Abstract:
A method for producing potassium-doped pyrogenic oxides involves mixing a gaseous mixture including a pyrogenic oxide precursor and an aqueous aerosol containing a potassium salt to form an aerosol-gaseous mixture which is then reacted in a flame under conditions suitable for producing pyrogenic oxides by flame oxidation or flame hydrolysis to form the potassium-doped pyrogenic oxides product. The particle product is spherical, has a BET surface between 1 and 1000 m 2 /g and a narrow distribution of particle size of at least 0.7. The doped oxides can be used as polishing material (CMP application).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention is relative to pyrogenic oxides doped by means of aerosol with potassium, to the method of their production and to their usage. 
         [0003]    2. Description of Related Art 
         [0004]    The doping of pyrogenic oxides by means of aerosol is described in DE 196 50 500. It shows how an aerosol is additionally fed into a flame in which a pyrogenic oxide is produced by flame hydrolysis. 
         [0005]    A salt of the compound(s) to be doped is in this aerosol. 
         [0006]    It was found that when potassium salts are used as doping component the structure, that is, the degree of intergrowth and also the morphology (that is, the outward image) of the primary particles, is decisively changed. According to the invention this change of the morphology begins at a potassium content of more than 0.03% by wt. 
       SUMMARY OF THE INVENTION 
       [0007]    Subject matter of the invention is constituted by pyrogenically produced oxides of metals or metalloids which oxides are doped by means of aerosol with potassium and are characterized in that the base component is an oxide that is pyrogenically produced in the manner of flame oxidation or preferably of flame hydrolysis and is doped with potassium of more than 0.03 to 20% by wt. and in that the doping amount is preferably in a range of 500 to 20,000 ppm, the doping component is a salt of potassium and the BET surface of the doped oxide is between 1 and 1000 m 2 /g. 
         [0008]    The breadth of the distribution of particle size is defined as the quotient d n /d a  with d n  as arithmetic particle diameter and d a  the average particle diameter over the surface. If the quotient d n /d a  has the value of 1, a monodisperse distribution is present. That is, the closer the value is to 1 the closer the distribution of particle size is. 
         [0009]    The close distribution of particle size, defined by the value d n /d a , assures that no scratches are caused by large particles during the chemical-mechanical polishing. 
         [0010]    The average particle size can be less than 100 nanometers and the breadth of the distribution of particle size is at least 0.7. 
         [0011]    The oxide can preferably be silicon dioxide. The pH of the doped, pyrogenic oxide, measured in a 4% aqueous dispersion, can be more than 5, preferably from 7 to 8. The BET surface of the doped oxide can be between 1 and 1000 m 2 /g, preferably between 60 and 300 m 2 /g. 
         [0012]    The (DBP number) dibutylphthalate absorption can not show any measurable end point and the BET surface of the doped oxide can be between 1 and 1000 m 2 /g. 
         [0013]    Further subject matter of the invention is constituted by a method of producing the pyrogenic oxides of metals or metalloids, which oxides are doped by means of aerosol with potassium, which is characterized in that an aerosol produced from a potassium salt solution with a potassium chloride content greater than 0.5% by wt. KCl is fed into a flame like the one used to produce pyrogenic oxides, preferably silicon dioxide in the manner of flame oxidation or preferably of flame hydrolysis, that this aerosol is homogeneously mixed before the reaction with the gaseous mixture of flame oxidation or flame hydrolysis, then the aerosol-gaseous mixture is allowed to react in a flame and the pyrogenic, potassium-doped oxides produced are separated in a known manner from the gas flow, that a potassium salt solution containing the potassium salt serves as starting product of the aerosol and that the aerosol is produced by atomization by means of an aerosol generator preferably in accordance with the gas-atomizing (two-fluid) nozzle method. 
         [0014]    The method of producing pyrogenic oxides such as, e.g., silicon dioxide is known from Ullmann&#39;s Encyclopädie der technischen Chemie, 4 th  edition, volume 21, page 464 (1982). In addition to silicon tetrachloride any liquefiable compound of silicon such as, e.g., methylmonochlorosilane can be used as starting material. 
         [0015]    DE 196 50 500 teaches a method of producing silicon dioxide doped with aerosol. 
         [0016]    In the method of the invention oxygen can be additionally added. 
