EP1749935A2 - Method for making tissue paper - Google Patents

Abstract

The method involves dissolving a dry raw stock, halfstuff and an old paper in a water. The dry raw stock, halfstuff and the old paper are converted into a pumpable state to form a pulp. The pulp is sent to a mixing chest and concentrated in a concentrator (5). The pulp is diluted in a dilution tank with the water. The re-diluted pulp is then sent to a stock chest, where the pulp is mixed in the stock chest with a suspension. The pulp is diluted with a mesh water and sent to a headbox.

Description

This invention relates to a process for the production of tissue paper and to a process for the preparation of a pulp suspension for particular use in the manufacture of tissue paper.

Tissue paper ideally has high absorbency and high water absorption coupled with high tear resistance.

Absorbency and water absorbency are significantly determined by the volume and porosity of the tissue paper.

To increase the volume was already in the prior art in the WO03 / 062528 proposed to press the tissue paper web only zonal during their production, so as to obtain only slightly pressed or unpressed voluminous areas and pressed tear-resistant areas.

The porosity and permeability of the tissue paper are significantly determined by the degree of beating of the fibers in the stock suspension from which the tissue paper is made. In this case, a high freeness causes a high fines content in the suspension, which leads to a low porosity and permeability in the tissue paper web produced.

Furthermore, a high freeness causes a high water retention value for the fibers of the pulp suspension, whereby the tissue paper is poorly drainable in its manufacturing process.

In addition, by a high freeness, ie high fines content, due to too low porosity and permeability, the drainability of the Tissue paper web reduced in their production, resulting in high production speeds, such as, for example, 1200m / minute, often too low dry content. Thus, for example, a certain dry content is required in front of the Yankee drying cylinder in order to prevent lifting of the tissue paper web from the Yankee drying cylinder by evaporation of water from the tissue paper web through its contact with the hot jacket surface of the tissue drying cylinder. This effect is especially pronounced in the case of such tissue paper, which is only partially compressed to increase its absorbency during its production (so-called bulky tissue), since in the non-compressed or only slightly compressed regions the liquid remains particularly stored if the tissue paper is stored too low a porosity and permeability is insufficiently dehydrated.

On the other hand, the tissue paper must be tear-resistant in both the unfinished state and as the final product.

The tear resistance is influenced both by the manufacturing process and by the degree of grinding of the fibers in the stock suspension. To increase tear strength, the tissue paper must be densified in its manufacture, i. be compressed. In order to obtain a high tensile strength, further the fines content must be high. The requirements for tear resistance are in particular the abovementioned requirements for water absorption, absorbency and drainability.

It is the object of the present invention to propose a method for producing a tissue paper web, with which it is possible to produce high-productivity tear-resistant tissue paper with high water absorption and absorbency.

It is further the object of the present invention to propose a method for producing a stock suspension, which in the inventive method for producing a tissue web can be used.

The invention is achieved by a method having the features of patent claim 1 and by a method having the features of patent claim 53.

The process according to the invention for the production of a tissue paper web which is produced from a stock suspension comprising fibers provides that the stock suspension has a freeness of less than 21 ° SR and is such that from the stock suspension a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen ) whose tear length, measured according to TAPPI 220 and TAPPI 494, at least one specific freeness (MW _specific ) is greater than or equal to the value which is 0.55 (km / SR) * (MW _specific -10 ° SR), the specific freeness being selected from a freeness range of 15 ° SR to less than 21 ° SR, especially 15 ° SR to 19 ° SR.

Experiments have shown that, in particular in tissue paper, which is partially compressed more in its production than in other areas sufficient porosity and dewatering are given when the freeness of the fibers in the stock suspension is less than 21 ° SR (Schopper bar). A sufficient tensile strength of the tissue paper web is provided, as experiments have shown, if a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) can be produced from the stock suspension, whose breaking length, measured according to TAPPI 220 and TAPPI 494, at at least one specific degree of grinding ( MW _specific ) is greater than or equal to the value resulting from 0.55 (km / SR) * (MW _specific -10 ° SR), the specific freeness from a freeness range from 15 ° SR to less than 19 ° SR, in particular 15 ° SR to 20 ° SR is selected.

The laboratory sheet produced according to TAPPI 205 SP 95 (Rapid Köthen) has a weight per unit area of 60 g / m ² .

The dependence of the breaking length on the freeness given by the function 0.55 (km / SR) * (MW _specific -10 ° SR) results in a steep increase in the change in the breaking length with a slight increase in the freeness. It has been found that it is precisely such stock suspensions, in which the dependence of the breaking length on the freeness is greater than or equal to the functional dependency shown above, are particularly suitable for the production of tissue paper, in particular such that it is pressed less strongly in regions than in other areas.

Furthermore, it has been found that for the preparation of the stock suspension with the o.g. Properties only a little grinding energy is necessary to achieve the required strength values.

Experiments have shown that a sufficient porosity of the tissue paper produced is given if the pulp suspension has a freeness of less than or equal to 19 ° SR, preferably less than or equal to 17 ° SR. Furthermore, tests have shown that the finished product has sufficient strength and that this can be produced with high productivity, ie high machine speed, when the breaking length of the laboratory blade produced according to TAPPI 205 SP 95 (Rapid Köthen) in a specific degree of grinding (MW _specific ). from 15 ° SR to 19 ° SR, preferably 15 ° SR to 17 ° SR is greater than or equal to the value giving 0.55 (km / SR) * (MG _specific -10 ° SR).

Preferably, the freeness of the stock suspension used is 19 ° SR or less, more preferably 17 ° SR or less. By reducing the freeness, it is also possible to increase the dry content in the process described in the figures to produce a tissue paper web before the drying step on the Yankee drying cylinder by 3-4%.

Experiments have shown that the tissue paper can be produced at a high machine speed, ie 1200 m / min or more, if from the stock suspension at a maximum grinding degree of 17 ° SR a TAPPI 205 SP 95 (Rapid Köthen) having a breaking length of 4.0km or more, preferably 4.3km or more, as measured by TAPPI 220 and TAPPI 494.

Experiments have shown that the stock suspension meets the requirements of porosity, absorbency and tear resistance, especially when the fiber content of the stock suspension for the most part comprises pulp, preferably 60% or more, more preferably 80% or more. Most preferably, the fiber content of the stock suspension is formed from 100% pulp.

Experiments have shown that the tissue paper web can be easily dewatered during its production in order to achieve a satisfactory dry content if the fibers of the stock suspension have a retention value of 1.5 g / g or less, preferably 1, at a freeness of 17 ° SR. 4g / g measured after TAPPI UM 256.

