Method for the production of tissue paper

Abstract

A method for the production of a tissue paper web, which is produced from a pulp suspension comprised of fibers, the pulp suspension having a refining degree of less than 21° SR and being of such condition that it is possible to produce from said pulp suspension a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) whose breaking length measured according to TAPPI 220 and TAPPI 494 at at least a specific refining degree (RD specific ) is greater than or equal to the value resulting from 0.55(km/SR)*(RD specific −10° SR), whereby the specific refining degree is selected from a refining range from 15° SR to less than 21° SR, in particular 15° SR to 19° SR.

1 . A method for the production of a tissue paper web, which is produced from a pulp suspension comprised of fibers, said pulp suspension having a refining degree of less than 21° SR and being of such condition that it is possible to produce from said pulp suspension a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) whose breaking length measured according to TAPPI 220 and TAPPI 494 at at least a specific refining degree (RD specific ) is selected from a refining range from 15° SR to less than 21° SR, is greater than or equal to the value resulting from 0.55(km/SR)*(RD specific −10° SR).  
   
   
       2 . The method according to  claim 1 , wherein the pulp suspension used is of such condition that it is possible to produce from said suspension a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) whose breaking length measured according to TAPPI 220 and TAPPI 494 at a specific refining degree (RD specific ) from 15° SR to 19° SR, is greater than or equal to the value which results from 0.55(km/SR)*(RD specific −10° SR).  
   
   
       3 . The method according to  claim 2 , wherein the pulp suspension used is of such condition that it is possible to produce from said suspension a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) whose breaking length measured according to TAPPI 220 and TAPPI 494 at a specific refining degree (RD specific ) from 15° SR to 17° SR, is greater than or equal to the value which results from 0.55(km/SR)*(RD specific −10° SR).  
   
   
       4 . The method according to  claim 1 , wherein the pulp suspension used has a refining degree of 19° SR or less.  
   
   
       5 . The method according to  claim 1 , wherein it is possible to produce from the pulp suspension at a maximum refining degree of 17° SR a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) with a breaking length of 4.3 km or more, measured according to TAPPI 220 and TAPPI 494.  
   
   
       6 . The method according to  claim 5 , wherein it is possible to produce from the pulp suspension at a maximum refining degree of 17° SR a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) with a breaking length of 4.0 km or more, measured according to TAPPI 220 and TAPPI 494.  
   
   
       7 . The method according to  claim 1 , wherein the pulp suspension used comprises a suspension fraction which was produced from a low-consistency feed pulp suspension of high strength with a consistency of less than 10%.  
   
   
       8 . The method according to  claim 7 , wherein the pulp suspension used comprises a suspension fraction which was produced from a low-consistency feed pulp suspension of high strength with a consistency of less than 5%.  
   
   
       9 . The method according to  claim 7 , wherein the suspension fraction has a refining degree of 15° SR or more and was produced by at least one refining pass from the low-consistency feed pulp suspension of high strength at a refining degree of less than 15° SR.  
   
   
       10 . The method according to  claim 9 , wherein from the low-consistency feed pulp suspension of high strength it is possible to produce a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) whose breaking length measured according to TAPPI 220 and TAPPI 494 at a refining degree of 15° SR is greater than 3.0 km.  
   
   
       11 . The method according to  claim 10 , wherein the pulp suspension used comprises a suspension fraction which was produced from a high-consistency feed pulp suspension of low strength with a consistency of 20% or more.  
   
   
       12 . The method according to  claim 11 , wherein the pulp suspension used comprises a suspension fraction which was produced from a high-consistency feed pulp suspension of low strength with a consistency of 20 to 40%.  
   
   
       13 . The method according to  claim 12 , wherein the pulp suspension used comprises a suspension fraction which was produced from a high-consistency feed pulp suspension of low strength with a consistency of 25 to 35%.  
   
   
       14 . The method according to  claim 11 , wherein the suspension fraction has a refining degree of 15° SR or more and was produced by at least one refining pass from the high-consistency feed pulp suspension of low strength at a refining degree of less than 15° SR.  
   
