Articles comprising binders, cross-linking agents and/or other components, and related methods

A filter medium, comprising:

• a first phase comprising a first plurality of fibers and a second plurality of fibers different from the first plurality of fibers;
• a second phase comprising a third plurality of fibers and a fourth plurality of fibers different from the third plurality of fibers, the third plurality of fibers being the same as or different from the first or second plurality of fibers and the fourth plurality of fibers being the same as or different from the first or second plurality of fibers;
• and
• a transition phase between the first and second phases, wherein the transition phase comprises at least a portion of the first plurality of fibers, at least a portion of the second plurality of fibers, at least a portion of the third plurality of fibers, and at least a portion of the fourth plurality of fibers, and wherein at least a portion of the first plurality of fibers, at least a portion of the second plurality of fibers, at least a portion of the third plurality of fibers, and at least a portion of the fourth plurality of fibers are intermingled with each other;
• wherein the air permeability of the first plurality of fibers is higher than the air permeability of the second plurality of fibers, and the air permeability of the third plurality of fibers is higher than the air permeability of the fourth plurality of fibers;
• wherein a weight ratio of the first plurality of fibers to the second plurality of fibers is from 50:50 to 97:3;
• wherein the first and second phases form a wet laid structure;
• wherein the first, second, third, and fourth pluralities of fibers are wet laid;
• wherein the basis weight ratio of the first phase to the second phase is from 30:70 to 70:30;
• wherein the filter medium has a dust holding capacity from 1 g to 3 g measured according to a Palas flat sheet test;
• and
• wherein the filter medium has a mean flow pore size of at least 25 microns and at most 1000 microns.

A filter medium, comprising:

• a first phase comprising a first plurality of fibers and a second plurality of fibers different from the first plurality of fibers;
• a second phase comprising a third plurality of fibers and a fourth plurality of fibers different from the third plurality of fibers, the third plurality of fibers being the same as or different from the first or second plurality of fibers and the fourth plurality of fibers being the same as or different from the first or second plurality of fibers;
• and
• a transition phase between the first and second phases, wherein the transition phase comprises at least a portion of the first plurality of fibers, at least a portion of the second plurality of fibers, at least a portion of the third plurality of fibers, and at least a portion of the fourth plurality of fibers, and wherein at least a portion of the first plurality of fibers, at least a portion of the second plurality of fibers, at least a portion of the third plurality of fibers, and at least a portion of the fourth plurality of fibers are intermingled with each other;
• wherein the air permeability of the first plurality of fibers is higher than the air permeability of the second plurality of fibers, and the air permeability of the third plurality of fibers is higher than the air permeability of the fourth plurality of fibers;
• wherein a weight ratio of the first plurality of fibers to the second plurality of fibers is from 50:50 to 97:3;
• wherein the first and second phases form a wet laid structure;
• wherein the first, second, third, and fourth pluralities of fibers are wet laid;
• wherein the basis weight ratio of the first phase to the second phase is from 30:70 to 70:30;
• and
• wherein the filter medium has a dust holding capacity from 1 g to 3 g measured according to a Palas flat sheet test.