Depending on whether, for example, hygiene paper, so-called toilet paper, or kitchen paper, so-called Towel Paper to be produced by the method according to the invention, the stock suspension used may comprise softwood and / or hardwood alone or in different proportions.

If Toilet Paper is to be produced by the process according to the invention, the fiber content of the pulp suspension used comprises, for example, preferably about 30% softwood and about 70% hardwood.

If it is desired to produce Towel Paper with the method according to the invention, the fiber content of the pulp suspension used comprises, for example, preferably about 70% softwood and about 30% hardwood. Good results for towel paper are also achieved if the fiber content of the pulp suspension used comprises about 70% softwood and about 30% chemi-thermomechanically treated pulp (CTMP).

The method of the invention is then particularly effective in increasing dewaterability during production and increasing the water absorbency and buoyancy of the finished product with satisfactory tear strength when the tissue paper web is made to include regions that compress more during manufacture be considered other areas.

If the tissue paper web should comprise areas of different compression, it makes sense if the tissue paper web from the stock suspension is already formed on a structured, in particular 3-dimensional structured sieve.

In such a structured sieve, the side facing the tissue paper web comprises at least partially recessed regions and elevated regions relative to the recessed regions, the tissue paper web being formed at least in sections in the recessed and raised regions of the structured sieve. The sections of the tissue paper web formed in the recessed areas of the structured screen in this case have a higher volume and basis weight than the sections formed in the raised areas of the screen.

As a result, a 3-dimensional tissue paper web is formed. The tissue paper web here has bulky pillow-like high area (pillow area) portions formed in the recessed areas of the structured screen and intervening lower loft lower weight portions formed in the raised areas of the structured screen.

The structured screen may comprise a TAD screen or a DSP screen. A TAD screen has the advantage of high permeability, ensuring rapid dewatering during formation.

Regarding the structure of the structured sieve and regarding the formation of the tissue paper web on the structured sieve is on the PCT / EP2005 / 050203 referenced, which is hereby incorporated in full in this application.

After the formation of the tissue paper web, the tissue paper web is preferably passed in a dewatering step between an upper textured, in particular 3-dimensional, and permeable fabric and a lower permeable fabric, wherein in the dewatering step along a Entwässerungsstrecke pressure on the upper fabric, the tissue paper web and the lower clothing is exercised.

The pressure exerted here on the arrangement of structured and permeable covering, tissue paper web and lower permeable covering can be effected by a gas flow. Additionally or alternatively, the pressure exerted can be effected by a mechanical pressing force.

In order to compress the tissue paper web only partially by the action of pressure and thus to provide a tissue paper with regions - in the unpressed or less pressed areas - high volume for good absorbency and with areas - in the more compressed areas - high strength, it makes sense when the side of the structured fabric facing the tissue paper web comprises recessed regions and elevated regions relative to the recessed regions. As a result, as already mentioned, the tissue paper web is less strongly compressed in the recessed areas than in the raised areas.

The upper structured and permeable fabric is preferably a structured fabric, in particular TAD fabric or DSP fabric, and the lower permeable fabric is preferably a felt having a sufficiently high water absorption capacity for the water extruded from the tissue paper web. Regarding the structure of the lower clothing is on the PCT / EP2005 / 050198 referred to in full in this application.

Preferably, the compressibility (thickness change in mm with force in N) of the upper clothing smaller than the compressibility of the lower clothing. As a result, the voluminous structure of the tissue paper web is maintained at the pressure.

Experiments have shown that a particularly good and gentle dewatering is possible if the dynamic stiffness (K) as a measure of the compressibility of the upper clothing 3000N / mm or more.

Hard or too hard bottom fabric would not compress the voluminous pillow-like portions of the tissue paper web at all. Due to the compressible structure of the lower fabric, the voluminous pillow-like sections of the tissue paper are pressed lightly and thus gently dewatered. Experiments have shown in this context that the dynamic stiffness (K) as a measure of the compressibility of the lower fabric is 100000N / mm or less, preferably 90000N / mm, more preferably 70000N / mm or less.

It is likewise advantageous if the G-modulus as a measure of the elasticity of the lower clothing is 2N / mm ² or more, preferably 4N / mm ² or more.

Furthermore, tests have shown that the water stored in the lower clothing, for example the felt, can be expelled more easily with a gas stream if the permeability of the lower clothing is not too high. It proves to be advantageous if the permeability of the lower clothing 80cfm or less, preferably 40cfm or less, more preferably 25cfm or less. In the areas mentioned above, rewetting of the tissue paper web by the lower clothing is largely prevented.

Preferably, in the dewatering step, first the upper fabric then the tissue paper web and then the lower fabric is traversed by a gas. The drainage of the paper web takes place in the direction of the lower Covering instead.

Additionally or optionally to the gas flow through the above-mentioned arrangement, it can be provided that in the dewatering step the arrangement of upper covering, tissue paper web and lower covering is guided at least in sections along the dewatering section between a tensioned press belt and a smooth surface, wherein the press belt on the upper clothing acts and the lower fabric is supported on the smooth surface. Here also a dewatering of the tissue paper web takes place in the direction of the lower clothing.

Preferably, the arrangement of upper covering, tissue paper web and lower covering is at least partially flowed through in the region of the dewatering section of the gas stream, so that the dewatering takes place simultaneously by the pressing force of the press belt and the flow of the gas.

Experiments have shown that the gas flow through the tissue paper web is about 150m ³ per minute and meter length along the drainage path.

The gas flow can be generated by a suction zone in a roller. In this case, the suction zone has a length in the range between 200mm and 2500mm, preferably between 800mm and 1800mm, more preferably between 1200mm and 1600mm and the negative pressure in the suction zone is between -0.2bar and -0.8bar, preferably between -0, 4bar and -0,6bar.

Optionally or additionally, the gas flow can also be generated by an overpressure hub arranged above the upper clothing.

In the latter case, the temperature of the gas flow between 50 ° C and 180 ° C, preferably between 120 ° C and 150 ° C and the pressure is less as 0.2bar, preferably less than 0.1bar, and more preferably less than 0.05bar. The gas can be hot air or steam.

By a high tension of the press belt, the pressing force can be increased. Experiments have shown that for sufficient drainage, in particular of the non-voluminous sections of the tissue paper, the press belt is under a tension of at least 30 kN / m, preferably at least 60 kN / m or 80 kN / m.

The press belt can in this case have a spiral structure and, for example, be designed as a so-called SiralLinkFabric. Furthermore, it is possible that the press belt has a woven structure.

