EP1618253A2

EP1618253A2 - Method for creating a fibrous substance suspension used for producing a tissue web or hygiene web

Info

Publication number: EP1618253A2
Application number: EP04703404A
Authority: EP
Inventors: Klaus Dölle
Original assignee: Voith Paper Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2003-01-24
Filing date: 2004-01-20
Publication date: 2006-01-25
Also published as: US20060113051A1; DE10302783A1; WO2004065690A2; CN1742136A; CA2514297A1; WO2004065690A3; BRPI0406948A

Abstract

The invention relates to a method for creating a fibrous substance suspension used for producing a tissue web or hygiene web, during which the fibers obtained in the fiber suspension are, in an online process, directly loaded with a loading material in the tissue preparation line by a chemical precipitation reaction.

Description

Process for producing a fiber suspension intended for the production of a tissue or hygiene web

The invention relates to a method for producing a fiber suspension intended for the production of a tissue or hygiene web. It also relates to tissue products produced from a fiber suspension produced by such a method.

The production of tissue requires large amounts of water, due to the extremely low consistency or consistency of the fiber suspension to be fed to the paper or tissue machine in question. Tissue is also produced with a very low basis weight between 8 to 40 g / m ² , depending on the respective end product, such as cellulose wadding (8 to 30 g / m ² ), hygiene tissue (14 to 25 g / m ² ) , Hygienic paper (8 to 30 g / m ² ), napkin paper (20 to 30 g / m ² ) and towel paper (20 to 40 g / m ² ).

In addition, these products have a low degree of grinding, which is necessary to ensure adequate drainage and drying of the web to be produced. As is well known, grinding now contributes significantly to the mechanical properties of the end product. As a result, the low degree of grinding often conflicts with the requirements with regard to mechanical properties.

Tissue products are in most cases made from a bleached sulfite or sulfate pulp suspension, sometimes mixed with bleached pulp, and / or recovered pulp (e.g. broken rubber, broke, waste paper, etc.) and / or some type of pulp suspension. pension in a single-cylinder or four-wire Yankee machine. This applies regardless of whether the respective tissue product contains filler that was generated by a grinding process or another manufacturing process. The material used in the conventional process is currently either precipitation material or another material such as calcium carbonate, talc, TiO ₂ , silica, etc.

In order to achieve the strongest possible binding of the fillers to the fiber surface with each replacement of fiber material with filler, the corresponding treatment has recently been carried out by a so-called "Fiber Loading ™" process, as described, among other things. in US-A-5 223 090. In such a "Fiber Loading ™" process, at least one additive, such as, for example, is applied to the wetted fiber surfaces of the fiber material. Filler stored. The fibers can be loaded with calcium carbonate, for example. For this purpose, calcium oxide and / or calcium hydroxide is added to the moist, disintegrated fiber material in such a way that at least a part thereof is associated with the water present in the fiber material. The fiber material treated in this way is then subjected to carbon dioxide.

In the processes of the type mentioned at the beginning of US Pat. No. 6,413,365 B1 and DE 101 07 448 A, a disperser is used, which can also be used as a reactor for the chemical precipitation reaction.

The invention has for its object to provide an improved method of the type mentioned, with which the efficiency and economy of the manufacture of appropriate tissue or hygiene products is further optimized. This object is achieved according to the invention by a process for producing a fiber suspension intended for the production of a tissue or hygiene web, in which the fibers contained in the fiber suspension are loaded with a filler in an online process directly in the tissue preparation line by a chemical precipitation reaction become.

The conventional fillers are therefore replaced by a filler produced by a chemical precipitation reaction in accordance with the "Fiber Loading ™" process. The fiber pulp suspension treated accordingly has a higher drainage capacity and a lower degree of grinding. In addition, the fibers loaded with filler have a lower water retention value. The respective tissue product can be produced more economically after the water of the fiber suspension has been removed much faster and the tissue web can be dried faster. When the fibers are loaded in accordance with the "Fiber Loading ™" process, there are higher values with regard to dewatering ability with the same degree of grinding, so that a higher degree of grinding can be achieved, which means better mechanical properties for the end product. The lower water retention or better drainage capacity and the better drying prove to be particularly advantageous if the respective end product is subsequently printed.

