Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B33/00—Silicon; Compounds thereof
  • C01B33/20—Silicates
  • C01B33/36—Silicates having base-exchange properties but not having molecular sieve properties
  • C01B33/38—Layered base-exchange silicates, e.g. clays, micas or alkali metal silicates of kenyaite or magadiite type
  • C01B33/40—Clays
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/63—Inorganic compounds
  • D21H17/67—Water-insoluble compounds, e.g. fillers, pigments
  • D21H17/68—Water-insoluble compounds, e.g. fillers, pigments siliceous, e.g. clays

Definitions

• the present invention relates to a method for processing crude benlonilc, processed bcntonitc obtainable by the method according to the present invention, the use of this benlonitc in paper making and/or paper finishing, in particular as a filler, a coating pigment, a retention agent or a rheological additive, as a pilch control agent, to control sticky deposits in the paper machine or to mask and/or reduce residual chemicals in pigments.
• Bcntonitc is a mineral comprising a mixture of various clay minerals and containing as the most important component mo ⁇ lmoril ⁇ onitc, which explains its high water absorbency and swcliab ⁇ ity.
• Other concomitant minerals include quart/, mica, feldspar, pyrite or calcitc.
• Montmorillonite is a highly dispersed layered aluminum silicate in which negative excess charges appear due to the nonstoichiomctric substitution of cations in the crystal lattice, compensating for the exchange cations in the interstitial space. This is the explanation for the high water absorbency of bcntonitc. Water penetrates into the interstitial space of montmorillonite, hydrates its surface and the exchange cations.
• benlonitc is used in various ways in a wide variety of areas, e.g., in paper production or paper finishing. Due to its flocculation properties and high adsorption capacity, bentonite increases fiber and filler retention and improves the dcwatcring behavior during the sheet-forming process.
• the processing of the crude benlonile determines not only whether the bentonite will have the desired properties but also whether, for example, any abrasive constituents are still present which could damage the paper or the equipment, e.g., the wire of a papermaking machine or the blade of a coating unit, as well as having a negative effect on the efficiency of the product.
• the processing of the crude bentonitc which may comprise, depending on the area of use, the separation of the bentonite or montmorillonite from unwanted constituents, activation with alkali salts, e.g., sodium salts, size reduction and homogcnization, etc., is a multistage process which is time-consuming, expensive and involves a high consumption of raw materials; optimization of this process has often been the subject of efforts at further development.
• alkali salts e.g., sodium salts, size reduction and homogcnization, etc.
• DE 197 28 503 Cl relates to an improved method for delamination of calcium montmoriilonitcs with the object of increasing the surface area of montmorillonite agglomerates to such an extent that the efficiency values of the typical parameters that are relevant from the standpoint of application technology arc altered in the sense of increasing them, e.g., the adsorption capacity for albumins in stabilization of wine, thixotropy in application of a gelation agent and the opacity in use as a coating pigment in the paper industry.
• the raw material is suspended in water, optionally purified and adjusted to a preselectable solids content, whereupon the concentrated suspension is exposed to high shearing forces with preselectable dwell times and layer thicknesses.
• the concentrated suspension should preferably not be treated with shearing equipment in which mainly compressive and impact forces occur in addition to frictional forces because the former also lead to an unwanted reduction in the size of the lamellae across the surface, e.g., in vibration mi lls or oscillating mills or in agitated ball mills.
• US 4,483,934 describes the processing of crude bentonite, again in multiple steps, by treating an aqueous suspension of crude bentonite to provide a bentonite that is whiter and has a greater purity by preventing discoloration of same by iron oxide.
• the bentonite suspension which is essentially free of iron oxide due to mechanical or chemical methods, is treated with a base, dewatered, washed, rcsuspended in water, subjected to shearing forces in a homogenizer, dried and optionally dry- ground with an alkali metal salt to adjust properties that are not defined in greater detail.
• the resulting product has a good whiteness and is therefore used as a tablet disintegrant, emulsifier, thickener or thixotropic gelation agent in cleaning compositions, pharmaceutical formulations or cosmetic compositions.