In order to achieve both a good drainage of the tissue paper web by the mechanical stress of the press belt and due to the gas flow through the press belt, it makes sense if the press belt has an open area of at least 25% and a contact area of at least 10% of its total to the upper clothing has facing surface.

By increasing the contact surface of the press belt, a uniform mechanical pressure is exerted on the arrangement of structured upper clothing, tissue paper and lower clothing.

With all of the following information on contact surface and open area of the press belt satisfactory result can be achieved.

Accordingly, it is envisaged that the press belt has an open area between 75% and 85% and a contact area between 15% and 25% of its total surface facing the upper clothing.

Furthermore, it is envisaged that the press belt has an open area between 68% and 76% and a contact area between 24% and 32% of its total surface facing the upper clothing.

Very good results in terms of dry content and bulkiness of the tissue paper are achieved when the press belt has an open area of between 51% and 62% and a contact area of between 38% and 49% of its total upper facing surface.

In particular, by forming the press belt with a woven structure, it is possible that the press belt has an open area of 50% or more and a contact area of 50% or more of its entire upper clothing facing surface. In this way, both a good gas flow through the press belt as well as a homogeneous pressing force can be provided by means of the press belt.

The smooth surface is preferably formed by the lateral surface of a roller.

By the dewatering process described above, it is possible for the tissue paper web to leave the dewatering section at a dry content of between 25% and 55%.

In order to ensure that the voluminous sections of the tissue paper are only slightly pressed in the dewatering step, it makes sense if the structured sieve in the dewatering step is the same sieve as that in the formation of the tissue paper web. Hereby, the voluminous pillow-like portions of the tissue paper web will remain in the recessed areas of the structured screen during pressurization, greatly protecting the bulky portions from pressure and exerting much less pressure on them than the intervening sections of the tissue paper web. The voluminous structure of the pillow-like sections therefore remains obtained at the dewatering step.

Preferably, the tissue paper web is guided in a further dewatering step subsequent to the dewatering step together with the structured covering of the dewatering step through a press nip and further dehydrated.

Furthermore, the tissue paper web in the press nip b is preferably arranged between the structured and permeable upper clothing and a, in particular smooth and heated, roller surface, wherein the heated and smooth surface is preferably formed by the jacket surface of a Yankee drying cylinder.

The transfer of the tissue paper web on the structured upper clothing through the press nip ensures that even in this dewatering step, the voluminous pillow-like sections of the tissue paper are pressed less strongly than the intervening sections.

Preferably, the recessed areas and the relatively elevated areas of the structured and permeable clothing are designed and arranged in such a way that only 35% or less, in particular only 25% or less, of the tissue paper web is pressed in the press nip.

If the structured upper clothing, as already mentioned, is the same structured clothing on which the tissue paper was formed, then the 3-dimensional structure of the paper is already formed during the formation. On the other hand, in the prior art methods, the 3-dimensional structure of the tissue paper is only formed in a subsequent dewatering step by pressing the tissue paper web into a structured screen, thereby forming a substantially two-sidedly waved tissue paper.

In the method according to the invention, the formation of the tissue paper between the structured fabric and a forming fabric having a relatively smooth surface forms a tissue paper web which is substantially smooth on the side formed on the smooth forming fabric. When passing through the press nip, this side comes into contact with the jacket surface of the Yankee drying cylinder, which prevents burning of the tissue paper web at high temperatures of the Yankee drying cylinder due to the relatively large contact surface compared to the prior art. As a result, the temperature of the Yankee drying cylinder over the prior art can be increased, resulting in a higher dry content of the tissue paper web produced.

For a gentle pressing in the press nip, it makes sense if the press nip is an extended press nip, i. is formed by the roller surface and a shoe press unit.

If the aim is to increase the dry content, which is based on the bulkiness of the tissue paper web produced, it may also be provided that the press nip is formed by a suction press roll and the roll surface instead of the shoe press unit and the roll surface.

In order to remove water which is carried along in the structured upper clothing and which impedes dewatering in the press nip, it is expedient for the tissue paper web to be guided together with the structured clothing around an evacuated deflection roller, the structured clothing between the tissue paper web and the paper web sucked deflecting roller is arranged.

There are different possibilities conceivable how the stock suspension can be composed. According to one possible embodiment of the invention, the pulp suspension used comprises a suspension fraction which has been prepared from a low-consistency, high-strength starting material suspension having a consistency of less than 10%. This proportion of suspension has this one Freeness of 15 ° SR or more and was prepared by at least one milling operation from the low consistency, high strength stock suspension with a freeness of less than 15 ° SR.

A low-consistency starting material suspension of high strength is to be understood as one from which a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) can be produced whose tear length, measured according to TAPPI 220 and TAPPI 494, at a freeness of 15 ° SR is greater than 3.0 km is.

Furthermore, it is possible that the stock suspension used comprises a suspension portion prepared from a high consistency low strength stock suspension having a consistency of 20% or more, preferably 20% to 40%, most preferably 25% to 35%.

This suspension fraction here has a freeness of 15 ° SR or more and was prepared by at least one grinding of the high-consistency raw material suspension of low strength with a freeness of less than 15 ° SR.

For example, the high-consistency, low-strength starting suspension can be made from a low-consistency, low-strength starting suspension by thickening it.

A low-consistency initial suspension of low strength is to be understood as one from which a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) can be produced whose tear length, measured according to TAPPI 220 and TAPPI 494, at a freeness of 15 ° SR less than or equal 3,0km is.

• Bereitstellen einer Fasern umfassenden hochkonsistenten Ausgangsstoffsuspension mit einer Konsistenz von mehr als 20% und einem Mahlgrad von weniger als 15°SR,
• Mahlen der Ausgangsstoffsuspension auf einen Mahlgrad von 15°SR oder mehr zum Erhalt des Suspensionsanteils.

Furthermore, a method for producing a fiber suspension comprising fibers is provided, in which at least one suspension component with following steps is made:

• Providing a fiber-comprising high-consistency raw material suspension having a consistency of more than 20% and a freeness of less than 15 ° SR,
• Grinding the stock suspension to a freeness of 15 ° SR or more to obtain the suspension fraction.

By means of the process according to the invention it is possible to provide a stock suspension from which a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) can be produced whose tear length, measured according to TAPPI 220 and TAPPI 494, is greater for at least one specific freeness (MW _specific ) or equal to the value resulting from 0.55 (km / SR) * (MW _specific -10 ° SR), the specific freeness being from a freeness range of 14 ° SR to less than 21 ° SR, in particular 15 ° SR until 20 ° SR is selected.

