Abstract:
An aqueous aluminium silicate suspension having a content of aluminium silicate of at least 30 wt. % is prepared by liquefaction of the aluminium silicate filter cake or by dispersion of aluminium silicate powder in water with the addition of aluminium silicate powder, surfactant and aluminium sulfate. It can be employed in papermaking.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from German Application No. DE 198 21 143.0, filed on May 12, 1998, the subject matter of which is hereby incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an aqueous aluminium silicate suspension, a process for its preparation and its use. 
     2. Background Information 
     Aluminium silicate, such as, for example, P 820 is described in Ullmanns Enzyklopädie der technischen Chemie [Ullmann&#39;s Encyclopaedia of Industrial Chemistry], 4th edition, volume 21, page 467, table 12. It is employed as a pulp filler in papermaking. The printability of newspaper and thin printing paper can be improved by using aluminium silicate. Aluminium silicate is a white powder which is marketed in this form. In papermaking, however, almost all educts are employed in the form of aqueous suspensions. Aluminium silicate therefore has the disadvantage that for its use in papermaking separate devices must be built and used for the processing, because of its pulverulent consistency. This disadvantage can be overcome if the aluminium silicate powder can be employed in papermaking in the form of an aqueous suspension. 
     SUMMARY OF THE INVENTION 
     There is therefore the object of converting pulverulent aluminium silicate into an aqueous, storage-stable suspension which has a high solids content and can be used in papermaking. 
     The invention provides an aqueous aluminium silicate suspension, which is characterized in that, in addition to water, it comprises at least 30 wt. %, preferably at least 35 wt. %, aluminium silicate, 0.1 to 3.0 wt. % aluminium sulfate and 0.1 to 5.0 wt. % surfactants. 
     In a preferred embodiment of the invention, aluminium silicate P 820 can be employed as the aluminium silicate. Surfactants which can be employed are known nonionic surfactants, such as, for example, polyethylene oxide. 
     Anionic and/or cationic surfactants can furthermore be employed as surfactants. Such surfactants are, for example, polyacrylates, dodecylbenzenesulfonate and sodium citrate. 
     In a preferred embodiment, the solids content of the suspension can be 35 to 45 wt. %, in particular 35 to 40 wt. %. The pH of the suspension can be between 4.5 and 9.5, preferably between 5.0 and 8.0. 
     The invention also provides a process for the preparation of the aluminium silicate suspension, which is characterized in that an aluminium silicate is precipitated by a synthetic route from aluminium sulfate and water-glass and filtered off, the aluminium silicate filter cake is liquefied by stirring and/or subjecting to shear with an aqueous aluminium sulfate solution, at least one surfactant is added, pulverulent aluminium silicate is added to the liquefied aluminium silicate filter cake, while stirring and/or subjecting to shear, and the mixture is optionally stirred and/or subjected to shear once more. 
     In one embodiment of the invention, the aluminium silicate filter cake can be washed and dried. The resulting aluminium silicate powder can be mixed with an aqueous aluminium sulfate solution, while stirring and/or subjecting to shear, at least one surfactant can be added, further pulverulent aluminium silicate can be added to this suspension, while stirring and/or subjecting to shear, and the mixture can optionally be stirred and/or subjected to shear once more. 
     The aqueous aluminium silicate suspension according to the invention advantageously has a high solids content. Sedimentation of the solid does not occur even over a relatively long storage time. 
     Grinding for destructuring is not necessary. 
     The aqueous aluminium silicate suspension according to the invention can be employed in papermaking. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     EXAMPLES 
     The starting materials are characterized in table 1: 
     
       
         
               
             
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Physico-chemical data of P 820A powder and filter cake 
               
             
          
           
               
                   
                 P 820A 
                 P 820 A 
               
               
                   
                 powder 
                 filter cake 
               
               
                   
                   
               
             
          
           
               
                   
                 Tamped density [g/l] 
                 237 
                 — 
               
               
                   
                 Loss on drying [%] 
                 6.4 
                 70.0 
               
               
                   
                 Solids content [%] 
                 93.6 
                 30 
               
               
                   
                 Average particle size [μm] 
                 5.6 
                 7.5 
               
               
                   
