Method and apparatus for forming a non-woven fibrous web from a foamed fiber furnish

Claim 2

Method of producing a non-woven fibrous web which comprises a. forming by a vigorous shearing action an aqueous foam consisting essentially of air dispersed in the form of very small bubbles in an aqueous solution containing a surface active agent, the number average diameter of said bubbles being not more than substantially 0.2mm, said foam having a viscosity of at least 22 seconds as measured by Ford Cup Type B-4 at 20* C and having an air content by volume of at least about 65 percent; b. forming a dispersion of fibers in said aqueous foam to produce a mixture possessing thixotropic properties with low viscosity and rapid rate of release of said fibers when subjected to draining action; and c. depositing said fiber dispersion on a foraminous support with concomitant collapse of the foam and formation of a non-woven web on said support accompanied by drainage of residual water from the web.

Claim 3

The method of claim 1 in which the dispersion of fibers in said aqueous foam is formed by subjecting surfactant-containing water in which the fibers are dispersed to the vortical foaming action of an impeller which creates a vortex of liquid drawn towards the impeller at the base of the vortex.

Claim 4

A method according to claim 2, wherein surfactant-containing water and fibers to be dispersed therein are continuously supplied so as to be subjected to said vortical mixing action and wherein foam having the defined properties and characteristics is continuously removed from the region adjacent the base of the vortex.

Claim 5

Method of producing a non-woven fibrous web which comprises a. forming a foam of surfactant-containing water, said foam being formed by a vigorous shearing action and consisting essentially of air dispersed in the form of very small bubbles, the average diameter of said bubbles being not more than substantially 0.2 mm, said foam having a viscosity of at least 22 seconds is measured by Ford Cup Type B-4 at 20* C and having an air content by volume of at least about 65 percent, by subjecting water containing an effective amount of a foam-producing surfactant to the vortical foaming action of an impeller which creates a vortex of liquid drawn towards the impeller at the base of the vortex together with some air that is emulsified by the action of the impeller with return flow of foam to the mouth of the vortex carrying with it coarse bubbles which at least in part are drawn into the vortex; b. removing foam from the region adjacent the base of the vortex while it is in the condition produced in that region by the action of the impeller; c. dispersing fibers in said removed foam; and d. depositing the dispersion of fibers in the removed foam on a foraminous support with concomitant collapse of the foam and formation of a non-woven web on said support accompanied by drainage of residual water from the web.

Claim 6

Method of producing a non-woven fibrous web which comprises a. forming a foam of surfactant-containing water, said foam being formed by a vigorous shearing action and consisting essentially of air dispersed in the form of very small bubbles, the average diameter of said bubbles being not more than substantially 0.2 mm, said foam having a viscosity of at least 22 seconds is measured by Ford Cup Type B-4 at 20* C and having an air content by volume of at least about 65 percent, by subjecting water containing an effective amount of a foam-producing surfactant to the vortical foaming action of an impeller which creates a vortex of liquid drawn towards the impeller at the base of the vortex together with some air that is emulsified by the action of the impeller with return flow of foam to the mouth of the vortex carrying with it coarse bubbles which at least in part are drawn into the vortex; b. removing foam from the region adjacent the base of the vortex while it is in the condition produced in that region by the action of the impeller; c. dispersing fibers in said removed foam; and d. depositing the dispersion of fibers in the removed foam on a foraminous support with concomitant collapse of the foam and formation of a non-woven web on said support accompanied by drainage of residual water from the web.

Claim 7

A method according to claim 4, wherein the fibers to be formed into the web are dispersed in the foam as it is formed by said vortical foaming action.

Claim 8

A method according to claim 4, wherein fibers are dispersed in the foam after removal of the foam from adjacent the base of the vortex and the foam with the fibers contained therein is subjected to a second vortical foaming step from which foam containing fibers therein is removed at the region adjacent the base of the vortex.

Claim 9

A method according to claim 4, wherein surfactant-containing water having Fibers dispersed therein is subjected to a succession of vortical foaming steps with effluent from one flowing into the next, foam of emulsified air with the fibers dispersed therein being removed from adjacent the base of the vortex of the last vortical mixing step and being directed for deposit on the foraminous support of the web-forming machine.

