Continuous papermaking machines and methods for continuous papermaking

Abstract

A continuous papermaking machine including a headbox for discharging a suspension of cellulose fibers in water, a forming wire moving in a process direction, the forming wire receiving the suspension from the headbox such that a web is formed on the forming wire, a top former above the forming wire for upwardly removing water from the web, the top former comprising a lead out roll, a dewatering device below the forming wire and downstream from the top former, and an applicator positioned above the forming wire and downstream from the lead out roll of the top former, the applicator discharging onto the web a mixture that includes microfibrillated cellulose and a carrier.

1 . A continuous papermaking machine, comprising:
 a headbox discharging a suspension of cellulose fibers in water;   a forming wire moving in a process direction, the forming wire receiving the suspension from the headbox such that a web is formed on the forming wire;   a top former above the forming wire for upwardly removing water from the web, the top former comprising a lead out roll;   a dewatering device below the forming wire and downstream from the top former; and   an applicator positioned above the forming wire and downstream from the lead out roll of the top former, the applicator discharging onto the web a mixture comprising microfibrillated cellulose and a carrier.   
     
     
         2 . The continuous papermaking machine of  claim 1 , wherein the applicator is positioned upstream from the dewatering device. 
     
     
         3 . The continuous papermaking machine of  claim 1 , wherein the dewatering device comprises a vacuum box. 
     
     
         4 . The continuous papermaking machine of  claim 1 , wherein the dewatering device comprises a gravity box. 
     
     
         5 . The continuous papermaking machine of  claim 1 , further comprising a pressing section downstream from the dewatering device for mechanically squeezing water from the web. 
     
     
         6 . The continuous papermaking machine of  claim 5 , wherein the pressing section comprises a plurality of rolls for squeezing the web. 
     
     
         7 . The continuous papermaking machine of  claim 5 , further comprising a drying section downstream from the pressing section for removing water by heating the web. 
     
     
         8 . The continuous papermaking machine of  claim 7 , wherein the drying section comprises a plurality of heated rolls for heating the web. 
     
     
         9 . The continuous papermaking machine of  claim 1 , wherein the applicator comprises a basin defined by one or more basin walls for holding the mixture. 
     
     
         10 . The continuous papermaking machine of  claim 9 , wherein the applicator comprises a first flow control barrier for limiting a flow of the mixture. 
     
     
         11 . The continuous papermaking machine of  claim 10 , wherein the applicator further comprises a second flow control barrier for limiting a flow of the mixture from the first flow control barrier. 
     
     
         12 . The continuous papermaking machine of  claim 10 , wherein the applicator further comprises a flow-down surface for flowing the mixture from the first flow control barrier. 
     
     
         13 . The continuous papermaking machine of  claim 1 , wherein the applicator comprises a first flow control slope for flowing the mixture. 
     
     
         14 . The continuous papermaking machine of  claim 13 , wherein the applicator further comprises a second flow control slope for flowing the mixture from the first flow control slope. 
     
     
         15 . The continuous papermaking machine of  claim 14 , wherein the applicator further comprises a flow direction change surface for reversing a flow of the mixture from the first flow control slope to the second flow control slope. 
     
     
         16 . The continuous papermaking machine of  claim 1 , wherein the mixture comprises about 0.01 percent by weight to about 10 percent by weight microfibrillated cellulose. 
     
     
         17 . The continuous papermaking machine of  claim 1 , wherein the mixture further comprises a flow modifying agent. 
     
     
         18 . A continuous papermaking machine, comprising:
 a headbox discharging a suspension of cellulose fibers in water;   a forming wire moving in a process direction, the forming wire receiving the suspension from the headbox such that a web is formed on the forming wire;   a dewatering device positioned below the forming wire; and   an applicator positioned upstream from the dewatering device, the applicator discharging onto the web a mixture comprising microfibrillated cellulose and a carrier.   
     
     
         19 . A method for continuous papermaking, comprising:
 discharging a suspension of cellulose fibers in water onto a moving forming wire to yield a web on the forming wire;   draining water from the web through the forming wire;   upwardly removing water from the web;   applying a mixture comprising microfibrillated cellulose and a carrier on top of the web after the step of upwardly removing water from the web; and   passing the web having the mixture thereon over one or more dewatering devices to downwardly remove water from the web.   
     
     
         20 . A method for continuous papermaking, comprising:
 discharging a suspension of cellulose fibers in water onto a moving forming wire to yield a web on the forming wire;   draining water from the web through the forming wire;   passing the web over a dewatering device to downwardly remove water from the web; and   prior to passing the web over the dewatering device. applying on top of the web a mixture comprising microfibrillated cellulose and a carrier.