DE102004060587A1 - Bentonites for impurity binding in papermaking - Google Patents

Abstract

A process for impurity binding in papermaking is described, comprising the following steps: DOLLAR A a) Providing a bentonite, wherein the proportion of monovalent cations in the cation exchange capacity (CEC) of the bentonite is at least 0.7 and the CEC more than 85 meq / 100 g, preferably more than 90 meq / 100 g, in particular more than 95 meq / 100 g; DOLLAR A b) adding the bentonite according to a) to the paper pulp or pulp mass; DOLLAR A c) binding of the impurities to the bentonite in the pulp or pulp suspension.

Description

The The present invention relates to the use of specific bentonites with a high cation exchange capacity upon binding or removal of impurities in papermaking.

The removing contaminants or binding in papermaking is becoming increasingly important. The The problem is also based on the fact that in papermaking accumulating water is circulated, with impurities gradually accumulate in it. These contaminants can be the most diverse product disorders to lead, such as. for forming deposits on the rolls of the paper machine, for Glueing the screens, etc. These effects lead to interruptions the paper production. To minimize the number of production stops, it is desirable to bind the resulting in the circulating water impurities by Polymers or adsorbents already used in the headbox. The most relevant contaminants are negatively charged. These are for example to humic acids, Resin colloids, lingin derivatives, lignosulfonates derived from the fibers be entered in the paper cycle. There are also anionic ones impurities, which are entered into the paper machine by recycling paper broke. This paper break is typically redispersed and in introduced the paper machine. As a result, the contained therein Ingredients and aids completely recycled. registered will be additional e.g. Carboxymethylcelluloses, polyacrylates, polyphosphonates and Silicates. Other anionic charged impurities are the latexes may be used in the paper coating which, while typically hydrophobic are, but also carry anionic charges. These tend to be strong for agglomeration, wherein the agglomerates as sticky, white residues on deposited on the paper machine (so-called white pitch).

in the State of the art is already extensive the discharge of sticky Substances (so-called "stickies") through use of talcum (talc). Thus, according to P. Biza, E. Gaksch and P. Emperor "Improved Dispensing of Stickies through the Use of Talcum ", Wochenblatt für Papierfabrikation 11/12 (2002) P. 759ff. no later than Since the beginning of the last century, the effect of talc on Reduction of adhesive deposits documented. Almost all known natural and synthetic adhesives are hydrophobic. Talc is for binding these stickies insofar best suited because it has an inherently hydrophobic surface, which makes it light on adhesive surfaces adsorb and this by wrapping less sticky.

Furthermore, for example, in the US 5,368,962 the use of montmorillonites such as bentonite to control impurities in the pulp described. Also, the alkali treatment of bentonites is addressed as a possibility.

In the US 4,964,955 Also, a method for reducing the impurities in papermaking is described. Therein, for impurity binding, a particulate composition comprising (a) a water-soluble cationic polymer coated on (b) a substantially water-insoluble particulate substrate. The polymer should be sufficiently electropositive so that the particulate composition has a zeta potential of at least about +30 mV. The polymer is preferably a poly (dialkyldialylammonium halide). The substrate is, for example, a phyllosilicate mineral.

Similarly, the EP 0 760 406 A2 a combination of a poly (dadmac / acrylamide) and a bentonite in impurity binding.

In the GB 2 297 334 A again discloses the use of a smectite clay for impurity control wherein the smectite clay is modified as follows: monovalent exchangeable cations are present in an equivalent ion content in the range of 0.20 to 0.60; a first type of bivalent exchangeable cations is present in an equivalent ion content in the range of 0.40 to 0.80; and a second type of bivalent exchangeable cations is present in an equivalent ion content in the range of 0.00 to 0.20, the first type of bivalent exchangeable cations comprising calcium and the second type of bivalent exchangeable cations comprising magnesium.

