DE102006061046A1 - Preparation of raw bentonite - Google Patents

Abstract

The present invention relates to a process for the treatment of crude bentonite, prepared bentonite obtainable by the process according to the invention, the use of this bentonite in papermaking and / or finishing, in particular as a filler, coating pigment, retention agent or rheological additive, as a resin-controlling agent, for the control of sticky deposits in the paper machine or for masking and / or reducing residual chemicals in pigments.

Description

The The present invention relates to a process for the preparation of Rohbentonit, processed bentonite obtainable by the method according to the invention, the use of this bentonite in papermaking and / or finishing, in particular as a filler, Coating pigment, retention agent or rheological additive, as Pitch control means to control sticky deposits in the paper machine or for masking and / or reducing residual chemicals in pigments.

bentonite is a rock that is a mixture of different clay minerals consists of montmorillonite and what is the most important ingredient its strong water absorption and swelling capability explained. Further Accompanying minerals are quartz, mica, feldspar, pyrite or too Calcite. Montmorillonite is a highly dispersed, layered aluminum silicate, in that because of the non-stoichiometric Substitution of cations of the crystal lattice negative closure charges appear that the exchange cations that are in the interlayer space to compensate. This is the cause of the high water absorption capacity of bentonite. Water penetrates into the interlayer space of montmorillonite one hydrates its surface and the replacement cations. This causes the swelling of the mineral. Different composition of the exchange cations produces different Swelling behavior. Upon further dissolution in water, such bentonites form a stable tough Suspension. A special group of bentonites is created when one Part of the replacement cations represent fatty amines. One speaks then of organophilic bentonites found in organic solvents sources.

by virtue of Bentonite has many uses in these properties Areas such. B. in papermaking or finishing. by virtue of its flocculation behavior and high adsorption capacity elevated Bentonite the fiber and filler retention and improves drainage behavior while the leaf formation.

He is still used for the adsorption of contaminants during waste paper recycling and problems with resins or sticky residues in the Machine cycle to avoid.

Before Bentonite, however, can be used in the above processes, it must be made from crude bentonite, which, as mentioned above, consists of a mixture of several Clay minerals or other unwanted constituents, be won.

From The processing of raw bentonite therefore not only depends on whether the bentonite has the desired properties has, but also, for example, still abrasive ingredients are included, the paper or equipment, z. B. the sieve a paper machine or the blade of a coating unit, can damage as well like the efficiency of the product.

The Processing of the raw bentonite, depending on the application, the separation of bentonite or montmorillonite of undesirable components which Activation with alkali salts, eg. As sodium salts, comminution and homogenization, etc., is a multi-step time, resource-consuming and costly process, its optimization frequently Subject of further development efforts was.

So have been various methods for improving the properties of Bentonite or montmorillonite in various fields of application proposed.

DE 197 28 503 C1 relates to an improved process for the delamination of calcium montmorillonites with the aim of increasing the surface of montmorillonite agglomerates in such a way that the effect values of the parameters typical for this purpose and application technology are changed in an increasing manner, eg. B. the adsorption capacity for albumin in wine stabilization, the thixotropy when used as gelling agent and the opacity when used as a coating pigment in the paper industry. The raw material is suspended in water, optionally purified and adjusted to a predefinable solids content, whereupon the concentrated suspension with predetermined residence times and layer thicknesses is exposed to high shear forces. The concentration before the shear causes the formation of a necessary for the desired delamination thixotropic system in which the free mobility of the particles is so far prevented that it can no longer come to segregation of different particle sizes by gravity. It should be noted that the concentrated suspension should not be treated as possible with shear devices in which in addition to frictional forces predominantly compressive and impact forces occur, which also lead to an unwanted crushing of the slats transverse to the surface, z. B. in vibration or Vibratory mills or in stirred ball mills. Due to application requirements, eg. For example, the enhancement of the thixotropic properties can be done according to DE 197 28 503 also be beneficial to activate calcium bentonite. This activation takes place by addition of sodium carbonate with a Zwangsmischer upstream of the dispersing machine. Thus, a still multi-step process for delamination of concentrated, optionally previously activated montmorillonite to describe the properties of montmorillonite is described.

US 4,483,934 also describes the multistage treatment of crude bentonite by treating an aqueous suspension of crude bentonite to provide purer and whiter bentonite by preventing discoloration thereof by iron oxide. The bentonite suspension essentially free from iron oxide by mechanical or chemical processes is treated with a base, dehydrated, washed, resuspended in water, subjected to shearing forces in a homogenizer, dried and, if appropriate, dry-milled with an alkali metal salt for setting unspecified properties. The product thus obtained has a good whiteness and is therefore used as a tablet disintegrants, emulsifier, thickener or thixotropic gelling agent in cleaning, pharmaceutical or cosmetic compositions. The relatively complex multi-stage process of US 4,483,934 thus serves primarily the aesthetic enhancement of bentonite in addition to increased bacteriological resistance due to heating in the treatment with the base.

Further improving approaches in the processing and processing of bentonite affect the poor handling Bentonite due to its high swelling capacity and associated Transport and storage difficulties.

So describes EP 0 485 124 A1 a papermaking process comprising providing a cellulosic suspension, admixing a bentonite swelling clay into the suspension wherein the clay is in the form of an aqueous suspension, and dewatering the cellulose pulp, the bentonite swelling clay being provided as a fluid concentrated dispersion comprising at least 15% by weight dry weight of bentonite in non-swollen form and a certain amount of dissolved monomeric electrolyte sufficient to prevent swelling of the bentonite. The amount of electrolyte, which may also be an activator such as sodium carbonate, is significantly greater than the amount usually used for activation, resulting in inhibition of swelling. By diluting the concentrate before adding it to the pulp suspension or in the pulp suspension, the electrolyte concentration is also diluted so that the bentonite can swell. There is then in the pulp a conventional mixture of bentonite and electrolyte or optionally activator. Thus, a better handling of the otherwise poorly processed swollen clay is achieved.

The same applies in principle to the in WO 97/33041 A1 in which a concentrate of alkaline earth bentonite with water and alkali metal, ammonium or sodium citrate as activator and stabilizer prepared and the pulp is optionally added with prior dilution.

