WO2015036357A1

WO2015036357A1 - Method for producing paper

Info

Publication number: WO2015036357A1
Application number: PCT/EP2014/069062
Authority: WO
Inventors: Johann Schulte; Frank HÜPPERLING; Markus Dörk
Original assignee: DEFOTEC Entschäumer Vertriebs GmbH
Priority date: 2013-09-11
Filing date: 2014-09-08
Publication date: 2015-03-19
Also published as: EP3044364A1; EP3044364B1; DE102013109991A1

Abstract

The invention relates to a method for producing paper with at least one fibrous material, a polymer, water and calcium oxide and/or calcium hydroxide, comprising the steps of disintegrating the fibrous material with water in a pulper for producing a fibrous material suspension and transferring the fibrous material suspension into a vat. The method is characterised in that in the disintegration of the fibrous material in the pulper calcium oxide and/or calcium hydroxide having a proportion of active substance between 0.1 kg per tonne of oven-dry fibrous material and 50 kg per tonne of fibrous material for setting of a pH value between 9 and 12 is added to the fibrous material suspension, and in the vat an acrylamide copolymer having a proportion of active substance between 0.1 kg per tonne of oven-dry fibrous material and 10 kg per tonne of fibrous material is added.

Description

Process for the production of paper

The present invention relates to a process for the production of paper in which besides at least one fibrous material, polymer, water, calcium oxide and / or calcium hydroxide are used.

Methods of making paper are known. Here, in a first step, a suspension is prepared from at least water and fibers, which are mostly of vegetable origin, which are then mechanically dehydrated, thermally dried and rolled up in a paper machine. In addition to pulp and mechanical pulp, fiber materials today are in particular recovered paper, which is offered in different qualities on the recovered paper market. Furthermore, the

Fibrous suspension also added additives with which the manufacturing process is improved or the quality of the finished product can be influenced. Such

Additives are auxiliaries and additives of natural and synthetic origin.

Starting from this basic procedure, it is now the task of

Papermaking process, from the available

Starting materials to provide a finished product, in which in addition to the printability and the mechanical properties are adapted to the papermaking processing stages subsequent. The paper strength, for example, measured as bursting pressure (DIN 53141 / DIN ISO 2758), the

Streak Shock Resistance (SCT) Value (DIN 54518) or Flat Shock Resistance (CMT) Value (DIN EN ISO 7263)

Determine the quality characteristics of the paper. Moreover, it is advantageous if the finished product with appropriate mechanical properties a Has as high a proportion of fillers, since they are cheaper than fibers and improve the printability. These are added either as mineral fillers such as chalk, kaolin, talc, bentonite, titanium dioxide or gypsum or as modified mineral fillers such as cationized calcium carbonates, calcined kaolin, anhydrite and / or added in the use of waste paper on this in the pulp suspension.

With regard to the use of recovered paper as a main source of pulp, however, it has now been found that its paper quality in terms of strength and fiber properties (among other things due to the high recycling rate) is getting worse and paper production is almost forced, the lack of strength of the paper

Base material through the use of chemical additives to improve. These include in particular the use of natural and synthetic

Dry strength agents such as starch, guar, xanthan, polyacrylamides, polyvinylamines, glyoxals, etc.

Based on this prior art, it is an object of the present invention to overcome the disadvantages known in the prior art at least partially or to improve and especially in the use of

Waste paper to show a method in which either the paper properties can be improved with the same input of raw materials and / or increase the proportion of inexpensive raw materials in the paper, but without loss

especially with regard to mechanical paper properties.

This object is achieved by the method for producing a paper according to claim 1. Preferred alternative embodiments are the subject of the dependent claims.

The inventive method for the production of paper used as

Raw materials at least one fiber material, a polymer, water and calcium oxide and / or calcium hydroxide. The raw materials are preferably in the following

Processed steps and for the manufacturing process on or in one

Paper machine prepared as follows:

The first step involves the impact of the fiber material with water in a pulper to produce a pulp suspension with the subsequent Transfer of the pulp suspension into a chest, according to the invention during the impact of the fiber material in the pulper, or following thereto, calcium oxide and / or calcium hydroxide with an active ingredient content between 0.1 kg per tonne otro fiber material and 50 kg per tonne fiber material for setting a pH Value is added between 8 and 12 in the pulp suspension. Furthermore, the pulp suspension is added as polymer an acrylamide copolymer having an active ingredient content of between 0.1 kg per tonne otro fiber material and 5 kg per tonne fiber material.

