Process for producing tissue paper

Abstract

The invention relates to a process for producing a tissue web, which is produced from a stock suspension including fibers. In this case, the volume and the tearing length are to be improved with the lowest possible freeness by the stock suspension containing lignocellolosic fibrous material made of wood or annual plants which has a tearing length of more than 6.5 km at 12°SR or a tearing length of more than 8.0 km at 15°SR and a lignin content of at least 15%, based on the oven-dry fibrous material, for coniferous wood in the unbleached state, or a tearing length of more than 4.5 km at 20°SR and a lignin content of at least 12%, based on the oven-dry fibrous material, for deciduous wood in the unbleached state, or a tearing length of more than 3.5 km at 20°SR and a lignin content of at least 10%, based on the oven-dry fibrous material, for annual plants in the unbleached state.

1 . A process for producing a tissue web, said process comprising the steps of:
 producing the web from a stock suspension including a plurality of fibers, wherein said stock suspension includes lignocellulosic fibrous material made of one of wood and annual plants which has one of (1) one of a tearing length of more than 6.0 km at 12°SR and a tearing length of more than 7.5 km at 15°SR and a lignin content of at least 15%, based on an oven-dry fibrous material, for a coniferous wood in an unbleached state, (2) a tearing length of more than 4.5 km at 20°SR and a lignin content of at least 12%, based on said oven-dry fibrous material, for a deciduous wood in said unbleached state, and (3) a tearing length of more than 3.5 km at 20°SR and a lignin content of at least 10%, based on said oven-dry fibrous material, for said annual plants in said unbleached state.   
   
   
       2 . The process as claimed in  claim 1 , wherein said plurality of fibers forms a fibrous material, wherein said lignin content of unbleached said fibrous material (1) in the case of said coniferous wood is one of at least 15%, at least 18%, and at least 21%, of said oven-dry fibrous material, (2) in the case of said deciduous wood is one of at least 12%, at least 14%, and at least 16%, of said oven-dry fibrous material, and (3) in the case of said annual plants is one of at least 10%, at least 12%, and at least 19%, of said oven-dry fibrous material. 
   
   
       3 . The process as claimed in  claim 1 , wherein said tearing length for a coniferous wood fiber stock at 12°SR is one of greater than 7 km, greater than 7.5 km, and greater than 8 km. 
   
   
       4 . The process as claimed in  claim 1 , wherein said tearing length for a coniferous wood fiber stock at 15°SR is one of greater than 9 km, greater than 9.5 km, and greater than 10 km. 
   
   
       5 . The process as claimed in  claim 1 , wherein said tearing length for a deciduous wood fiber stock at a freeness of 20°SR is one of greater than 6 km, greater than 7 km, and greater than 7.5 km. 
   
   
       6 . The process as claimed in  1 , wherein said tearing length for an annual plant fiber stock at 20°SR is one of greater than 3.5 km, greater than 4 km, and greater than 4.5 km. 
   
   
       7 . A process for producing a tissue web, said process comprising the steps of:
 producing the web from a stock suspension including a plurality of fibers, wherein said stock suspension includes lignocellulosic fibrous material made of one of wood or annual plants which has one of (1) a tearing length of more than 7.5 km at 15°SR and a lignin content of at least 13%, based on an oven-dry fibrous material, for a coniferous wood in a bleached state, (2) a tearing length of more than 5.0 km at 20°SR and a lignin content of at least 10%, based on said oven-dry fibrous material, for a deciduous wood in said bleached state, and (3) a tearing length of more than 5.5 km at 20°SR and a lignin content of at least 10%, based on said oven-dry fibrous material, for said annual plants in said bleached state.   
   
   
       8 . The process as claimed in  claim 7 , wherein said tearing length for a coniferous wood fiber stock at 15°SR is one of greater than 9 km and greater than 10 km. 
   