Concentrates of EP 0 485 124 A1 and the WO 97/33041 A1 thus represent conventional activated bentonites with the difference that they are initially present in concentrated form to facilitate handling. Functionally, they do not ultimately differ from known products as soon as they enter the pulp. There they can be used as already known for these mixtures as a resin dispersant or with the addition of a retention aid to the pulp before mixing the bentonite. An improvement of the related properties is not described.

Have the same objective US 5,266,538 and US 5,391,228 US-A-5,211,014, which describes a process for producing a stable aqueous bentonite, preferably sodium bentonite slurry having a low viscosity and a high solids content. Here, bentonite is mixed with the least possible shearing with a non-dispersing salt, in particular sodium chloride, or a sodium or lithium salt in combination with a potassium salt, which prevent the swelling of the bentonite, in order to improve the transport and storage properties. The inhibition of swelling is reversible and can be reversed by dilution of the concentrate before the intended use, for example, as a conventional retention aid in papermaking again without having an effect on the known function.

Incidentally, will be approaches to simplify the Bentonitaufbereitung described.

US 5,248,641 For example, has a simplified compared to the prior art method for Increased viscosity of bentonite in aqueous media. Here, the crude bentonite is sheared in the form of a slurry in a mixing drum and then dried. Then, by adding an activating metal salt such as sodium carbonate, a dry mixture is prepared which is finally pulverized. Accordingly, the simplification of the process consists in that, in order to improve the viscosity properties of the bentonite, the complicated aging or activation process described in the prior art is not required, but the activation by dry mixing of the sheared and dried bentonite with the activator is possible.

None However, the above-mentioned documents thus describes a simplification of the method while improving the functional properties bentonite in papermaking and / or paper finishing and at the same time good handling.

One the biggest problems z. In the papermaking or refining process abrasiveness the substances used, for example, to increased Siebverschleiß or abrasion the doctor blade when stroking and thus to a reduction the production performance up to the machine standstill and consequently not only to a reduction in production efficiency but also to considerable Costs leads.

The desired low abrasiveness can practically not be achieved with the known dry milling process, without previous treatment steps such as predrying. The problem here is the high naturally associated water content of Rohbentonits up to 35 wt .-%. This gives the products a greasy, slippery consistency. It is therefore not possible to mill such crude bentonites without predrying to <20% by weight, better still to 8-12% by weight of residual moisture in dry mills to high finenesses. This pre-drying is done mainly thermally, on the one hand by solar radiation and on the other hand by electrical and / or generated by combustion heat. The former has the disadvantage of long duration. The latter results in increased CO ₂ emission and therefore does not comply with the Kyoto Protocol.

These Disadvantages can by the method according to the invention and the resulting available Bentonites are significantly reduced.

Consequently the present invention is based on the one to provide a simplified method of processing raw bentonite. Here, the goal is to reduce the individual, necessary time and energy intensive process steps. Object of the invention it is the process or upgrading steps of raw bentonite reduce to a maximum of two, maximum three steps, until the end application.

Farther One goal in the process is to use organic complexing agents such as NTA, EDTA, DTPA and salts of polyacrylic acid in support of Activation to renounce, on the one hand to the environmental impact reduce and on the other hand disturbances by avoiding such chemicals in the later applications. For example, it is known that complexing agents contain heavy metals Mercury from water sediments can solve and thus increased Values in drinking water can.

A Another object of the present invention is the provision a bentonite having improved properties, in particular in terms of abrasiveness, without the otherwise necessary functionality of the bentonite negative influence or even support it when used in papermaking and / or refining and its use as an aid in Papermaking and refining process.

to solution The objects are as defined in the independent claims Characteristics.

advantageous Embodiments of the present invention will become apparent from the dependent claims and the following description.

The The object of the invention is achieved by the method according to the invention for processing raw bentonite.

According to this Process becomes an aqueous slurry comprising crude bentonite having a maximum solids content of 19% by weight which are wet-ground to an average particle size of less than 1 μm becomes.

Raw bentonite is found all over the world, such. In the USA, Uruguay, Argentina, New Zealand, China, Russia, Morocco, Turkey as well as in Europe, for example in Greece and Germany. Usable according to the invention are all commercially available crude bentonites, in particular bentonite from Morocco, Milos (Greece), bakirgol (Turkey) and New Zealand.

Of the Bentonite contained in the crude bentonite is preferably alkaline earth metal Bentonite, in which the smectite group almost exclusively with Calcium and / or magnesium ions in the intermediate layers occupied is. Such bentonites come z. In Germany and Greece in front. But it can also be used Rohbentonit, the bentonite contains its smectite group predominantly is occupied by sodium ions in the intermediate layers. Such bentonites come z. In the USA. Also possible is the use of raw bentonite, its intermediate layers with both sodium and calcium and / or Magnesium ions are occupied. Such bentonites come z. In Morocco in front. Also can other alkali ions such as potassium ions may be present.

As mentioned in the beginning contains the raw bentonite for usually various clay minerals such as in particular montmorillonite as the main constituent, but also quartz, mica, feldspar, pyrite, calcite and / or cristobalite. These minerals can in changeable Shares are present as well as other components, depending on Place of origin.

For the inventive method particularly suitable are bentonites with a montmorilonite content of> 60 wt .-%, preferably> 80 wt .-%, z. B. between 85 and 95 wt .-%.

The slurry of the crude bentonite is carried out in an aqueous medium, preferably using a conventional agitator or dispersing aggregate.

During the slurry and grinding step can change the temperature of the mixture from room temperature up to 40 to 100 ° C, preferably 50 to 80 ° C elevated become. Particularly preferably, the heating here comes through the inner Friction energy to conditions and must not be supplied externally. This has the advantage that, for example, dispersibility and millability continues to increase and a possible chemical reaction with inorganic Chemicals, as activation reagents are accelerated.

Of the Rohbentonit solids content in the aqueous slurry is maximum 19% by weight. In a specific embodiment, it may be 2 to 19 Wt .-%, preferably 5 to 15 wt .-%, more preferably 7 to 12 wt .-%, in particular 8 to 10 wt .-%, z. B. 9 wt .-% amount.

The Concentration of the solid is chosen so that the viscosity of the slurry for efficiency is optimal in the milling, d. H. between 10 and 5000 mPa · s, better 100 to 1000 mPa · s and preferably in the range of 150 to 600 mPa · s, measured with a Brookfield viscometer (as described in the examples). The optimal concentration is dependent from occurrence, d. H. the chemical and mineralogical composition of crude bentonite and its swellability, which in turn affects the viscosity.