Alternatively to the order shown, the addition of calcium oxide and / or calcium hydroxide and acrylamide copolymer may also be reversed. In this case, first, the acrylamide copolymer, for example, in the pulper or a downstream chest and then calcium oxide and / or

Added calcium hydroxide. It is also within the meaning of the present invention that according to a preferred embodiment of the invention

Method, the addition of the calcium oxide and / or calcium hydroxide in the pulper and then in a further chest, the addition of the acrylamide copolymer takes place.

In accordance with the present invention, calcium oxide and / or calcium hydroxide is added to the water-suspended fiber material. Here, calcium oxide, which is also referred to as quicklime, quicklime, quicklime, lime or quicklime, a white powder that reacts with water with a strong evolution of heat. The reaction with water forms calcium hydroxide (slaked lime, lime water). On an industrial scale, calcium oxide is produced by lime burning. From a temperature of about 800 ° C limestone (calcium carbonate) is deacidified, that is, carbon dioxide is expelled and it produces calcium oxide.

Alternatively, calcium oxide can be the pulp as already with water

suspended calcium oxide (so-called milk of lime or calcium hydroxide)

be added, which may in particular contain dispersants.

It is essential here that with the addition of calcium oxide and / or

Calcium hydroxide, the pH of the pulp suspension in the pulper is set to a value between 8 and 12, for which purpose usually calcium oxide must be added as a commodity in an amount between 0.1 kg and 50 kg. According to a preferred embodiment of the present invention, the pulp suspension calcium oxide and / or calcium hydroxide is added in such a way that the active ingredient content of calcium oxide and / or calcium hydroxide between 2 kg per tonne otro fiber material and 30 kg per tonne fiber material, preferably between 5 kg per tonne otro Fiber material and 20 kg per ton of fiber material, is.

As an alternative to a purely quantitative addition of calcium oxide and / or calcium hydroxide, this addition is controlled or regulated such that the pH of the pulp suspension after the addition of calcium oxide and / or calcium hydroxide is between 7 and 13, preferably between 8 and 12 and in particular between 9 and 1 1 lies.

The impact of the fiber material in the pulper with water is further carried out according to a further preferred embodiment of the present invention at a pulp density in the pulper between 1 wt .-% and 26 wt .-%, preferably between 4 wt .-% and 7 wt .-% ( Standard pulper) or 10% by weight and 24% by weight

(High consistency pulper) and in particular between 3.5 wt .-% and 6 wt .-% for standard pulper or 12 wt .-% and 20 wt .-% high consistency pulper, wherein for adjusting the consistency preferably circulated water of

Papermaking process is used, which in particular has a pH which is between 5.5 and 7.5, preferably between 6 and 7.

According to a further particularly preferred embodiment of the present invention, the chest, in which the whipped pulp suspension is transferred from the pulper, an intermediate chest, a mixing chest, a Ableerbütte and / or a machine chest, wherein it is also within the meaning of the present invention that the Pulp suspension is transferred from the pulper in a Ableerbütte and then into an intermediate and / or mixing chest, in which, for example, the polymer, additives and / or the calcium oxide and / or calcium hydroxide is added or be.

According to a particularly preferred embodiment of the present invention, the addition of the acrylamide copolymer takes place in a single chest, ie a single metering point, this being, for example, both the intermediate chest, the Mischbütte, the Ableerbütte, the machine chest or even the pulper can be.

The fibrous materials used according to the present invention are preferably selected from a group of fibrous materials, which primary and secondary fibrous materials and especially waste paper, pulp such as sulfate or sulfite pulp, wood pulp, stone pulp, refiner pulp, thermo-mechanical pulp, Chemi-mechanical pulp, chemi-thermo-mechanical pulp, combinations thereof, and the like.