   
       15 . The method according to  claim 14 , wherein the high-consistency feed suspension of low strength is produced from a low-consistency feed suspension of low strength through concentration of the same.  
   
   
       16 . The method according to  claim 15 , wherein from the low-consistency feed suspension of low strength it is possible to produce a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) whose breaking length measured according to TAPPI 220 and TAPPI 494 at a refining degree of 15° SR is less than or equal to 3.0 km.  
   
   
       17 . The method according to  claim 1 , wherein the fiber fraction of the pulp suspension is comprised of cellulose for at least 60% or more.  
   
   
       18 . The method according to  claim 17 , wherein the fiber fraction of the pulp suspension is comprised of cellulose for at least 80% or more.  
   
   
       19 . The method according to  claim 18 , wherein the fiber fraction of the pulp suspension is comprised of cellulose for at least 100% or more.  
   
   
       20 . The method according to  claim 1 , wherein the fibers of the pulp suspension at a refining degree of 17° SR have a water retention value of 1.5 g/g or less, measured according to TAPPI UM 256.  
   
   
       21 . The method according to  claim 20 , wherein the fibers of the pulp suspension at a refining degree of 17° SR have a water retention value of 1.4 g/g or less, measured according to TAPPI UM 256.  
   
   
       22 . The method according to  claim 1 , wherein the pulp suspension used comprises softwood and/or hardwood.  
   
   
       23 . The method according to  claim 22 , wherein the fiber fraction of the pulp suspension used can be comprised of around 30% softwood and around 70% hardwood.  
   
   
       24 . The method according to  claim 23 , wherein the fiber fraction of the pulp suspension used can be comprised of around 70% softwood and around 30% hardwood.  
   
   
       25 . The method according to  claim 24 , wherein the fiber fraction of the pulp suspension used can be comprised of around 100% softwood and around 0% hardwood.  
   
   
       26 . The method according to  claim 1 , wherein a tissue paper web is produced and comprises regions that are more intensively compressed than other regions during production.  
   
   
       27 . The method according to  claim 1 , wherein the tissue paper web is formed from the pulp suspension on a 3-dimensionally structured mesh.  
   
   
       28 . The method according to  claim 27 , wherein the side of the structured mesh facing the tissue paper web comprises depressed regions and raised regions relative to the depressed regions.  
   
   
       29 . The method according to  claim 28 , wherein the tissue paper web is formed in the depressed and raised regions of the structured mesh.  
   
   
       30 . The method according to  claim 29 , wherein the structured mesh comprises a TAD mesh or a DSP mesh.  
   
   
       31 . The method according to  claim 1 , wherein the tissue paper web is conveyed in a dewatering step between an upper structured and permeable skin and a lower permeable skin, whereby pressure is exerted on the upper skin, the tissue paper web and the lower skin during the dewatering step along a dewatering section.  
   
   
       32 . The method according to  claim 31 , wherein the side of the structured skin facing the tissue paper web comprises depressed regions and raised regions relative to the depressed regions.  
   
   
       33 . The method according to  claim 32 , wherein the tissue paper web is compressed less intensively in the depressed regions than in the raised regions.  
   
   
       34 . The method according to  claim 31 , wherein the upper structured and permeable skin is a structured mesh and the lower permeable skin is a felt.  
   
   
       35 . The method according to  claim 31 , wherein a compressibility of the upper skin is less than that of the lower skin.  
   
   
       36 . The method according to  claim 31 , wherein a dynamic rigidity (K), as a measure for the compressibility of the upper skin, is 3000 N/mm or more.  
   
   
       37 . The method according to  claim 36 , wherein the dynamic rigidity (K), as a measure for the compressibility of the lower skin, is 100,000 N/mm or less.  
   
   
       38 . The method according to  claim 37 , wherein the dynamic rigidity (K), as a measure for the compressibility of the lower skin, is 90,000 N/mm or less.  
   
   
       39 . The method according to  claim 38 , wherein the dynamic rigidity (K), as a measure for the compressibility of the lower skin, is 70,000 N/mm or less.  
   