If the crude bentonite slurry the desired Consistency, it is subjected to wet grinding, in which also abrasive impurities are ground so small, that at the later Application no longer have an abrasive effect.

The viscosity can be diluted be regulated with water and optimize the solids content.

Of the Bentonite solids content in the aqueous slurry after the wet grinding is preferably from 2 to 19% by weight, more preferably from 5 to 18% by weight, more preferably from 6 to 12% by weight, e.g. B. 7 wt .-%.

To the abrasive impurities which can be produced in the crude bentonite and be ground, count For example, silicates such as quartz, feldspar and chlorites

The Raw bentonite slurry is wet-ground to an average particle diameter of preferably less than 1 μm, preferably less than 0.8 μm, in particular smaller than 0.5 μm, z. In a range of 0.05 to 0.3 μm, more preferably 0.1 to 0.2 μm, for example 0.15 μm, determined by sedimentation analysis (on the Sedigraph 5100, Micrometrics) ground.

In a particularly preferred embodiment indicate after wet grinding> 50 % By weight, better> 80 % By weight, in particular> 90 % By weight of the particles have a spherical equivalent diameter of <0.2 μm (determined by sedimentation analysis on the Sedigraph 5100, Micrometrics).

were Bentonites with a high content of calcium and / or magnesium ions used, there is still the possibility of this with inorganic Activating agents such as alkali carbonate salts, to activate. For example, sodium carbonate, Potassium carbonate or mixtures thereof.

In a particularly preferred embodiment according to the present Invention, the activation takes place in the wet grinding, by one or more of said activating substances together are ground with the bentonite.

These are preferred for this purpose in an amount of 0.5 to 10 Wt .-%, more preferably in an amount of 1 to 8 wt .-%, in particular in an amount of 3 to 6% by weight, for example 5% by weight on the weight of the montmorillonite contained in the bentonite to the bentonite slurry added.

The molar concentration of exchangeable alkali metal ions in the aqueous Phase is in this case only <0.1 Mol / liter, more preferably 0.01 to 0.05 mol / liter, in particular 00:02 to 12:04 Moles / liter. Despite this very low concentration, the Exchange much more efficient and faster than the usual dry and semi-dry activation method.

The Grinding can be done in all the specialist for the wet milling of minerals known milling devices are performed. Particularly suitable are for this for example usual horizontal or vertical. Ball mills, jet plate mills, colloid mills or attritor, as they are z. B. sold by the company Dynomill.

When grinding media are preferably grinding balls with a diameter of 0.1 to 5 mm, more preferably 0.2 to 3 mm, in particular 0.5 to 2 mm, for example 1 mm, but also sand, z. B. quartz sand, with a diameter of used for example 0.1 to 2 mm.

The Grinding balls are preferably made of a material selected from the group comprising zirconium, cerium or yttrium stabilized Zirconium and zirconium silicate.

One suitable weight ratio from bentonite to grinding balls in this case for example from 1:10 to 1: 100, from 1:20 to 1:80, from 1:30 to 1:60, preferably 1:50.

To wet grinding, the bentonite slurry can be concentrated. The concentration can be up to a solids content of up to 30% by weight, preferably to a range of 12 to 17% by weight. The concentration after milling is preferably 3 to 15 Wt .-%, more preferably about 10 wt .-%, z. B. increased from 7 wt .-% to 17 wt .-%.

Especially The concentration is advantageous, for example, in an external Production to optimize the storage and transport properties. For an on-side installation with the later user For example, the slurry be used directly.

The Concentration can be with for common to this purpose Devices take place, for example by means of a centrifuge or filter press. It can also be carried out thermally.

The inventive method thus provides a much simplified process for the processing of Raw bentonite, especially for reducing its abrasiveness Milling the bentonite along with its undesirable abrasive components, if necessary with prior separation very coarse Ingredients.

by virtue of the fact that the usual in the prior art and required drying, milling and subsequent resuspension steps be replaced by a single step, the wet grinding can, represents the inventive method also an energy and cost saving new development, in particular, there, if necessary, in addition also the activation for usually also represents a separate step in the wet grinding step can be integrated and the process without organic complexing agents gets along.

Incidentally supplies the inventive method Bentonites, which are not only equivalent to bentonites of the state of the art, but even superior to it in many ways.

A another solution The present invention thus provides a processed bentonite that is, with the inventive method available is.

This Bentonite has several advantages, such as a much lower one Abrasion as usual in papermaking and / or finishing, for example as filler or coating pigment used bentonites.

The Abrasion of this bentonite, measured on the abrasion tester AT 2000 the company Einlehner, Germany, which the Siebverschleiß in the Paper machine simulated, for example, less than 3 mg, preferably less than 2 mg, for example 1 mg. The abrasion, measured on the AT 1000, also from the company Einlehner, Germany, which a measure of knife wear when painting is preferably less than 30 mg, more preferably less than 20 mg, more preferably less than 15 mg, in particular less than 10 mg, z. B. from 7 to 9 mg, but also less than 5 mg, z. 4 or 2 mg.

In Considering these outstanding low abrasive properties is therefore another solution of present invention, the use of the bentonites according to the invention in papermaking and in paper finishing processes like brushing, where they are used to advantage as additives can.

He can be used here in particular as a filler, Coating pigment, retention aids, in particular filler and Total retention aid, or rheological additive such as the outstanding Swell source volumes in the examples show.

A Further use of the bentonite according to the invention is the use for masking and / or reducing residual chemicals.

in this connection is the bentonite in a particularly preferred embodiment together with other minerals and / or the residual chemicals or Residual chemicals containing minerals according to the inventive method wet ground.

Of further shows the bentonite according to the invention also special advantages when used as a resin control agent, in particular in the fight of colloidal wood resin.

Especially Good results are achieved in the combination of bentonite with talc due to its lubricating properties and its chemical properties Inertness and resulting insensitivity to pH and conductivity changes. Further contributes the talc in the mixture with the bentonite according to the invention due to its way solved Property that already existing agglomerates less be liable.

Of the Talc may be the bentonite of the invention simply mixed or ground with this, preferably in the wet milling step of the process of the invention.

Consequently not only does the inventive method simplify and thus improvement compared to known in the art Preparation process of bentonite, the bentonite thus obtained also has improved properties over conventionally processed bentonites and is diverse and economically in various steps of the papermaking and / or finishing process used.