Moreover, according to a particularly preferred embodiment, used as fibrous material is substantially waste paper.

The polymers used according to the present invention are preferably cationic acrylamide copolymers selected from the group consisting of ADAME (N, N-dimethylaminoethyl acrylate), DIMAPA (N, N-dimethylaminopropylacrylamide), MADAME (N, N-dimethylaminoethyl methacrylate) and DADMAC ( Diallyldimethylammonium chloride) in quaternized form and / or their acids. Alternatively to the use of a cationic acrylamide copolymer, an anionic acrylamide copolymer may also be used. Such an anionic acrylamide copolymer is, for example, sodium acrylate and acrylamide. Such acrylamide copolymers preferably have the following structural formulas or can be prepared as cationic polyacrylamide correspondingly from acrylamide and chloromethylated monomer:

= CH3: MADAME

According to a further particularly preferred embodiment of the present invention, the acrylamide copolymer is in the range from 10% by weight to 99% by weight, preferably 15% by weight to 90% by weight, more preferably 20% by weight. to 80 wt.%, most preferably 25 wt.% to 70 wt.%, in particular 30 wt.% to 60 wt.%, of cationic monomers, based on the total weight of the cationic acrylamide copolymer. Further and

particularly with regard to the use of the inventive method, the acrylamide copolymer has an average molecular weight which is between 0.5x10 ⁶ g / mol to 10x10 ⁷ g / mol, preferably between 2x10 ⁶ g / mol to 5x10 ⁷ g / mol and in particular between 7x10 ⁶ g / mol to 8x10 ⁷ g / mol. In addition, the acrylamide copolymer according to another particularly preferred

Embodiment a cation activity, which is between 5 mol .-% and 100 mol .-%, preferably between 20 mol .-% and 80 mol .-% and in particular between 30 mol .-% and 60 mol .-%. The metering of the acrylamide copolymer is furthermore preferably carried out as an aqueous solution which is added as a dispersion, emulsion or suspension (prepared from a powder or granules) to the pulp suspension. Alternatively, the acrylamide copolymer as the solid directly

Pulp suspension are added.

In addition to the addition of the above-described polymers or of the calcium oxide and / or calcium hydroxide, it is also within the meaning of the present invention that the fibrous suspension is additionally added at least one further additive which is selected from a group comprising starch, in particular native starch, cationically or anionically modified starch, guar, xanthan, polyvinylamine, anionic starch, CMC, polyvinyl alcohol and / or glyoxal, polyamidoamine-epichlorohydrin, melamine-formaldehyde, urea-formaldehyde, polyaluminum chloride, polyaluminum nitrate, alum, combinations thereof, and the like.

The metering of the acrylamide copolymer is further carried out in a manner such that the reaction time of the acrylamide copolymer with the pulp suspension is between 5 minutes and 120 minutes, preferably between 10 minutes and 80 minutes and in particular between 20 minutes and 60 minutes before the

Fiber suspension further processed and in particular the paper on the

Paper machine is produced. The metered amount of acrylamide copolymer according to the present invention with an active ingredient content between 0.5 kg per tonne otro fiber material and 10 kg per tonne fiber material, preferably between 1, 0 kg per tonne otro

Fiber material and 3 kg per ton of fiber material.

The invention will be illustrated with reference to individual embodiments. It should be noted, however, that these embodiments are only

are to be understood as examples and the modifications and additions, as would make the skilled person, are also in the context of the present invention. Furthermore, the invention should not be limited to the examples presented here, which serve to illustrate and explain the principle and application of the method according to the invention.

Showing: Fig. 1 is a list of the corresponding specifications of the acrylamide copolymers used in the experiments;

Figures 2a to 2d are graphs and a table for laboratory experiments;

3a to 3c graphics and a table for further laboratory experiments;

4a to 4d graphics and a table for further laboratory experiments;

Fig. 5a to 5d graphics and a table for further laboratory experiments;

Fig. 6a to 6e graphics and a table for further laboratory experiments;

FIGS. 7a to 7c are graphs and a table for further laboratory experiments;

Figs. 8a to 8c are graphs and a table of industrial experiments;

9 shows a variant of a flowchart for carrying out the

inventive method;

10a to 10c are graphs and a table for retention experiments. The laboratory tests were carried out as follows:

In a paper factory for packaging papers, a fabric sample was taken after the pulper. This has a consistency of 4%. Raw material here is mixed waste paper, as it is commonly used for the production of packaging paper.