Lots the means used in the prior art for impurity binding are quite expensive and for certain Störstoffzusammensetzungen not optimal. There is thus a constant need for funds for Binding of contaminants in papermaking.

task The present invention was therefore an improved process for impurity binding in papermaking, in which a simple and economical can be used and that is a high Measure Impurities, also of hydrophobic shares possible.

These The object is achieved by the method according to claim 1.

So was surprisingly found in the context of the present invention that through the use of a bentonite, which is a proportion of monovalent Cations at cation exchange capacity (herein referred to as CEC (from the English) or KAK) of at least about 0.7 (i.e., 70%) and a CEC (total) of at least 85 meq / 100g, a surprising good contaminant binding in a process for impurity binding can be provided in papermaking.

Under impurities are both sticky in the context of the present invention Substances, also referred to in the literature as "adhesives" or "stickies", as well as the so-called "pitch". primarily tree resin components, Understood. Here can on the made in the introduction versions to the impurities be evicted. A detailed listing of the "Pitch" and "Stickies" components will be found For example, in WO01 / 09424 and pages 1 and 2, and the local disclosure is hereby expressly incorporated by reference the present description was included.

As stated above, are the impurities thus primarily anionic (negatively charged) or hydrophobic. So it was even more surprising that the invention used highly activated bentonites with high CEC both anionic and hydrophobic contaminant components bind very well and in their harmful Neutralize effect. The inventively used Bentonites themselves have a relatively high negative layer charge then put this high (negative) surface charge in the delaminated Shape of the pulp available. That would you do not have good binder binding for anionic or hydrophobic contaminants expect. Also would be to expect that a calcium bentonite better such impurities binds because a lot the charges of the bentonite is saturated by the calcium ions and this e.g. above Soap formation and fatty acids in tree resin impurities could immobilize. In particular, the stickies such as resin particles contain many more non-polar (hydrophobic) components, e.g. Triglycerides. These should especially good at non-polar surfaces, such as. which bind by talc. Talc has no surface charges and therefore also in the prior art is considered optimal for binding of (hydrophobic) impurities described.

The Results in the context of the present invention, according to which in the inventive method with bentonites, which is a big one surface with numerous negative charges available, both nonpolar as well as anionic impurities can be tied efficiently were therefore unexpected.

The inventive method using the specific bentonite described herein generally in all paper or board making processes be used. Accordingly, the terms paper pulp and pulp generally all pollutants Compositions or streams which are used in papermaking. Otherwise the terms "pulp" and "pulp suspension" are familiar to those skilled in the art and have to not closer here explained become.

According to a preferred embodiment of the invention, the pulp or pulp suspension is a wood (fine) slurry-containing suspension. Wood pulp is generally finely digested (finely ground wood, usually without further chemical or thermal treatment). The wood pulp suspension is either used directly after crushing or subjected to peroxide bleaching, in which case so-called peroxide-bleached wood pulp is produced. It has surprisingly been found that the bentonite used in accordance with the invention shows particularly good results in wood pulp or peroxide-treated pulp-containing paper grades. The inventive method can also be used advantageously in other types of paper. Thus, for example, the pulp or pulp suspension (in addition to the groundwood) may also contain highly purified fiber fractions, as is the case with so-called news print paper, for example. The invention further provides very good results in so-called "deinked pulp" (DIP substance). It is a pulp made from waste paper. In particular, there are hydrophobic stickies, from the glue of magazines and newspapers. These, too, can easily be incorporated into the end product using the bentonite used according to the invention. Further so-called paper materials in which the bentonite according to the invention can be advantageously used comprise TMP material (Thermo Mechanical Pulp), sulphate pulp, sulphite pulp and mixtures of different pulps. Depending on Paper type and localization of the paper mill, such pulps are mixed in different proportions and adapted to the material requirements of the final product.

Of the preferred proportion of groundwood in the paper pulp or pulp suspension is according to an advantageous embodiment of the invention at least 10th Wt .-%; in particular at least 30 wt .-%, each based on the Dry weight of the entire pulp or suspension.