                 Surface area [m 2 /g] 
                 66 
                 — 
               
               
                   
                 DBP adsorption [g/100 g] 
                 90 
                 — 
               
               
                   
                 pH 
                 9.5 
                 8.9 
               
               
                   
                   
                   
                 (slurry) 
               
               
                   
                   
               
             
          
         
       
     
     Preparation of the Slurry 
     2400 g aluminium silicate P 820A paste are gradually added to a 5 l measuring beaker and subjected to shear with a Dispermat at 8500 rpm. At the same time, 30 ml Al 2 (SO 4 ) 3  solution with a concentration of 90 g/l are added in stages. The shear time of the liquefaction is 14 min. The influence of the added aluminium sulfate and of the shearing can be seen from tables 2 and 3. 
     
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
             
             
               
                   
                   
               
               
                   
                 Aluminium sulfate 
                   
                 Viscosity 
               
             
          
           
               
                   
                 [ml solution] 
                 [g/100 g slurry] 
                 pH 
                 [mPa*s] 
               
               
                   
                   
               
               
                   
                 0 
                 0 
                 8.9 
                 2000 
               
               
                   
                 0.5 
                 0.02 
                 8.9 
                 2000 
               
               
                   
                 2 
                 0.09 
                 8.2 
                 1800 
               
               
                   
                 4 
                 0.18 
                 6.8 
                 1600 
               
               
                   
                 6 
                 0.27 
                 6.1 
                 1500 
               
               
                   
                 8 
                 0.36 
                 5.7 
                 1430 
               
               
                   
                 10 
                 0.45 
                 5.3 
                 1400 
               
               
                   
                 12 
                 0.54 
                 5.1 
                 1500 
               
               
                   
                 14 
                 0.63 
                 4.9 
                 1900 
               
               
                   
                 16 
                 0.72 
                 4.8 
                 1650 
               
               
                   
                 18 
                 0.81 
                 4.6 
                 1650 
               
               
                   
                 20 
                 0.90 
                 4.5 
                 1450 
               
               
                   
                 25 
                 1.13 
                 4.4 
                 1200 
               
               
                   
                   
               
             
          
         
       
     
     
       
         
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Shear 
                   
                 Average 
               
               
                 time 
                 Viscosity 
                 particle size 
               
               
                 [min] 
                 [mPa*s] 
                 d 50  [μm] 
               
               
                   
               
             
             
               
                  0 
                 2600  
                 7.7 
               
               
                  5 
                 100  
                 7.1 
               
               
                 10 
                 80 
                 7.1 
               
               
                 15 
                 65 
                 7.1 
               
               
                 20 
                 55 
                 7.1 
               
               
                   
               
             
          
         
       
     
