Vapor retarding building materials and methods for making them
The present disclosure relates generally to vapor retarding building materials and methods for making them. The present inventors have found simple and cost-efficient materials that have low water vapor permeability at low relative humidities and that can be provided as a coating on a building material substrate. Notably, in many embodiments, the materials can have high water vapor permeability at high relative humidities. In one embodiment, the disclosure provides vapor retarding articles comprising a building material substrate; and a polymeric coating layer coated on the building material substrate, the polymeric coating layer comprising an inorganic hydrophilic particulate filler dispersed in a continuous organic phase comprising a hydrophobic polymer, wherein the content of the filler is from about 30% to about 85% by weight of the polymeric coating layer, the vapor retarding article configured to have a water vapor permeance of no more than about 1 Perm at 25% relative humidity.
1. A vapor retarding membrane, comprising
a building material substrate sheet, the building material substrate sheet being a sheet of paper or fabric; and
a polymeric coating layer coated on the building material substrate sheet, the polymeric coating layer being different from the building material substrate sheet, the polymeric coating layer comprising an inorganic hydrophilic particulate filler comprising kaolin, the inorganic hydrophilic particulate filler being dispersed in a continuous organic phase comprising a hydrophobic polymer comprising a styrene butadiene copolymer, a styrene acrylic copolymer, or a poly(vinylidene dichloride) polymer, wherein the content of the particulate filler is from about 35% to about 85% by weight of the polymeric coating layer, and wherein the combined content of the particulate filler and the hydrophobic polymer is at least about 90% by weight of the polymeric coating layer;
wherein the vapor retarding membrane is configured to have a water vapor permeance of no more than about 1 Perm at 25% relative humidity,
in the range of about 0.3 to about 6 Perms at 45% relative humidity,
in the range of about 5 to about 12 Perms at 75% relative humidity, and
at least about 8 Perms at 95% relative humidity,
as tested by ASTM E96 at 23° C.
2. The vapor retarding membrane of claim 1 , wherein the building material substrate sheet is paper.
3. The vapor retarding membrane of claim 1 , wherein the hydrophobic polymer is a styrene butadiene copolymer.
4. The vapor retarding membrane of claim 1 , wherein the hydrophobic polymer is coated onto the substrate sheet from an aqueous dispersion of the hydrophobic polymer dispersed in water or from an aqueous emulsion of the hydrophobic polymer.
5. The vapor retarding membrane of claim 1 , wherein the hydrophobic polymer is present in the continuous organic phase of the polymeric coating layer in an amount of at least about 70 wt %, based on the total weight of the continuous organic phase of the polymeric coating layer.
6. The vapor retarding membrane of claim 1 , wherein the particulate filler has a median particle size of about 2 to about 10 μm.
7. The vapor retarding membrane of claim 1 , wherein the particulate filler further comprises alumina trihydrate.
8. The vapor retarding membrane of claim 1 , wherein the particulate filler is present in the polymeric coating layer in an amount of at least 54 wt %, based on the total dry weight of the polymeric coating layer.
9. The vapor retarding membrane of claim 1 , wherein the continuous organic phase further comprises a lower molecular weight organic material in an amount up to 15 wt % of the continuous organic phase.
10. The vapor retarding membrane of claim 1 , wherein the continuous organic phase has an amount of polymeric hydrophilic components that is less than 0.5 wt %.
11. The vapor retarding membrane of claim 1 , wherein the polymeric coating layer has a coat weight of at least about 10 g/m 2 .
12. A method for making a vapor retarding membrane of claim 1 , the method comprising
providing the building material substrate sheet; and
coating the polymeric coating layer onto the building material substrate sheet, the polymeric coating layer being different from the building material substrate sheet.
13. The method of claim 12 , wherein coating the polymeric coating layer onto the substrate sheet includes providing a coating liquid comprising the hydrophobic polymer dispersed in a volatile aqueous liquid; coating the coating liquid onto the building material substrate sheet; and allowing the coated liquid to cure by drying to provide the polymeric coating layer.
14. The method of claim 13 , wherein the hydrophobic polymer is present in the coating liquid in the form of a polymer dispersion or a polymer emulsion in water.
15. The vapor retarding membrane of claim 1 , wherein the combined content of the particulate filler and the hydrophobic polymer is at least about 97.5% by weight of the polymeric coating layer.
16. The vapor retarding membrane of claim 1 , wherein the building material substrate sheet is a non-woven fabric.
17. The vapor retarding membrane of claim 1 , wherein the hydrophobic polymer is a styrene-butadiene copolymer and the hydrophobic filler is kaolin alone.
18. The vapor retarding membrane of claim 1 , wherein the hydrophobic polymer is a styrene-butadiene copolymer and the particulate filler is aluminum trihydrate in combination with kaolin.
19. The vapor retarding membrane of claim 1 , wherein the hydrophobic polymer is a styrene-acrylic copolymer.