• the relatively complex multistage method of US 4,483,934 thus serves primarily to improve the aesthetic appearance of bentonite in addition to achieving an increased bacteriological resistance due to its heating in treatment with a base. Additional suggestions for improvement in work-up and processing of bcntonite pertain to the poor handleability of bentonitc because of its high swcllability plus the associated problems in shipping and storage.
• EP 0 485 124 A 1 describes a papermaking process comprising the preparation of a cellulose suspension, admixture of a bentonitc swelling clay to the suspension, where the clay is present in the form of an aqueous slurry, and then dcwatcring of the cellulose half-slock, where the bentonite swelling clay is prepared as a fluid concentrated dispersion containing at least 15 wt% bentonitc, based on dry weight, in a nonswollen form and a certain amount of dissolved monomc ⁇ c electrolytes sufficient to prevent swelling of the bentonite.
• the amount of electrolyte which may also be an activator such as sodium carbonate, is much greater than the amount usually used for activation, which leads to inhibition of swelling.
• the electrolyte concentration is also diluted, so that the bentonitc can swell.
• the pulp contains a conventional mixture of bentonitc and electrolyte and/or optionally an activator.
• WO 97/33041 Al in which a concentrate of alkaline earth bentonite with water and alkali metal citrate, ammonium citrate or sodium citrate as the activator and stabilizing agent is prepared and added to the pulp, optionally after prior dilution.
• US 5,248,641 relates to a method for increasing the viscosity of bcntonitc in aqueous media by a simplified procedure in comparison with the state of the art.
• the crude bentonitc in the form of a slurry is subjected to shearing in a mixing drum and then dried.
• an activating metal salt such as sodium carbonate
• a dry mixture is prepared and then pulverized.
• the simplification of the method thus consists of the fact that the complex aging and activation method described in the prior art is no longer necessary to improve the viscosity properties of the bcntonite but instead activation is possible by dry mixing the sheared and dried bentonite with the activator.
• the desired low abrasiveness cannot be achieved under practical conditions with the known dry grinding methods without prior processing steps such as prcdrying.
• the problem is the high water content of the crude bcntonile of up to 35 wl% naturally associated with it. This imparts a greasy slippery consistency to the products. It is therefore impossible to mill such crude bentonites to a high degree of fineness in a dry mill without prcdrying to ⁇ 20 wt% residual moisture content or, better yet, to 8 to 12 wt%.
• This prcdrying is accomplished primarily by thermal means, the first by solar exposure and secondly by electric heat and/or heat generated by combustion.
• the former has the disadvantage of the long duration required while the latter yields increased CCb emissions and therefore is not consistent with the Kyoto Protocol.
• the object of the present invention is thus first to provide a simplified method for processing crude benlonite.
• the object is to reduce the individual process steps required, which are very time-consuming and energy-intensive.
• the object of the present invention is to reduce the process steps and/or finishing steps for crude bc ⁇ lonitc to the end use to two steps or three steps at most.
• Another object in this method is to avoid the use of organic complexing agents such as NTA, EDTA, DTPA and salts of poiyacrylic acid to support the activation, first to reduce environmental pollution and secondly to prevent problems caused by such chemicals in subsequent applications.
• organic complexing agents such as NTA, EDTA, DTPA and salts of poiyacrylic acid
• complcxing agents are capable of dissolving heavy metals such as mercury out of sediments in natural bodies of water and can therefore lead to elevated levels in drinking water.
• Another object of the present invention is to provide a bentonite having improved properties, in particular with regard to abrasiveness, without having a negative effect on the functionality of the bentonite that is otherwise necessary and/or even supporting this in use in papcrmaking and/or paper finishing as well as its use as an aid in the papcrmaking process and paper finishing process.
• the object of the present invention is achieved by the method for processing crude bentonite according to the present invention.
• an aqueous slurry comprising crude bentonite with a solids content of max. 19 wt% is provided, which is wet-ground to a mean particle si/c of less than 1 ⁇ m.
