POLYESTER/POLY(METHYL METHACRYLATE) ARTICLES AND METHODS TO MAKE THEM
A polymeric composition comprised of poly(methylmethacrylate) (PMMA) and polylactic acid (PLA) having a surface charge potential of at least about 50 volts in the absence of any other charge enhancing component may be made by melt blending PMMA and PLA, extruding the melt blend through a die and cooling at a rate through Tg of the PLA of at 10° C./min to 1000° C./second. The polymeric composition may be made by melt blowing into a nonwoven fabric. The nonwoven fabric may be charged to a surface potential of at least about 50 electron volts. Such filters may have greater than 95% efficiency at a pressure drop of less than 2 mm Hg even after being exposed to high temperatures (~70° C.) for an hour or more.
1 . A method of producing a non-woven material comprising:
a) providing a feed mixture comprising polymethyl methacrylate and polylactic acid to a melt blown extrusion device;
b) liquefying the feed mixture in the extrusion device to form a liquified feed mixture;
c) blowing the liquified feed mixture through at least one nozzle to form a spray;
d) depositing the spray on a surface;
e) reducing a temperature of the spray such that the spray solidifies on the surface to form a sheet of non-woven material comprised of fibers.
2 . The method of producing the non-woven material of claim 1 further comprising: forming a filtering mask comprised of filtering layer comprised of the non-woven material.
3 . The method of claim 1 , wherein the sheet of non-woven material is thermoformable without deforming the fibers of the non-woven material.
4 . The method of claim 1 , wherein the sheet of non-woven material has a filtering efficiency greater than 98%.
5 . The method of claim 4 , wherein the sheet of non-woven material has a pressure drop that is less than or equal to two millimeters of mercury.
6 . The method of claim 1 , further comprising passing the fabric through an electric field.
7 – 34 . (canceled)
35 . A filter comprising at least one layer of a nonwoven fabric comprised of fibers of poly(methylmethacrylate) and polylactic acid that have a diameter of about 0.5 micrometer to 15 micrometers and average diameter of about 2 to 8 micrometers.
36 . The filter of claim 35 , wherein at least about 90% by number of the fibers are longer than 500 micrometers.
37 . The filter of claim 36 , wherein the nonwoven fabric has a fabric weight of 50 to 300 grams/m 2 .
38 . The filter of claim 37 , wherein the nonowoven fabric has a fabric weight of about 100 to 200 grams/m 2 .
39 . The filter of claim 35 , wherein the filter has a pressure drop of at most about 5 mm Hg.
40 . The filter of claim 35 , wherein the filter has a filter efficiency of at least 95%.
41 . The filter of claim 40 , wherein the filter efficiency is at least 98%.
42 . The filter of claim 35 , wherein the filter has a surface potential of at least about 50 volts.
43 . The filter of claim 42 , wherein the surface potential decays at most about 5% after exposure to 70° C. for one hour.
44 . The filter of claim 43 , wherein the efficiency is at least 95%.
45 – 49 . (canceled)