     The surfactant additive is stirred in at a low speed of rotation. The suspension is then subjected to dispersion for one minute at 8500 rpm. The amount added is shown in tables 5 to 7. 
     The desired solids content is now established with P 820A powder. 
     35% SC: addition of 217.1 g powder 
     40% SC: addition of 456.3 g powder 
     The time for the concentration is 15 min. The suspension obtained in this way is subjected to dispersion at 8500 rpm for a further 30 min. 
     Finally, the slurry is subjected to shear once again for 15 min with an Ultra-Turrax, while simultaneously stirring with an IKA laboratory stirrer (dispersing disc φ=6 cm, 1000 rpm). 
     The sedimentation, pH, viscosity, grindometer value and time for redispersion by vibration and rotation are determined on the aluminium silicate (P 820 A) suspensions, which keep at room temperature. After one day, the actual solids content is additionally determined. These values are determined 1 d, 4 weeks and 14 weeks after preparation of the suspension. 
     DESCRIPTION OF THE METHODS USED 
     Sedimentation 
     The individual layers of the suspension are measured on a centimeter scale. A distinction can be made between the following three types: 
     1. Supernatant water 
     2. Suspension 
     3. Sediment 
     Liquefaction by Vibration 
     The sample bottles are clamped upside down in the vibrating screen (Retsch, AS 200 digit) and vibrated at intervals with an amplitude of 100. The time taken for the suspension to redisperse completely is determined. If no redispersion is to be achieved, the experiment is interrupted after 10 min. 
     Liquefaction by Rotation 
     The samples are rotated on a roller mixer (setting 1) until a homogeneous suspension has formed again. Here also, the maximum treatment time is 10 min. 
     Measurement of the pH 
     The liquefied suspension is mixed thoroughly on a magnetic stirrer for 5 min. After the stirrer has been switched off, the pH is read. 
     Measurement of the Viscosity 
     Immediately after the pH has been determined, the viscosity is measured with a Brookfield DV-II+viscometer (spindle no. 62, 100 RPM). Here also, the value is read after 5 min. 
     Grindometer 
     After thorough mixing of the suspension, the particle size of the suspension is determined with a grindometer. 
     Solids Content 
     100 g of the redispersed suspension are dried to constant weight in a drying cabinet at 105° C. 
     If liquefaction of the suspension cannot be effected by vibration or rotation, an attempt is made to liquefy the suspension with a spatula. 
     The pH, viscosity, grindometer value and solids content are determined only on a completely redispersed suspension. 
     The data determined by the test methods described are listed in tables 6-8. To evaluate the suitability of an additive for improving the properties of the suspension, three factors are to be considered more closely: The ease of incorporation of the additive, the sedimentation properties of the suspension and the redispersibility of the sediment. 
     Sedimentation Properties 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 show the sedimentation properties of suspensions to which various stabilizers have been added, for solids contents of approx. 35 wt. % and 40 wt. % respectively. The heights of the sediment and water phase are shown in these figures. For each additive (demarcated by the small transverse line on the left-hand edge of the graph) the values for storage after 1 d (bottom bar), after 4 weeks (middle bar) and 14 weeks (top bar) are plotted. A good storage stability exists if no solid sediment forms and if no clear aqueous phase forms above the suspension, that is to say always if the sum of the sedimentation height and the height of the aqueous phase tends towards zero. This is the case for all the polyacrylates investigated and for polyethylene oxide at a solids content of both 35% and 40%. It was possible to investigate sodium citrate and dodecylbenzenesulfonate only at a solids content of 35%, and a very low tendency towards sedimentation is likewise found. 
     Redispersiblity 
     Although the suspensions are liquid after the preparation, they become paste-like on cooling. This cannot be prevented even by addition of the additives investigated. However, the suspensions differ very widely in the energy expenditure with which liquefaction can take place. An attempt is made to determine this introduction of energy needed by defined vibration or rotation of the sample glass. For some samples, liquefaction can be achieved in this way. However, there are also suspensions which cannot be liquefied merely by vibration and rotation, but liquefy immediately after the surface of the suspension is penetrated with a spatula. To evaluate the redispersibility, all the observations are therefore combined and assigned subjectively to a scale from very good to very poor. The results are listed in table 4. 
     Ease of Incorporation 
     Ease of incorporation is to be understood as meaning how the incorporation of the powder for concentration of the slurry took place after addition of the stabilizer. This parameter cannot be determined by measurement, and the subjective evaluation of the person performing the test has therefore been used for this. 
     
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Evaluation of the various stabilizers 
               
             
          
           
               
                   
                 Ease of 
                 Sedimentation 
                   
               
               
                 Stabilizer 
                 incorporation 
                 properties 
                 Redispersibility 
               
               
                   
               
               
                 Polyethylene oxide 
                 + 
                 ++ 
                 + 
               
               
                 Polyacrylate 
                 + 
                 + 
                 + 
               
               
                 (MW = 1,200) 
                   
                   
                   
               
               
                 Polyacrylate 
                 + 
                 + 
                 + 
               
               
                 (MW = 8,000) 
                   
                   
                   
               
               
                 Polyacrylate 
                 + 
                 + 
                 + 
               
               
                 (MW = 15,000) 
                   
                   
                   
               
               
                 Sodium citrate 
                 − 
                 + 
                 + 
               
               
                 EDTA 
                 ++ 
                 − 
                 −− 
               
               
                 Polyethylene glycol 
                 ++ 
                 − 
                 −− 
               
               
                 (MW = 200) 
                   
                   
                   