Of the Bentonite in the process according to the invention Probably works without the invention to the correctness limited to this assumption would be by he the impurities binds or interacts with these and thus aggregation and deposition on the parts of the paper machine, e.g. the rollers, counteracts.

It is according to the invention essential that the bentonite used has a cation exchange capacity (CEC) of at least 85 meq / 100g, preferably at least 90 meq / 100g, especially at least 95 meq / 100g.

Under "Cation Exchange Capacity" (CEC) will be included the sum of all exchangeable cations understood, stated in mVal / 100g and determined by the CEC analysis method as follows before the example part (determination of the cation exchange capacity) explained. The Cation exchange capacity So, for example, includes the sum of all exchangeable two- and monovalent cations such as calcium, magnesium, sodium, lithium and potassium ions. To determine the cation exchange capacity of the bentonite with a Ammonium chloride solution treated. Due to the high affinity of the ammonium ions to bentonite virtually all exchangeable cations are exchanged by ammonium ions. After separation and washing, the nitrogen content of the bentonite determined and calculated from the content of ammonium ions.

It can both natural Bentonites as well as by activation e.g. of calcium bentonites recovered bentonites are used, provided the above conditions for the Proportion of monovalent cations at CEC and minimum values for the CEC are complied with. Method for generating or activating Bentonites are known to the skilled person as such and must be here not closer explained become. For example, of a calcium bentonite with suitable CEC and this with an alkali carbonate, e.g. sodium be treated. In the treatment or activation of the layered silicate can to bring in contact to any of those skilled in the art Manner, e.g. by producing a solid mixture, a suspension with the layered silicate and the sodium carbonate or applying or spraying of the layered silicate with a solution of sodium carbonate.

For example After the first process variant, a calcium-containing crude bentonite with a water content of about 25 to 40 wt .-% with solid sodium carbonate kneaded, dried and ground. The raw bentonite is placed on pieces of Prefabricated less than 3 cm in diameter. If the crude bentonite does not have the specified water content, this is by spraying with Water adjusted.

The Activation can for example also be as follows: 350 g Rohbentonit with a water content of about 30 to 35 wt .-%, are in a Mixing device (e.g., a Werner & Pfleiderer mixer (kneader)) and for Kneaded for 1 minute. Then, while continuing to run the mixing device the manganese was added to sodium carbonate (soda), which is the difference between CEC and sodium content of the bentonite, and further kneaded for 10 min. The amounts added to the anhydrous bentonite based. If necessary, some distilled water is added, so that the plasticine "shears" well. The plasticine will then in small pieces crushed and in a convection oven at about 75 ° C for 2 to 4 hours. on a water content of 10 ± 2% dried. The dry material is then placed in a rotary rotor mill (e.g. in a Retsch mill) over one Grind 0.12 mm sieve. The CEC and the proportion of sodium ions on it was determined as described below. An overactivation bentonite e.g. with soda is also possible, with more soda used can be considered as complete Activation of the bentonite stoichiometric would be required.

To a particularly preferred embodiment of the invention relates to indicated proportion of monovalent cations on the proportion of sodium, Potassium and lithium ions, especially the sodium ions.

According to a preferred embodiment of the invention, the bentonite used has a swelling capacity of at least 25 ml / 2 g, in particular of at least 30 ml / 2 g, more preferably min at least 35 ml / 2g. Thus, it has surprisingly been found that bentonites with such high swelling capacity enable a particularly advantageous impurity binding. The swelling volume is determined as follows: A calibrated 100 ml graduated cylinder is distilled with 100 ml. Filled with water. 2.0 g of the substance to be measured are slowly added in portions of 0.1 to 0.2 g on the water surface. After lowering the material, the next quantum is abandoned. After completion of the addition, wait for 1 hour and then read the volume of the swollen substance in ml / 2g.

Farther has been shown that the proportion of iron ions at the CEC is preferable below about 0.005 (0.5%). It has been shown that such bentonites give better results in terms of whiteness deliver the pulp.

