Microporous articles with a three-dimensional porous network of acid-sintered interconnected silica nanoparticles and methods of making the same
Articles are described including a first microfiltration membrane layer having a first major surface and a second major surface disposed opposite the first major surface, and a first silica layer directly attached to the first major surface of the first microfiltration membrane layer. The first silica layer includes a polymeric binder and acid-sintered interconnected silica nanoparticles arranged to form a continuous three-dimensional porous network. A method of making an article is also described, including providing a first microfiltration membrane layer having a first major surface and a second major surface disposed opposite the first major surface, and forming a first silica layer on the first major surface.
1. A multilayer article comprising:
a) a first microfiltration membrane layer, the first microfiltration membrane layer having a first major surface and a second major surface disposed opposite the first major surface; and
b) a first silica layer directly attached to the first major surface of the first microfiltration membrane layer, the first silica layer comprising a polymeric binder and a plurality of acid-sintered interconnected silica nanoparticles arranged to form a continuous three-dimensional porous network.
2. The multilayer article of claim 1 , wherein the polymeric binder comprises poly(vinyl alcohol) (PVA), dextran, a urethane resin, or an acrylate resin.
3. The multilayer article of claim 1 , wherein the first silica layer further comprises a surfactant.
4. The multilayer article of claim 1 , wherein the silica nanoparticles comprise average particle size diameters less than or equal to 200 nanometers (nm).
5. The multilayer article of claim 1 , wherein a weight ratio of the silica nanoparticles to the polymer binder is in a range from 90:10 to 70:30.
6. The multilayer article of claim 1 , wherein the first microfiltration membrane comprises an asymmetric membrane.
7. The multilayer article of claim 1 , wherein the first major surface of the first microfiltration membrane comprises an average pore size of 50 nm to 500 nm.
8. The multilayer article of claim 1 , wherein the first silica layer comprises an average pore size of 1 nm to 100 nm.
9. The multilayer article of claim 1 , wherein the first silica layer comprises an average thickness of 0.1 to 10.0 μm.
10. The multilayer article of claim 1 , wherein the article is a battery separator or an ultrafiltration membrane.
11. A method of making a multilayer article comprising:
a) providing a first microfiltration membrane layer, the first microfiltration membrane layer having a first major surface and a second major surface disposed opposite the first major surface; and
b) forming a first silica layer on the first major surface, comprising a polymeric binder and a plurality of acid-sintered interconnected silica nanoparticles arranged to form a continuous three-dimensional porous network.
12. The method of claim 11 , wherein forming the first silica layer comprises preparing a dispersion containing the polymer and the silica nanoparticles acidified with an acid having a pKa less than 3.5 to a pH in a range of 2 to 5, coating the dispersion on the substrate to form a coating, and drying the coating to form the plurality of acid-sintered silica nanoparticles.
13. The method of claim 12 , wherein the dispersion further comprises an alcohol.
14. The method of claim 11 , wherein the drying comprises subjecting the coating to a temperature of 40 degrees Celsius to 250 degrees Celsius.
15. The method of claim 11 , wherein the silica nanoparticles comprise average particle size diameters less than or equal to 200 nanometers (nm).
16. A multizone article comprising:
a) a first porous zone comprising first average pore size; and
b) a second porous zone integral with the first porous zone and having a second average pore size, the second porous zone comprising a polymeric binder and a plurality of acid-sintered interconnected silica nanoparticles arranged to form a continuous three-dimensional porous network.
17. The multizone article of claim 16 , wherein the polymeric binder comprises poly(vinyl alcohol) (PVA), dextran, a urethane resin, or an acrylate resin.
18. The multizone article of claim 16 , wherein the silica nanoparticles comprise average particle size diameters less than or equal to 200 nanometers (nm).
19. The multizone article of claim 16 , wherein the first porous zone comprises an asymmetric membrane and the second porous zone is integral to the asymmetric membrane at a portion comprising a smaller average pore size than the pores of a major surface of the asymmetric membrane opposite the second porous zone.
20. The multizone article of claim 16 , wherein the second porous zone comprises an average pore size of 1 nm to 100 nm.