               
               
                 Polyethylene glycol 
                 + 
                 − 
                 − 
               
               
                 (MW = 2,000) 
                   
                   
                   
               
               
                 Polyethylene glycol 
                 + 
                 − 
                 ∘ 
               
               
                 (MW = 10,000) 
                   
                   
                   
               
               
                 Dodecylbenzenesulfonate 
                 −− 
                 ∘ 
                 −− 
               
               
                   
               
               
                 ++ very good  
               
               
                 + good  
               
               
                 ∘ adequate  
               
               
                 − poor  
               
               
                 −− very poor  
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Investigation of the storage stability of aqueous P 820A suspensions with various additives and solids contents 
               
             
          
           
               
                   
                 Example 
                   
               
             
          
           
               
                   
                 1 
                 2 
                 3 
                 4 
                 5 
                 6 
                 7 
               
               
                   
                   
               
             
          
           
               
                 Additive Concentration 
                 Sample without additive 
                 Polyacrylate (M w  = 1,200) 
                 Polyethylene glycol (M w  = 200) 
                 Sodium citrate 
               
             
          
           
               
                   
                 — 
                 — 
                 2.0% (39.6 ml) 
                 2.0% (43.3 ml) 
                 1.0% (23.3 ml) 
                 1.0% (25.4 ml) 
                 2.0% (52.3 g) 
               
               
                 Storage: 
                   
                   
                   
                   
                   
                   
                   
               
               
                 1 d 
               
               
                 Analysis: 
               
               
                 clear layer [%] 
                 5.6 (cloudy) 
                 — 
                 0.7 (clear) 
                 — 
                 5.6 (cloudy) 
                 1.6 (cloudy) 
                 — 
               
               
                 Slurry [%] 
                 73.6 (liquid) 
                 97.3 (pasty) 
                 99.3 (pasty) 1   
                 100 (pasty) 1   
                 75.0 (liquid) 
                 93.8 (liquid) 
                 100 (pasty) 
               
               
                 Sediment [%] 
                 20.8 (solid) 3   
                 2.7 (solid) 3   
                 — 
                 — 
                 19.4 (solid) 3   
                 4.7 (solid) 3   
                 — 
               
               
                 Liq. by vibration [min · s] 
                 n. redisp. 
                 2.44 
                 n. redisp. 
                 5.33 
                 n. redisp. 
                 4.41 
                 1.22 
               
               
                 Liq. by rotation [min · s) 
                 8.30 
                 2.30 
                 1.30 
                 10.00 
                 7.00 
                 3.30 
                 6.45 
               
               
                 pH 
                 7.7 
                 8.0 
                 7.8 
                 7.8 
                 7.9 
                 7.9 
                 8.0 
               
               
                 Visc. [mPasxs] 
                 39 
                 79 
                 42 
                 104 
                 40 
                 53 
                 49 
               
               
                 Grind. [um] 
                 &gt;100 
                 80 
                 70 
                 80 
                 65 
                 70 
                 65 
               
               
                 SC [%] 
                 35.3 
                 42.4 
                 35.9 
                 41.7 
                 36.1 
                 41.4 
                 36.5 
               
               
                 4 w 
               
               
                 clear layer [%] 
                 31.4 (cloudy) 
                 5.3 (clear) 
                 1.4 (clear) 
                 — 
                 32.4 (cloudy) 
                 6.3 (cloudy) 
                 — 
               
               
                 Slurry [%] 
                 — 
                 89.3 (pasty) 
                 98.6 (pasty) 1   
                 100 (pasty) 1   
                 — 
                 84.4 (pasty) 
                 100 (pasty) 1   
               
               
                 Sediment [%] 
                 68.6 (solid) 
                 5.3 (solid) 3   
                 — 
                 — 
                 67.6 (solid) 
                 9.4 (solid) 
                 — 
               
               
                 Liq. by vibration [min · s] 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 4   
                 n. redisp. 4   
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 4   
               
               
                 Liq. by rotation [min · s] 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
               
               
                 pH 
                 — 
                 8.1 
                 7.9 
                 8.0 
                 — 
                 — 
                 8.1 
               