According to a further preferred embodiment of the invention, the BET surface area (determined according to DIN 66131) of the bentonites used is less than 100 m ² / g, in particular less than 90 m ² / g. It is surprising that bentonite with a relatively low specific BET surface shows a particularly advantageous impurity binding compared to bentonites, which can provide a higher specific surface area for Störstoffadsorption.

typically, decreases in performance the method according to the invention the need for cationic charges in the paper headbox. This demonstrates the binding of the negatively charged impurities by charge interactions.

The Concentration of impurities in papermaking is typically in the white water through the three common Procedure cation requirement (cationic charge requirement), turbidity measurement and chemical oxygen demand determined. When cation needs it is assumed that the impurities are all negatively charged and filtered the white water in short chain cationic polyelectrolyte. Consumption is converted into the so-called cation requirement. In the turbidity measurement you go away from that the contaminants to Part colloid present and their concentration on the caused by the turbidity Extinction can be determined. At the chemical oxygen demand will over an oxidizing agent is the amount of organic compounds present tested. Although these methods are very common in the paper world recent studies have shown that these are beyond the Whole ingredients in white water average and especially critical impurities only partially capture. This results, for example, from the fact that the so-called tree resin colloids, some of which are hydrophobic compounds are composed of low surface charges and can carry thus contribute little to the cation requirement. On the other hand, lignins have a high cation requirement; if they are in the white water, they disturb very little in papermaking. Newer investigations continue to show that the correlation between the turbidity measurement and the concentration of colloidal impurities are not always given is. Because of this recent experience with the common contaminant determination methods have been the additives of the invention about that also characterized in their effect with newer methods. there For example, it is a gas chromatographic analysis of the white water according to the method of F. Orsa and B. Holmbom "A Convenient Method for the Determination of Wood Exctractives in Papermaking Process Waters and Effluents ", Journal of Pulp and Paper Science, Vol. 12 December 1994, pp J361. In the production of wood pulp-containing paper, the single tree resin components in their concentration over a Gas chromatographic method determined. These are to a complete, quantitative analysis during the standard determination methods such as turbidity, cation requirement and chemical Oxygen demand actually only as semi-quantitative at best to be evaluated. Furthermore, by L. Vähäsalo et al. (supra, see "Flow cytometric Analysis of white water ", below) that the so-called flow cytometry is very suitable for determining the number of colloidal impurities in paper sifting waters. Therefore, this new method has been used in the present invention also used the impurity to show reducing activity of the bentonites according to the invention.

The addition of the bentonite used according to the invention to the pulp or pulp suspension can take place at any point in the papermaking industry suitable for the person skilled in the art. Especially recommended is the addition directly in the pulper, because there is the possibility of a long contact time to the pulp, and the likelihood of a high level of impurity binding is given. Additional additions are in the entire so-called thick matter area. Also conceivable is an addition for the "dissolved air flotation" for water purification. In many cases, an already existing addition point for additives, for example in the form of a metering device or metering pump, will also be present in the respectively used papermaking apparatus which can be used for the addition of the bentonite used according to the invention. The bentonite can be used both in powder form, as well as in the form of a suspension or slurry. The suspension or slurry will in many cases allow better dosability and is easier to automate in large-scale, continuous processes.

It has further shown that the effect of the invention used Bentonite is particularly positive when adhering to a particular pond size becomes. Thus, according to a particularly preferred embodiment the invention, the particle size of the bentonite chosen so that the wet sieve residue on 45 μm smaller 2 wt .-%, preferably less than 1 wt .-%, in particular less than 0.5 % By weight. The determination of wet sieve residue is before the examples even closer explained. The preferred particle size can also be determined by the light scattering method (Malvern). To a particularly preferred embodiment of the invention is the average particle size (D50) (relative to the sample volume) between 0.5 and 10 microns, in particular between 2 to 6 μm, more preferably between 3 and 5 microns.

in the It has also surprisingly been found within the scope of the present invention that the use of the invention used Bentonite leads to a particularly good impurity binding, if in the process of using talc omitted. Also the use cationic polymers, e.g. Poly (dadmac) or polyacrylamide according to the state The technique can be reduced by means of the bentonite used according to the invention be or even completely omitted.

