FILTER MEDIA HAVING A DENSITY VARIATION
Filter media including a density variation are described.
1 . A filter media comprising:
a first layer comprising synthetic fibers,
the first layer having a bottom surface and a top surface and a thickness that extends from the bottom surface to the top surface,
the first layer having a density that changes from a maximum density to a minimum density,
wherein the density changes non-linearly with thickness from the bottom surface to the top surface,
wherein the change in density between the bottom surface to a dimensional thickness of 0.25 from the bottom surface is less than 20% of the maximum density, and
wherein the change in density between a dimensional thickness of 0.5 from the bottom surface to a dimensional thickness of 0.75 from the bottom surface is less than 20% of the maximum density; and
a second layer comprising fibers and adjacent to the bottom surface of the first layer.
2 . A filter media comprising at least a first layer, wherein the weight of the synthetic fibers comprises at least 90% of the total weight of fibers in the first layer,
the first layer having a bottom surface and a top surface and a thickness that extends from the bottom surface to the top surface,
the first layer having a density that changes from a maximum density to a minimum density,
wherein the density changes non-linearly with thickness from the top surface to the bottom surface,
wherein the change in density between the bottom surface to a dimensional thickness of 0.25 from the bottom surface is less than 20% of the maximum density, and
wherein the change in density between a dimensional thickness of 0.5 from the bottom surface to 0.75 from the bottom surface is less than 20% of the maximum density.
3 . The filter media of claim 1 , wherein the change in density between the bottom surface to a dimensional thickness of 0.35 from the bottom surface is less than 12% of the maximum density.
4 . The filter media of claim 1 , wherein the density between a dimensional thickness of 0.5 from the bottom surface to a dimensional thickness of 0.75 from the bottom surface is between 65% and 75% of the maximum density.
5 . The filter media of claim 1 , wherein the weight of the synthetic fibers in the first layer comprises at least 90% of the total weight of fibers in the first layer.
6 . The filter media of claim 1 , wherein the weight of the synthetic fibers in the filter media comprises at least 90% of the total weight of fibers in the filter media.
7 . The filter media of claim 1 , wherein the weight of the synthetic fibers in the first layer comprises substantially all of the total weight of fibers in the first layer.
8 . The filter media of claim 1 , wherein the weight of the synthetic fibers in the filter media comprises substantially all of the total weight of fibers in the filter media.
9 . The filter media of claim 1 , wherein the change in density between the bottom surface to a dimensional thickness of 0.25 from the bottom surface is less than 15% of the maximum density.
10 . The filter media of claim 1 , wherein the change in density between the bottom surface to a dimensional thickness of 0.35 from the bottom surface is less than 15% of the maximum density.
11 . The filter media of claim 1 , wherein the change in density between a dimensional thickness of 0.5 from the bottom surface to 0.75 from the bottom surface is less than 15% of the maximum density.
12 . The filter media of claim 1 , wherein the first layer includes a first region formed on a second region.
13 . The filter media of claim 12 , further comprising a transition region between the first region and the second region.
14 . The filter media of claim 12 , wherein the second region extends from the bottom surface to at least a dimensional thickness of 0.25 from the bottom surface.
15 . The filter media of claim 12 , wherein the first region extends from at least a dimensional thickness of 0.5 from the bottom surface to at least a dimensional thickness of 0.75 from the bottom surface.
16 . The filter media of claim 12 , wherein the second region comprises fibers having an average fiber diameter less than an average diameter of fibers in the first region.
17 . The filter media of claim 1 , wherein the density changes with thickness following a two-step density curve from the bottom surface to the top surface.
18 . The filter media of claim 1 , wherein the first layer is a pre-filter and the second layer is a main filter.
19 . The filer media of claim 1 , wherein the first layer is configured to capture greater than 70% of the dust captured by the filter media following a dust holding capacity test
20 . The filter media of claim 1 , wherein the second layer includes multiple layers.
21 . The filter media of claim 1 , wherein the second layer comprises a meltblown layer.
22 . The filter media of claim 1 , wherein the first layer comprises a wet-laid layer.
23 . A hydraulic filter element comprising the filter media according to claim 1 .