The hereinafter described figures, examples and experiments serve the explanation of the invention and are not intended to limit this in any way.

Brief Description:

1 shows the X-ray diffraction images of the samples (3/2) and sample (3/4)

2 shows the turbidity of the mineral treated TMP filtrate in NTU depending on the bentonite sample used

3 shows the COD analysis of the mineral-treated TMP filtrate in mg O ₂ per liter, depending on the bentonite sample used

4 shows the turbidity of the mineral-treated TMP filtrate in NTU as a function of the amount of bentonite added per liquid filtrate

5 shows the turbidity of the mineral-treated TMP filtrate in NTU as a function of the amount of bentonite added per dried filtrate

6 Figure ₃ shows the COD analysis of the mineral-treated TMP filtrate in mg O ₂ per liter, depending on the amount of bentonite added per liquid filtrate

7 Figure 9 shows the COD analysis of the mineral-treated TMP filtrate in mg O ₂ per liter, depending on the amount of bentonite added per dried filtrate

EXAMPLES:

1. Examples of production processes according to the invention

1.1 Materials used / comparison materials

to execution The experiments were those listed and characterized in Table 1 known commercially available Raw materials used

The Particle size distribution was determined by means of Sedigraph 5100.

The Moisture was measured using a Mettler dry balance (Mettler AG, Greifensee, Switzerland).

The swelling volume was determined according to the following procedure:
A 100 ml graduated cylinder is filled up to the measuring mark with 100 ml deionised water. 2.0 g of the sample are weighed on a sample boat (accuracy of the weighing: 10 mg). With a spatula or directly from the weigh boat, the sample is slowly added in portions to the surface of the water, so that touching the Messzylinderwandung and meniscus edge is avoided. Wait for the amount of added portion to decrease before adding the next, making sure that no air is pulled down. If entrained air can not be removed by knocking, the determination must be repeated. After the 2 g sample has been added and dropped onto the measuring cylinder bottom, the height of the swollen soil body is read 2 hours after filling the sample.

Evaluation:

The swelling volume was determined immediately after addition of the 2 g sample, after 2 hours and after 24 hours. It is calculated according to the following formula. When specifying the swelling volume, the water content of the weighed sample should be taken into account:

The Abrasion was tested on the abrasion testers AT 2000 and AT 1000 of the Company Einlehrer, Germany, determined.

• * Schwankungsbereich innerhalb verschiedener Proben
• ** gemessen nach Trocknen auf 11 Gew.-% Restfeuchte im Sprühtrockner
• *** aufgrund hohem Grobanteil nur bis zu dem angegebenen Wert bestimmbar, um das Prüfgerät nicht zu beschädigen.
• **** Die Proben wurden bei 2 mm gesiebt. Danach waren die Proben immer noch zu grob, um auf dem Sedigraph 5100 gemessen zu werden. Deshalb wurde eine orientierende 100 μm Siebung durchgeführt.

The following results were obtained for the materials used: Table 1: No. bentonite Moisture [% by weight] Grain size distribution [% by weight] Abrasion: AT 2000 AT 1000 Source volume (time after entry) ** 1 Na-bentonite (Morocco, Rheobent SF white, OMYA) 10 ± 0.5 98% <2 μm 94% <1 μm 70% <0.2 μm 6.3-15 mg * 8.7-14 mg * 25 ml (immediately) 30 ml (2 hours) 40 ml (24 hours) 2 Ca-bentonite (Morocco, OMYA) 16 ± 1 46% <2 μm 41% <1 μm 25% <0.2 μm 15 mg 18 mg <15 ml (24 hours) 3 Raw Ca bentonite (Morocco) 35 ± 5 100% <2 mm <10% <100 μm **** > 15 mg ***> 25 mg *** <15 ml (24 hours) 4 Raw Ca bentonite (Milos (Greece)) 35 ± 5 100% <2 mm <10% <100 μm **** > 15 mg ***> 25 mg *** <15 ml (24 hours) 5 Raw Ca bentonite (Bakirgol (Turkey)) 35 ± 5 100% <2 mm <10% <100 μm **** > 15 mg ***> 25 mg *** <15 ml (24 hours) 6 Raw Ca Bentonite (New Zealand Stock Pile) 35 ± 5 100% <2 mm <10% <100 μm **** > 15 mg ***> 25 mg *** <15 ml (24 hours)

• * Fluctuation range within different samples
• ** measured after drying to 11 wt .-% residual moisture in the spray dryer
• *** due to high coarse fraction only up to the specified value determined so as not to damage the tester.
• **** The samples were screened at 2 mm. After that, the samples were still too coarse to be measured on the Sedigraph 5100. Therefore, an orienting 100 μm sieving was performed.

1.2. Inventive Production Process

• a) The respective crude bentonite from Table 1 (Sample No. 3-6) was slurried at a solids content of about 12%. The Crude products were screened off at 3 mm each before use, for damage at the mill used to avoid excessive coarse fraction).
• b) The slurry was using a peristaltic pump at a speed from 150-240 liters / hour through the Dynomill ball mill (Content 1.4 liters, sales: Willy A. Bachofen, Basel) pumped (pump Brand finder; Hose: inner diameter 7 mm). The pressure at the mill entrance was 0.2-0.5 bar. The slurry was diluted to> 1 bar with water as the pressure increased. It has been in circulation for so long ground until the desired Particle size distribution was achieved. Optionally, sodium carbonate was added at the beginning of the milling (5 wt .-% based on the dry bentonite) as an activating agent added. It can be used as a solid or else pre-dissolved in water liquid be dosed. A portion of the slurry was then washed with a GEA NIRO A / S spray dryer (Type Mobil Minor 3247, built in 2005) dried to the swelling capacity to determine in water.

1.3 hoof concentration

The in Table 2 (3/4), which after grinding one Solids content of 7.2 wt .-% had was using a pressure filter at 6 bar by 10 wt .-% to 17.3 wt .-% concentrated. The Brookfield viscosity of the concentrated slurry measured at 100 rpm, spindle 7, was 17,000 mPas.

2. Properties of after the method according to the invention prepared bentonites

2.1 Abrasiveness, swelling volume / activating ability

The Bentonites prepared by the process described above first on their properties in terms of abrasiveness, swelling volume and the Aktivierungsmhigkeit examined.