Claim 10

A method according to claim 7, wherein at a point between the first vortical mixing step and the second any unfoamed surfactant-containing water is separated and is returned to the vortex maintained during the first vortical foaming step.

Claim 11

The method of claim 4, in which there are concurrently introduced from separate sources fibers and surfactant-containing water into a foam-producing zone in which said foam is produced by a vigorous shearing action to form a fiber dispersion possessing thixotropic properties with low viscosity and a rapid rate of release of said fibers when subjected to draining action.

Claim 12

A method according to claim 9, wherein fibers are introduced while dry.

Claim 13

A method according to claim 9, wherein fibers are introduced in the form of a thick stock of fibers dispersed in water that is substantially free of surfactant.

Claim 14

A method according to claim 9, wherein surfactant-containing water is drained from the web during its formation on the foraminous support, and wherein said surfactant-containing water drained from the web is introduced into the foam-producing zone simultaneously with the introduction of fibers into said zone.

Claim 15

A method according to claim 9, wherein the foam having fibers dispersed therein is continuously removed from the foam-producing zone and the rate of introduction into the foam-producing zone of surfactant-containing water drained from the web during its formation is controlled responsive to the level of the liquid head in the foam-producing zone.

Claim 16

Method of producing a non-woven fibrous web which comprises a. forming a suspension of fibers in water; b. thickening the suspension of fibers to form a thickened fibrous stock; c. mixing the thickened fibrous stock with surfactant-containing water to form a dilute fiber furnish of web-forming consistency; d. foaming the dilute furnish by subjecting the furnish to vigorous shearing action to produce therein an aqueous foam consisting essentially of air in the form of very small bubbles in an aqueous solution containing a surfactant, the number average diameter of said bubbles being not more than substantially 0.2 mm, said foam having a viscosity of at least 22 seconds as measured by Ford Cup Type B-4 at 20* C and having an air content by volume of at least about 65 percent; e. depositing said foamed furnish on a foraminous support to form a web with concomitant drainage of surfactant-containing water so as to partially dry the web; f. removing partially dried web; g. returning surfactant-containing water to the mixing step (c); and h. substantially balancing the water introduced into said mixing step with the thickened stock, with the amount of surfactant-containing water contained in the partially dried web removed from web-forming step (e).

Claim 17

Method of producing a non-woven fibrous web which comprises a. forming a suspension of fibers in water; b. thickening the suspension of fibers to form a thickened fibrous stock; c. mixing the thickened fibrous stock with surfactant-containing water to form a dilute fiber furnish of web-forming consistency; d. foaming the dilute furnish by subjecting the furnish to vigorous shearing action to produce therein an aqueous foam consisting essentially of air in the form of very small bubbles in an aqueous solution containing a surfactant, the number average diameter of said bubbles being not more than substantially 0.2 mm, said foam having a viscosity of at least 22 seconds as measured by Ford Cup Type B-4 at 20* C and having an air content by volume of at least about 65 percent; e. depositing said foamed furnish on a foraminous support to form a web with concomitant drainage of surfactant-containing water so as to partially dry the web; f. removing partially dried web; g. returning surfactant-containing water to the mixing step (c); and h. substantially balancing the water introduced into said mixing step with the thickened stock, with the amount of surfactant-containing water contained in the partially dried web removed from web-forming step (e).

Claim 18

The method of claim 14, in which a portion of the surfactant-containing water drained from the web during its formation in step (e) is added to the surfactant-containing water that is introduced substantially free of fibers into the foam producing step (d); another portion of surfactant-containing water drained from the web is admixed with waste portions of the formed web to form a dispersion of fibers in surfactant-containing water; and said fiber dispersion is introduced into the foam-producing step.

Claim 19

A method according to claim 14, wherein the fibers are introduced into the foam-producing zone at a substantially constant rate and the rate of introduction of said surfactant-containing water that is substantially free of fibers is controlled responsive to the level of liquid in tHe foam-producing zone.

