MORPHOLOGICAL IMPROVEMENTS IN FILTER MEDIA
Filter media comprising surface-treated fiber webs having one or more advantageous physical properties are generally described. Certain improvements in the surface-treated fiber webs described herein may be realized in filter media comprising nanofiber layers. The improvements herein are, in some embodiments, related to favorable distributions of cavities in surface-treated fiber webs, such as those used in backers of the filter media.
1 . A filter media, comprising:
a fiber web comprising a plurality of surface cavities, wherein:
the fiber web comprises synthetic fibers in an amount of at least 50 wt % of the fiber web;
the synthetic fibers have an average length of less than or equal to 40 mm;
the fiber web has a developed interfacial area ratio greater than or equal to 0.1; and
the cavities of the fiber web have an average cross-dimensional frequency of greater than or equal to 3,000 surface cavities per meter.
2 . A filter media as in claim 1 , wherein the filter media comprises a plurality of nanofibers disposed on the fiber web.
3 . A filter media as in claim 1 , wherein the nanofibers are at least partially disposed within the cavities of the plurality of cavities.
4 . A filter media as in claim 1 , wherein the fiber web is a first layer of the filter media, and the nanofibers form a second layer disposed on top of the first layer.
5 . A filter media, comprising:
a first layer comprising a fiber web comprising a plurality of surface cavities, wherein:
the fiber web comprises synthetic fibers in an amount of at least 50 wt % of the fiber web,
the synthetic fibers of the fiber web have an average length of less than or equal to 40 mm,
the fiber web has a developed interfacial area ratio greater than or equal to 0.1, and
the cavities of the fiber web have an average cross-dimensional frequency of greater than or equal to 3,000 surface cavities per meter; and
a second layer comprising a plurality of nanofibers disposed on the fiber web.
6 . A filter media as in claim 5 , wherein the second layer, when separated from the first layer and laid flat, has an interfacial area ratio less than or equal to 0.1.
7 . A filter media as in claim 1 , wherein the fiber web is non-woven.
8 . A filter media according to claim 1 , wherein the intermediate and large cavities of the plurality of cavities together have an average area of less than or equal to 500 microns 2 .
9 . A filter media according to claim 1 , wherein the large cavities of the plurality of cavities have an average area of less than or equal to 1300 microns 2 .
10 . A filter media according to claim 1 , wherein the nanofibers comprise a matrix polymer.
11 . A filter media according to claim 10 , wherein the nanofibers comprise an impact modifier dispersed in the matrix polymer.
12 . A filter media according to claim 11 , wherein the weight percent of the impact modifier in the nanofibers is greater than or equal to 1 wt. % and less than or equal to 25 wt. % of the total weight of the nanofibers.
13 . A filter media according to claim 1 , wherein the matrix polymer comprises only polymers with a molecular weight of greater than 3 kDa.
14 . A method of making the filter media of claim 1 , comprising first preparing a precursor fiber web and fluid enhancing the precursor fiber web to produce the fiber web.
15 . The method of claim 14 , further comprising depositing a layer on the fiber web.
16 . A filter media according to claim 1 , further comprising an additional layer at least partially disposed on the fiber web.
17 . A filter media according to claim 1 , wherein the additional layer comprises a fiber web.
18 . A filter media according to claim 1 , wherein the fiber web of the additional layer comprises a plurality of glass fibers.