• *¹ nach Trocknen auf 10 Gew.-% Feuchte im Sprühtrockner

Tabelle 3: Erfindungsgemäße Probe (Ausgangs-material: Proben (4)–(6) aus Tabelle 1): (4/1) nass vermahlen Mahldauer: 50 min. (4/2) nass vermahlen mit 5 Gew.-% Na₂CO₃ bezogen auf trockenen Bentonit Mahldauer: 120 min. (5/1) nass vermahlen Mahldauer: 360 min. (5/2) nass vermahlen mit 5 Gew.-% Na₂CO₃ bezogen auf trockenen Bentonit Mahldauer: 140 min. Feststoff-gehalt (Gew.-%) 11.2 8.3 14.0 10.0 Korngrößen-verteilung KVK Sedigraph [Gew.-%] 99% < 2 μm 98% < 1 μm 94% < 0.2 μm 98% < 2 μm 98% < 1 μm 95% < 0.2 μm 99% < 2 μm 99% < 1 μm 85% < 0.2 μm 100% < 2 μm 100% < 1 μm 90% < 0.2 μm Abrasion: AT 2000 AT 1000 1 mg 8 mg 1.3 mg 9 mg 1.6 mg 2 mg 1.4 mg 4 mg Quellvolumen nach Eintrag* 6 ml 7 ml (2 Std.) 8 ml (24 Std.) 22 ml 26 ml (2 Std) 27 ml (24 Std) 6 ml 6 ml (2 Std.) 7 ml (24 Std.) 20 ml 36 ml (2 Std.) 28 ml (24 Std.)

• * nach Trocknen auf 10 Gew.-% Feuchte im Sprühtrockner

The corresponding results are shown in Tables 2 and 3. The measurements of the individual parameters were carried out as indicated above: TABLE 2 Inventive sample (starting material: sample (3) from Table 1): (3/1) wet grinding grinding time: 40 min. (3/2) wet grinding grinding time: 80 min. (3/3) wet grinding grinding time: 160 min. (3/4) wet milled 5 wt .-% Na ₂ CO ₃ based on dry bentonite; Grinding time: 120 min. Solids content (% by weight) 9.6 8.6 7.6 7.2 Grain size distribution KVK Sedigraph [wt .-%} 85% <2 μm 78% <1 μm 63% <0.2 μm 96% <2 μm 92% <1 μm 94% <0.2 μm 98% <2 μm 97% <1 μm 94% <0.2 μm 98% <2 μm 97% <1 μm 95% <0.2 μm Abrasion: AT2000 AT1000 5.4 mg 7 mg 2.3 mg 7 mg 1 mg 7 mg 2.2 mg 13 mg Source volume after entry ^{* 1} not determined 15 ml (immediately) 20 ml (2 hrs) 20 ml (24 hrs) not determined 26 ml (immediately) 34 ml (2 hrs) 47 ml (24 hrs)

• * ¹ after drying to 10% by weight of moisture in the spray dryer

Table 3: Inventive sample (starting material: samples (4) - (6) from Table 1): (4/1) wet grinding grinding time: 50 min. (4/2) wet-ground with 5 wt .-% Na ₂ CO ₃ based on dry bentonite milling time: 120 min. Wet grinding (5/1) grinding time: 360 min. (5/2) wet ground with 5 wt .-% Na ₂ CO ₃ based on dry bentonite grinding time: 140 min. Solids content (% by weight) 11.2 8.3 14.0 10.0 Grain size distribution KVK Sedigraph [wt .-%] 99% <2 μm 98% <1 μm 94% <0.2 μm 98% <2 μm 98% <1 μm 95% <0.2 μm 99% <2 μm 99% <1 μm 85% <0.2 μm 100% <2 μm 100% <1 μm 90% <0.2 μm Abrasion: AT 2000 AT 1000 1 mg 8 mg 1.3 mg 9 mg 1.6 mg 2 mg 1.4 mg 4 mg Source volume after entry * 6 ml 7 ml (2 hours) 8 ml (24 hours) 22 ml 26 ml (2 hours) 27 ml (24 hours) 6 ml 6 ml (2 hours) 7 ml (24 hours) 20 ml 36 ml (2 hours) 28 ml (24 hours)

• * after drying to 10% by weight of moisture in the spray dryer

a) abrasiveness

The abrasiveness the samples according to the invention is significantly lower than the starting materials. That's how it is she originally at over 15 mg (AT 2000) or over 25 mg (AT 1000) during in the samples according to the invention, also with the activated ones in a range of <1 to 5.4 (AT 2000) resp. 2 to 13 mg (AT 1000).

Also activated in comparison with the dry-milled comparative samples 1 (Rheobent SF white, with 5 wt .-% NaCO ₃ at 18 wt .-% water content and then dry milled at 10 wt .-% ± 2 wt .-% solids content using a Ball mill with integrated classifier) and 2 show the samples according to the invention (3/1) to (3/4) significantly reduced abrasion values.

b) activation capacity / swelling volume

In the 1 X-ray diffraction patterns of sample (3/2) compared to the sample (3/4) clearly show that the activation of calcium to sodium bentonite in just 120 minutes at the low concentration of only about 0.03 mol Na ₂ CO ₃ / Liter was extremely successful.

Also shows the comparison of the swelling volume of the sample (3/4) with commercial -available dry-ground sodium bentonite (sample (1)) that activation to a better swelling ability led. The same applies to the sample according to the invention (3/2) compared with the dry-ground sample (2).

The Source volume is important in that it is an important feature for the Use as a rheological additive represents. In view of the The results obtained are the bentonites according to the invention clearly reduced abrasion equal to the known few if not even superior and thus ideal for use as a rheological additive.

2.2 attempts to support the Retention behavior of calcium carbonate by the bentonites according to the invention

a) materials

To test the retention aid effect of the bentonites according to the invention, a pulp of the following composition was prepared: TABLE 4 Component: Composition: Amount: Fiber: 80% by weight of birch cellulose / 20% by weight of pine cellulose, (freeness 23 ° SR) 6 g / l Filler: Calcium carbonate with a mean particle diameter of about 0.8 microns; 65% strength by weight slurry (for example hydrocarbyl HO-ME 65% strength by weight, OMYA) 6 g / l Retention agents: a) Bentonite b) Percol 47 (CIBA) 0-0.4 wt .-% 0.03 wt .-% based on pulp Dilution water: Clear filtrate of a paper machine (eg PM 8 M-real, Biberist, Switzerland) See under b) Measurement

When Retention aids were the known samples (1) and (2) (see Table 1) and the bentonite samples (3/1) according to the invention, (3/3) and (3/4) (see Table 2) and mixtures thereof with the known, Polyacrylamide based retention agent Percol 47 from CIBA used.

b) Measurement of retention:

The Experiments were carried out with the company's DFS 03 (Dynamic Filtration System) BRG / Mütec, Germany, carried out. It was worked according to the general description of operation of Mütec.

