Metering meltblowing system

A meltblowing die comprising

• (a) a die body having a mounting surface and plurality of separate polymer flow passages formed side-by-side therein in spaced apart relation, each flow passage having (i) an inlet and (ii) an outlet formed in the mounting surface of the die body;
• (b) a die tip assembly having (i) a base mounted on said mounting surface and having formed therein a plurality of elongate polymer header channels arranged in end-to-end relation, said base further including means for conducting polymer from each outlet to an associated one of the header channels;
• (ii) a die tip having a nosepiece extending outwardly from said base and terminating in an elongate apex and having polymer orifices arranged in a row along the apex at an equal spacing of from 10 to 50 orifices per inch and means interconnecting each polymer header channel with a longitudinal portion of the orifices, each longitudinal portion and each associated header channel having a length of from 1 to 8 inches;
• and (iii) air plates mounted on the die tip and having surfaces which in combination with the nosepiece define converging air channels which discharge at the apex of the nosepiece;
• (c) a rotary positive displacement pump for delivering a polymer melt to each inlet of the die body whereby the polymer melt flows through the die in parallel side by side streams, each stream comprising a polymer flow passage, a header channel and a longitudinal portion of the orifices;
• and
• (d) means for rotating the rotary pumps at substantially the same rpm whereby the flow rate of polymer melt to each header channel and each longitudinal portion of orifices is substantially the same.

A system for meltblowing a polymer melt to form microsized fibers which comprises

• (a) an elongate die body having first and second polymer flow passages formed therein;
• (b) an assembly die tip mounted on said die body and having (i) a die tip provided with first and second groups of orifices formed therein, and arranged in a line, and first and second flow chambers in fluid communication with said first and second die body flow passages, respectively, to distribute polymer to the orifices of the first and second groups of orifices, respectively;
• (c) means for delivering converging air sheets on each side of the orifices;
• (d) first and second rotary positive displacement pumps mounted on the die body to pump polymer melt into said first and second flow passages, respectively;
• (e) means for delivering the polymer melt to the first and second pumps, respectively;
• (f) first and second variable speed motors for driving the first and second pumps, respectively;
• (g) a collector for receiving filaments extruded from the first and second groups of orifices and as first and second strips, respectively;
• and
• (h) detector means for sensing a property of the filaments collected on the collector in the first and second strips, respectively, said first and second variable speed motors being operatively connected to the detector means to change the rotation rate and throughput of the first and second pumps, respectively, in response to deviations of the sensed property in the first and second strips from a predetermined control valve.

A die assembly comprising

• (a) a die body having (i) a mounting surface, and (ii) first and second polymer flow passages extending through the die body and having first and second outlets formed in the mounting surface at spaced apart locations;
• (b) a die tip having (i) a base mounted on the die body mounting surface and being coextensive therewith, (ii) a triangular nosepiece extending outwardly from the base and terminating in an apex which extends parallel to the plane of the mounting surface and being substantially coextensive therewith, (iii) air plates mounted on opposite sides of the nosepiece and being substantially coextensive therewith and therewith defining converging air channels which discharge at the apex, (iv) first and second header channels formed in the base and arranged in end-to-end relationship and extending parallel to said apex, (v) first and second conduits formed in the base for conducting polymer melt from the first and second polymer flow passage outlets to the first and second header channels, respectively, and (vi) first and second groups of orifices formed along the apex and, respectively, being in fluid communications with the first and second header channels, each of said first and second groups of orifices extending from 1 to 8 inches along the apex, the first and second groups of orifices having from 10 to 50 orifices per inch which are uniformly spaced along the full length of the apex;
• (c) a rotary positive displacement pump for delivering a polymer melt to each inlet of the die body whereby the polymer melt flows through the die assembly in parallel side by side streams, each stream comprising a polymer flow passage, a header channel and a longitudinal group of the orifices;
• and
• (d) means for rotating the rotary pumps at substantially the same rpm whereby the flow rate of polymer melt to each header channel and each longitudinal group of orifices is substantially the same.

A meltblowing assembly comprising

• (a) a meltblowing die having a plurality of side-by-side units formed therein, each unit being adapted to extrude a plurality of filaments therefrom;
• (b) a moving collector for collecting the filaments as a unitary web, each group of filaments forming a strip in the web whereby the web comprises a plurality of side-by-side longitudinal strips;
• (c) a pump for delivering a polymer melt to each unit of the meltblown die;
• (d) means mounted above the collector for monitoring a physical property of each strip in the web, said property being selected from the group consisting of the thickness, basis weight, and density;
• and
• (e) control means operatively connected to the monitoring means for controlling the polymer output of each pump in response to the monitoring means whereby the physical property of each strip may be controlled to a predetermined value.