The method according to the invention therefore makes it possible, in particular, to provide a stock suspension from which tissue paper with high tear strength can be created with high porosity and permeability by a production process in which the tissue paper web is compressed to only 35% or 25% during its production.

It is both possible for the stock suspension to be prepared only from the suspension prepared from a highly consistent stock suspension or for this suspension portion (first suspension portion) to be mixed with a suspension portion (second suspension portion) 1 to produce the stock suspension which is a low consistency Starting material suspension was prepared with a consistency of less than 10%.

Preferably, in this case, the second suspension portion has a higher freeness than the first suspension portion.

According to a specific embodiment of the invention, the high-consistency raw material suspension has a freeness of 12 ° SR to 13 ° SR and the suspension fraction prepared therefrom a freeness of 15 ° SR to 19 ° SR, preferably 15 ° SR to 17 ° SR.

In order to achieve the required strength, it may be useful if the grinding process is carried out several times in succession.

The best results with respect to the achieved strength at low freeness are achieved when the high-consistency raw material suspension is ground with a grinding energy in the range of 150kWh to 300kWh, especially 180kWh to 250kWh per ton.

Furthermore, tests have shown that for the stock suspension high strength can be achieved with low freeness when the high consistency stock suspension has a consistency in the range of more than 20% to 40%, preferably 25% to 35%.

Furthermore, it makes sense if the low-consistency starting material suspension enzymes and / or agents to increase the dry strength so-called. " D ry S trenght A gent" (DSA) and / or agents for increasing the wet strength, so-called " W et S trenght A gent "(WSA) be added. In such a case, for example, in a low-consistency starting material suspension with high strength can be completely dispensed with grinding.

The addition of DSA's makes it possible to further reduce the degree of grinding in the pulp suspension while maintaining the tear resistance constant.

As DSA, for example, carbon methyl cellulose can be used.

The highly consistent starting material suspension can be obtained by thickening a low-consistency starting suspension, with the thickening taking place, for example, by means of a screw press.

It has proved to be advantageous here if the enzymes of the low-consistency starting suspension are added at a temperature in the range from 25 ° C. to 70 ° C., preferably 30 ° C. to 60 ° C., particularly preferably at about 35 ° C. to 45 ° C. because their effectiveness is highest in this temperature range.

It is also useful to increase the activity of the enzymes if the enzymes of the low-consistency starting suspension are added at a pH in the range from 5 to 8, preferably 5.5 to 7.5, particularly preferably at about 6.5 to 7 ,

Good results are achieved if the enzymes act on the low-consistency starting suspension for an exposure time of 1-2 hours, preferably 1.5 hours.

The enzymes can be added, for example, in the pulper.

To adjust the above-mentioned advantageous properties of the stock suspension, it is useful if the high-consistency raw material suspension is milled at a temperature in the range between 20 ° C and 80 ° C, preferably at 40 ° C.

Fig. 1

Eine Vorrichtung zur Herstellung einer erfindungsgemäßen Stoffsuspension,

Fig. 2

ein Vergleich zwischen erfindungsgemäßen Stoffsuspensionen und solchen aus dem Stand der Technik,

Fig. 3

eine abschnittweise Darstellung einer Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens zur Herstellung von Tissuepapier,

Fig. 4

die Struktur einer Tissuepapierbahn bei deren Formation mit dem erfindungsgemäßen Verfahren,

Fig. 5

die Struktur einer Tissuepapierbahn bei deren Formation mit einem nach dem Stand der Technik bekannten Verfahren,

Fig. 6

die Struktur einer Tissuepapierbahn bei deren Entwässerung mit dem erfindungsgemäßen Verfahren,

Fig. 7

die Struktur einer Tissuepapierbahn bei deren 3-dimensionalen Strukturierung mit einem nach dem Stand der Technik bekannten Verfahren,

Fig. 8

die Struktur einer Tissuepapierbahn bei deren Entwässerung im Pressspalt mit dem erfindungsgemäßen Verfahren,

Fig. 9

die Struktur einer Tissuepapierbahn bei deren Entwässerung im Pressspalt mit einem aus dem Stand der Technik bekannten Verfahren,

Fig. 10

eine erste Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens,

Fig. 11

eine zweite Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens.

The invention will be explained in more detail with reference to the following schematic drawings. Show it:

Fig. 1

A device for producing a stock suspension according to the invention,

Fig. 2

a comparison between material suspensions according to the invention and such from the prior art,

Fig. 3

a section of a device for carrying out the method according to the invention for the production of tissue paper,

Fig. 4

the structure of a tissue paper web in its formation with the method according to the invention,

Fig. 5

the structure of a tissue paper web as it is being formed with a method known in the art;

Fig. 6

the structure of a tissue paper web during its dewatering with the method according to the invention,

Fig. 7

the structure of a tissue paper web in its 3-dimensional structuring with a method known from the prior art,

Fig. 8

the structure of a tissue paper web during its dewatering in the press nip with the method according to the invention,

Fig. 9

the structure of a tissue paper web during its dewatering in the press nip with a method known from the prior art,

Fig. 10

a first device for carrying out the method according to the invention,

Fig. 11

a second device for carrying out the method according to the invention.

FIG. 1 shows an apparatus 1 for providing a stock suspension according to the invention, which is subsequently used in the method according to the invention for producing a tissue paper web.

The device 1 comprises a pulper 2 in which the dry raw materials and pulp and waste paper are dissolved in water and converted into a pumpable state. Subsequently, the substance thus formed is fed to a Mischbütte 3. The fabric at this stage has a consistency of less than 10%, i. usually 5% or less and is referred to in this context as low-consistency starting material.

Depending on whether it is the low-consistency starting material with a high strength or one with low strength, this is subjected to a grinding process at low consistency or a grinding process at high consistency.

If, for example, it is a low-consistency starting material with low strength, it can be made into a TAPPI 205 SP 95 (Rapid Köthen) laboratory sheet having a small tear length of less than or equal to 3.0 km from this at a freeness of 15 ° SR.

Such a stock suspension is subjected to a high consistency milling process. For this purpose, the low-consistency starting material is a thickener 4, which may be formed, for example. As a screw press, and thickened in this example. From a consistency of 5% to a consistency of 25% to 35%, ideally about 30%, creating a highly consistent Starting material suspension is generated.

The high-consistency raw material suspension usually has a freeness of 12 ° SR to 13 ° SR.

Thereafter, the high-consistency raw material suspension in a heating channel 5 to a temperature up to 80 ° C, ideally about 40 ° C, heated and then fed to a refiner 6 for grinding.