With the appropriate treatment using a "Fiber Loading ™" process, crystalline precipitation product particles in particular can be generated in the online process. The precipitate is preferably calcium carbonate. In this case, according to a preferred practical embodiment of the method according to the invention, calcium oxide and / or calcium hydroxide are added to load the fibers of the fiber suspension and the precipitation is triggered by carbon dioxide or a gas containing carbon dioxide (for example flue gas or the like). The crystalline precipitation product particles are preferably generated in the gas atmosphere in question without the introduction of mixing energy.

When the fibers are loaded, calcium carbonate is thus stored here on the wetted fiber surfaces by adding calcium oxide and / or calcium hydroxide to the moist fiber material, at least some of which can be associated with the water in the amount of fiber. The fiber material treated in this way is then subjected to carbon dioxide or a gas containing carbon dioxide. In addition, the calcium carbonate (CaCO ₃ ) formed can form a suspension around and between the fibers.

The term "wetted fiber surfaces" can encompass all wetted surfaces of the individual fibers. This also includes in particular the case in which the fibers are loaded with calcium carbonate both on their outer surface and in their interior (lumen).

Accordingly, the fibers are loaded with the filler calcium carbonate, the attachment to the wetted fiber surfaces being carried out by a so-called "Fiber Loading ™" process, as is described as such in US Pat. No. 5,223,090. In this "Fiber Loading ™" process, the carbon dioxide reacts with the calcium hydroxide to form water and calcium carbonate. The fiber suspension is preferably fed to a treatment unit comprising a fluffer, a refiner, a disperser and / or the like. The treatment unit can, for example, have such a structure as is described in US Pat. No. 6,413,365 B1 and DE 101 07 448 A.

The fibers of the fiber suspension can be loaded with filler before or after the treatment unit comprising a fluffer, a refiner, a disperger and / or the like. In principle, however, such configurations of the method are also conceivable in which the treatment unit comprising a fluffer, a refiner, a disperger and / or the like is simultaneously used as a reactor for the chemical precipitation reaction. In this respect too, the method can be designed, for example, as described in the two publications mentioned above.

The calcium hydroxide can be added to the fiber suspension in liquid form or in dry form.

A preferred practical embodiment of the method according to the invention is characterized in that the fibrous suspension, e.g. the pulp suspension previously mixed with calcium hydroxide, to which a treatment unit comprising a fluffer, a refiner, a disperger and / or the like is fed with a consistency in a range from about 5 to about 60% and preferably in a range from about 15 to about 35 % lies.

The carbon dioxide or the gas containing carbon dioxide can be added before, after and / or in the treatment unit. The carbon dioxide or the gas containing carbon dioxide is advantageously added at a temperature which is in a range from about -15 to about 120 ° C. and preferably in a range from about 20 to about 90 ° C.

With the "Fiber Loading ™" process, individual precipitate particles can be generated, which are attached to or stored in the fibers at an even distance. In the gas zone provided for carrying out the precipitation reaction, the individual individual fibers can be exposed to the relevant gas atmosphere, whereupon the corresponding precipitation reaction takes place and the calcium carbonate (CaCO ₃ ) is obtained immediately thereafter.

For example, crystalline precipitate particles of a rhombohedral shape, a scalenohedral shape and / or spherical crystalline precipitate product particles can be produced. The respective amount of crystalline precipitation product particles depends, among other things, on the respective temperature range for the fiber stock suspension and the carbon dioxide as well as e.g. on the proportion of calcium hydroxide in the fiber suspension.

A treatment unit in the form of a disperser with two mutually opposite, relatively rotating plates and preferably in the form of a disperser with a rotor and a stator is advantageously used. The respective disperser can, for example, again have such a structure as the disperser described in US Pat. No. 6,413,365 B1 and DE 101 07 448 A. In a corresponding treatment unit, the dimensions of the crystalline precipitate particles are preferably influenced in the desired manner. For example, a corresponding distribution of crystalline precipitate particles in the fiber suspension can thus be achieved. Only small shear forces are preferably generated in the treatment unit concerned.

In particular, when passing through the treatment unit, for example, crystalline precipitation product particles can be generated, the maximum dimensions of which are in a range from approximately 0.05 to approximately 5 μm and preferably in a range from approximately 0.3 to approximately 2.5 μm.

Depending on the type of paper, for example, crystalline precipitation product particles can have a rhombohedral shape with a respective edge length in a range from about 0.05 to about

2 μm or crystalline precipitation product particles of a scalenohedral shape with a respective length in a range from approximately 0.05 to approximately 2 μm and a respective diameter in a range from approximately 0.01 to approximately 0.5 μm are produced.

