Method for producing a multi layer fiber web from cellulose fibers

Abstract

A process for the production of a multilayer fiber web from cellulose fibers by separately feeding at least two different fiber suspensions and water into a multilayer headbox, in which they are separated by separating elements from one another and from water and, after leaving the nozzle mouth of the headbox, reach an apparatus on which a web is formed, the water being transported in such a way that, after emerging from the nozzle mouth, it reaches the web-forming apparatus in the form of a layer between two layers of fiber suspensions and thus counteracts mixing of the different fiber suspensions, wherein, for improving the retention, drainage and formation, at least one retention aid and/or at least one drainage aid are metered into the fiber suspensions and/or into the water fed in.

1 . A process for the production of a multilayer fiber web from cellulose fibers by separately feeding in each case at least two different fiber suspensions and water into a multilayer headbox, in which they are separated by separating elements from one another and from water fed in and, after leaving the nozzle mouth of the headbox, reach a drainage apparatus on which a multilayer fiber web is formed, the water transported in such a way that, after emerging from the nozzle mouth, it reaches the web-forming apparatus in the form of a layer between two layers of fiber suspensions and thus counteracts mixing of the different fiber suspensions, wherein at least one retention aid, at least one drainage aid, or a combination thereof is metered into at least one of the fiber suspensions the water fed in. 
   
   
       2 . The process according to  claim 1 , wherein an aqueous solution of at least one retention aid, at least one drainage aid, or a combination thereof is metered into the paper stock stream at a point which is located after the last shearing stage of the paper stock and before the nozzle mouth of the headbox. 
   
   
       3 . The process according to  claim 1 , wherein the same retention aid is added to all streams of fiber suspensions and it is metered in such a way that at least two streams of fiber suspensions comprise a different concentration of this retention aid. 
   
   
       4 . The process according to  claim 1 , wherein at least two retention aids differing from one another are metered into at least two streams of fiber suspensions. 
   
   
       5 . The process according to  claim 4 , wherein at least two streams of fiber suspensions comprise a different concentration of retention aid. 
   
   
       6 . The process according to  claim 1 , wherein an aqueous solution of a retention aid and an aqueous dispersion of at least one filler are metered separately from one another or as a mixture into the paper stock. 
   
   
       7 . The process according to  claim 1 , wherein an aqueous solution of a retention aid and an aqueous dispersion of at least one filler are metered separately from one another or as a mixture into at least one stream of the water fed in. 
   
   
       8 . The process according to  claim 1 , wherein an aqueous dispersion of a filler is metered into at least one stream of the fiber suspension and wherein the water fed in comprises at least one retention aid. 
   
   
       9 . The process according to  claim 1 , wherein at least one retention aid is present in combination with at least one drainage aid. 
   
   
       10 . The process according to  claim 1 , wherein at least one retention aid is present in combination with a fixing agent. 
   
   
       11 . The process according to  claim 1 , wherein at least one retention aid is present in combination with an engine size. 
   
   
       12 . The process according to  claim 1 , wherein at least one retention aid is present in combination with a paper strength agent. 
   
   
       13 . The process according to  claim 1 , wherein the retention aid is at least one member selected from the group consisting of a cationic polymeric organic compound, an anionic polymeric organic compound, a nonionic polymeric organic compound an amphoteric polymeric organic compound, and a microparticle system. 
   
   
       14 . The process according to  claim 1 , wherein the retention aid is at least one member selected from the group consisting of a polyacrylamide, a polymethacrylamide a polymer comprising vinylamine units and a microparticle system. 
   
   
       15 . The process according to  claim 1 , wherein at least one retention aid is a polymer comprising vinylamine units. 
   
   
       16 . The process according to  claim 1 , wherein the drainage aid is a polymer comprising ethylenimine units. 
   
   
       17 . The process according to  claim 1 , wherein at least one of a polyacrylamide and a polymer comprising vinylamine units are metered into at least one stream of a fiber suspension, and a polymer comprising ethylenimine units is metered into a stream of another fiber suspension. 
   
   
       18 . The process according to  claim 1 , wherein a three-layer fiber web is produced,
 (a) a retention aid selected from the group consisting of a polyacrylamide, a polymethacrylamide, a polymer comprising vinylamine units, a microparticle system, and a mixture thereof is metered into the stream of the fiber suspension which forms the top of the fiber web,   (b) a drainage aid of a polymer comprising ethylenimine units, a retention aid selected from the group consisting of a polymer comprising vinylamine units, a cationic polyacrylamide, an anionic polyacrylamide, a nonionic polyacrylamide, a amphoteric polyacrylamide, a polymethacrylamide, and mixtures thereof, or a combination thereof is metered into the stream of the fiber suspension which forms the middle layer of the fiber web, and   (c) a retention aid selected from the group consisting of a polyacrylamide, a polymethacrylamide, a polymer comprising vinylamine units, a microparticle system, and a mixture thereof is metered into the stream of the fiber suspension which forms the bottom of the fiber web.   
   
   
       19 . The process according to  claim 1 , wherein a three-layer fiber web is produced,
 (a) a polymer comprising vinylamine units is metered as a retention aid into the stream of the fiber suspension which forms the top of the fiber web,   (b) a polymer comprising ethylenimine units is metered as a drainage aid into the stream of the fiber suspension which forms the middle layer of the fiber web, and   (c) a polymer comprising vinylamine units is metered as a retention aid into the stream of the fiber suspension which forms the bottom of the fiber web.   
   
   
       20 . The process according to  claim 1 , wherein the stream of water fed in comprises at least one retention aid and at least one thickener. 
   
   
       21 . The process according to  claim 1 , wherein the stream of water fed in comprises at least one retention aid and at least one binder. 
   
   
       22 . The process according to  claim 1 , wherein the stream of water fed in comprises at least one suspended filler. 
   
   
       23 . The process according to  claim 1 , wherein the stream of water fed in comprises at least one retention aid, a fixing agent, an engine size, a strength agent, a thickener or a combination thereof. 
   
   
       24 . The process according to  claim 1 , wherein an unstabilized engine size is metered into the stream of water fed in. 
   
   
       25 . The process according to  claim 1 , wherein a surface-active agent is present for improving the drainage.