The following stirring speeds and times were used in accordance with the general Mütec operating instructions: Table 5: step retention aids process Stirring speed [rpm] Stirring time [s] 1 Percol 47 dosage 800 5 2 mixture 1600 15 3 bentonite dosage 800 5 4 mixture 800 10

c) Results

The following results with regard to the retention aid properties of the products according to the invention for calcium carbonate were obtained in comparison with the known bentonites: TABLE 6 Retention Aid [wt%] Filler retention [wt.%] Percol 47 bentonite (1) (2) (3/1) (3/3) (3/4) 00:00 0.0 0 0 0 0 0 12:03 0.0 28 30 26 31 26 12:03 0.1 36 30 27 29 46 12:03 0.2 40 32 28 30 41 12:03 0.3 43 35 30 30 43 12:03 0.4 44 32 28 29 44 Table 7 Retention Aid [wt%] Total retention [% weight] Percol 47 bentonite (1) (2) (3/1) (3/3) (3/4) 00:00 0.0 44 44 44 44 44 12:03 0.0 61 61 59 58 59 12:03 0.1 65 62 60 60 67 12:03 0.2 67 63 59 60 67 12:03 0.3 68 64 60 60 68 12:03 0.4 69 62 61 60 67

Tables 6 and 7 show that the filler retention as well as the overall retention (ie filler and fiber retention) with the Ca-bentonites (3/1) and (3/3) according to the invention in the same range as those of the comparative sample (2). The primary goal to prevent abrasion thus has no negative impact on the retention aid properties of bentonites.

at The sample (3/4) is also the maximum high filler retention level already achieved with the addition of only 0.1 wt .-%. With the comparison sample (1) this level is reached only at 0.2 wt .-% addition.

Consequently fulfill the bentonites according to the invention not only outstanding the primary task the reduction of abrasiveness, but also have an at least equivalent, in the case of Activated bentonite even a significantly improved efficiency as a retention aid.

2.3. Attempts to adsorption behavior of the method according to the invention with marble-contaminated marble co-ground bentonites

Around the adsorption properties of the process according to the invention Bentonites manufactured Residual chemicals z. B. in present as marble calcium carbonate, as a filler or coating pigment used in papermaking / finishing will, check was the marble together with Rohbentonit the process of the invention ground and then the content of free residual chemicals determined.

a) materials

• – je 5 kg eines Österreichischen, Spanischen und Norwegischen Marmors mit einem mittleren Teilchendurchmesser von je ca. 45 μm und mit einem Restchemikaliengehalt von 15–25 ppm an Di-coco-dimethylammonium-chlorid (vorwiegend C₁₂-C₁₄Alkyl)
• – je 2.5 g Probe (5) (Roh-Ca-Bentonit ex Türkei) als Ausgangsmaterial

The following samples were used for the tests for adsorption of residual chemicals:

• - 5 kg each of an Austrian, Spanish and Norwegian marble with a mean particle diameter of approximately 45 μm each and with a residual chemical content of 15-25 ppm of di-coco-dimethylammonium chloride (predominantly C ₁₂ -C ₁₄ alkyl)
• - 2.5 g sample (5) (crude Ca bentonite ex Turkey) as starting material

b) Procedure

ever 5 kg of the Austrian, Spanish and Norwegian marble has been used by each 2.5 g sample (5) at 75 wt .-% solids content based on the marble and bentonite content slurried in water and by means of a peristaltic pump (brand FindeR; Inner diameter 7 mm) at a speed of 150-240 liters / hr. through a dynomill ball mill (Content 1.4 liters) pumped. The pressure at the mill entrance was 0.2-0.5 bar. It has been co-milled in the cycle, up to 80% by weight of the particles a spherical equivalent diameter of less than 1 μm (75% by weight smaller 0.2 μm) exhibited. (the particle size distribution was determined by Sedigraph 5100). As grinding media were Zirconsilicate beads with a diameter of approx. 0.7-1.5 mm used.

To 24 hours was the residual content of di-coco-dimethylammonium chloride determined in the samples compared to a blank. The production the blank was done in the same way, but without addition of bentonite.

• – 100 ml wässerige Lösung mit 0.1 Gew.-% Bromphenolblau + 0.1 Gew.-% Bromkresolgrün in Ethanol
• – 420 ml 0.1 M wässerige Citronensäurelösung
• – 580 ml 0.2 M Dinatriumhydrogenphosphatlösung

The determination of the quaternary ammonium compound was carried out colorimetrically by the following method:
First, the following standard solutions were produced:
Standard buffer solution (pH 5.6):

• - 100 ml of aqueous solution containing 0.1% by weight of bromophenol blue + 0.1% by weight of bromocresol green in ethanol
• - 420 ml of 0.1 M aqueous citric acid solution
• - 580 ml of 0.2 M disodium hydrogen phosphate solution

Standard solution of dicocodimethylammonium chloride

For this 200.0 mg of dicocodimethylammonium chloride were placed in a 1000 ml plastic flask submitted and filled up with distilled water.

Ca ²⁺ - standard solution:

There were 7.3 g of CaCl ₂ · 2H ₂ O (corresponding to 5.0 g CaCO _3; see below) in about 20 ml of demineralized water.

To this solution were 20.00 ml of buffer solution and increasing amounts of standard solution of dicocodimethylammonium chloride added and measured the respective extinction to create a comparative measurement curve (VIS spectrophotometer: Lambda 1 (from Perkin-Elmer), wavelength: 425 nm, cuvette thickness (d): 1 cm)

The sample solutions were prepared as follows:

5.0 g of CaCO ₃ or a quantity of slurry corresponding to this amount was dissolved with 10% excess 25% hydrochloric acid. To this solution was added 20.00 ml of the buffer solution. The pH was adjusted with stirring with 2 N NaOH, the final volume should be about 70 ml.