The fibrous suspension is advantageously diluted with water, preferably in a radially outer region of the treatment unit comprising two relatively rotating plates. The further the fibrous suspension on the rotor disk goes radially outwards, the lower the respective shear or shear force in view of the dilution water supplied.

The consistency of the fibrous stock suspension passed through the treatment unit is advantageously in a range of approximately 0.1 to about 50%, and preferably in a range from about 5 to about 35%.

It is expedient to ensure a constant supply of carbon dioxide or gas containing carbon dioxide. For this purpose, the carbon dioxide or the gas containing carbon dioxide is added, for example, under a pressure which is in a range from about 0.1 to about 6 bar and preferably in a range from about 0.5 to about 3 bar.

In this case, for example, a corresponding pressure can be provided in the relevant carbon dioxide supply line, via which the gas, that is to say the gas containing carbon dioxide or the carbon dioxide, is fed in, for example to form a gas ring, which are also generated in the treatment unit in question, for example can. As with a garden hose, the pressure in question is then increased accordingly when a higher amount of water is required. Since the carbon dioxide is a compressible gas, the amount of gas supplied can also be increased accordingly in order to ensure a complete precipitation reaction.

According to a preferred practical embodiment of the process according to the invention, an at least substantially complete conversion of the starting materials mentioned calcium oxide or calcium hydroxide and carbon dioxide into the reaction products calcium carbonate and water is ensured in the course of the chemical precipitation reaction by the pH of the fiber suspension, preferably via the feed of carbon dioxide or gas containing carbon dioxide is regulated or controlled accordingly. In particular, a pH can be set which is in a range from about 6 to about 10 and preferably in ranges from about 7 to about 8.5. Corresponding values can be provided in particular for the final reaction.

The energy introduced for such a chemical precipitation reaction is preferably in a range from approximately 0.3 to approximately 8 kWh / t and preferably in a range from approximately 0.5 to approximately 4 kWh / t.

Advantageously, so much dilution water to be mixed with the fibrous suspension is added that finally a consistency of the diluted fibrous suspension results which is in a range from approximately 0.1 to approximately 16% and preferably in a range from approximately 2 to approximately 6% ,

The pulp suspension can then be exposed to atmospheric pressure and fed to a subsequent machine or placed in a container or box. The fiber suspension can then, for example, be fed to the next process machine for producing a tissue or hygiene web.

The treatment unit is preferably operated in such a way that its rotating plate or rotor at the radially outer edge has a peripheral speed in a range from approximately 20 to approximately 100 m / s and preferably in a range from approximately 40 to approximately 60 m / s.

The width of the gap between the two relatively rotating plates of the treatment unit is advantageously in a range from approximately 0.5 to approximately 100 mm and preferably in a range from approximately 25 to approximately 75 mm. The diameter of the two plates of the treatment unit or of the rotor and of the stator rotating relative to one another is expediently in each case in a range from approximately 0.5 to approximately 2 m.

The reaction time for the chemical precipitation reaction can be, for example, in a range from approximately 0.01 min to approximately 1 min and preferably in a range from approximately 0.1 s to approximately 10 s.

If necessary, free, i.e. do not wash out calcium carbonate attached to and / or on the fibers.

A pressure vessel is generally not required.

In the method according to the invention, at least some of the variables mentioned below are used: fiber suspension, calcium oxide and / or calcium hydroxide in liquid or dry form, carbon dioxide, gas zone, rotor, stator, in a gas atmosphere without the introduction of mixing energy, crystals, mixing low shear force, no pressure vessel.

With the method according to the invention, individual crystalline precipitation product particles can be produced which are attached to or into the fibers in an evenly spaced manner in order to meet the requirements for the respective tissue product. For example, the particle sizes specified above can be generated. After the "Fiber Loading ™" process has been completed, the following advantages result in terms of the material properties for the tissue product:

The fiber suspension treated according to the "Fiber Loading ™" process has a higher dewatering capacity or a lower degree of grinding. The relevant values can be, for example, in a range from 5 to about 100 ml of CSF or in a range from about 0.2 to about 15 ° SR, depending on the drainage capacity or the degree of grinding. In addition, the correspondingly loaded fibers have lower

Water retention values, which can range, for example, from about 2 to about 25%, depending on the particular substance input. Tissue paper can now be produced more economically, since water can be removed from the fiber suspension much more quickly and the tissue web can be dried more quickly.

