Meltblown spinning with separate and independent air and polymer temperature control

Abstract

A meltblown system includes a die including a die inlet end to receive molten polymer from a polymer source, a cavity located downstream from the die inlet end through which the molten polymer flows, and a die outlet end to receive the molten polymer from the cavity and deliver to outlet orifices at the die outlet end. A fluid supply includes a channel that delivers fluid to the die outlet end to attenuate fibers formed from molten polymer emerging from the die outlet end. The fluid supply provides fluid at a temperature T2 that differs from a temperature T1 of the molten polymer within the cavity, and the meltblown system is configured to independently maintain the molten polymer within the cavity at the temperature T1 during operation of the meltblown system.

What is claimed: 
     
         1 . A meltblown system comprising:
 a die including a die inlet end to receive molten polymer from a polymer source, a cavity located downstream from the die inlet end through which the molten polymer flows, and a die outlet end to receive the molten polymer from the cavity and deliver to outlet orifices at the die outlet end; and   a fluid supply comprising a fluid inlet and a fluid channel connected with the fluid inlet and extending to the die outlet end so as to deliver fluid to the die outlet end to attenuate fibers formed from molten polymer emerging from the die outlet end;   wherein the fluid supply provides fluid at a temperature T2 that differs from a temperature T1 of the molten polymer within the cavity, and the meltblown system is configured to independently maintain the molten polymer within the cavity at the temperature T1 during operation of the meltblown system.   
     
     
         2 . The meltblown system of  claim 1 , wherein temperature T2 is greater than temperature T1. 
     
     
         3 . The meltblown system of  claim 1 , further comprising a plurality of channels extending from the cavity to outlet orifices at the die outlet end. 
     
     
         4 . The meltblown system of  claim 3 , wherein each channel of the plurality of channels has a L/D ratio of at least 50:1. 
     
     
         5 . The meltblown system of  claim 4 , wherein the gas inlet and fluid channel are disposed a distance from the cavity and located between the cavity and the die outlet end. 
     
     
         6 . The meltblown system of  claim 1 , wherein the die outlet end is disposed in a spin pack that is separable from a portion of the die including the die inlet end, and the spin pack includes the die outlet end. 
     
     
         7 . The meltblown system of  claim 6 , wherein the fluid supply further comprises at least one manifold securable to the spin pack that delivers fluid at the temperature T2 to the gas inlet. 
     
     
         8 . The meltblown system of  claim 7 , wherein the manifold is located a distance from the cavity and located between the cavity and the die outlet end. 
     
     
         9 . The meltblown system of  claim 1 , wherein the die cavity has a volume no greater than about 50 cm 3  per meter of cross dimension (CD) of the cavity. 
     
     
         10 . A method of forming a meltblown product, comprising:
 directing molten polymer within a die of a meltblown system through a plurality of orifices at a die outlet, the molten polymer having a temperature T1; and   directing a fluid to contact the molten polymer emerging from the die outlet to form fibers from the polymer emerging from the die outlet, the fluid having a temperature T2 that differs from the temperature T1;   wherein the molten polymer within the die is maintained at the temperature T1 when the polymer emerges from the die outlet and contacts the fluid.   
     
     
         11 . The method of  claim 10 , wherein temperature T2 is greater than temperature T1. 
     
     
         12 . The method of  claim 10 , wherein the fluid comprises heated air. 
     
     
         13 . The method of  claim 10 , wherein a difference between temperature T1 and temperature T2 is at least about 30° C. 
     
     
         14 . The method of  claim 10 , wherein a difference between temperature T1 and temperature T2 is at least about 50° C. 
     
     
         15 . The method of  claim 10 , wherein the die includes a cavity and a plurality of channels disposed below the cavity that extend to outlet orifices of the die outlet, the fluid is directed from a fluid source securable with a portion of the die into a fluid channel within the die, and the fluid source and fluid channel are distanced from the cavity and disposed between the cavity and the outlet orifices. 
     
     
         16 . The method of  claim 10 , wherein the molten polymer has a decomposition temperature of no greater than 245° C., and the temperature T2 of the fluid is at least about 260° C. 
     
     
         17 . The method of  claim 10 , wherein the molten polymer includes an additive having a decomposition temperature of no greater than 245° C., and the temperature T2 of the fluid is at least about 260° C. 
     
     
         18 . The method of  claim 10 , wherein the molten polymer comprises an additive, the additive comprising magnesium stearate. 
     
     
         19 . The method of  claim 10 , wherein the molten polymer has a melt flow index (MFI) at least about 8 grams/10 minutes. 
     
     
         20 . The method of  claim 10 , wherein the molten polymer comprises one or more of a polyamide, a polyethylene terephthalate, a polyurethane, a polyetherimide, a polyether ether ketone, a polyether ketone ketone, and an ether-based polyurethane foam.