   
       40 . The method according to  claim 31 , wherein a G modulus, as a measure for the elasticity of the lower skin, is 2 N/mm 2  or more.  
   
   
       41 . The method according to  claim 31 , wherein a permeability of the lower skin is 80 cfm or less.  
   
   
       42 . The method according to  claim 41 , wherein a permeability of the lower skin is 40 cfm or less.  
   
   
       43 . The method according to  claim 41 , wherein a permeability of the lower skin is 25 cfm or less.  
   
   
       44 . The method according to  claim 31 , wherein in the dewatering step first the upper skin is charged with gas, then the tissue paper web and finally the lower skin.  
   
   
       45 . The method according to  claim 31 , wherein the arrangement of upper skin, tissue paper web and lower skin is conveyed during the dewatering step at least in some areas along the dewatering section between a tensioned press belt and a smooth surface, whereby the press belt acts on the upper skin and the lower skin rests on the smooth surface.  
   
   
       46 . The method according to  claim 31 , wherein the arrangement of upper skin, tissue paper web and lower skin is charged with a gas flow at least in some areas in the region of the dewatering section.  
   
   
       47 . The method according to  claim 46 , wherein the gas flow through the tissue paper web amounts to approx. 150 m 3  per minute and meter length along the dewatering section.  
   
   
       48 . The method according to  claim 45 , wherein the press belt is under a tension of at least 30 kN/m, preferably at least 60 kN/m or 80 kN/m.  
   
   
       49 . The method according to  claim 45 , wherein the press belt has a spiralized structure.  
   
   
       50 . The method according to  claim 45 , wherein the press belt has a woven structure.  
   
   
       51 . The method according to  claim 45 , wherein the press belt has an open area of at least 25% and a contact area of at least 10% of its total area facing the upper skin.  
   
   
       52 . The method according to  claim 51 , wherein the press belt has an open area of between 75% and 85% and a contact area of between 15% and 25% of its total area facing the upper skin.  
   
   
       53 . The method according to  claim 51 , wherein the press belt has an open area of between 68% and 76% and a contact area of between 24% and 32% of its total area facing the upper skin.  
   
   
       54 . The method according to  claim 51 , wherein the press belt has an open area of between 51% and 62% and a contact area of between 38% and 49% of its total area facing the upper skin.  
   
   
       55 . The method according to  claim 51 , wherein the press belt has an open area of 50% or more and a contact area of 50% or more of its total area facing the upper skin.  
   
   
       56 . The method according to  claim 45 , wherein the smooth surface is formed by the circumferential surface of a roller.  
   
   
       57 . The method according to  claim 56 , wherein the gas flow is generated by a suction zone in the roller.  
   
   
       58 . The method according to  claim 57 , wherein the suction zone has a length of between 200 mm and 2500 mm.  
   
   
       59 . The method according to  claim 58 , wherein a vacuum in the suction zone amounts to between −0.2 bar and −0.8 bar.  
   
   
       60 . The method according to  claim 59 , wherein the gas flow is generated by a pressure hood arranged above the upper skin.  
   
   
       61 . The method according to  claim 31 , wherein the tissue paper web leaves the dewatering section with a dry content of between 25% to 55%.  
   
   
       62 . The method according to  claim 31 , wherein a structured mesh in the formation of the tissue paper is the same mesh as in the dewatering step.  
   
   
       63 . The method according to  claim 62 , wherein after the dewatering step the tissue paper web is conveyed together with the structured skin of the dewatering step through a press nip in a further dewatering step.  
   
   
       64 . The method according to  claim 63 , wherein the tissue paper web in the press nip is arranged between the structured and permeable skin and a smooth roller surface.  
   
   
       65 . The method according to  claim 63 , wherein the depressed and by comparison relatively raised areas of the structured and permeable skin are constructed and arranged in relation to each other such that only 35% or less of the tissue paper web is pressed in the press nip.  
   
   
       66 . The method according to  claim 65 , wherein the depressed and by comparison relatively raised areas of the structured and permeable skin are constructed and arranged in relation to each other such that only 25% or less of the tissue paper web is pressed in the press nip.  
   