• Crude bentonite occurs throughout the world, e.g., in the United States, convinced, Argentina, New Zealand, China, Russia, Sydney, Turkey and Europe, e.g., Greece and Germany.
• all commercially available crude bcntonitcs can be used, in particular the bentonite from Morocco, Milos (Greece), Bakirgol (Turkey) and New Zealand.
• the bentonite contained in crude bentonite is preferably bentonite containing alkaline earth, in which the smectite group is occupied almost exclusively with calcium and/or magnesium ions in the interstitial layers.
• Such benlonitcs occur in Germany and Greece, for example.
• crude bentonite containing bentonite in which the smectite group is occupied primarily by sodium ions in the interstitial spaces may also be used.
• Such bcntonites occur in the United States, for example.
• Use of crude bentonite whose interstitial layers arc occupied with sodium as well as calcium and/or magnesium ions is also possible.
• Such bcntonites occur in Morocco, for example.
• other alkali ions such as potassium ions may also be present.
• the crude bentonite usually contains various clay minerals such as in particular montmorillonite as the main component, but also quartz, mica, feldspar, pyrite, calcite and/or cristobalite. These minerals may be present in variable amounts, as well as other components, depending on the site of origin.
• Benlonitcs with a montmorillonite content of >60 wt%, preferably >80 wt%, e.g., between 85 and 95 wt% are especially suitable for the method according to the present invention.
• the crude bentonite is slurried in an aqueous medium, preferably using a traditional stirrer or dispersion apparatus.
• the temperature of the mixture may be increased from room temperature to 40 to 100 0 C 5 preferably 50 to 80 0 C.
• the heating especially preferably comes about due to the internal frictional energy and needs not be supplied externally. This has the advantage, for example, that the dispcrsibility and millability are further increased and any chemical reaction with inorganic chemicals such as activating reagents is accelerated.
• the crude bcntonitc solids content in the aqueous slurry amounts to max. 19 wt%. In a special 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%, e.g., 9 wt%.
• the concentration of the solids is selected so that the viscosity of the slurry is optimal for efficiency in grinding, i.e., between 10 and 5000 mPa-s, preferably 100 to 1000 mPa-s, and especially in the range of 1 50 to 600 mPa.s, measured with a Brookficld viscometer (as described in the examples).
• the optimal concentration depends on the occurrence, i.e., the chemical and mineralogical composition of the crude bcntonitc and its swcllability, which in turn influences (he viscosity.
• the crude bcntonitc slurry has the desired consistency, it is subjected to wet grinding in which even abrasive impurities are ground until they arc so small that they no longer have an abrasive effect in the subsequent application.
• the viscosity can be regulated by dilution with water and optimizing the solids content.
• the bcntonitc solids content in the aqueous slurry after wet grinding preferably amounts to 2 to 19 wt%, more preferably 5 to 18 wt%, especially preferably 6 to 12 ⁇ vt%, e.g., 7 wt%.
• the abrasive impurities that may occur in crude bcntonitc and be ground include for example silicates such as quartz, feldspar and chlorites.
• the crude bcntonitc slurry is ground to a mean particle diameter of preferably less than 1 ⁇ m, especially less than 0.8 ⁇ m, in particular less than 0.5 ⁇ m, e.g., in the range of 0.05 ⁇ m to 0.3 ⁇ m, more preferably 0.1 to 0.2 ⁇ m, e.g., 0.15 ⁇ m, as determined by sedimentation analysis (on a Microme ⁇ tics Sedigraph 51 00).
• >50 wt%, preferably >80 wt%, especially >90 wt% of the particles have a spherically equivalent diameter of ⁇ 0.2 ⁇ m (determined by sedimentation analysis on a Micromeritics Scdigraph 5100).
• the activation is performed in wet grinding by grinding one or more of the aforementioned activating substances together with the bentonite.