For tissue applications for which no specific filler content is required, the free precipitated calcium carbonate, that is to say the calcium carbonate not deposited in or on the fibers, can be removed by a washing process before the pulp suspension of the concerned one

Tissue machine is supplied or, if necessary, before the grinding process. As a result, the fibers remain covered with calcium carbonate, which has the advantage that the drainage is facilitated and the drying is accelerated and there is also less rewetting of the final tissue product.

The "Fiber Loading ™" process can basically be used before grinding, after grinding or during grinding, depending on the requirements of the respective end product. Since loading the fibers with a precipitation product results in a higher dewatering capacity with the same degree of grinding, stronger grinding is possible, which leads to better mechanical properties of the end product.

The lower water retention and the better drying is particularly advantageous if the product in question is subsequently printed.

1 and 2, two purely exemplary embodiments of the invention are shown in a simplified schematic representation.

1 shows an exemplary embodiment in which the fiber suspension 10 is first fed to the "Fiber Loading ™" process 12 and then treated accordingly in a treatment unit 14 comprising, for example, a refiner or the like. Following this, free calcium carbonate can, if necessary, be washed out in a washing step 16. As can be seen from the above, such a washing step 16 can also be omitted. The correspondingly treated fibrous suspension 10 of a tissue is then

Machine 18 fed, which finally the desired tissue or hygiene web 20 and thus the tissue end product in question is obtained.

The exemplary embodiment shown in FIG. 2 differs from that of FIG. 1 only in that the fibrous suspension 10 first of all comprises the treatment unit 14, for example comprising a refiner or the like, and only then the "Fiber Loading ™" Process is fed. In this case too, the washing step 16 is in no way mandatory.

In both cases, the fibers contained in the fiber suspension 10 are loaded with a filler in an online process directly in the tissue preparation line by a chemical precipitation reaction, crystalline precipitation product particles being generated in the online process. The precipitate is preferably calcium carbonate. In this case, calcium oxide and / or calcium hydroxide is added to the fiber suspension for loading the fibers. The precipitation is then triggered by carbon dioxide or a gas containing carbon dioxide (for example flue gas or the like). The crystalline precipitation product particles are generated in the gas atmosphere in question without the introduction of mixing energy. The fiber suspension can in particular be fed to a treatment unit 14 comprising a fluffer, a refiner, a disperser and / or the like. The fibers of the fiber suspension 10 can be loaded with filler before or after the treatment unit 14. In principle, it is also conceivable to use the treatment unit 14 at the same time as a reactor for the chemical precipitation reaction.

LIST OF REFERENCE NUMBERS

Fibrous suspension "Fiber Loading ™" process Treatment unit Washing step Tissue machine Tissue or hygiene web

Claims

Patent claims

1. A method for producing a fiber suspension (10) intended for the production of a tissue or hygiene web, in which the fibers contained in the fiber suspension (10) are subjected to an online process directly in the tissue preparation line by means of a chemical precipitation reaction (12) with a filler be loaded.

2- Method according to claim 1, characterized in that crystalline precipitation product particles are generated in the online process.

3. The method according to claim 1 or 2, characterized in that the precipitation product is calcium carbonate.

4. The method according to claim 1, characterized in that calcium oxide and / or calcium hydroxide is added to load the fibers of the fiber suspension and the precipitation is triggered by carbon dioxide or a gas containing carbon dioxide to load the fibers.

5. The method according to claim 4, characterized in that the crystalline precipitate in the relevant Gas atmosphere can be generated without the introduction of mixing energy.

6. The method according to any one of the preceding claims, characterized in that the fiber suspension is fed to a treatment unit (14) comprising a fluffer, a refiner, a disperser and / or the like.

7. The method according to claim 6, characterized in that the fibers of the fiber suspension are loaded with filler before or after the treatment unit (14) comprising a fluffer, a refiner, a disperser and / or the like.

8. The method according to claim 6, characterized in that the treatment unit (14) comprising a fluffer, a refiner, a disperser and / or the like is simultaneously used as a reactor for the chemical precipitation reaction.

9. The method according to any one of the preceding claims, characterized in that the calcium hydroxide is added to the fiber suspension in liquid form.

10. The method according to any one of claims 1 to 8, characterized in that the calcium hydroxide is added to the fiber suspension in dry form.

11. The method according to any one of the preceding claims, characterized in that the fibrous suspension (10), preferably the previously mixed with calcium hydroxide fibrous suspension (10), the fluffer, a refiner, a disperser and / or the like comprising a treatment unit (14) Material density is supplied, which is in a range from about 5 to about 60% and preferably in a range from about 15 to about 35%.