               
                 Visc. [mPasxs] 
                 — 
                 75 
                 65 
                 122 
                 — 
                 — 
                 43 
               
               
                 Grind. [um] 
                 — 
                 75 
                 70 
                 80 
                 — 
                 — 
                 80 
               
               
                 14 w 
               
               
                 clear layer [%] 
                 34.2 (cloudy) 
                 4.2 (cloudy) 
                 1.4 (clear) 
                 — 
                 32 (cloudy) 
                 9.5 (cloudy) 
                 — 
               
               
                 Slurry [%] 
                 — 
                 90.3 (pasty) 
                 98.6 (pasty) 1   
                 100 (pasty) 2   
                 — 
                 77.8 (pasty) 
                 100 (pasty) 2   
               
               
                 Sediment [%] 
                 65.8 (solid) 
                 5.6 (solid) 3   
                 — 
                 — 
                 68.0 (solid) 
                 12.7 (solid) 
                 — 
               
               
                 Liq. by vibration [min · s] 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 4   
                 n. redisp. 4   
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 4   
               
               
                 Liq. by rotation [min · s) 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
               
               
                 pH 
                 — 
                 8.1 
                 7.9 
                 8.0 
                 — 
                 — 
                 8.0 
               
               
                 Visc. [mPasxs] 
                 — 
                 160 
                 65 
                 134 
                 — 
                 — 
                 62 
               
               
                 Grind. [um] 
                 — 
                 80 
                 70 
                 80 
                 — 
                 — 
                 70 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Investigation of the storage stability of P 820A slurries with various additives and solids contents 
               
             
          
           
               
                   
                 Example 
                   
               
             
          
           
               
                   
                 8 
                 9 
                 10 
                 11 
                 12 
                 13 
                 14 
               
               
                   
                   
               
             
          
           
               
                 Additive Concentration  
                 EDTA 
                 Dodecylbenzene- 
                 Polyethylene oxide 
                 Polyacrylate (M w  = 8,000) 
                   
               
             
          
           
               
                   
                 3.0% (78.5 g) 
                 3.0% (85.7 g) 
                 sulfonate 
                 1.5% (39.3 g) 
                 1.5% (42.8 g) 
                 2.0% (40.2 ml) 
                 2.0% (43.9 ml) 
               
               
                   
                   
                   
                 0.5% (13.1 g) 
               
             
          
           
               
                 Storage: 
                   
                   
                   
                   
                   
                   
                   
               
               
                 1 d 
               
               
                 Analysis: 
               
               
                 clear layer [%] 
                 1.3 (cloudy) 
                 3.0 (cloudy) 
                 — 
                 — 
                 — 
                 0.7 (clear) 
                 — 
               
               
                 Slurry [%] 
                 84.8 (liquid) 
                 89.6 (liquid) 
                 94.3 (liquid) 
                 100 (paste-liq.) 
                 100 (pasty) 
                 99.3 (pasty) 
                 100 (pasty) 1   
               
               
                 Sediment [%] 
                 13.9 (solid) 3   
                 7.5 (solid) 3   
                 5.7 (pasty) 
                 — 
                 — 
                 — 
                 — 
               
               
                 Liq. by vibration [min · s] 
                 n. redisp. 
                 n. redisp. 
                 0.21 
                 immediately 
                 1.34 
                 2.20 
                 n. redisp.4 
               
               
                   
                   
                   
                   
                 without vibr. 
               
               
                 Liq. by rotation [min · s] 
                 7.30 
                 7.00 
                 2.00 
                 immediately 
                 0.07 
                 1.45 
                 n. redisp. 
               
               
                   
                   
                   
                   
                 without rot. 
               
