Inorganic fiber webs and methods of making and using

1. A method of making a gravity-laid inorganic fiber web, comprising:

introducing inorganic fibers into a forming chamber that comprises a plurality of fiber-separating rollers provided in at least one row within the forming chamber, and that comprises a moving endless belt screen;

mechanically separating at least some of the inorganic fibers with the fiber-separating rollers;

capturing any remaining agglomerates of the inorganic fibers by the moving endless belt screen and returning the captured agglomerates to the fiber-separating rollers to be mechanically separated by the fiber-separating rollers;

collecting the mechanically separated inorganic fibers as a gravity-laid inorganic fiber mat;

removing the gravity-laid inorganic fiber mat from the forming chamber; and,

consolidating the gravity-laid inorganic fiber mat to form a gravity-laid inorganic fiber web.

2. The method of claim 1 wherein the method comprises introducing inorganic fibers of at least two different types into the forming chamber and blending the fibers within the forming chamber so as to collect a gravity-laid inorganic fiber mat that comprises a blend of the at least two different types of inorganic fibers.

3. The method of claim 1 wherein the consolidation comprises needle-punching.

4. The method of claim 1 further comprising adding at least one binder to the inorganic fibers or to the gravity-laid inorganic fiber mat, wherein the consolidation comprises activating the binder.

5. The method of claim 1 further comprising introducing at least one inorganic particulate additive into the forming chamber and blending the additive with the inorganic fibers.

6. The method of claim 5 wherein the inorganic particulate additive comprises an intumescent additive.

7. The method of claim 5 wherein the inorganic particulate additive comprises an endothermic additive comprising an inorganic compound capable of liberating water at temperatures of between 200° C. and 600° C.

8. The method of claim 5 wherein the inorganic particulate additive comprises an insulative additive.

9. A gravity-laid inorganic fiber web.

10. The inorganic fiber web of claim 9 wherein the web is a blended fiber web comprising a blend of at least two types of inorganic fibers.

11. The inorganic fiber web of claim 9 wherein substantially all of the inorganic fibers of the web are biosoluble ceramic fibers.

12. The inorganic fiber web of claim 9 wherein at least about 5% by weight of the inorganic fibers of the web are long basalt fibers.

13. The inorganic fiber web of claim 9 wherein at least some of the inorganic fibers are long inorganic fibers of at least 5 cm in length.

14. The inorganic fiber web of claim 9 wherein the web comprises an inorganic particulate additive.

15. The inorganic fiber web of claim 14 wherein the inorganic particulate additive comprises an intumescent additive.

16. The method of claim 1 wherein the gravity-laid inorganic fiber web exhibits a thickness that is substantially equal to a thickness of the gravity-laid inorganic fiber mat from which the gravity-laid inorganic fiber web was formed.

17. The inorganic fiber web of claim 9 wherein the web comprises mineral wool blended with long inorganic fibers chosen from the group consisting of long glass fibers and long basalt fibers, wherein from about 40% to about 95% by weight of the inorganic fibers of the web are mineral wool fibers, and wherein from about 5% to about 60% by weight of the inorganic fibers of the web are long inorganic fibers.

18. The inorganic fiber web of claim 9 wherein the web comprises a blend of short inorganic fibers of length at most about 1 cm, and long inorganic fibers of length at least about 5 cm.

19. The inorganic fiber web of claim 9 wherein the web comprises an organic binder that comprises bicomponent organic polymeric fibers present at from about 0.5% to about 5% by weight based on the total weight of the web.

20. The inorganic fiber web of claim 9 wherein the web contains substantially no organic binder.