First of all, the required amount of lime in the form of CaO, Ca (OH) ₂ or lime milk was added to this mixed substance mixture (STWG). For example, 500 ml STWG were placed in a blender and then mixed with lime for about 30 sec. The pH of the STWG is then about pH 10 - 10.5. The corresponding amount of polymer was then mixed into the STWG and stirred vigorously for a further 30 sec. The STWG was then poured into a plastic bottle and stored for about 30 to 60 minutes. Subsequently, sheets of the appropriate weight were produced on a Rapid-Köthen sheet former. The appropriate amounts of substance were removed from the bottle. In another embodiment, the polymer was added first and then the amount of lime needed.

The test sheets were then conditioned in a climate room for 24 hours and then the weight determined. The basis weight was calculated. The corresponding strength tests were then carried out on the leaves.

Bursting pressure according to DIN 53141 (DIN ISO 2758), SCT value according to DIN 54518, CMT value according to DIN E ISO 7263.

From the leaves, the ash content was determined by ashing in a muffle furnace. This is stated in% ash. Subsequently, a test protocol was created and the tests were evaluated. The strengths were fixed

Basis weight of eg 100 g / m ² converted, so you can compare this better. With strong variations of the ash contents, these were then also compensated. We assumed that 1% filler change brings about 2% strength changes. Figure 1 shows an overview of various acrylamide copolymers, which were investigated and used in the present experiments.

In the tables of Figures 2d, 3c, 4d, 5d, 6e, 7c and 8c are the

Experimental parameters and results for various industrial and laboratory experiments. Here, in the table of FIG. 2d, the blank sample for a test without polymer or calcium oxide, Poly 49 for the addition of the polymer poly 49 according to the table of Figure 1 and lime for the addition of calcium oxide.

In the experiments according to the table from FIG. 3c, the influence of calcium oxide and polymer, as well as an experiment using magnesium oxide (sample number 7), were investigated and evaluated. The quantities of polymer, calcium oxide or magnesium oxide used are those used

Amount of waste paper stated and at which consistency the dosage was carried out. The polymers used result from the abbreviations used and the specification in the table from FIG. 1. The same applies to the table according to FIG. 4d, whereby in particular the influence of different cationic polymers was investigated in this series of experiments. The following cationic polymers were tested:

ADA E-based, MADAME-based, DIMAPA-based and DADMAC-based acrylamide copolymers;

Poly 49, Poly 35 and Poly 25 are ADAME based products;

Poly M65 and M99 are MADAME based products;

- Poly 853 is a DIMAPA based product;

- Dadmac is a DADMAC based product. All products were tested in combination with lime, compared to zero and only polymer (poly49) alone. More information about the used

Polymers result from the abbreviations used and the specification in the table from FIG. 1.

In the experiments according to the table from FIG. 5 d, starch was used as an additional additive in addition to previous attempts. The

Combination with cationic starch adds an extra

Increase in strength. The starches used here are cereal flours, which are specified below as MK21, MK01 and MK5025:

In the tables of Figures 6 to 8, the experimental parameters for various industrial experiments and laboratory experiments are reproduced. It is in the table from Fig. 6, the blank sample for a test without polymer / base, 1 or 2 kg of poly for the addition amount of polymer per ton of solid and lime or NaOH for the adjustment of the pH by means of sodium hydroxide or calcium oxide. In the table of FIG. 7, basically only lime was used to adjust the pH, with 3 kg / t of polymer and 10 kg / t of calcium oxide being added in the test series. The zero value indicates the comparative value without polymer and calcium oxide, Poly 49 the addition of the polymer without calcium oxide, Poly 49 lime the addition of the polymer with calcium oxide, SFC 60 another polymer without lime and SFC 60 lime the addition of the second polymer with calcium oxide. The same applies to the table according to Figure 8, these experiments were carried out as industrial experiments.