During the grinding process, the high-consistency raw material suspension is ground to a freeness of 15 ° SR or more. The high-consistency stock suspension produced thereby generally has a freeness in the range of 16 ° SR to 19 ° SR, preferably in the range of 16 ° SR to 18 ° SR.

To obtain the highly consistent stock suspension, the highly consistent feedstock suspension with a total grinding energy in the range of 150kWh up to 300kWh, especially 180kWh to 250kWh per ton ground, and it is conceivable to carry out the grinding process in one step or in several grinding steps in succession.

Before the grinding process, enzymes and agents for increasing the dry strength (DSA) can be added to the substance, for example already in the pulper 2.

Particularly advantageous in terms of the desired properties with respect to the later formed tissue paper web in terms of their porosity and permeability coupled with high tensile strength, it turns out that the enzymes of the low-consistency starting suspension at a temperature in the range of 25 ° C to 70 ° C, preferably 30 ° C to 60 ° C, particularly preferably added at about 35 ° C to 45 ° C, wherein the low-consistency starting suspension has a pH in the range of 5 to 8, preferably 5.5 to 7.5, particularly preferably at ca 6.5 to 7 and the duration of the action of the enzymes on the low-consistency starting suspension is 1-2 hours, preferably 1.5 hours.

Subsequently, the stock suspension obtained by the Hochkonsistenzmahlvorgang is diluted in a dilution tank 7 with water, which is at least partially recovered during thickening in the thickener 5 of the low-consistency feedstock suspension.

Thereafter, the thus obtained re-diluted suspension of a machine chest 8 is supplied. In the machine chest 8, the pulp suspension obtained by the high consistency milling operation may be mixed with a suspension obtained by a low consistency pulp milling process, i.e., a pulp mill. less than 20%, was won.

Thus, in the machine chest 8, a stock suspension may be formed comprising a suspension portion made with a high consistency milling operation and comprising a different other suspension portion, which in a Consistency less than 20% was ground.

In this case, the suspension fraction which has been milled from a low-consistency starting material has a higher freeness than the suspension fraction which has been milled from a high-consistency starting material.

Of course, it is also possible that the stock suspension comprises only the suspension produced by the Hochkonsistenzmahlvorgang.

Furthermore, it is also conceivable if, for example, already the low-consistency starting material comprises a high strength, that the stock suspension comprises only one stock suspension, which was prepared with a grinding process at low consistency.

Under a low-consistency raw material with high strength in this context is a substance from which at a freeness of 15 ° SR a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) can be produced with a breaking length of 3.0km or more.

After the machine chest 8, the stock suspension is very strongly diluted with white water 9 and fed to a headbox 10.

Regardless of how the stock suspension is obtained, it is important for the production of tissue paper that the stock suspension 10 exiting stock suspension has a freeness of less than 21 ° SR and is such that from this a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) whose tear length, measured according to TAPPI 220 and TAPPI 494, for at least one specific freeness (MW _specific ) is greater than or equal to the value consisting of 0.55 (km / SR) * (MW _specific -10 ° SR), the specific freeness from a freeness range of 15 ° SR to less than 21 ° SR, preferably 15 ° SR to 19 ° SR, more preferably 17 ° SR to 19 ° SR is selected.

FIG. 2 shows the dependence of the breaking length on the degree of grinding for various substances.

In FIG. 2, two different softwoods called "softwood 1" and "softwood 2" are compared before and after the grinding process. The coordinates tear length vs. Grinding degree before the grinding process are indicated by the points A, as the coordinates tear length vs. Mahlgrad after the grinding process with the points B are designated.

• A_SW1= Ausgangssuspension vom Weichholzstoff "Softwood 1", wobei "Softwood 1" eine hohe Festigkeit hat,
• B_SW1LC=Stoffsuspension nach Mahlvorgang bei niederer Konsistenz vom Weichholzstoff "Softwood 1"
• A_SW2= Ausgangssuspension vom Weichholzstoff "Softwood 2", wobei "Softwood2" eine geringe Festigkeit hat,
• B_SW2LC=Stoffsuspension nach Mahlvorgang bei niederer Konsistenz vom Weichholzstoff "Softwood 2",
• B_SW2HC=Stoffsuspension nach Mahlvorgang bei hoher Konsistenz vom Weichholzstoff "Softwood 2"

Listed individually, the points represent the following:

• A _SW1 = initial suspension of softwood material "Softwood 1", where "Softwood 1" has high strength,
• B _SW1LC = _pulp suspension after grinding at low consistency of the softwood material "Softwood 1"
• A _SW2 = initial suspension of softwood material "Softwood 2", where "Softwood2" has low strength,
• B _SW2LC = _pulp suspension after grinding at low consistency of softwood material "Softwood 2",
• B _SW2HC = _pulp suspension after high-consistency grinding of softwood material "Softwood 2"

On the connecting lines between the points A and B are the breaking lengths, which would result in approximately at between grindings.

As can be seen from FIG. 2, both B _SW1LC and B _{SW2HC are} suitable for the method _according to the invention for the production of tissue paper at a freeness of less than 21 ° SR since the property according to the invention is given for both material suspensions, namely that a laboratory sheet can be produced according to TAPPI 205 SP 95 (Rapid Köthen) whose tear length, measured according to TAPPI 220 and TAPPI 494, at least one specific freeness (MW _specific ) is greater than or equal to the value resulting from 0.55 (km / SR) * (MW _specific -10 ° SR), the specific freeness being from a freeness range from 15 ° SR to less than 21 ° SR.

The inventive functional dependency between tear length and freeness is shown in FIG. 2 by the dashed line.

As can be seen in particular from FIG. 2, the fabric "Softwood 2" milled at high consistency and the material "Softwood 1" milled at low consistency in particular fulfill the property of producing a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) at least one specific freeness (MW _specific ) is greater than or equal to 4.0 km, the specific freeness (MW _specific ) being selected from a freeness range less than or equal to 17 ° SR ,

The further method will now be explained further in the following FIGS. 3 to 11, wherein FIGS. 10 and 11 show two embodiments of different apparatuses for carrying out the method.

A pulp suspension 11 with the above-mentioned properties emerges from the headbox 10 in such a way that it is injected into the incoming gap between a forming fabric 12 and a structured, in particular 3-dimensional structured fabric 13, whereby a tissue paper web 14 is formed.

The forming fabric 12 has a side facing the tissue paper web 14 that is smooth relative to that of the structured fabric 13.

