Method for treating fibrous web materials
View Patent ↗The present invention provides an efficient method for topically treating and drying fibrous web materials such as nonwoven web materials and nonwoven laminate materials without unduly damaging the materials due to excessive heating during drying.
1. A method for treating a fibrous web material comprising the steps of:
a) providing a fibrous web material;
b) treating the fibrous web material with a topical treatment, the topical treatment comprising a treatment chemical and a liquid carrier medium;
c) partially drying the fibrous web material, wherein after partial drying the fibrous web material comprises about 40 percent to about 10 percent by weight residual moisture; and thereafter
d) passing the fibrous web material through a radio frequency energy field, wherein after passing through the radio frequency energy field the fibrous web material comprises less than about 5 percent by weight residual moisture.
2. The method of claim 1 wherein the step of partially drying the web is performed by applying vacuum or external heat to the fibrous web material.
3. The method of claim 2 wherein the fibrous web material is a thermoplastic nonwoven web material.
4. The method of claim 3 wherein the topical treatment is a liquid-repellent treatment, a hydrophilic treatment or an anti-static treatment, and further wherein the liquid carrier medium comprises water.
5. The method of claim 4 wherein the thermoplastic nonwoven web material is a nonwoven barrier laminate material.
6. The method of claim 5 wherein the topical treatment is a fluorochemical in aqueous emulsion.
7. The method of claim 4 wherein the external heat is applied by streams of heated air or contacting at least one planar surface of the web material with at least one heated canister.
8. The method of claim 6 wherein the external heat is applied by contacting at least one planar surface of the web material with at least one heated canister.
9. The method of claim 8 wherein the step of treating with a topical treatment is performed by dip saturation, spraying or foaming.
10. The method of claim 7 wherein after the step of partial drying the fibrous web material comprises about 20 percent to about 10 percent by weight residual moisture.
11. The method of claim 8 wherein after the step of partial drying the fibrous web material comprises about 20 percent to about 10 percent by weight residual moisture.
12. The method of claim 10 wherein after the step of passing through the radio frequency energy field the fibrous web material comprises less than about 2 percent by weight residual moisture.
13. The method of claim 12 wherein after the step of passing through the radio frequency energy field the fibrous web material comprises less than about 1 percent by weight residual moisture.
14. The method of claim 13 wherein after the step of passing through the radio frequency energy field the fibrous web material comprises less than about 0.5 percent by weight residual moisture.
15. The method of claim 11 wherein after the step of passing through the radio frequency energy field the fibrous web material comprises less than about 2 percent by weight residual moisture.
16. The method of claim 15 wherein after the step of passing through the radio frequency energy field the fibrous web material comprises less than about 1 percent by weight residual moisture.
17. The method of claim 16 wherein after the step of passing through the radio frequency energy field the fibrous web material comprises less than about 0.5 percent by weight residual moisture.
18. The method of claim 1 wherein the radio frequency energy field is applied at a frequency of from about 10 megahertz to about 50 megahertz.