               
                 pH 
                 4.3 
                 4.3 
                 7.5 
                 7.8 
                 7.8 
                 7.7 
                 7.7 
               
               
                 Visc. [mPasxs] 
                 37 
                 53 
                 36 
                 206 
                 681 
                 83 
                 166 
               
               
                 Grind. [um] 
                 70 
                 70 
                 55 6   
                 70 
                 65 
                 70 
                 75 
               
               
                 SC [%] 
                 36.2 
                 42.1 
                 35.4 
                 36.6 
                 42.4 
                 36.6 
                 42.5 
               
               
                 4 w 
               
               
                 clear layer [%] 
                 5.7 (cloudy) 
                 31.1 (cloudy) 
                 — 
                 0.7 (clear) 
                 — 
                 1.5 (clear) 
                 — 
               
               
                 Slurry [%] 
                 22.9 (liquid) 
                 — 
                 93.2 (pasty) 
                 99.3 (pasty) 
                 100 (pasty) 1   
                 98.5 (pasty) 1   
                 100 (pasty) 1   
               
               
                 Sediment [%] 
                 71.4 (solid) 
                 68.9 (solid) 
                 6.8 (solid) 
                 — 
                 — 
                 — 
                 — 
               
               
                 Liq. by vibration [min · s] 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 7.34 
                 n. redisp. 5   
                 n. redisp. 4   
                 n. redisp. 4   
               
               
                 Liq. by rotation [min · s] 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 2.30 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
               
               
                 pH 
                 — 
                 — 
                 — 
                 7.9 
                 7.9 
                 7.8 
                 7.8 
               
               
                 Visc. [mPasxs] 
                 — 
                 — 
                 — 
                 240 
                 568 
                 77 
                 149 
               
               
                 Grind. [um] 
                 — 
                 — 
                 — 
                 70 
                 60 
                 65 — 
                 70 
               
               
                 14 w 
               
               
                 clear layer [%] 
                 31.5 (cloudy) 
                 27.5 (cloudy) 
                 4.4 (cloudy) 
                 — 
                 — 
                 — 
                 — 
               
               
                 Slurry [%] 
                 — 
                 — 
                 86.8 (pasty) 
                 100 (pasty) 1   
                 100 (pasty) 1   
                 100 (pasty) 1   
                 100 (pasty) 1   
               
               
                 Sediment [%] 
                 68.5 (solid) 
                 68.5 (solid) 
                 8.8 (solid) 
                 — 
                 — 
                 — 
                 — 
               
               
                 Liq. by vibration [min · s] 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 4   
                 n. redisp. 5   
                 n. redisp. 5   
                 n. redisp. 2   
               
               
                 Liq. by rotation [min · s] 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
               
               
                 pH 
                 — 
                 — 
                 — 
                 7.8 
                 7.8 
                 7.8 
                 7.8 
               
               
                 Visc. [mPasxs] 
                 — 
                 — 
                 — 
                 286 
                 710 
                 90 
                 194 
               
               
                 Grind. [um] 
                 — 
                 — 
                 — 
                 70 
                 70 
                 70 
                 70 
               
               
                   
               
               
                   1 easy to redisperse by stirring with a spatula  
               
               
                   2 can be redispersed with a spatula with some effort  
               
               
                   3 difficult to redisperse by stirring with a spatula  
               
               
                   4 redisperses immediately after penetration  
               
               
                   5 redisperses after max. 1 min after penetration  
               
               
                   6 grind. determ. difficult, since suspension foamed  
               
             
          
         
       
     
     
       
         
               
             
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 Investigation of the storage stability of Pasilex A slurries with various additives and solids contents 
               
             
          
           
               
                   
                 Example 
               
             
          
           
               
                   
                 15 
                 16 
                 17 
                 18 
                 19 
                 20 
               
               
                   
                   
               
             
          
           
               
                 Additive Concentration 
                 Polyacrylate M w  = 15,000 
                 Polyethylene glycol (M w  = 2,000) 
                 Polyethylene glycol (M w  = 10,000) 
               
             
          
           
               
                   
                 2.0% (41.8 ml) 
                 2.0% (45.7 ml) 
                 2.0% (52.3 g) 
                 2.0% (57.1 g) 
                 3.0% (78.5 g) 
                 3.0% (85.7 g) 
               
               
                 Storage: 
                   
                   
                   
                   
                   
                   
               
               
                 1 d 
               
               
                 Analysis: 
               
               
                 clear layer [%] 
                 0.7 (clear) 
                 — 
                 4.2 (cloudy) 
                 4.3 (cloudy) 
                 3.0 (cloudy) 
                 1.6 (cloudy) 
               