The numerical results of the experiments are also shown in excerpts in FIGS. 2a to 2c, 3a, 3b, 4a to 4c, 5a to 5c, 6a to 6d, 7a, 7b, 8a and 8b. In addition to the bursting pressure, the SCT value and the CMT value were used as relevant quantities for the assessment of the mechanical properties of the paper thus produced and compared with the respective zero value.

As can be seen from the illustrations of FIGS. 2a to 2c, the strength values of the bursting pressure and of the SCT value increase continuously up to the addition amount of 3000 g / t of polymer and decrease significantly as the amount added increases further. At present, it is assumed that if the dosage is too high, a very strong flocculation of the waste paper fibers takes place, which is another

Increased strength prevented. This effect is also likely to be seen in the CMT value, with the drop occurring only at a higher addition level of polymer. The development of the bursting pressure and of the SCT value in the second series of experiments is shown in extracts in FIGS. 3a and 3b. The tests according to the table of Figure 3c show the comparison to the zero value only with lime (# 10) and polymer, and experiments with magnesium oxide (# 7) as a substitute for lime. Only lime alone brings a slight increase. By adding a

corresponding polymer also takes place here from the test series 2d known slight increase. The combination of lime and polymer brings the highest

Increases in strength. Likewise, the dosing order (Sample Nos. 3 and 13) has been changed. Both methods show similar increases in strength. In the trial 8 and 9, an anionic polymer was tested. Here is also an increase in strength in conjunction with lime to recognize. In experiment 11 and 12 an emulsion polymer was tested, here you can see the same

Strength increases as in the addition of powder polymers. FIGS. 4a and 4c show the development of the bursting pressure, the SCT value and the CMT value for the various polymers investigated. For the CMT value and the SCT value resulted in comparable conditions and

The highest values are given by the polymer "Poly 25." At bursting pressure, the polymer "Poly 35" gave the highest value. All in all, however, all the polymers used show the desired improvement of the investigated mechanical

Paper properties.

FIGS. 5a and 5c show the development of the bursting pressure, the SCT value and the CMT value for the test series according to the table from FIG. 5d, starch being used as an additional additive in addition to previous attempts. Here, too, shows a significant increase in mechanical strengths, which turned out to be the highest, especially in the combination of poly 49 with strength MK 5025 and MK01.

The numerical results of experiments 6, 7 and 8 are also given in excerpts in the corresponding figures to the tables. Here it can be seen that the use of lime and polymer significantly increases the

Bursting pressure could be achieved, which was compared to the use of caustic soda instead of lime by 8% better and also performs significantly better in terms of the use of the polymer without alkali. Furthermore, it is clear that without the addition of a base, despite an increase in the use of the polymer, no improvement in the bursting pressure, but its reduction was effected.

The same is true with regard to the SCT value in FIG. 6b, which, when using 2 kg of polymer in combination with calcium oxide, is significantly better than when using sodium hydroxide solution. Here, however, in comparison to the experiment without base, the increase in the polymer could bring about an improvement in the SCT value. With regard to the CMT value of Figure 6c, no significant difference between the use of calcium oxide and caustic soda could be shown, Surprisingly, when using smaller amounts of polymer in combination with calcium oxide the best values could be achieved.

FIGS. 7a and 7b show the development of the bursting point and the SCT value for different amounts of polymer used in combination with lime

shown. In particular, the combination of 2000 g / t "Poly49" as polymer with 15 kg / t lime showed the best results both for the bursting pressure and for the SCT value.

FIGS. 8a and 8b show the results of the industrial tests for the use of "Poly 49" and "SFC 60" as polymers in combination with lime and in comparison to the blank test. Here, too, the best results are achieved in the combination of "Poly 49" with lime.

In addition to the mechanical properties, the filler content in the paper sheet produced was also examined in the test series, which allows a conclusion on the retention behavior of the material system. This shows that when using the polymer in combination with calcium oxide, the highest filler content in the sheet was effected and still the mechanical strengths were significantly improved.