• these substances arc preferably added io the bentonite slurry in an amount of 0.5 to 10 wt%, more preferably in an amount of 1 to 8 wt%, especially in an amount of 3 to 6 wt%, e.g., 5 wt%, based on the weight of the montmorillonitc present in the bentonite.
• the molar concentration of exchangeable alkali metal ions in the aqueous phase preferably amounts to only >0. i mol/L, more preferably 0.01 to 0.05 mol/L, especially 0.02 to 0.04 mol/L. Despite this very low concentration, the exchange is much more efficient and more rapid than is the case with the conventional dry and semidry activation methods.
• the grinding may be performed in any grinding equipment with which those skilled in the art arc familiar for wet grinding of minerals.
• the conventional horizontal or vertical ball mills, jet plate mills, colloid mills or attritor mills, such as those distributed by the Dynomill Co., for example are especially suitable for this purpose.
• the grinding media used are preferably grinding beads with a diameter of 0.1 to 5 mm. more preferably 0.2 to 3 mm, especially 0.5 to 2 mm, e.g., 1 mm, but also sand, e.g., quartz sand, with a diameter of 0.1 to 2 mm, for example, may be used.
• the grinding beads arc preferably made of a material selected from the group comprising zirconium, cerium-stabilized zirconium or yttrium-stabilized zirconium and zirconium silicate.
• suitable weight ratio of bcnlonitc to grinding beads is, for example, 1 :3 to I : I 00, preferably 1 : 10 to 1 :90, especially preferably 1 :20 to 1 :80, most preferably 1 :30 to 1 :60, e.g., 1 :50.
• the bentonite slurry may be concentrated. It may be concentrated to a solids content of up to 30 wt%, preferably to the range of 12 to 17 wt%. After grinding, the concentration is preferably increased by 3 to 15 wt%, especially preferably by approximately 10 wt%, e.g., from 7 wt% to 17 wt%.
• Concentration is especially advantageous, e.g., in an external production to optimize storage and shipping properties.
• the slurry may be used directly.
• Concentration may be performed with the conventional equipment used for this purpose, e.g., by means of a centrifuge or filter press. It may also be performed as a thermal process.
• the inventive process thus constitutes a greatly simplified process for work-up of crude bentonite, especially for a reduction of its abrasivencss by grinding the bentonite together with its unwanted abrasive constituents, optionally after first separating out the very coarse constituents. Due to the fact that the drying, grinding and subsequent rcsuspcnding steps which arc otherwise conventional and necessary in the state of the art can be replaced by a single step, namely that of wet grinding, the method according to the present invention is therefore also an energy-saving and cost-saving new development because activation, which is usually also a separate step, may additionally be integrated into the wet grinding step, if necessary, and the method may be performed without the use of organic complexing agents.
• the method according to the present invention supplies bcntonite that is not only equivalent to the bcntonites of the state of the art but is actually superior to them in many regards.
• Another aspect of the present invention thus consists of a processed bcntonite which is obtainable by the method according to this invention.
• This bcntonite has various advantages, e.g., a much lower abrasion than that of bentonitcs customarily used in papermaking and/or finishing, e.g., as a filler or coating pigment.
• the abrasion of this bcntonite, measured on the AT 2000 abrasion tester from the company Einlchner, Germany, which simulates the wear on the wire in the paper machine is less than 3 mg, for example, preferably less Chan 2 mg, e.g., 1 mg
• the abrasion measured on the AT 1000, likewise by the company Einlehncr, Germany, which simulates a measure of the wear on the blade in coating, is preferably less than 30 mg, more preferably less than 20 mg, especially preferably less than ! 5 mg, in particular less than 10 mg, e.g., 7 to 9 mg, but also less (ban 5 mg, e.g., 4 or 2 mg.
• another aspect of the present invention therefore involves the use of the bcntonites obtainable by the method of the present invention in papermaking and in the paper finishing processes such as coating, where they can be advantageously used as additives.
• the bentonite is wet-ground together with other minerals and/or the residual chemicals or minerals containing residual chemicals by the method according to this invention.