In this case, the side 15 of the structured screen 13 facing the tissue paper web 14 has recessed areas 16 and elevated areas relative to the recessed areas 16 17, so that the tissue paper web 14 is formed in the recessed areas 16 and the raised areas 17 of the structured screen 13. The height difference between the recessed areas 16 and the raised areas 17 is preferably 0.07 mm and 0.6 mm. The area formed by the raised areas 16 is preferably 10% or more, more preferably 20% or more, and most preferably 25% to 30%. In the embodiment shown in FIG. 3, the structured screen 13 is designed as a TAD screen 13.

In the embodiment shown in Figure 3, the array of TAD wire 13, tissue paper web 14 and forming wire 12 is directed around a forming roll 18 and the tissue paper web 14 is substantially dewatered through the forming wire 12 before the forming wire 12 is removed from the tissue paper web 14 and the tissue paper web 14 is further transported on the TAD screen 13.

FIG. 4 shows the structure of the tissue paper web 14 formed between the flat forming fabric 12 and the TAD wire 13. The voluminous pillow-like portions C 'of the tissue paper web 14 formed in the recessed areas 16 of the TAD mesh 13 have a higher volume and a higher basis weight than the portions A' of the tissue paper web 14 formed in the raised areas 17 of the TAD mesh 13.

The tissue paper web 14 therefore already has a 3-dimensional structure due to its formation on the structured sieve 13.

FIG. 5 shows a tissue paper web 114 formed between two smooth forming fabrics 112 and 112 '.

The tissue paper web 114 is formed due to their formation between two smooth Formiersieben 112 and 112 'substantially smooth and without 3-dimentionale structure.

In a subsequent dewatering step to form the tissue web 14, the tissue paper web 14 is guided between the structured wire 13, which is arranged at the top, and a lower, permeable fabric 19 which is formed as a felt 19, wherein pressure is applied to the structured wire 13 in the dewatering step along a dewatering path. the tissue paper web 14 and the felt 19 are exerted in such a way that the tissue paper web 14 is dewatered in the direction of the felt 19, as indicated by the arrows 20 in FIG.

By dewatering the tissue paper web 14 in the direction of the felt 19 during this dewatering step and by dewatering the tissue paper web 14 on the structured wire 13 on which it has already been formed, the bulky portions C 'are compressed less than the portions A'. so that, as a result, the bulky structure of the sections C 'is maintained.

FIG. 7 shows the generation of a 3-dimensional structure of the tissue paper web 114 formed in FIG. To create the 3-dimensional structure, the tissue paper web 114 must be pressed into a structured sieve 113. To this end, the tissue paper web 114 is stretched in the sections C which are pressed into the recessed areas 116 of the structured screen 113, which reduces the weight per unit area in the sections C. Furthermore, the tissue paper web 114 is strongly pressed in the sections C, so that also the volume of the sections C is reduced.

The pressure for dewatering the tissue paper web 14 is generated in the dewatering step at least in sections simultaneously by a gas flow and by a mechanical pressing force.

The gas stream flows through first the structured sieve 13 then the tissue paper web 14 and then the formed as a felt 19 lower fabric. The gas flow through the tissue paper web 14 is about 150m ³ per minute and meter of web length.

In the present case, the gas flow is generated by a suction zone 25 in the roller 24, wherein the suction zone 25 has a length in the range between 200mm and 2500mm, preferably between 800mm and 1800mm, more preferably between 1200mm and 1600mm.

The negative pressure in the suction zone 25 is between -0.2bar and -0.8bar, preferably between -0.4bar and -0.6bar.

With regard to the execution of the dewatering step performed by mechanical pressing force and optionally or additionally with gas flow, as well as to the various configurations of devices for carrying out such a dewatering step, the PCT / EP2005 / 050198 be fully included in the disclosure of the present application.

The mechanical pressing force is generated by the fact that in the dewatering step, the arrangement of structured wire 13, tissue paper web 14 and felt 19 a dewatering section 21 between a tensioned press belt 22 and a smooth surface 23 is guided, wherein the press belt 22 on the structured sieve 13th acting and the felt 19 is supported on the smooth surface 23.

The smooth surface 23 is in this case formed by the lateral surface 23 of a roller 24.

The dewatering section 21 is essentially defined by the wrap-around region of the press belt 22 around the lateral surface 23 of the roller 24, wherein the wrap-around region is determined by the spacing of the two deflection rollers 25 and 26.

The press belt 22 is under a tension of at least 30 kN / m, preferably at least 60kN / m or 80kN / m and has an open area of at least 25% and a contact area of at least 10% of its total upper facing area.

In this specific case, the press belt is designed as a spiral link fabric and 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 clothing.

With regard to the structure of the press belt, the PCT / EP2005 / 050198 be fully included in the disclosure of the present application.

The tissue paper web 14 leaves the dewatering section 21 with a dry content of between 25% and 55%.

Subsequently, the tissue paper web 14 is guided in a further dewatering step subsequent dewatering step together with the structured screen 13 through a press nip 27, wherein the tissue paper web 14 is disposed in the press nip 27 between the structured wire 13 and a smooth roll surface 28 of a Yankee drying cylinder 29. The press nip 27 is in this case a shoe press nip formed by the Yankee drying cylinder 29 and a shoe press 30.

The tissue paper web 14 rests on one side with a relatively large area on the lateral surface 28 of the Yankee drying cylinder 29, wherein the tissue paper web 14 rests on the structured sieve 13 on the other side.

The recessed areas 16 and the relatively elevated areas 17 of the structured screen 13 are in this case designed and arranged relative to one another such that the pillow-like sections C 'in the press nip 27 are essentially not pressed, this is 35% or less, in particular 25% or less, of the tissue paper web 14. On the other hand, the sections A 'are pressed, whereby the strength of the tissue paper web 14 is further increased (FIG. 8).

The tissue paper web 114 known from the prior art comes into contact with the jacket surface 128 of the Yankee drying cylinder in comparison to the tissue paper web 14 with a relatively small area. This has the disadvantage that the tissue paper 114 can burn on the lateral surface, which is why the temperature of the Yankee cylinder must be kept lower in the method known from the prior art. This has the consequence that with the method known from the prior art, a lower dry content can be achieved (Figure 9).

No further dewatering step, which can be carried out by means of a device 31, may be provided between the two described dewatering steps.

Optionally, it can be provided that the tissue paper web 14 before it passes through the press nip 27 is guided together with the structured wire 13 around an evacuated deflection roller, the structured wire 13 being arranged between the tissue paper web 14 and the evacuated deflection roller (not shown).

