Method of manufacturing an inorganic fiber filter tube and product

Claim 1

A method of preparing a nonwoven, fibrous, self-supporting, semirigid, all-inorganic, silicate-bound, filter tube consisting essentially of a plurality of interrelated, nonwoven fibers having interstices therebetween, the fibers bonded at the crossover points of the fibers with a bonding agent, which method comprises: (a) preparing an aqueous slurry comprising an admixture of low-melting-point, glass-binder fibers and high-melting-point, inorganic, filter fibers, the difference in melting point being greater than 100° F., the glass-binder fibers being present in an amount sufficient to act as a bonding agent for the inorganic filter fibers, the inorganic fibers being present in an amount sufficient to provide for a formed, porous, filter tube; (b) forming the fibers from the slurry into a nonwoven filter tube comprising a wet mass of the fibers; (c) heating the filter tube so formed to dry the filter tube; (d) heating the dried filter tube for a timed period and to a temperature greater than the melting point of the low-melting-point, glass-binder fibers and less than the melting point of the high-melting-point, inorganic filter fibers, to melt substantially all of the low-melting-point, glass-binder fibers and to have the low-melting-point molten material move to the crossover points of the inorganic filter fibers, the heating carried out, without any substantial softening of the inorganic filter fibers; and (e) cooling and recovering the porous filter tube of inorganic fibers, wherein the glass of the glass fibers forms the bonding agent for the inorganic filter tube.

Claim 2

A method of preparing a nonwoven, fibrous, self-supporting, semirigid, all-inorganic, silicate-bound, filter tube consisting essentially of a plurality of interrelated, nonwoven fibers having interstices therebetween, the fibers bonded at the crossover points of the fibers with a bonding agent, which method comprises: (a) preparing an aqueous slurry comprising an admixture of low-melting-point, glass-binder fibers and high-melting-point, inorganic, filter fibers, the difference in melting point being greater than 100° F., the glass-binder fibers being present in an amount sufficient to act as a bonding agent for the inorganic filter fibers, the inorganic fibers being present in an amount sufficient to provide for a formed, porous, filter tube; (b) forming the fibers from the slurry into a nonwoven filter tube comprising a wet mass of the fibers; (c) heating the filter tube so formed to dry the filter tube; (d) heating the dried filter tube for a timed period and to a temperature greater than the melting point of the low-melting-point, glass-binder fibers and less than the melting point of the high-melting-point, inorganic filter fibers, to melt substantially all of the low-melting-point, glass-binder fibers and to have the low-melting-point molten material move to the crossover points of the inorganic filter fibers, the heating carried out, without any substantial softening of the inorganic filter fibers; and (e) cooling and recovering the porous filter tube of inorganic fibers, wherein the glass of the glass fibers forms the bonding agent for the inorganic filter tube.

Claim 19

A method of preparing a self-supporting, semirigid, all-inorganic, silicate-bound, nonwoven, porous, filter tube, which method comprises: (a) providing an acidic aqueous slurry containing from about 1% to 60% by weight of an admixture of binder fibers and filter fibers, the fibers having a diameter of from about 0.01 to 10 microns, the binder fibers comprising about 5% to 60% by weight of the fiber admixture, the filter fibers composed of quartz fibers having a melting point of from about 1800° F. to 2200° F., and the binder fibers composed of borosilicate glass and having a melting point of from about 1000° F. to 1500° F.; (b) forming a wet mass of the nonwoven fiber admixture into a filter tube on the surface of a cylindrical vacuum mandrel; (c) drying the filter tube so formed; (d) heating the dried filter tube to a temperature of from about 1500° F. to 2200° F. and for a time period sufficient to melt the glass-binder fibers and to have the molten borosilicate glass move to the crossover points of the quartz filter fibers, the heating carried out without any substantial softening of the quartz filter fibers; and (e) cooling and recovering a filter tube consisting essentially of the borosilicate material as a bonding agent for the quartz filter fibers of the filter tube.

Claim 20

A method of preparing a self-supporting, semirigid, all-inorganic, silicate-bound, nonwoven, porous, filter tube, which method comprises: (a) providing an acidic aqueous slurry containing from about 1% to 60% by weight of an admixture of binder fibers and filter fibers, the fibers having a diameter of from about 0.01 to 10 microns, the binder fibers comprising about 5% to 60% by weight of the fiber admixture, the filter fibers composed of quartz fibers having a melting point of from about 1800° F. to 2200° F., and the binder fibers composed of borosilicate glass and having a melting point of from about 1000° F. to 1500° F.; (b) forming a wet mass of the nonwoven fiber admixture into a filter tube on the surface of a cylindrical vacuum mandrel; (c) drying the filter tube so formed; (d) heating the dried filter tube to a temperature of from about 1500° F. to 2200° F. and for a time period sufficient to melt the glass-binder fibers and to have the molten borosilicate glass move to the crossover points of the quartz filter fibers, the heating carried out without any substantial softening of the quartz filter fibers; and (e) cooling and recovering a filter tube consisting essentially of the borosilicate material as a bonding agent for the quartz filter fibers of the filter tube.