   
       9 . The process as claimed in  claim 7 , wherein said tearing length for a deciduous wood fiber stock at 20°SR is greater than 5.5 km. 
   
   
       10 . The process as claimed in  claim 7 , wherein said tearing length for an annual plant fiber stock at 20°SR is one of greater than 4 km, greater than 4.5 km, and greater than 5 km. 
   
   
       11 . The process as claimed in  claim 7 , wherein said stock suspension contains only said lignocellulosic fibrous material. 
   
   
       12 . The process as claimed in  claim 7 , wherein said stock suspension is only partly formed from said lignocellulosic fibrous material. 
   
   
       13 . The process as claimed in  claim 12 , wherein said plurality of fibers forms a fibrous material, wherein one of between 20 and 80% and between 30 and 50% of said fibrous material of said stock suspension is formed from said lignocellulosic fibrous material. 
   
   
       14 . The process as claimed in  claim 7 , wherein, during a dewatering step, the tissue web is led between an upper structured and permeable belt and between a lower permeable belt, pressure being exerted on said upper belt, the tissue web, and said lower belt along a dewatering section. 
   
   
       15 . The process as claimed in  claim 14 , wherein, during said dewatering step, a gas flows firstly through said upper belt, then the tissue web, and then said lower belt. 
   
   
       16 . The process as claimed in  claim 15 , wherein, during said dewatering step, an arrangement including said upper belt, the tissue web, and said lower belt is led, at least in some sections of said arrangement, between a press belt under tension and a smooth surface, said press belt acting on said upper belt and said lower belt being supported on said smooth surface. 
   
   
       17 . The process as claimed in  claim 16 , wherein said gas flows through said arrangement, at least in some sections of said arrangement in said dewatering section. 
   
   
       18 . The process as claimed in  claim 17 , wherein a gas flow of said gas through the tissue web is about 150 m 3  per minute and meter length along said dewatering section. 
   
   
       19 . The process as claimed in  claim 16 , wherein said press belt is under a tension of one of at least 30 kN/m, at least 60 kN/m, and 80 kN/m. 
   
   
       20 . The process as claimed in  claim 16 , wherein said press belt has an open area of more than 50% and a contact area of at least 15%. 
   
   
       21 . The process as claimed in  claim 16 , wherein said smooth surface is formed by a circumferential surface of a roll. 
   
   
       22 . The process as claimed in  claim 21 , wherein a gas flow of said gas is formed by a suction zone in said roll. 
   
   
       23 . The process as claimed in  claim 15 , wherein a gas flow of said gas is produced by a positive pressure hood arranged above said upper belt. 
   
   
       24 . A process for producing a stock suspension including a plurality of fibers for use in producing a tissue web, said process comprising the steps of:
 providing that at least a proportion of the stock suspension is produced from one of wood and annual plants having a lignin content of at least 15% for a coniferous wood, at least 12% for a deciduous wood, and at least 10% for said annual plants, in each case based on an oven-dry fiber stock, by the following steps:
 producing a chemical solution one of with more than 5% of chemicals (calculated as NaOH) for coniferous wood, with more than 3.5% of chemicals (calculated as NaOH) for deciduous wood, and with more than 2.5% of chemicals (calculated as NaOH) for annual plants, in each case based on an oven-dry quantity of said wood; 
 mixing said chemical solution with one of said wood and said annual plants in a predefined liquor ratio; 
 heating said chemical solution and one of said wood and said annual plants to a temperature above room temperature; and then one of: 
 (1) removing a free-flowing said chemical solution and digesting one of said wood and said annual plants in a vapor phase, and 
 (2) digesting one of said wood and said annual plants in a liquid phase and separating said free-flowing chemical solution and one of said wood and said annual plants. 
   
