Machine And Method For Producing A Fibrous Web

Abstract

A process for producing a web ( 1 ) of paper, cardboard or other fibrous material using a device ( 28 ) for applying starch is characterised in that the dry content of the web ( 1 ) of fibrous material is of less than 70% while the starch becomes adhesive, and in that the web ( 1 ) of fibrous material is heated to a temperature which is sufficient for causing the starch to become adhesive.

1 . Method for producing a paper web, paperboard web or other fibrous web ( 1 ) using an apparatus ( 28 ) for applying starch, wherein during the gelatinizing of the starch the dry content of the fibrous web ( 1 ) is less than 70%, and wherein the fibrous web ( 1 ) is heated to a temperature which is sufficient for the starch to gelatinize. 
     
     
         2 . Method according to  claim 1 , wherein the water required for gelatinizing the starch is made available through the water content of the fibrous web ( 1 ). 
     
     
         3 . Method according to  claim 1 , wherein the evaporation and vaporization of water contained in the fibrous web ( 1 ) is obstructed or prevented during the gelatinizing of the fibrous web ( 1 ). 
     
     
         4 . Method according to  claim 1 , wherein the surface of the fibrous web ( 1 ) is covered during the gelatinizing by a skin ( 3 ,  5 ;  10 ,  11 ;  14 ,  15 ;  18 ,  19 ;  32 ) with a high resistance to diffusion while heat is supplied simultaneously to the fibrous web ( 1 ). 
     
     
         5 . Method according to  claim 1 , wherein the surface of the fibrous web ( 1 ) is covered during the gelatinizing by a skin ( 3 ,  5 ;  10 ,  11 ;  14 ,  15 ;  18 ,  19 ;  32 ) which is impermeable to steam and/or air while heat is supplied simultaneously to the fibrous web ( 1 ). 
     
     
         6 . Method according to  claim 3 , wherein the surroundings of the fibrous web ( 1 ) are created with a very high relative humidity. 
     
     
         7 . Method according to  claim 1 , wherein the method is performed downstream from the press section or at the beginning of the drying section ( 2 ,  7 ). 
     
     
         8 . Method according to  claim 1 , wherein the fibrous web ( 1 ) is heated to the gelatinizing temperature in the mesh section or in the press section. 
     
     
         9 . Method according to  claim 1 , wherein the gelatinizing begins at a dry content of the fibrous web ( 1 ) of more than 15%. 
     
     
         10 . Method according to  claim 1 , wherein the gelatinizing is triggered and supported by the input of heat, whereby the fibrous web ( 1 ) is heated by contact with at least one of heated surfaces steam, or radiation. 
     
     
         11 . Method according to  claim 1 , wherein the temperature is increased during the gelatinizing by external pressure applied to the fibrous web ( 1 ). 
     
     
         12 . Method according to  claim 11 , wherein the external pressure is built up by at least one of meshes and/or belts ( 3 ,  5 ;  10 ,  11 ;  14 ,  15 ;  18 ,  19 ;  32 ), hydrostatic or pneumatic means, a drying cylinder ( 8 ) covered by a pressure hood ( 9 ), a pulse drying unit, and combinations thereof. 
     
     
         13 . Method according to  claim 1 , wherein the gelatinizing takes place in a temperature range between 50 and 150° C., preferably in a range between 60 and 130° C. 
     
     
         14 . Method according to  claim 13 , wherein a maximum temperature of between 60 and 150° C., preferably between 70 and 130° C., is reached during the gelatinizing process. 
     
     
         15 . Method according to  claim 1 , wherein the time available for the gelatinizing amounts to between 5 and 80% of the total dwell time in the drying section, preferably between 5 und 50%. 
     