It can be seen from FIG. 11 that the gas flow can be additionally generated by an overpressure hub 31 arranged above the structured sieve 13, the dewatering step in this case taking place without mechanical pressing force, ie. In contrast to FIG. 10, no press belt 22 is provided which wraps around the roller 24 in sections.

Claims (74)

Method of making a tissue paper web made from a stock suspension comprising fibers
characterized,
that the stock suspension has a freeness of less than 21 ° SR, and is configured such that out of this a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) can be produced, the breaking length, measured according to TAPPI 220 and TAPPI 494, specific for at least one Grinding degree (MW _specific ) is greater than or equal to the value resulting from 0.55 (km / SR) * (MW _specific -10 ° SR), the specific freeness from a freeness range of 15 ° SR to less than 21 ° SR, in particular 15 ° SR to 19 ° SR is selected. Method according to claim 1,
characterized,
the pulp suspension used is such that it can be used to produce a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) whose tear length, measured according to TAPPI 220 and TAPPI 494, in a specific freeness range (MW _specific ) from 15 ° SR to 19 ° SR, preferably 15 ° SR to 17 ° SR is greater than or equal to the value resulting from 0.55 (km / SR) * (MG _specific -10 ° SR). Method according to claim 1 or 2,
characterized,
that the suspension used has a degree of beating of 19 ° SR or below, preferably of 17 ° SR or less. Method according to one of claims 1 to 3,
characterized,
that from the stock suspension at a freeness of 17 ° SR a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) with a breaking length of 4.0km or more, preferably 4.3km or more, measured according to TAPPI 220 and TAPPI 494, can be formed , Method according to one of claims 1 to 4,
characterized,
in that the pulp suspension used comprises a suspension fraction which has been prepared from a low-consistency, high-strength starting material suspension having a consistency of less than 10%, preferably less than 5%. Method according to claim 5,
characterized,
that the suspension fraction has a freeness of 15 ° SR or more and a grinding process from the low consistency pulp slurry output high strength was produced having a freeness of less than 15 ° SR by at least. Method according to claim 5 or 6,
characterized,
that from the low-consistency starting material suspension of high strength, a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) can be produced, the tearing length, measured according to TAPPI 220 and TAPPI 494, at a freeness of 15 ° SR is greater than 3.0km. Method according to one of claims 1 to 7,
characterized,
that the suspension used comprises a suspension portion which was prepared from a high consistency low strength starting material suspension having a consistency of 20% or more, preferably 20% to 40%, most preferably 25% to 35%. Method according to claim 8,
characterized,
that the suspension fraction has a freeness of 15 ° SR or more and a grinding process from the high consistency pulp slurry output low strength was prepared having a freeness of less than 15 ° SR by at least. Method according to one of claims 8 or 9,
characterized,
that the high-consistency low-strength starting slurry is produced from a low-consistency low-strength starting slurry by thickening thereof. Method according to claim 10,
characterized,
that from the low-consistency initial suspension of low strength, a laboratory sheet according to TAPPI 205 SP 95 (Rapid Köthen) can be produced, the tearing length, measured according to TAPPI 220 and TAPPI 494, with a freeness range of 15 ° SR is less than or equal to 3.0km. Method according to one of claims 1 to 11,
characterized,
that the fiber content of the stock suspension for the most part comprises pulp, preferably 60% or more, more preferably 80% or more, most preferably 100%. Method according to one of claims 1 to 12,
characterized,
that the fibers of the stock suspension at a freeness of 17 ° SR has a retention value for water of 1.5 g / g or less, preferably 1.4 g / g or less measured according to TAPPI UM 256. Method according to one of claims 1 to 13,
characterized,
that the pulp suspension used softwood and / or hardwood comprises. Method according to claim 14,
characterized,
that the fiber content of the pulp suspension used comprises about 30% softwood and about 70% hardwood. Method according to claim 15,
characterized,
that the fiber content of the pulp suspension used comprises about 70% softwood and about 30% hardwood, preferably 100% softwood. Method according to one of claims 1 to 16,
characterized,
to produce a tissue paper web comprising areas that are more compressed during manufacture than other areas. Method according to one of claims 1 to 17,
characterized,
that the tissue paper web is formed from the stock suspension on a structured, in particular 3-dimensionally structured sieve. Method according to claim 18,
characterized,
in that the side of the structured screen facing the tissue paper web comprises recessed regions and elevated regions relative to the recessed regions. Method according to claim 18 or 19,
characterized,
that the tissue paper web is formed in the recessed and elevated areas of the textured sieve. Method according to one of claims 18 to 20,
characterized,
that the structured mesh comprises a TAD wire or a DSP sieve. Method according to one of claims 1 to 21,
characterized,
in that the tissue paper web is guided in a dewatering step between an upper structured, in particular 3-dimensionally structured, permeable fabric and between a lower permeable fabric, wherein pressure is exerted on the upper fabric, the tissue paper web and the lower fabric in the dewatering step along a dewatering path , Method according to claim 22,
characterized,
in that the side of the structured fabric facing the tissue paper web comprises recessed regions and elevated regions relative to the recessed regions. Method according to claim 23,
characterized,
that the tissue paper web is less compressed in the recessed areas than in the raised areas. Method according to one of claims 22 to 24,
characterized,
that the upper structured and permeable fabric, a structured wire, in particular TAD wire or DSP sieve, and the lower permeable skin is a felt. Method according to one of claims 22 to 25,
characterized,
that the compressibility of the upper clothing is smaller than that of the lower clothing. Method according to one of claims 22 to 26,
characterized,
that the dynamic stiffness (K) as a measure of the compressibility of the upper fabric is 3000N / mm or more. Method according to one of claims 22 to 27,
characterized,
in that the dynamic stiffness (K), as a measure of the compressibility of the lower clothing, is 1 00000N / mm or less, preferably 90000N / mm, more preferably 70000N / mm or less. Method according to one of claims 22 to 28,
characterized,
that the G-modulus is a measure of the elasticity of the lower skin 2 N / mm ² or more, preferably 4N / mm ² or more. Method according to one of claims 22 to 29,
characterized,
that the permeability of the lower skin 80cfm or less, preferably 40cfm or less, particularly preferably 25cfm or less. Method according to one of claims 22 to 30,
characterized,
that in the dewatering step, first the upper clothing then the tissue paper web and then the lower clothing is traversed by a gas. Method according to one of claims 22 to 31,
characterized,
that in the dewatering step, the arrangement of upper fabric, tissue paper web and lower fabric at least in sections along the dewatering section between a tensioned press belt and a smooth surface is performed, the press belt acts on the upper fabric and the lower fabric is supported on the smooth surface , Method according to one of claims 22 to 32,