In summary, it can thus be stated that in the production of a paper structure according to the method according to the invention, i. the impact of the waste paper in the pulper with water and the addition of calcium oxide or

Calcium hydroxide and the addition of an acrylamide copolymer as a polymer not only surprisingly significantly increased the filler content in the paper, but also the required mechanical strengths, in particular the bursting pressure and the SCT and CMT value could be significantly improved. In addition, it was found in industrial experiments that the dewatering ability of the pulp suspension could be significantly improved. Thus, the water level on the wire of the paper machine reduced by about 1 to 2 m by the use of the appropriately prepared pulp suspension. Furthermore, the steam consumption in the dryer group was reduced - which can be understood as an indication of a higher dry content after the mechanical dewatering of the paper sheet - and the torque was reduced on the sieve suction roll. All these features show that that is

Has improved drainage behavior of the pulp suspension and thus with improved quality values of the finished product less energy u.a. was needed to dry the paper texture. In addition, there is an economic advantage due to the lower market price of calcium oxide compared to

Sodium hydroxide solution. FIG. 9 shows a variant of a flowchart according to the invention. In this case, in point 1, the waste paper with water (H2O) pitched, so that, for example, a pulp suspension is provided which has a consistency of 4%. The required amount of limescale in the form of CaO or Ca (OH> 2) is first added to this mixture of substances in point 2. The pH of the substance mixture is then about pH 10 - 10.5 The mixed substance mixture is then mixed in position 4 for about 30 to 60 minutes

Paper machine PM fed under point 5.

Alternatively, both the order of addition of the CaO or Ca (OH> 2 or the polymer can be reversed or in particular the addition of CaO or Ca (OH) 2 or the polymer already under point 1, for example in the pulper of a stock preparation plant, respectively.

Graphs 10a and 10b and Table 10c show test results for retention studies in which the product combination, lime and polymer were also tested as retention aids. As a material system, a fine paper pulp was selected, which had about 70% pulp and 30% filler. The retention measurements were performed in the laboratory with a Britt Jar (Britt Dynamic

Drainage Jar) under standard conditions (see also TAPPI method T-261 (80)) performed. As can be seen from the graphs and the table, there are further clear advantages. By way of comparison, the retention improvement can be recognized as an existing retention system known as "Hydrocol" is. For lime (10kg / t) + SFC60 (800g / t) an overall retention of 88.1% and an ash retention of 46.4% are obtained. The use of lime (10 kg / t) + C 49 (800 g / t) resulted in a total retention of 87.6% and an ash retention of 55.9%. Thus, with the system according to the invention, the total retention was above the reference value in all studies

"Hydrocol" system and also the ash retention could be further improved by using C 49.

Claims

claims

1. A process for producing paper with at least one fiber material, a polymer, water and calcium oxide and / or calcium hydroxide, comprising the steps of:

- Impact of the fiber material with water in a pulper to produce a pulp suspension;

- Transferring the pulp suspension in a BÃ¼lt thereby

characterized in that during or after the impact of the fiber material calcium oxide and / or calcium hydroxide is added with an active ingredient content between 0.1 kg per tonne otro fiber material and 50 kg per ton of fiber material to adjust a pH between 8 and 12 in the pulp suspension and a Acrylamide copolymer with an active ingredient content between 0.1 kg per tonne otro fiber material and 10 kg per ton of fiber material is added.

2. The method according to claim 1, characterized in that the addition of the calcium oxide and / or calcium hydroxide in the pulper and then in a further chest, the addition of the acrylamide copolymer takes place.

3. The method according to claim 1, characterized in that the addition of the acrylamide copolymer takes place before the addition of the calcium oxide and / or calcium hydroxide.

4. The method according to any one of claims 1 to 3, characterized in that the active substance content of calcium oxide and / or calcium hydroxide between 2 kg per tonne otro fiber material and 30 kg per tonne fiber material,

preferably between 5 kg per tonne otro fiber material and 20 kg per tonne fiber material.