The Quantities of the bentonite in the process according to the invention can be from Be determined routinely on the basis empirical experiments. In the most cases Amounts between 0.5 and 12 kg / t paper pulp or pulp suspension, preferably between 1 and 8 kg / t, in particular between 1.5 and 7 kg / t, in each case based on the anhydrous pulp / suspension (dry weight), be beneficial.

Surprisingly was also found in the context of the present invention that the inventive method not only a very good binding of anionic impurity fractions, like fatty acids, allows but also an outstanding bond or removal of hydrophobic Contaminant fractions, such as Sterols, steryl esters and triglycerides. The results obtained surprisingly surpass both those with conventional Bentonites were obtained, as well as those of talc.

One Another aspect of the present invention relates to the use of a bentonite as described herein for impurity binding in papermaking. As mentioned above, In this case, the bentonite is preferably in a paper pulp or pulp suspension used, which contains groundwood parts. However, they are all paper types or pulp of the use according to the invention. Especially preferred are the paper types mentioned above such as groundwood or peroxide treated wood pulp containing paper grades, such which contain (in addition to the wood pulp) also highly purified fiber components, as e.g. in so-called news print paper the case is so-called "deinked pulp" (DIP-fabric), TMP-fabric (Thermo Mechanical Pulp), sulphate pulp, sulphite pulp as well Blends of different pulps.

Methods section:

So far Unless stated otherwise, the analytical methods given below were used:

1. Determination of cation exchange capacity (CEC analysis) and the cation shares

• Principle: The clay is treated with a large excess of aqueous NH ₄ -Cl solution, washed out and the amount of NH ₄ ⁺ remaining on the clay determined according to Kjeldahl. Me ⁺ (clay) ^- + NH ₄ ⁺ - NH ₄ ⁺ (clay) ^- + Me ⁺ (Me ⁺ = H ⁺ , K ⁺ , Na ⁺ , 1/2 Ca ²⁺ , 1/2 Mg ²⁺ ....)
• Equipment: Sieve, 63 μm; Erlenmeyer grinding flasks, 300 ml; Analytical balance; Membrane suction filter, 400 ml; Cellulose nitrate filters, 0.15 μm (Sartorius); Drying oven; Reflux condenser; hot plate; Distillation unit, VAPODEST-5 (Gerhardt, No. 6550); Volumetric flask, 250 ml; Flame AAS
• Chemicals: 2N NH ₄ Cl solution Nessler's reagent (Merck, item No. 9028); Boric acid solution, 2%; Caustic soda, 32%; 0.1 N hydrochloric acid; NaCl solution, 0.1%; KCl solution, 0.1%
• Procedure: 5 g of clay are sieved through a 63μm sieve and dried at 110 ° C. Then weigh exactly 2 g on the analytical balance in differential weighing into the Erlenmeyer grinding flask and add 100 ml of 2N NH ₄ Cl solution. The suspension is boiled under reflux for one hour. In the case of strongly CaCo ₃ -containing bentonites, ammonia development can occur. In these cases, must be as long as NH ₄ Cl solution is added until there is no odor of ammonia perceiving more. Additional control can be done with a wet indicator paper. After a standing time of approx. 16 h, the NH ₄ ⁺ bentonite is filtered off via a membrane filter chute and allowed to carry on with virtually no ions Washed deionised water (about 800 ml). The proof of the ionic freedom of the wash water is on NH ₄ ⁺ ions with the. for sensitive Nessler's reagent. The washing rate can vary between 30 minutes and 3 days depending on the key. The washed out NH ₄ ⁺ bentonite is removed from the filter, dried at 110 ° C for 2 hours, ground, sieved (63 micron sieve) and dried again at 110 ° C for 2 hours. Thereafter, the NH ₄ ⁺ content of the bentonite is determined according to Kjeldahl.
• Calculation of the CEC: The CEC of the clay is the Kjeldahl NH ₄ ⁺ content of the NH ₄ ⁺ bentonite (CEC of some clay minerals, see Appendix). The data are given in mval / 100 g clay (meq / 100g).
• Example: nitrogen content = 0.93%;
• Molecular weight: N = 14.0067 g / mol
  