     
         16 . Machine for producing a fibrous web ( 1 ) using a method according to  claim 1 , wherein in the drying section ( 2 ,  7 ) there is at least one of a skin ( 3 ,  5 ;  10 ,  11 ;  14 ,  15 ;  18 ,  19 ;  32 ) with a high diffusion resistance or a skin ( 3 ,  5 ;  10 ,  11 ;  14 ,  15 ;  18 ,  19 ;  32 ) impermeable to steam or air, and wherein the fibrous web ( 1 ) can be passed through the drying section ( 2 ,  7 ) together with the skin ( 3 ,  5 ;  10 ,  11 ;  14 ,  15 ;  18 ,  19 ;  32 ). 
     
     
         17 . Machine according to  claim 16 , wherein the machine comprises a drying cylinder ( 8 ) covered by a pressure hood ( 9 ), whereby the fibrous web ( 1 ) can be passed through between the drying cylinder ( 8 ) and the pressure hood ( 9 ) together with at least one skin ( 10 ). 
     
     
         18 . Machine according to  claim 16 , wherein the skin is heated. 
     
     
         19 . Machine according to  claim 16 , wherein the machine comprises at least one steam blower box ( 12 ,  13 ) on the upper and/or lower side of the fibrous web ( 1 ). 
     
     
         20 . Machine according to  claim 16 , wherein the machine comprises a pulse drying unit or a radiant heater ( 16 ,  17 ). 
     
     
         21 . Machine according to  claim 16 , wherein the machine comprises at least one heatable pressure hood ( 20 ,  24 ). 
     
     
         22 . Machine according to  claim 21 , wherein the at least one pressure hood ( 20 , 24 ) comprises a multiplicity of chambers ( 21 ,  23 ;  26 ,  27 ) in which, per chamber ( 21 ,  23 ;  26 ,  27 ), the pressure can be lowered gradually in steps in the web running direction of the fibrous web ( 1 ). 
     
     
         23 . Machine according to  claim 16 , wherein the machine comprises a press nip ( 31 ) with a heated press roller ( 29 ) and/or a heated press shoe ( 33 ) and/or a heated skin carried along on the press shoe side. 
     
     
         24 . Machine according to  claim 16 , wherein the fibrous web ( 1 ) can be passed through the drying section ( 2 ,  7 ) underneath the skin ( 3 ,  5 ;  10 ,  11 ;  14 ,  15 ;  18 ,  19 ;  32 ). 
     
     
         25 . Machine according to  claim 16 , wherein the fibrous web ( 1 ) can be passed through the drying section ( 2 ,  7 ) sandwiched between two skins ( 3 ,  5 ;  10 ,  11 ;  14 ,  15 ;  18 ,  19 ;  32 ) impermeable to steam or air or with a high resistance to diffusion. 
     
     
         26 . Method according to  claim 6 , wherein the surroundings of the fibrous web ( 1 ) are created through a low level of air exchange. 
     
     
         27 . Method according to  claim 6 , wherein the surroundings of the fibrous web ( 1 ) are created through use of at least one steam blower box ( 12 ,  13 ). 
     
     
         28 . Method according to  claim 10 , wherein the fibrous web ( 1 ) is heated by contact with at least one of the circumferential surface of a drying cylinder ( 4 ), a heated belt or a heated mesh. 
     
     
         29 . Method according to  claim 10 , wherein the fibrous web ( 1 ) is heated by steam from a steam blower box ( 12 ,  13 ). 
     
     
         30 . Method according to  claim 10 , wherein the fibrous web ( 1 ) is heated by radiation in the IR or NIR range. 
     
     
         31 . Method according to  claim 10 , wherein the fibrous web ( 1 ) is heated by gas-heated or electrically heated radiators ( 16 ,  17 ), microwaves, electroinductive heating or a combination of these heat sources. 
     
     
         32 . Method according to  claim 1 , wherein the gelatinizing takes place in a temperature range between 60 and 130° C. 
     
     
         33 . Method according to  claim 13 , wherein a maximum temperature of between 70 and 130° C. is reached during the gelatinizing process. 
     
     
         34 . Method according to  claim 1 , wherein the time available for the gelatinizing amounts to between 5 and 50% of the total dwell time in the drying section.