• the bentonite obtainable by the method of the present invention also exhibits special advantages when used as a pitch control agent, in particular in controlling colloidal wood resin.
• Pitch is a term used to refer to organic hydrophobic material that is released as fine 0 droplets into water in processing wood to wood fibers.
• Pitch consists of fats and fatty acids, sterols and sterol esters, tcrpenes and waxes.
• Colloidal stabilization of pitch particles is accomplished by iignosuifonatcs and polysaccharides. If pitch particles arc destabilized, they can agglomerate and form deposits on the paper machine. These can lead to an inferior paper quality and tears in the paper sheets. 5
• the deposits may develop in the files of the wire section and press section as well as on the rolls in the dry section, For an effective reduction in pitch deposits, it is important for the pitch particles to be already adsorbed in colloidal form and thereby passivatcd. 0 In addition to these species of pitch, there arc also problems with so-cailed while pitch. These deposits arc often caused by binders such as slyrene-acrylates or styrcnc-butadicne latex and other additives. The combination with fillers and pigments from the coated brokes may lead to what is called white pitch.
• Stickies arc sticky impurities from recycled paper processing and include hot-melt adhcsives, binders and other thermoplastic materials.
• the chemical components arc mainly adhesivcs, styrcnc-butadicne binders, rubber, vinyl acrylatcs, polyisoprcnc, polybutadienc, polyvinyl acetate, etc..
• talc contributes toward less adhesion of pre-existing agglomerates due to its adhesion releasing property.
• the talc may be simply added to the benlonilc obtainable by the method of the present invention or ground together with it, preferably in the wet grinding step of the method according to the present invention.
• the method according to the present invention thus not only constitutes a simplification and therefore also an improvement in comparison with processing methods for bcnlonitc known in the prior art, but also the resulting bcntonite has improved properties with respect to bcnlonilcs processed by traditional methods and it can be used economically and in a variety of ways in various steps m the papcrmaking and/or finishing process.
• Figure 1 shows the x-ray diffraction diagrams of the samples (3/2) and sample (3/4).
• Figure 2 shows the turbidity of the TMP filtrate treated with mineral in NTU as a function of the bentonitc sample used.
• FIG. 3 shows the COD analysis of the TMP filtrate treated with the mineral in mg
• Figure 4 shows the turbidity of the TMP filtrate treated with the mineral in NTU as a function of the amount of bentonitc added per liquid filtrate.
• Figure 5 shows the turbidity of the TMP filtrate treated with the mineral in NTU as a function of the quantity of benionite added per dried filtrate.
• Figure 6 shows the COD analysis of the TMP filtrate treated with the mineral in mg O 2 per liter as a function of the quantity of bentonitc added per liquid filtrate.
• Figure 7 shows the COD analysis of the TMP filtrate treated with the mineral in mg OT per liter as a function of the quantity of bentonite added per dried nitrate.
• Figure 8 shows the turbidity of a polyacrylalc containing sample and a polyvinyl acetate containing sample treated with bentonite obtained by the method of the present invention.
• Figure 9 shows the COD analysts of a polyacrylate containing sample and a polyvinyl acetate containing sample treated with bentonite obtained by the method of the present invention.
• the grain size distribution was determined using a Sedigraph 5100.
• the moisture was determined by using a Mettler dry balance (Mettler AG, Grci fcnsee, Switzerland).
• the swelling volume was determined according to the following procedure:
• a 100 niL graduated cylinder was filled accurately up to the measurement mark with 100 niL deionized water.
• 2.0 g of the sample is weighed onto a sample boat (accuracy of the weight: 10 mg).
• the sample is added slowly in portions onto the surface of the water, so that contact between the wall of the graduated cylinder and the meniscus edge is avoided.
• the next portion is added, being sure that no air is entrained downward. If entrained air cannot be removed by tapping on the graduated cylinder, the measurement must be repeated.
• the height of the swollen solid phase is read 2 hours after filling the cylinder.
• the swelling volume was determined immediately after adding the 2 g sample, after 2 hours and after 24 hours.