  CEC = 66.4 meq / 100g NH ₄ ⁺ bentonite

Exchanged cations and their shares:

The cations released by the exchange are in the wash water (Filtrate). The proportion and type of monovalent cations ("exchangeable cations") were in the filtrate according to DIN 38406, Part 22, determined spectroscopically. For example, for AAS determination the washing water (filtrate) is concentrated, transferred to a 250 ml volumetric flask and filled with deionised water to the mark. Suitable measurement conditions for FAAS are to be taken from the following tables.

Calculation of cations:

• Molar masses (g / mol): Ca = 20.040; K = 39.096; Li = 6.94; Mg = 12.156; Na = 22.990; Al = 8.994; Fe = 18.616

at so-called over-activated Bentonites, i. those with a greater than stoichiometric Amount of e.g. Soda activated, the sum of the determined Amounts of monovalent cations determined as indicated above CEC excel. In such cases is the total content of monovalent cations (Li, K, Na) as 100 the CEC.

The Invention will now be described with reference to the following non-limiting Examples closer illustrated.

2. Determination of the BET surface area:

The Determination was carried out according to DIN 66131 (Multi-point determination).

3. Determination of wet sieving residue:

• Geräte: Analysenwaage, Plastikbecher, Pendraulik LD 50; Sieb: 200 mm Durchmesser, Maschenweite 0,025 (25 μm), 0,045 mm (45 μm), 0,053 mm (53 μm) oder 0,063 mm (63 μm); Ultraschallbad.

In the use of pigments and fillers, it is of interest whether and how much coarse fraction contains the material to be examined, which differ in their grain size from the normal particles. These proportions are determined by screening an aqueous suspension with water as the rinsing liquid. Wet residue is the residue determined under specified conditions.

• Instruments: Analytical balance, plastic cup, Pendraulik LD 50; Sieve: 200 mm diameter, mesh size 0.025 (25 μm), 0.045 mm (45 μm), 0.053 mm (53 μm) or 0.063 mm (63 μm); Ultrasonic bath.

It was first prepared a 5% suspension of bentonite (otro, ie after drying at 110 ° C) in 2000 g of water. For this purpose, the bentonite is stirred in at 930 rpm in about 5 minutes. After stirring for a further 15 minutes at 1865 rpm, the suspension is poured into the cleaned and dried sieve (mesh 45 μm wide) and washed with running tap water under tapping until the wash water runs clear. After washing the sieve residue with tap water, place the sieve in an ultrasonic bath for 5 minutes to sift off the remaining fines. It is important to ensure that when inserting the sieve in the ultrasonic bath between the water surface and sieve bottom no air remains. Rinse briefly with tap water after sonication. Thereafter, the screen is removed and the water renewed in an ultrasonic bath. The Ar beitsvorgang in the ultrasonic bath is repeated until no contamination of the water is more visible. The sieve with the remaining residue is dried to constant weight (otro) in a circulating air drying cabinet. After cooling, the residue is transferred with the brush into a bowl. Evaluation: wet sieve residue (NSR) in (%) based on the weight.

4. Particle size determination to Malvern:

there it is a common one Method. It became a mastersizer of the company Malvern Instruments Ltd, UK, used according to the manufacturer's instructions. The Measurements were carried out with the provided dry powder feeder in air and determines the values related to the sample volume.