The Sample is transferred to the PTFE hopper with approx. 10 ml of water. Then 20.0 ml of methylene chloride are added and extracted. As soon as only a slight overpressure developed, the mixture is shaken intensively for two minutes.

The Sample is discharged into a centrifuge tube and at 4000-4500 rpm. 15 minutes. centrifuged. Then you suck with a 20 ml syringe, with long needle, the lower, yellow phase on. It is too Make sure that no impurities of the upper phase are dragged along become.

On the photometer is at 425 nm with methylene chloride autozero carried out. Thereafter, the methylene chloride solution is metered into the cuvette and measures the extinction. Before reading, the signal must remain constant; often a slight haze (too high absorbance) occurs at first which disappears after a few minutes.

Calculation of dicoco dimethyl ammonium chloride content:

From the standard solutions, the calibration curve is calculated by linear regression: (extinction E, slope a, intercept b) mg dicocodimethylammonium chloride = a · E + b ppm dicocodimethylammonium chloride mg dicoco dimethyl ammonium chloride · 1000 E [g 100%]

c) Results

The results of the adsorption experiments are shown in Table 8. Table 8: Content of free di-coco-dimethylammonium chloride reduction blank after grinding with sample (5) Marble from Austria 22 ppm 10 ppm 55% Marble from Spain 13 ppm 9 ppm 31% Marble from Norway 12 ppm 9 ppm 25%

The Results clearly show that a strong reduction of residual chemicals at 25-55 % By weight. Raw Ca bentonite, in accordance with the invention co-ground with calcium carbonate, has very good adsorption properties across from quaternized fatty amines.

2.4. Trials with resin the method according to the invention prepared bentonite

2.4.1 Materials

Comparative example

• - Sample (2)
• - Finntalc P05, MONDO Minerals
• - Finntalc P60, MONDO Minerals,

Examples according to the invention

• - Sample (3/3)
• - Sample (3/6): Sample (3/6) was prepared by co-milling 50% by weight of Finntalc P60 with 50 wt .-% sample (3) each based on the total weight from Finntalc P60 and sample (3) analogously to the preparation of the sample (3/3) obtained (milling time: 180 min)

2.4.2 qualitative determination

a) Procedure

It were 2 kg of thermomechanical pulp (TMP) with a solids content of 3.7% by weight over a 2 μm Filter filtered and 2 liters of filtrate. There were 200 each g of this filtrate distributed on 8 glass bottles and each with 20 g of a 10% by weight slurry offset the above materials.

• – 45 ml zur Messung der Trübung
• – 2 ml zur Bestimmung des Gesamtgehalts an organischen Bestandteilen – Chemischer Sauerstoffbedarf (chemical Oxygen demand; COD)

Then the bottles are closed and stirred for 2 hours and then the suspension for 30 min. centrifuged (C312 IG from Juoan, Winchester, USA; at 3500 rpm). The upper and lower phases are separated. The upper liquid phase was analyzed as follows:

• - 45 ml to measure turbidity
• - 2 ml for the determination of the total content of organic matter - Chemical Oxygen demand (COD)

b) Analyzes

turbidity:

All investigated minerals and mineral mixtures were able to reduce the turbidity of the TMP filtrate ( 1 ).

The Filtered TMP showed turbidity from 412 NTU.

The Talc treatment reduced turbidity on 187 NTU.

The Sample (2) (prior art) reduced the colloidal particles to 18 NTU, d. H. to <10% the original value of 412 NTU.

The sample according to the invention (3/3) similarly reduced the colloidal particles to <10% of the original Value (28 NTU).

The sample according to the invention (3/6) showed the same good adsorption effect as the samples (2) and (3/3), viz also a reduction to <10% the original value of 412 NTU (38 NTU). Because of the co-grinding Both the talc and the bentonite were comminuted as starting material for the Co-grinding of coarse crude Ca bentonite (Sample (3)) and the coarse talc.

The Results clearly show that the primary object of the invention, the Reduction of the abrasion of bentonites has no negative influence on the elimination of colloidal resin.

Also the presence of talc in the milling of the bentonite results no adverse effect on colloidal application Pitch reduction.

A Co-grinding of bentonite and talc is therefore advantageous since Talk a positive effect on sticky, hydrophobic deposits (in the field of white pitch called) has and thus helps such Impurities, if present, eliminate and also due to its lubricating Features for less tearing when rolling up the paper and less abrasion on the paper machine leads. Furthermore, that depends Adsorption potential of the specific surface of the talc from and it is therefore advantageous to change the surface of the talc to that of the bentonite to increase in the same grinding process.

This combination of bentonite and talc provides a highly potent adsorbent that is not just one has lower abrasion than conventional adsorbents, but also shows otherwise positive properties in the production and processing of paper.

COD:

The original untreated TMP filtrate has a COD of 4291 mg O ₂ per liter. Finntalc P05 reduced the COD to 3616 mg O ₂ per liter. All investigated bentonite forms as well as the bentonite / talc mixture showed a similar reduction potential and reduced the COD value to approx. 2700 ± 100 mg O ₂ per liter ( 2 ), the values of the samples according to the invention being better than the untreated sample (2).

2.4.3 Quantitative determination

The following attempts were made to determine the minimum effective Concentration of the bentonites according to the invention carried out.

a) Procedure

It were 2 kg of a thermomechanical pulp (TMP) with a solids content of 3.5% by weight over a 2 μm Filter filtered and 2 liters of filtrate. After that were ever Distribute 200 g of this filtrate on 8 glass bottles and with each varying amounts of a 10% by weight slurry of the sample (3/3).

Then the bottles are closed and stirred for 2 hours and subsequently is the suspension for 30 min. centrifuged (C312 IG from Juoan, Winchester, USA; at 3500 U / min). The upper and lower phases are separated.

The upper liquid Phase was analyzed by adding 100 ml for the quantification of the total were removed from material in 100 ml of filtrate.

Around the minimum effective concentration of bentonite mineral per dry mass to determine the filtrate liquid for recovery of dry fibers into a pre-weighed aluminum container (125 ml; Diameter 96 mm, height 24 mm), dried in an oven (95 ° C., 24 hours) and the residue weighed.

b) Analyzes

cloudiness

In the 4 and 5 It can be seen that the minimum effect concentration is about 0.01% by weight clear filtrate, or 0.2% by weight, based on dry pulp.