12. The method according to any one of the preceding claims, characterized in that the carbon dioxide or the gas containing carbon dioxide is added at a temperature which is in a range from about -15 to about 120 ° C and preferably in a range from about 20 to about 90 ° C.

13. The method according to any one of the preceding claims, characterized in that crystalline precipitation product particles of a rhombohedral shape are produced.

14. The method according to any one of the preceding claims, characterized in that crystalline precipitate product particles are produced from a scalenohedral shape.

15. The method according to any one of the preceding claims, characterized in that that spherical crystalline precipitate particles are produced.

16. The method according to any one of the preceding claims, characterized in that a treatment unit (14) is used in the form of a disperser with two mutually opposite, relatively rotating plates and preferably in the form of a disperser with a rotor and a stator.

17. The method according to claim 16, characterized in that the dimensions of the crystalline precipitation product particles are influenced by the treatment unit (14).

18. The method according to any one of the preceding claims, characterized in that crystalline precipitate particles are generated, the maximum dimensions of which are in a range from approximately 0.05 to approximately 5 μm and preferably in a range from approximately 0.3 to approximately 2.5 μm m lie.

19. The method according to any one of the preceding claims, characterized in that crystalline precipitation product particles of a rhombohedral shape with a respective edge length in a range from about 0.05 to about 2 / ιm are generated.

20. The method according to any one of the preceding claims, characterized in that crystalline precipitation product particles of a scalenohedral shape with a respective length in a range from about 0.05 to about 2 microns and a respective diameter in a range from about 0.01 to about 0.5 -m can be generated.

21. The method according to any one of the preceding claims, characterized in that the fibrous suspension (10) is diluted with water in a radially outer region of the treatment unit (14) comprising two relatively rotating plates.

22. The method according to any one of the preceding claims, characterized in that the consistency of the fiber suspension (10) passed through the treatment unit (14) is in a range from approximately 0.1 to approximately 50% and preferably in a range from approximately 5 to approximately 35 % lies.

23. The method according to any one of the preceding claims, characterized in that a constant supply of carbon dioxide or gas containing carbon dioxide is ensured.

24. The method according to any one of the preceding claims, characterized in that the carbon dioxide or the gas containing carbon dioxide is added under a pressure which is in a range from about 0.1 to about 6 bar and preferably in a range from about 0.5 to about 3 bar.

25. The method according to any one of the preceding claims, characterized in that in the course of the chemical precipitation reaction for an at least substantially complete conversion of said starting materials calcium oxide or calcium hydroxide and carbon dioxide into the reaction products calcium carbonate and water is ensured by the pH of the fiber suspension (10) preferably regulated or controlled accordingly via the supply of carbon dioxide. becomes.

26. The method according to claim 25, characterized in that a pH value is set which is in a range from approximately 6 to approximately 10 and preferably in a range from approximately 7 to approximately 8.5.

27. The method according to claim 25 or 26, characterized in that the energy introduced for the chemical precipitation reaction in a range from about 0.3 to about 8 kWh / t and preferably in a range from about 0.5 to about 4 kWh / t lies.

28. The method according to any one of the preceding claims, characterized in that dilution water is added and mixed with the fibrous suspension (10) in order to finally obtain a consistency of the diluted fibrous suspension (10) which is in a range from about 0.1 to about 16%, and preferably in a range from about 2 to about 6%.

29. The method according to any one of the preceding claims, characterized in that the treatment unit (14) is operated such that its rotating plate or rotor at the radially outer edge has a peripheral speed in a range from approximately 20 to approximately 100 m / s and preferably in has a range from about 40 to about 60 m / s.

30. The method according to any one of the preceding claims, characterized in that the width of the gap between the two relatively rotating plates of the treatment unit (14) in a range from about 0.5 to about 100 mm and preferably in a range from about 25 to is about 75 mm.

31. The method according to any one of the preceding claims, characterized in that the diameter of the two relatively rotating plates of the treatment unit (14) is in a range from approximately 0.5 to approximately 2 m.

32. The method according to any one of the preceding claims, characterized in that the reaction time for the chemical precipitation reaction is in a range from about 0.01 min to about 1 min and preferably in a range from about 0.1 s to about 10 s.

33. The method according to any one of the preceding claims, characterized in that free, i. E. calcium carbonate is not washed out in and / or on the fibers.

34. Tissue product made from a fiber suspension (10) produced by the method according to one of the preceding claims.