   
   
       25 . The process as claimed in  claim 24 , wherein a fibrous material is produced one of (1) which has a lignin content of one of at least 15%, at least 18%, at least 21%, and at least 24%, based on an oven-dry fibrous material, for said coniferous wood, (2) which has a lignin content of one of at least 14%, at least 16%, and at least 18%, based on said oven-dry fibrous material, for said deciduous wood, and (3) which has a lignin content of one of at least 10%, at least 12%, and at least 19%, based on oven-dry fibrous material, for said annual plants. 
   
   
       26 . The process as claimed in  claim 24 , wherein a quinine component is used to produce said chemical solution. 
   
   
       27 . The process as claimed in  claim 24 , wherein, in order to digest said coniferous wood, one of at most 15% of said chemicals and between 9 and 11% of said chemicals are used. 
   
   
       28 . The process as claimed in  claim 24 , wherein, in order to digest said deciduous wood, one of at most 10% of said chemicals, between 4 and 10% of said chemicals, and between 6 and 9% of said chemicals are used. 
   
   
       29 . The process as claimed in  claim 24 , wherein, in order to digest said annual plants, one of at most 10% of said chemicals and between 3 and 10% of said chemicals are used. 
   
   
       30 . The process as claimed in  claim 24 , wherein, in order to produce said chemical solution, sulfites and sulfides are used, one of individually and in a mixture. 
   
   
       31 . The process as claimed in  claim 30 , wherein, in order to produce said chemical solution, at least one of an acid, an alkaline component, sulfur dioxide, sodium hydroxide, and a carbonate is used. 
   
   
       32 . The process as claimed in  claim 24 , wherein, for purposes of digestion, an alkaline component and an acid component are used, the acid component being SO 2 , a ratio of said alkaline component:SO 2  being set one of in a range from 5:1 to 1.6:1 and at 2:1. 
   
   
       33 . The process as claimed in  claim 24 , wherein the process is carried out at a pH of one of between 6 and 11, between 7 and 11, and between 7.5 and 10. 
   
   
       34 . The process as claimed in  claim 24 , wherein a liquor ratio of said wood:said chemical solution of one of between 1:1.5 and 1:6 and between 1:2 and 1:4 is set. 
   
   
       35 . The process as claimed in  claim 24 , wherein said chemical solution and one of said wood and said annual plants are heated to up to one of 130° C., 120° C., and 110° C. 
   
   
       36 . The process as claimed in  claim 24 , wherein one of said wood and said annual plants are heated for up to one of 120 minutes, 60 minutes, 30 minutes, and 10 minutes. 
   
   
       37 . The process as claimed in  claim 24 , wherein one of said wood and said annual plants and said chemical solution are heated for up to one of 120 minutes, 60 minutes, 30 minutes, and 10 minutes. 
   
   
       38 . The process as claimed in  claim 24 , wherein one of said wood and said annual plants are digested at temperatures one of between 120° C. and 190° C., between 150° C. and 180° C., and between 160° C. and 170° C. 
   
   
       39 . The process as claimed in  claim 24 , wherein a digestion of one of said wood and said annual plants lasts for up to one of 180 minutes, 90 minutes, 60 minutes, 30 minutes, and 2 minutes. 
   
   
       40 . The process as claimed in  claim 39 , wherein a digestion time is chosen as a function of said liquor ratio. 
   
   
       41 . The process as claimed in  claim 24 , wherein a consumption of said chemicals during a digestion is up to one of 80%, 60%, 40%, 20%, and 10% of said chemicals put in at a start of said digestion. 
   
   
       42 . The process as claimed in  claim 24 , wherein a composition of said chemical solution that is one of removed and separated is registered and subsequently adjusted to a prescribed composition for a renewed use for producing a plurality of fibers. 
   
   
       43 . The process as claimed in  claim 24 , wherein said chemical solution liberated after defibering of digested lignocellulosic material is removed and supplied to further use. 
   
   
       44 . The process as claimed in  claim 24 , wherein said chemical solution liberated after defibering and refining of digested lignocellulosic material is removed and supplied to further use.