Of the optimal area for The paper industry lies between 0.5 and 2% by weight, based on dry pulp.

COD

Of the Trend is also supported by the COD measurements where there 1-5 wt.% based on dry fiber is preferred.

Claims (34)

Process for the preparation of crude bentonite comprising the steps - Provision a watery one slurry comprising crude bentonite having a maximum solids content of 19% by weight, - wet grinding the resulting bentonite slurry to an average particle size of smaller 1 μm. Method according to claim 1, characterized in that that the crude bentonite mainly comprises bentonite, whose smectite group predominantly is occupied by calcium and / or magnesium ions. Method according to claim 2, characterized in that that the smectite group of crude bentonite with a minority of sodium and / or potassium ions is occupied. Method according to one of claims 1 to 3, characterized that the raw bentonite is selected from various clay minerals the group comprising montmorillonites and accompanying minerals such as quartz, Mica, feldspar, pyrite, calcite and cristobalite. Method according to one of claims 1 to 4, characterized that the crude bentonite has a montmorillonite content of> 60 wt .-%, preferably> 80 wt .-%, z. B. between Has 85 and 95 wt .-%. Method according to one of claims 1 to 5, characterized that the crude bentonite solids content in the aqueous slurry wet grinding from 2 to 19% by weight, preferably from 5 to 15% by weight, particularly preferably from 7 to 12% by weight, in particular from 8 to 10% by weight, z. B. 9 wt .-% is. Method according to one of claims 1 to 6, characterized that the crude bentonite solid content in the aqueous slurry so chosen will that viscosity the slurry in a range of 10 to 5000 mPa · s, more preferably 100 to 1000 mPa · s and preferably in the range of 150 to 600 mPa · s. Method according to one of claims 1 to 7, characterized that the bentonite solids content in the aqueous slurry after wet grinding from 2 to 19% by weight, preferably from 5 to 18% by weight, more preferably from 6 to 12% by weight, e.g. B. 7 wt .-% is. Method according to one of claims 1 to 8, characterized that in the production and the grinding of the crude bentonite slurry Temperature in the slurry and / or grinding step from room temperature to a range of about 40 to 100 ° C, preferably 50-80 ° C is increased. Method according to claim 9, characterized in that that warming not supplied externally but comes from the grind itself. Method according to one of claims 1 to 10, characterized wet grinding of the bentonite slurry to an average particle size is preferred smaller than 0.8 μm, in particular smaller than 0.5 μm, z. In a range of 0.05 to 0.3 μm, more preferably 0.1 to 0.2 μm, for example 0.15 μm he follows. Method according to one of claims 1 to 11, characterized that after wet milling the bentonite slurry is based on the total weight of the bentonite slurry> 50 wt .-%, better> 80 wt .-%, in particular> 90 wt .-% of the particles a spherical equivalent diameter of less than 0.2 μm. Method according to one of claims 1 to 12, characterized that the wet grinding of bentonite in the presence of one or several inorganic activating agents such as alkali carbonate salts takes place. Method according to claim 13, characterized in that that the alkali carbonate salt is selected from the group comprising Sodium carbonate, potassium carbonate and mixtures thereof. Method according to one of claims 13 or 14, characterized in that the alkali metal carbonate salts are present in an amount of from 0.5 to 10% by weight, preferably 1 to 8 wt .-%, more preferably 3 to 6 wt .-%, for example 5% by weight based are present on the weight of montmorillonite contained in the bentonite. Method according to one of claims 13 to 15, characterized that the molar concentration of exchangeable alkali metal ions in the watery Phase <0.1 mol / liter, preferably 0.01 to 0.05 mol / liter, in particular 0.02-0.04 mol / liter is. Method according to one of claims 1 to 16, characterized that the wet grinding of bentonite in a mill, preferably in a horizontal or vertical ball mill, a radiant plate mill, a attrition mill or a colloid mill he follows. A method according to claim 17, characterized in that the wet grinding of the bentonite using grinding balls with a diameter of 0.1 to 5 mm, preferably 0.2 to 3 mm, in particular 0.5 to 2 mm, for example 1 mm, or quartz sand having a diameter of, for example, 0.1 to 2 mm, or mixtures thereof. Method according to one of claims 17 or 18, characterized that the wet grinding of bentonite using grinding balls selected from a material from the group comprising zirconium, cerium or yttrium stabilized Zirconium and zirconium silicate. Method according to one of claims 18 or 19, characterized that the weight ratio from bentonite to grinding balls 1:10 to 1: 100, preferably 1:20 to 1:80, more preferably 1:30 to 1:60, for example 1:50. Method according to one of claims 1 to 20, characterized that the viscosity the bentonite slurry through change the solids content regulated by addition of water during wet grinding becomes. Method according to one of claims 1 to 21, characterized that the bentonite slurry is concentrated after wet grinding. Method according to claim 22, characterized in that that the bentonite slurry after wet grinding to a solids content of up to 30 Wt .-%, preferably concentrated to a range of 12 to 17 wt .-% becomes. Method according to one of claims 1 to 23, characterized that the concentration of the wet-milled bentonite slurry by means of a centrifuge or a filter press or thermally. Bentonite available by a method according to any one of claims 1 to 24. Bentonite according to Claim 25, characterized that the bentonite AT 2000 abrasion of less than 3 mg, preferred less than 2 mg, especially about 1 mg or less. Bentonite according to one of claims 25 or 26, characterized that the bentonite has an AT 1000 abrasion of less than 30 mg, smaller 20 mg, preferably less than 15 mg, more preferably less than 10 mg, z. B. from 7 to 9 mg, but also less than 5 mg, z. B. 4 or 2 mg. Use of the bentonite according to one of claims 25 to 27 as an additive in papermaking and / or finishing. Use of the bentonite according to claim 28 as a filler, Coating pigment, retention agent, in particular filler and total retention aids, and / or rheological additive. Use of the bentonite according to claim 25 for masking and / or reduction of residual chemicals. Use of the bentonite according to claim 30, characterized characterized in that the bentonite along with other minerals and / or the residual chemicals or residual chemicals containing minerals wet grinding. Use of the bentonite according to claim 25 as a resin control agent. Use of the bentonite according to claim 32, characterized characterized in that the bentonite is used in a mixture with talc becomes. Use of the bentonite according to claim 33, characterized characterized in that the bentonite is ground with talc.