Method for preparing multiple component meltblown webs

Abstract

A process for forming multiple component meltblown webs in which a poor-spinning polymer is co-spun with a good-spinning polymer in a meltblowing process using high throughput and short die-to-collector distances.

What is claimed is:  
     
         1 . A process for forming a multiple component meltblown web comprising the steps of: 
 melt blowing at least first and second molten polymers through a die comprising a plurality of spin orifices to form multiple component meltblown fibers; and    collecting the multiple component meltblown fibers as a multiple component meltblown web on a collector surface at a die-to-collector distance of less than 15.2 cm.    
     
     
         2 . The process according to  claim 1  wherein the die-to-collector distance is between about 7.6 to 14 cm.  
     
     
         3 . The process according to  claim 2  wherein the die-to-collector distance is between about 11.4 to 14 cm.  
     
     
         4 . The process according to  claim 1  wherein the total polymer throughput is greater than about 0.5 g/orifice/min.  
     
     
         5 . The process according to  claim 4  wherein the total polymer throughput is greater than about 0.6 g/orifice/min.  
     
     
         6 . The process according to  claim 1  wherein the first polymer is a good-spinning polymer when meltblown to form a single component web at a die-to-collector distance of less than 15.2 cm and the second polymer is a poor-spinning polymer when meltblown to form a single component web at a die-to-collector distance of less than 15.2 cm.  
     
     
         7 . The process according to  claim 6  wherein the first polymer has a specific heat less than about 1.6 kJ/kg/° K and a glass transition temperature greater than about 25° C. and the second polymer has a specific heat of greater than about 1.6 kJ/kg/° K and a glass transition temperature less than about 25° C.  
     
     
         8 . The process according to  claim 7  wherein the first polymer is selected from the group consisting of poly(ethylene terephthalate), poly(hexamethylene adipamide), poly(ε-caprolactam), and polystyrene and the second polymer is a polyolefin.  
     
     
         9 . The process according to  claim 8  wherein the first polymer is poly(ethylene terephthalate) and the second polymer is polyethylene.  
     
     
         10 . The process according to  claim 8  wherein the first polymer is poly(ethylene terephthalate) and the second polymer is polypropylene.  
     
     
         11 . The process according to  claim 8  wherein the multiple component meltblown fibers are bicomponent fibers.  
     
     
         12 . The process according to  claim 11  wherein the first and second polymers are arranged in a side-by-side configuration.  
     
     
         13 . A process for forming a multiple component meltblown web comprising the steps of: 
 melt blowing at least first and second molten polymers through a die comprising a plurality of spin orifices to form multiple component meltblown fibers; and    collecting the multiple component meltblown fibers on a collector surface at a die-to-collector distance of less than about 20.3 cm;    wherein a formation ratio of less than about 30 cm·orifice·min/g is used.    
     
     
         14 . The process according to  claim 13  wherein the die-to-collector distance is less than about 15.2 cm.  
     
     
         15 . The process according to  claim 13  wherein the first polymer is a good-spinning polymer and the second polymer is a poor-spinning polymer when each polymer is meltblown separately to form single component webs using a die to collector distance of less than about 20.3 cm and a formation ratio of less than about 30 cm·orifice·min/g.  
     
     
         16 . The process according to  claim 14  wherein the first polymer is a good-spinning polymer and the second polymer is a poor-spinning polymer when each polymer is meltblown separately to form single component webs using a die-to-collector distance of less than about 15.2 cm and a formation ratio of less than about 30 cm·orifice·min/g.  
     
     
         17 . The process according  claim 13  wherein the first polymer has a specific heat less than about 1.6 kJ/kg/° K and a glass transition temperature greater than about 25° C. and the second polymer has a specific heat of greater than about 1.6 kJ/kg/° K and a glass transition temperature less than about 25° C.  
     
     
         18 . The process according to  claim 17  wherein the glass transition temperature of the second polymer is less than about 0° C.  
     
     
         19 . The process according to  claim 13  wherein the formation ratio is less than about 20 cm·orifice·min/g.  
     
     
         20 . The process according to  claim 13  wherein the formation ratio is between about 14 and 18 cm·orifice·min/g.  
     
     
         21 . The process according to either of claims  1  or  13  wherein the polymers are blown by a high velocity gas jet at a temperature within about 30° C. of the temperature of the polymers as they exit the die.  
     
     
         22 . The process according to  claim 21  wherein the gas jet is heated to a temperature within about 10° C. of the temperature of the polymers as they exit the die.  
     
     
         23 . The process according to  claim 13  wherein the first polymer is selected from the group consisting of polyamides, polyesters, and polystyrene and the second polymer is a polyolefin.  
     
     
         24 . The process according to  claim 23  wherein the first polymer is selected from the group consisting of poly(ethylene terephthalate), poly(hexamethylene adipamide), poly(ε-caprolactam), and polystyrene and the second polymer is selected from the group consisting of polyethylene and polypropylene.  
     
     
         25 . The process according to  claim 24  wherein the first polymer is poly(ethylene terephthalate) and the second polymer is polyethylene.  
     
     
         26 . The process according to  claim 24  wherein the first polymer is poly(ethylene terephthalate) and the second polymer is polypropylene.  
     
     
         27 . The process according to  claim 17  wherein the multiple component fibers are bicomponent fibers.  
     
     
         28 . The process according to  claim 27  wherein the first and second polymers are arranged in a side-by-side configuration.  
     
     
         29 . The process according to either of claims  1  or  13  wherein the meltblown web has a basis weight of between about 2 and 40 g/m 2  and a hydrostatic head of greater than about 30 cm H 2 O, the hydrostatic head being measured when the meltblown web is in a thermally point-bonded spunbond-meltblown-spunbond composite having a bonded area of between about 10 to 30 percent.