5. Investigation of impurity binding:

at the investigation of impurity binding the procedure was as follows:

a) Production of paper pulp and filtration:

Of the elected Pulp (e.g., 45% pulp and 55% peroxide bleached wood pulp) can either be obtained directly from the paper mill, or before use in the fridge be kept. The stock was then shaken well 20g at 2% with warm deionized water in a 2000ml beaker diluted. While stirred at 400 rpm was heated the paper stock approach using a hot plate to 40 ° C. Will the Temperature reached, the test amount of adsorbent with Help of a Pasteur pipette added to the stock batch. Then it is set the adsorption time in the batch at 30 ° C at 40 ° C. and the mixture is stirred at 400 rpm. After that, the paper stock approach with the adsorbent to 1% solids content using deionized Water (40 ° C) diluted.

For the production of white water 1000g of this will be diluted Mixture (1% solids by weight) in the drainage and retention device (Mütek DF3 03 of the company Mütek, DE) dehydrated for 420 seconds (sieve 170 μm, Stirring speed 700 rpm). The white water samples are analyzed analytically.

b) Flow cytometric analysis of white water:

The so-called flow cytometry was used here, as described in Vähäsalo et al., "Use of Flow Cytometry In Wet End Research", Paper Technology, 44 (1), p. 45, February 2003 and additionally in "Effects of pH and calcium chloride on pitch in peroxide-bleached mechanical pulp suspensions ", 7 ^th European workshop on Lignocellulosics and Pulp, August 26 to 29, 2002, Åbo / Finland described. In short, a light scattering method for counting the particles is combined with a fluorescent label.

c) gas chromatographic Analysis of the white water:

Here became the method of F. Orsa and B. Holmbom "A Convenient Method for the Determination of Wood Exctractives in Papermaking Process Waters and Effluents ", Journal of Pulp and Paper Science, Vol. 12, December 1994, pp J361.

It demonstrate:

1 shows a graph of the dependence of the concentration of impurity particles in the white water (filtrate water) on the type and amount of adsorbent used (bentonite or talc).

The Invention will now be described with reference to the following non-limiting Examples further illustrated.

Example 1:

It the following materials for contaminant binding were investigated.

1. Calcium bentonite (bentonite 1)

The Analytical data of the calcium bentonite used are in Table 1 summarized. The shares in the CEC can be found in the table Second

Table 1: Analytical data of the calcium bentonite (bentonite 1 = EX M1289

Of the wet sieve residue (45μm) was at less than 0.5% by weight.

Table 2: Proportion of monovalent cations in the cation exchange capacity (CEC) of the calcium bentonite (bentonite 1); CEC (total) = 106 meq / 100 g

2. Cationized talc (Product Malusil 75-7 K of the company Talc de Luzenac)

3. Bentonite according to the invention (Bentonite 2)

Bentonite 2 was obtained from bentonite 1 by kneading bentonite 1 with 5% by weight soda based on the anhydrous bentonite according to the above method, dried to a water content of 10% by weight and then to a corresponding particle size such as bentonite 1 (comparison Table 2) was ground. These processing steps do not alter the mineralogical data of the bentonite, so that the montmorillonite content and the content of accompanying minerals remain unchanged. The BET surface area was 85 ± 2 m ² / g.

The analytical data for Bentonite 2 are shown in Table 3.

Table 3: proportion of monovalent cations and the cation exchange capacity (CEC) of the bentonite (bentonite 2) according to the invention; CEC (total) = 102 meq / 100 g Benton

With the two bentonites 1 and 2, the impurity binding as in the method part described examined. To carry out the filtration experiments a pulp was used which was taken from a paper machine was and made of 45% long-fiber pulp and 55% peroxide-bleached groundwood duration.

To the Comparison was a "zero sample" driven, i. it were no adsorbents for impurity binding used.

For the characterization of the filtrate waters (white water) with a view to a reduction of interfering substances, the above flow cytometry was used. The results are in 1 shown. The amount of adsorbent used (bentonite or talc) is plotted against it Concentration of Störstoffteilchen in white water. It can be clearly seen that bentonite 2 according to the invention, even at a low input quantity of three kilograms per tonne, based on the paper pulp / suspension in dry matter, exhibits a significantly better binding of contaminant than bentonite 1 or talc.

