot draw attenuator having opposing side walls and opposing end walls defining an elongate entrance slot positioned for receiving extruded filaments from said extruding means, an elongate exit slot from which the filaments are expelled, a slot-shaped passageway extending between said entrance and said exit and through which the filaments travel, and means cooperating with said opposing walls for introducing a flow of air through the slot-shaped passageway sufficient for drawing, stretching and attenuating the filaments passing through said slot-shaped passageway;
• c) an endless moving belt positioned for receiving the filaments expelled from said attenuator and for forming a filamentary web;
• d) a corona device for electrostatically charging the filaments that are expelled from said attenuator, said corona device comprising a plurality of corona electrodes fixed to one of said walls of said attenuator adjacent said exit slot, a ground connected to the wall of said attenuator opposite said corona electrodes, and a high voltage power source connected to said corona electrodes so as to form an electrostatic field through which the filaments travel so that the filaments become charged and electrostatic repelling forces are induced in the filaments to more uniformly spread the filaments before they are deposited on said belt to form a web;
• and
• e) means for bonding the filaments together after they have been formed into a web on said belt.

An apparatus for producing a web of spunbonded thermoplastic filaments comprising:

• a) a spinning beam for extruding filaments of a thermoplastic polymer;
• b) a slot draw attenuator having opposing side walls and opposing end walls defining an elongate entrance slot positioned for receiving extruded filaments from said spinning beam, an elongate exit slot from which the filaments are expelled, and a slot-shaped passageway extending between said entrance and said exit and through which the filaments travel while being drawn and attenuated, said slot draw attenuator including an adductor for inducing a flow of air through said slot draw attenuator for drawing, stretching and attenuating the filaments;
• c) an endless moving belt positioned for receiving the filaments expelled from said attenuator and for forming a filamentary web;
• d) a corona device for electrostatically charging the filaments that are expelled from said attenuator, said corona device comprising an elongate insulator bar carried by one of said opposing attenuator walls adjacent said exit slot, an electrically conductive buss carried by said insulator bar, a plurality of corona electrodes mounted at spaced locations along said elongate insulator bar and electrically connected to said conductive buss, a ground connected to the wall of said attenuator opposite said corona electrodes, and a high voltage power source connected to said corona electrodes through said conductive buss so as to form an electrostatic field through which the filaments travel so that the filaments become charged and electrostatic repelling forces are induced in the filaments to more uniformly spread the filaments before they are deposited on said belt to form a web;
• e) a calendar nip for bonding the filaments together after they have been formed into a web on said belt;
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• f) a windup roll for winding the spunbonded web after passage through said calendar nip.

A method for producing a web of spunbonded thermoplastic filaments comprising the steps of:

• a) forming a plurality of filaments of fiber-forming thermoplastic polymer and directing the filaments into and through an attenuator passageway in the form of an elongate slot-shaped venturi while causing air to flow through the slot-shaped venturi so as to entrain the filaments and attenuate, stretch and draw them as they travel through the attenuator passageway;
• b) generating a corona of ionized air in the attenuator passageway adjacent the exit end thereof and in the path of the advancing filaments so that the filaments become electrostatically charged;
• c) expelling the electrostatically charged filaments from the attenuator passageway and permitting the filaments to fall onto an underlying collection surface while repelling forces induced in the electrostatically charged filaments cause separation and spreading of the filaments;
• e) advancing the collection surface as the filaments are deposited thereon to form a web;
• and
• f) thermally bonding the filaments to form a unitary web.