   
       67 . The method according to  claim 65 , wherein the press nip is a shoe press nip.  
   
   
       68 . The method according to  claim 63 , wherein the press nip is formed between a roller surface and a suction press roller.  
   
   
       69 . The method according to  claim 68 , wherein the roller surface is formed by the circumferential surface of a Yankee drying cylinder.  
   
   
       70 . The method according to  claim 69 , wherein the tissue paper web is conveyed together with the structured skin around an evacuated deflector roller, whereby the structured skin is arranged between the tissue paper web and the evacuated deflector roller.  
   
   
       71 . A method for the production of a pulp suspension comprised of fibers, with which at least one suspension fraction is produced with the following steps: 
 providing a high-consistency feed pulp suspension comprised of fibers and having a consistency of more than 20% and a refining degree of less than 15° SR; and    refining the high-consistency feed pulp suspension to a refining degree of 15° SR or more to obtain the suspension fraction.    
   
   
       72 . The method according to  claim 71 , wherein the suspension fraction for producing the pulp suspension is mixed with another suspension fraction, whereby the other suspension fraction is refined from a low-consistency feed pulp suspension with a consistency of less than 10%.  
   
   
       73 . The method according to  claim 72 , wherein the suspension fraction for producing the pulp suspension is mixed with a another suspension fraction, whereby the other suspension fraction is refined from a low-consistency feed pulp suspension with a consistency of less than 5%.  
   
   
       74 . The method according to  claim 72 , wherein the suspension fraction produced from a low-consistency feed pulp suspension has a higher refining degree than the suspension fraction produced from a high-consistency feed pulp suspension.  
   
   
       75 . The method according to  claim 74 , wherein the high-consistency feed pulp suspension has a refining degree of 12° SR to 13° SR and the suspension fraction produced therefrom has a refining degree of 15° SR to 19° SR.  
   
   
       76 . The method according to  claim 75 , wherein the high-consistency feed pulp suspension has a refining degree of 12° SR to 13° SR and the suspension fraction produced therefrom has a refining degree of 15° SR to 17° SR.  
   
   
       77 . The method according to  claim 71 , wherein the refining operation is performed several times in succession.  
   
   
       78 . The method according to  claim 71 , wherein the high-consistency feed pulp suspension is refined with a refining energy in the range from 150 kWh to 300 kWh.  
   
   
       79 . The method according to  claim 78 , wherein the high-consistency feed pulp suspension has a consistency in the range from more than 20% to 40%.  
   
   
       80 . The method according to  claim 72 , wherein enzymes are added to the low-consistency feed pulp suspension for refinement.  
   
   
       81 . The method according to  claim 71 , wherein the high-consistency feed suspension has a low strength produced from a low-consistency feed suspension of low strength.  
   
   
       82 . The method according to  claim 81 , wherein the concentration is performed by means of a worm extruder.  
   
   
       83 . The method according to  claim 72 , wherein at least one of enzymes and agents for at least one of increasing the dry strength (dry strength agents) and increasing the wet strength (wet strength agents) are added to the low-consistency feed pulp suspension.  
   
   
       84 . The method according to  claim 83 , wherein the dry strength agent is comprised of carbon methyl cellulose.  
   
   
       85 . The method according to  claim 80 , wherein the enzymes are added to the low-consistency feed suspension at a temperature in the range from 25° C. to 70° C.  
   
   
       86 . The method according to  claim 85 , wherein the enzymes are added to the low-consistency feed suspension with a pH-value in the range from 5 to 8.  
   
   
       87 . The method according to  claim 86 , wherein the enzymes are allowed to work for a period of 1 to 2 hours on the low-consistency feed suspension.  
   
   
       88 . The method according to  claim 87 , wherein the enzymes are added in the pulper.  
   
   
       89 . The method according to  claim 71 , wherein the high-consistency feed pulp suspension is refined at a temperature up to 80° C.  
   
   
       90 . A method for the production of a fibrous web, with a pulp suspension produced by the method according to  claim 76.