• the swelling volume is calculated according to the following formula. When expressing the swelling volume, the water content of the weighed sample must be taken into account:
• the abrasion was determined on the AT 2000 and AT 1000 abrasion testers from the company Einfchncr, Germany.
• sodium carbonate (5 wt%. based on the dry bcntonitc) or Potassium carbonate (6.5 wt%, based on the dry bcnionitc) was added as an activation agent. It may be added as a solid or as liquid prcdissolvcd in water.
• ⁇ portion of the slurry was then dried using a GEA NlRO ⁇ /S spray dryer (Mobil Minor 3247 model, year of construction 2005) for samples (3/1 ) to (3/4) or a Biichi spray dryer (Typ 190 Mini Spray Dryer) for sample (3/6), respectively, to determine the swcllability in water.
• GEA NlRO ⁇ /S spray dryer Mobil Minor 3247 model, year of construction 2005
• a Biichi spray dryer Typ 190 Mini Spray Dryer
• Bentonitcs produced by the method described above were first tested for their properties with regard to abrasiveness, swelling volume and activation ability.
• the abrasivcncss of the samples according to the present invention is much lower than that of the starting materials. It is originally more than 15 mg (AT 2000) or more than 25 mg (AT 1000), whereas with the inventive samples, even those that have been activated, the abrasiveness is in a range of ⁇ 1 to 5.4 mg (AT 2000) or 2 to 1 3 mg (AT 1000).
• the swelling volume is important inasmuch as it is an important property for use as a rhcological additive.
• the bcntonites obtainable by the method according to the present invention arc at icast equivalent if not superior to the known bentonites while having a greatly reduced abrasion and arc therefore excellent for use as a rheo logical additive.
• Tables 6 and 7 show lhal the filler retention and total retention (i.e., filler and fiber retention) with the inventive Ca bcnlonites (3/1 ) and (3/3) were in the same range as those of comparative sample (2).
• the primary goal of preventing abrasion thus does not have a negative effect on the retention aid properties of the bcntonitcs.
• the bcntonitcs obtainable by the method according to the present invention thus not only excellently fulfill the primary task of reducing abrasivcness but also have at least an equivalent efficacy as retention aids, or in the case of activated bentonites even have a significantly improved efficacy.
• the marble was ground together with the crude bcnto ⁇ itc by the method according to the present invention and then the free residual chemical content was determined.
• residual chemicals e.g., the calcium carbonate present as marble, which is used as a filler or coating pigment in pape ⁇ naking/finishing
• the residual dicoco dimethyl ammonium chloride in the samples was determined in comparison with a blank sample.
• the blank sample was produced in0 the same way but without the addition of bentonitc.
• the quaternary ammonium compounds were determined by colo ⁇ mctry according to the following procedure:
• the sample was transferred to the PTFE agitator funnel with approx. 10 ml, water. Then 20.0 ml methylene chloride was added and extraction was performed. As soon as only a slight excess pressure had developed, the mixture was agitated intensely for 2 minutes.
• the measurement sample was poured into a centrifuge glass and ccntri fugcd for 1 5 minutes at 4000 io 4500 rpm. Then the bottom yellow phase was drawn off using a 20 in L syringe with a long needle, being sure that no contaminates were entrained from the upper phase.
• Sample (3/6) was obtained by co-grinding 50 wt% Finntalc P60 with 50 wt % sample (3), each based on the total weight of Finntalc P60 and sample (3), by a method like that used to prepare sample (3/3) (grinding lime: 180 min)
• thermomcchanical pulp (TMP) with a solids content of 3.7 w(% was filtered through a 2 ⁇ m filter, yield 2 L of filtrate. 200 g portions of this filtrate were each placed in eight glass bottles and each was mixed with 20 g of a 10 wt% slurry of the materials listed above.
• the upper and lower phases were separated from one another.
• the upper liquid phase was analyzed as follows:
• the talc treatment reduced turbidity to 187 NTU.
• Sample (2) (state of the art) reduced the colloidal particles to 18 NTU, i.e., to ⁇ 10% of the original value of 412 NTU.