characterized,
that the arrangement of upper covering, tissue paper web and lower covering is flowed through at least in sections in the region of the dewatering section of the gas stream. Method according to one of claims 31 to 33,
characterized,
that the gas flow through the tissue paper web is about 150m ³ per minute and meter length along the drainage path. Method according to one of claims 32 to 34,
characterized,
that the press belt is under a tension of at least 30 kN / m, preferably at least 60 kN / m or 80 kN / m. Method according to one of claims 32 to 35,
characterized,
that the press belt has a spiral structure. Method according to one of claims 32 to 35,
characterized,
that the press belt has a woven structure. Method according to one of claims 32 to 37,
characterized,
that 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 clothing. Method according to claim 38,
characterized,
that the press belt has an open area of between 75% and 85% and a contact area of between 15% and 25% of its total upper facing surface. Method according to claim 38,
characterized,
that the press belt has an open area of between 68% and 76% and a contact area of between 24% and 32% of its total upper facing surface. Method according to claim 38,
characterized,
that the press belt has an open area of between 51% and 62% and a contact area of between 38% and 49% of its total upper facing surface. Method according to claim 38,
characterized,
that the press belt has an open area of 50% or more and a contact area of 50% or more of its entire upper clothing facing surface. Method according to one of claims 32 to 42,
characterized,
that the smooth surface is formed by the lateral surface of a roller. Method according to claim 43,
characterized,
that the gas flow is generated by a suction zone in the roller. A method according to claim 44,
characterized,
that the suction zone has a length in the range between 200mm and 2500mm, preferably between 800mm and 1800mm, more preferably between 1200mm and 1600mm. Method according to claim 44 or 45,
characterized,
that the negative pressure in the suction zone between -0.2 bar and -0.8 bar, preferably between -0.4 bar and -0,6bar. Method according to one of claims 1 to 46,
characterized,
that the gas flow is produced by an above the upper skin arranged overpressure substance. Method according to one of claims 22 to 47,
characterized,
that the tissue paper web leaves the dewatering section with a dry content between 25% and 55%. Method according to one of claims 22 to 48,
characterized,
that the structured sieve in the formation of the tissue paper web is the same sieve as in the dewatering step. Method according to one of claims 1 to 49,
characterized,
that the tissue paper web is performed in a subsequent dewatering step the further dewatering step, together with the struktuierten stringing of the dewatering step by a press nip. Method according to claim 50,
characterized,
in that the tissue paper web is arranged in the press nip between the structured and permeable clothing and a particularly smooth roll surface. Method according to claim 50 or 51,
characterized,
that the recessed and elevated relative to regions of the structured and permeable skin is configured and arranged to each other are that only 35% or less, in particular only 25% or less of the tissue paper web is pressed in the press nip. Method according to one of claims 50 to 52,
characterized,
that the press nip is a shoe press nip. Method according to one of claims 50 to 52,
characterized,
that the press nip between the roll surface and a suction press roll is formed. Method according to one of claims 51 to 54,
characterized,
that the roll surface is formed by the lateral surface of a Yankee drying cylinder. Method according to one of claims 1 to 55,
characterized,
that the tissue paper web is guided together with the structured fabric around an evacuated guide roller, wherein the structured fabric between said tissue paper web and the evacuated guide roller is arranged. A process for producing a fiber suspension comprising fibers in which at least one suspension fraction is prepared by the following steps: Providing a fiber-comprising high-consistency starting material suspension having a consistency of more than 20% and a freeness of less than 15 ° SR, - Grinding the high-consistency raw material suspension to a freeness of 15 ° SR or more to obtain the suspension content. Method according to claim 57,
characterized,
in that the suspension fraction for producing the stock suspension is mixed with another portion of the suspension, the other portion of the suspension being ground from a low-consistency stock suspension having a consistency of less than 10%, preferably less than 5%. A method according to claim 57 or 58,
characterized,
that the suspension portion made of a low-consistency pulp slurry output a higher freeness than the suspension portion made of a high consistency pulp slurry output. Method according to one of claims 57 to 59,
characterized,
that the high-consistency raw material suspension has a freeness of 12 ° SR to 13 ° SR and that the suspension fraction prepared has a freeness of 15 ° SR to 19 ° SR, preferably 15 ° SR to 17 ° SR. Method according to one of claims 57 to 60,
characterized,
that the grinding process is carried out several times in succession. Method according to one of claims 57 to 61,
characterized,
that the highly consistent starting material suspension is ground with a grinding energy in the range of 150 kWh to 300 kWh, in particular 180 kWh to 250 kWh per tonne. Method according to one of claims 57 to 62,
characterized,
has the advantage that the high-consistency pulp slurry output a consistency in the range of more than 20% to 40%, preferably 25% to 35%. Method according to one of Claims 57 to 63,
characterized,
that enzymes are added to the low-consistency starting material suspension for grinding. Method according to one of claims 57 to 64,
characterized,
in that the high-consistency starting material suspension is obtained by thickening a low-consistency, low-strength starting suspension according to claim 11. Method according to claim 65,
characterized,
that the thickening takes place by means of a screw press. Method according to one of Claims 58 to 66,
characterized,
that the low-consistency starting suspension enzymes and / or means for increasing the dry strength (DryStrenghtAgent) and / or means for increasing the wet strength (WetStrenghtAgent) are added. Method according to claim 67,
characterized,
that DSA Carbon comprises methyl cellulose. Method according to one of claims 57 to 68,
characterized,
that the enzymes of the output low-consistency suspension at a temperature in the range from 25 ° C to 70 ° C, preferably 30 ° C to 60 ° C, particularly preferably at about 35 ° C to 45 ° C is added. Method according to one of claims 57 to 69,
characterized,
that the enzymes of the output low-consistency suspension at a pH in the range of 5 to 8, preferably 5.5 to 7.5, is more preferably added at about 6.5 to. 7 Method according to one of claims 57 to 70,
characterized,
that the enzymes act on the low-consistency starting suspension for an exposure time of 1-2 hours, preferably 1.5 hours. Method according to one of claims 57 to 71,
characterized,
that the enzymes are added in the pulper. Method according to one of claims 57 to 72,
characterized,
that the highly consistent starting material suspension is milled at a temperature of up to 80 ° C, preferably at 40 ° C. Process for the production of a fibrous web, in particular a tissue paper web, with a stock suspension produced by the process according to one of claims 57 to 73.

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