About the Gas chromatographic analysis (see method section) was the content of fatty acids, Lignins, sterols, steryl esters and triglycerides for the above Samples determined. The bentonites 1 and 2 were included with each 6 kg / t paper (dry weight) used; the cationized talc was used with 11.25 kg / t paper, since 6 kg / t poor results provided. The values obtained are shown in Table 4.

Table 4: Concentrations of individual contaminants after treatment with the substance binding agents in mg / L according to gas chromatography

As Table 4 shows that shows the bentonite according to the invention 2 treated sample both opposite the cation treated with the talc treated sample as well as with the non-inventive calcium bentonite (Bentonite 1) treated sample a significantly better binding / removal of fatty acids, Lignins, styrenes, styryl esters and triglycerides.

In Another example was the bentonite according to the invention with conventional Bentonites, while containing a proportion of monovalent cations at the CEC of at least 0.7 (70%), but a CEC of less than 85 meq / 100g.

It Again, a significantly better impurity binding of the bentonite according to the invention in Compared to the conventional ones Bentonites even at low input quantities.

Claims (17)

A process for impurity binding in papermaking, comprising the following steps: a) providing a bentonite, wherein the proportion of monovalent cations in the cation exchange capacity (CEC) of the bentonite is at least 0.7 and the CEC is more than 85 meq / 100g, preferably more than 90 meq / 100g, especially more than 95 meq / 100g. b) adding the bentonite according to a) to the paper pulp or pulp mass; c) binding of the impurities to the bentonite in the pulp or pulp suspension. Method according to claim 1, characterized in that that the proportion of monovalent cations in the CEC of bentonite at more than 0.7, especially at more than 0.8, preferably at is more than 0.85. Method according to one of the preceding claims, characterized characterized in that the particle size of the bentonite is chosen that the wet sieve residue to 45 microns less than 2 wt .-%, preferably less than 1 wt .-%, in particular smaller 0.5 wt .-% is. Method according to one of the preceding claims, characterized characterized in that the monovalent cations are sodium, Potassium and / or lithium, especially sodium. Method according to one of the preceding claims, characterized characterized in that the bentonite is in particulate form with a middle Particle size (D50, volume related) between 0.5 and 10 .mu.m, in particular between 2 to 6 μm, especially preferably between 3 and 5 microns is present. Method according to one of the preceding claims, characterized characterized in that the addition of the bentonite in the absence of Talk takes place. Method according to one of the preceding claims, characterized characterized in that the bentonite has a swelling capacity of at least 25 ml / 2 g, in particular of at least 30 ml / 2g, more preferably of at least 35 ml / 2g. Method according to one of the preceding claims, characterized characterized in that the bentonite to a proportion of iron ions preferably CEC is below about 0.005. Method according to one of the preceding claims, characterized in that the bentonite has a BET surface area of less than 100 m ² / g, in particular less than 90 m ² / g. Method according to one of the preceding claims, characterized characterized in that between about 0.5 and 10 kg per ton of paper pulp or pulp suspension (dry weight), in particular between 1 and 7 kg / t pulp or pulp suspension are added. Method according to one of the preceding claims, characterized in that the paper pulp or fibrous suspension comprises groundwood parts contains. Method according to one of the preceding claims, characterized characterized in that the wood pulp content in the paper pulp or the fiber suspension at least 10 wt .-%, in particular at least 30 wt .-% based on the total pulp or pulp suspension (Dry weight). Method according to one of the preceding claims, characterized characterized in that no additional addition from talc to paper pulp or pulp suspension. Use of a bentonite as in claim 1. a) defined for contaminant binding in papermaking. Use according to the preceding claim, characterized characterized in that the use in a paper pulp or pulp suspension done with wood pulp shares. Use according to one of the preceding claims, characterized characterized in that the use without the additional use of talc he follows. Use according to one of the preceding claims partial or complete Replacement for other means for removal of contaminants such as polyelectrolytes or talc.