• the inventive sample (3/3) also yielded a comparable reduction in the colloidal particles to ⁇ ] ()% of the original value (28 NTU).
• the inventive sample (3/6) had the same good adsorption effect as the samples (2) and (3/3), namely likewise a reduction to ⁇ 10% of the original value of 412 NTU (38 NTU).
• talc and bentonitc were reduced in size by co-grinding, the coarse crude Ca bcntonite (sample (3)) and the coarse talc were used as the starting materials for co-grinding.
• talc has a positive effect on sticky hydrophobic deposits such as pitch, white pitch and stickies and thus helps eliminating such interfering substances, if present, and also leads to fewer tears in rolling up the paper and less abrasion on the paper machine because of its lubricant properties
• the adsorption potential depends on the specific surface area of the talc and it is therefore advantageous to increase the surface area of the talc to that of the bcntonite in the same grinding operation.
• This combination of benlonite and talc is a highly potent adsorbent that not only has a lower abrasion than other customary adsorbents, but also has other positive properties in the production and finishing of paper.
• the original untreated TMP filtrate had a COD of 4291 mg O 2 per liter.
• Fmntalc P05 reduced the COD to 3616 mg Oj per liter.
• ⁇ ll the forms of bentonitc tested as well as the bentonitc/talc mixture had a similar reduction potential, reducing the COD value to approx. 2700 ⁇ 100 mg O2 per liter ( Figure 2), with the values of the inventive samples being better than those of the untreated sample (2).
• the filtrate liquid was added to a weighed aluminum container ( 125 mL; diameter 96 mm, height 24 mm) to obtain dry fibers; then the filtrate was dried in an oven (95 0 C; 24 h) and the residue was weighed.
• Figures 4 and 5 show that the minimum effective concentration is approx. 0.01 wt% clear filtrate or 0.2 wl%, based on the dry fiber substance.
• the optimum range for the paper industry on the basis of these results is between 0.5 and 2 wt%, based on the dry fiber substance.
• the resulting product had the following features:
• the Scdigraph grain size distribution yielded 98% ⁇ 2 ⁇ m, 97% ⁇ 1 ⁇ m and 94% ⁇ 0.2 ⁇ m.
• the resulting bentonite is used in various adsorption experiments with various polymers thai arc responsible for producing sticky deposits.
• Styrcnc polyacrylatc binder (Acronai V 212, BASF) was diluted to a solids content of 0.05 wl%.
• the pH was adjusted to 7.0-7.2 using 0.1 M hydrochloric acid or 0.1 M sodium hydroxide solution.
• the conductivity was adjusted to 1200 ⁇ S-cm ' by using I M sodium chloride solution.
• To 200 g of this latex suspension was added 4.04 g of the bentonite slurry described above, which was then stirred for 2 hours at room temperature. Next the sample was ccntrifuged for 30 minutes at 2580 g. The resulting supernatant was removed, and the turbidity and chemical oxygen demand (COD) were measured.
• COD chemical oxygen demand
• the turbidity was reduced from 470 NTU to 222 NTU. This corresponds to a 53% reduction (cf. Figure 8).
• the COD value was reduced from 740 mg Oi per dm 3 to 290 (cf. Figure 9).
• the bcntonilc obtained by the method of the present invention had a good adsorption effect for polystyrene polyacrylatc binder which occurs in stickics and white pitch.
• the pH was adjusted with 0.1 M I ICI and 0.1 M NaOH to 7.41.
• the conductivity was adjusted with IM NaCl solution to 141 1 ⁇ S-cirf '.
• the turbidity was reduced from 175 to 52 NTU. This corresponds (o a 70% reduction (cf. Figure 8).
• the COD value was reduced by 36% from 8170 mg O 2 per dm 3 to 5230 mg.
• the bcntonite obtained by the method of the present invention had a good to very good adsorption tendency for sticky compounds such as polyvinyl acetate (cf. Figure 9).

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• 2006
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• 2007
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