5. The method according to any one of claims 1 to 4, characterized in that the pH of the pulp suspension after the addition of calcium oxide and / or calcium hydroxide between 7 and 13, preferably between 8 and 12 and in particular between 9 and 1, is located.

6. The method according to any one of the preceding claims, characterized

in that the pulp density in the pulper is between 1% by weight and 26% by weight, preferably between 4% by weight and 7% by weight or 12% by weight and 24% by weight and in particular between 3 , 5 wt .-% and 4 wt .-% and 18 wt .-% and 20 wt .-%.

7. The method according to any one of the preceding claims, characterized

characterized in that the pH of the water, in particular the circulating water to

Suspension of the fiber material in the pulper between 5.5 and 7.5, preferably between 6 and 7, is located.

8. The method according to any one of the preceding claims 2 to 7, characterized

in that the chute is an intermediate chute, a discharge chute and / or a machine chest.

9. The method according to any one of the preceding claims, characterized in that

the fibrous material is selected from a group of fibrous materials, which primary and secondary fibrous materials and especially waste paper, pulp such as sulfate or sulfite pulp, wood pulp, stone pulp, refiner pulp, thermo-mechanical pulp, chemical mechanical pulp, Chemi Thermo-mechanical pulp,

Combinations thereof and the like.

10. The method according to any one of the preceding claims, characterized

characterized in that the addition of the acrylamide copolymer takes place only at a metering point.

1 1.Verfahren according to any one of the preceding claims, characterized

in that the acrylamide copolymer is cationic and is selected from a group comprising N, N-dimethylaminoethyl acrylate, N, N-dimethylaminopropylacrylamide, N, N-dimethylaminoethyl methacrylate and diallyldimethylammonium chloride in quaternized form and / or their acids, or the acrylamide copolymer is anionic and has, for example, sodium acrylate and acrylamide.

12. The method according to any one of the preceding claims, characterized

in that the acrylamide copolymer is in the range from 10% to 99% by weight, preferably 15% to 90% by weight, more preferably 20% to 80% by weight, most preferably from 25% to 70% by weight,

in particular 30 wt .-% to 60 wt .-%, cationic monomers based on the total weight of the cationic acrylamide copolymer.

3. The method according to any one of the preceding claims, characterized in that the acrylamide copolymer has an average molecular weight which is between 0.5x10 ⁶ g / mol to 10x10 ⁷ g / mol, preferably between 2x10 ⁶ g / mol to 5x10 ⁷ g / Mol and in particular between 7x10 ⁶ g / mol to 8x10 ⁷ g / mol.

14. The method according to any one of the preceding claims, characterized

in that the acrylamide copolymer is added as an aqueous solution prepared from powders or granules, dispersion, emulsion or suspension, or in solid form to the pulp suspension.

15. The method according to any one of the preceding claims, characterized

in that, in addition to the calcium oxide and / or calcium hydroxide or acrylamide copolymer, at least one additional additive is added to the pulp suspension which is selected from a group which starch, in particular native starch, cationically or anionically modified starch, guar, xanthan, polyvinylamines , anionic starch, CMC, polyvinyl alcohol and / or glyoxal, polyamidoamine-epichlorohydrin, melamine-formaldehyde, urea-formaldehyde, polyaluminum chloride, polyaluminum nitrate, alum, combinations thereof, and the like.

16. The method according to any one of the preceding claims, characterized

in that the reaction time of the acrylamide copolymer with the pulp suspension is between 5 minutes and 120 minutes, preferably between 10 minutes and 80 minutes and in particular between 20 minutes and 60 minutes.

7. The method according to any one of the preceding claims, characterized

characterized in that the acrylamide copolymer with an active ingredient content between 0.5 kg per tonne otro fiber material and 10 kg per tonne fiber material, preferably between 1, 0 kg per tonne otro fiber material and 3 kg per tonne

Fiber material is added.

18. The method according to any one of the preceding claims, characterized

in that the acrylamide copolymer has a cationic activity which is between 5 mol% and 100 mol%, preferably between 20 mol% and 80 mol% and in particular between 30 mol% and 60 mol. -% lies.