Claim 20

Apparatus for making a non-woven fibrous web which comprises in combination: a. fiber stock supply means; b. web-forming means provided with a foraminous support on which an aqueous fiber furnish is deposited with formation of fibrous web and drainage of aqueous liquid therefrom; c. foam-producing means including a casing having means for admission of air thereto, a blade impeller mounted within said casing so as to be rotatable about an axis at right angles to the upper surface of the casing, the upper edge of said impeller being situated closely adjacent to the upper inner surface of said casing so as to produce a vortex in the aqueous liquid supplied thereto, the distance between said upper edge of the impeller and the surface of the casing being in the range 0.010 inch to 0.125 inch and such as to form a foam wherein the number average diameter of the bubbles is not more than substantially 0.2 mm, by vigorous shearing action on said aqueous liquid; d. means for mixing said fiber furnish with said foam; e. means for directing fiber stock from said stock supply means selectively to said mixing means and to said foam-producing means; f. means for directing fiber furnish to said web-forming means selectively from said foam-producing means or from said mixing means; and g. means for directing aqueous liquid drained from said web-forming means selectively to said mixing means and to said foam-producing means.

Claim 21

Apparatus for making a non-woven fibrous web which comprises in combination: a. fiber stock supply means; b. web-forming means provided with a foraminous support on which an aqueous fiber furnish is deposited with formation of fibrous web and drainage of aqueous liquid therefrom; c. foam-producing means including a casing having means for admission of air thereto, a blade impeller mounted within said casing so as to be rotatable about an axis at right angles to the upper surface of the casing, the upper edge of said impeller being situated closely adjacent to the upper inner surface of said casing so as to produce a vortex in the aqueous liquid supplied thereto, the distance between said upper edge of the impeller and the surface of the casing being in the range 0.010 inch to 0.125 inch and such as to form a foam wherein the number average diameter of the bubbles is not more than substantially 0.2 mm, by vigorous shearing action on said aqueous liquid; d. means for mixing said fiber furnish with said foam; e. means for directing fiber stock from said stock supply means selectively to said mixing means and to said foam-producing means; f. means for directing fiber furnish to said web-forming means selectively from said foam-producing means or from said mixing means; and g. means for directing aqueous liquid drained from said web-forming means selectively to said mixing means and to said foam-producing means.

Claim 22

Apparatus according to claim 17, wherein fiber stock selectively directed to said foam-producing means from said fiber stock supply means is directed from said fiber stock supply means to stock thickening means and from said stock thickening means to said foam-producing means.

Claim 23

Apparatus for producing a non-woven fibrous web from a foamed fibrous furnish which comprises in combination: a. foam-producing means comprising a mixing compartment, a rotary impeller adjacent the bottom of said compartment, and means for rotating said impeller at high speed, said foam-producing means being capable of forming a foam by vigorous shearing action on aqueous liquid supplied thereto the distance between the adjacent edge of said impeller and the bottom of said compartment being in the range 0.010 inch and 0.125 inch; b. a web-forming apparatus including a travelling foraminous support on which an aqueous fiber furnish is deposited with formation of a fibrous web; and c. means for removing foam-containing dispersed fibers from adjacent said impeller near the bottom of said mixing compartment and directing them onto said travelling foraminous support.

Claim 24

Apparatus for producing a non-woven fibrous web from a foamed fibrous furnish which comprises in combination: a. foam-producing means comprising a mixing compartment, a rotary impeller adjacent the bottom of said compartment, and means for rotating said impeller at high speed, said foam-producing means being capable of forming a foam by vigorous shearing action on aqueous liquid supplied thereto the distance between the adjacent edge of said impeller and the bottom of said compartment being in the range 0.010 inch and 0.125 inch; b. a web-forming apparatus including a travelling foraminous support on which an aqueous fiber furnish is deposited with formation of a fibrous web; and c. means for removing foam-containing dispersed fibers from adjacent said impeller near the bottom of said mixing compartment and directing them onto said travelling foraminous support.

Claim 25

Apparatus according to claim 19, which comprises a reservoir, means for directing surfactant-containing liquid drained from said web during its formation on said foraminous support into said reservoir, and means for admitting surfactant-containing water from said reservoir into said compartment responsive to the level of liquid in said compartment.

Claim 26

The apparatus of claim 17, which further includes a reservoir for supplying surfactant-containing water to said foam-producing means, means for directing surfactant-containing water from said reservoir into said foam-producing means, means for collecting surfactant-containing water drained from said web-forming means, means for directing surfactant-containing water from said collecting means into said reservoir, and means for depositing foam produced by said foam-producing means having fibers disposed therein onto said foraminous support.