               
                 Slurry [%] 
                 99.3 (pasty) 
                 100 (pasty) 
                 84.5 (liquid) 
                 92.9 (paste-liq.) 
                 89.6 (liquid) 
                 96.8 (liquid) 
               
               
                 Sediment [%] 
                 — 
                 — 
                 11.3 (solid) 
                 2.9 (solid) 
                 7.5 (solid) 
                 1.6 (solid) 
               
               
                 Liq. by vibration [min · s] 
                 0.55 
                 1.34 
                 n. redisp. 
                 4.00 
                 0.51 
                 1.20 
               
               
                 Liq. by rotation [min · s] 
                 0.45 
                 8.15 
                 6.00 
                 3.15 
                 2.00 
                 0.30 
               
               
                 pH 
                 7.8 
                 7.9 
                 7.6 
                 7.7 
                 7.8 
                 7.9 
               
               
                 Visc. [mPasxs] 
                 46 
                 177 
                 42 
                 66 
                 84 
                 126 
               
               
                 Grind. [um] 
                 65 
                 65 
                 70 
                 70 
                 70 
                 65 
               
               
                 SC [%] 
                 36.1 
                 41.6 
                 36.6 
                 41.7 
                 36.9 
                 42.1 
               
               
                 4 w 
               
               
                 clear layer [%] 
                 1.5 (clear) 
                 — 
                 6.2 (cloudy) 
                 2.9 (cloudy) 
                 11.4 (cloudy) 
                 4.4 (cloudy) 
               
               
                 Slurry [%] 
                 98.5 (pasty) 1   
                 100 (pasty) 1   
                 20.0 (liquid) 
                 89.9 (pasty) 
                 77.1 (pasty) 
                 94.1 (pasty) 
               
               
                 Sediment [%] 
                 — 
                 — 
                 73.8 (solid) 
                 7.2 (solid) 3   
                 11.4 (solid) 2   
                 1.5 (solid) 1   
               
               
                 Liq. by vibration [min · s] 
                 n. redisp. 4   
                 n. redisp. 4   
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
               
               
                 Liq. by rotation [min · s] 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 7.30 
                 n. redisp. 
               
               
                 pH 
                 8.0 
                 8.0 
                 — 
                 7.8 
                 7.9 
                 7.9 
               
               
                 Visc. [mPasxs] 
                 75 
                 181 
                 — 
                 174 
                 131 
                 235 
               
               
                 Grind. [um] 
                 80 
                 85 
                 — 
                 70 
                 70 
                 70 
               
               
                 14 w 
               
               
                 clear layer [%] 
                 — 
                 — 
                 15.2 (cloudy) 
                 4.4 (cloudy) 
                 9.1 (cloudy) 
                 4.7 (cloudy) 
               
               
                 Slurry [%] 
                 100 (pasty) 1   
                 100 (pasty) 2   
                 39.4 (pasty) 
                 88.2 (pasty) 
                 74.2 (pasty) 
                 92.2 (pasty) 
               
               
                 Sediment [%] 
                 — 
                 — 
                 45.5 (solid) 
                 7.4 (solid) 3   
                 16.7 (solid) 
                 3.1 (solid) 
               
               
                 Liq. by vibration [min · s] 
                 n. redisp. 5   
                 n. redisp. 5   
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
               
               
                 Liq. by rotation [min · s] 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
                 n. redisp. 
               
               
                 pH 
                 8.0 
                 7.9 
                 — 
                 7.8 
                 — 
                 — 
               
               
                 Visc. [mPasxs] 
                 120 
                 254 
                 — 
                 268 
                 — 
                 — 
               
               
                 Grind. [um] 
                 80 
                 80 
                 — 
                 70 
                 — 
                 — 
               
               
                   
               
               
                   1 easy to redisperse by stirring with a spatula  
               
               
                   2 can be redispersed with a spatula with some effort  
               
               
                   3 difficult to redisperse by stirring with a spatula  
               
               
                   4 redisperses immediately after penetration  
               
               
                   5 redisperses after max. 1 min after penetration  
               
               
                   6 grind. determ. difficult, since suspension foamed