         [0017]    The silicon dioxide in accordance with the invention and doped with potassium by means of aerosol exhibits a distinctly narrower distribution of particle size curve than the known silicon dioxide. It is particularly suitable for this reason for use as an abrasion means in CMP (chemical mechanical polishing). The potassium is uniformly distributed in the case of the silicon dioxide of the invention. It can not be localized on EM photographs. 
         [0018]    The pyrogenic oxides doped in this manner with potassium surprisingly exhibit spherical, round primary particles in an electron microscope image that are only slightly intergrown with each other, which is expressed in the fact that no end point can be recognized in a “determination of structure” according to the DBP method. Furthermore, highly filled dispersions with a low viscosity can be produced from these pyrogenic powders doped with potassium. 
         [0019]    Further subject matter of the invention is constituted by the use of pyrogenic oxides doped with potassium by means of aerosol as filler, carrier material, catalytically active substance, starting material for producing dispersions, as polishing material (CMP applications), base ceramic material, in the electronic industry, in the cosmetic industry, as additive in the silicon industry and rubber industry, for adjusting the rheology of liquid systems, for the stabilization of heat protection and in the paint industry. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0020]      FIG. 1  shows an EM photograph of the pyrogenic silicic acid of reference example 1 (without doping). 
           [0021]      FIG. 2  shows an EM photograph of the pyrogenic silicic acid according to example 2 doped with potassium. 
           [0022]      FIG. 3  shows the DBP curve of the powders of reference example 1 (weighed portion 16 g): The take-up of force and the measured torque (in Nm) of the rotating blades of the DBP measuring device (Rheocord 90 of the company Haake/Karlsruhe) shows a sharply pronounced maximum with a subsequent decline at a certain addition of DBP. This curve form is characteristic for known pyrogenic oxides that are not doped. 
           [0023]      FIG. 4  shows the DBP curve of the powder of the pyrogenic oxide doped with potassium in accordance with the invention (16 g weighed portion) according to example 2. 
           [0024]      FIG. 5  shows the electron microscope photograph of the powder of example 3 with an enlargement of 1:50000. 
           [0025]      FIG. 6  shows the electron microscope photograph of the powder of example 3 with an enlargement of 1:100000. 
           [0026]      FIG. 7  shows the electron microscope photograph of the powder of example 3 with an enlargement of 1:200000. 
           [0027]      FIG. 8  shows the results of the particle count of the powders of example 1. 
           [0028]      FIG. 9  shows the results of the particle count of the powders of example 1. 
           [0029]      FIG. 10  shows the results of the particle count of the powders of example 1. 
           [0030]      FIG. 11  shows the results of the particle count of the powders of example 7. 
           [0031]      FIG. 12  shows the results of the particle count of the powders of example 7. 
           [0032]      FIG. 13  shows the results of the particle count of the powders of example 7. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    The subject matter of the invention will be explained and described in detail using the following examples: 
         [0034]    A burner arrangement is used like the one described in DE OS 196 50 500. 
       Example 1 
     Reference Example without Doping with Potassium Salts but with Water Vapor 
       [0035]    4.44 kg/h SiCl 4  are evaporated at approximately 130° C. and transferred into the central tube of the burner with a known design in accordance with DE 196 50 500 A1. 2.9 Nm 3 /h hydrogen as well as 3.8 Nm 3 /h air and 0.25 Nm 3 /h oxygen are additionally fed into this tube. This gaseous mixture flows out of the inner burner nozzle and burns into the combustion chamber of the water-cooled fire tube. Additionally, 0.3 Nm 3 /h (secondary) hydrogen and 0.3 Nm 3 /h nitrogen are fed into the jacket nozzle surrounding the central nozzle in order to avoid cakings. 
         [0036]    Approximately 10 Nm 3 /h air is drawn from the ambient into the fire tube standing under a slight vacuum (open burner operation). 
         [0037]    The second gaseous component that is fed into the axial tube consists in this reference example of hydrogen produced by superheating distilled water at approximately 180° C. Two gas-atomizing nozzles with an atomization power of 250 g/h water function thereby as aerosol generator. 
         [0038]    The atomized water vapor is conducted with the aid of a carrier gas current of approximately 2 Nm 3 /h air through heated conduits during which the water-vapor mist turns into gas at temperatures of approximately 180° C. 
         [0039]    After the flame hydrolysis the reaction gases and the pyrogenic silicic acid produced are drawn through a cooling system by applying a vacuum and the gaseous particle current cooled off thereby to approximately 100 to 160° C. The solid matter is separated from the current of waste gas in a filter or cyclone. 
         [0040]    The pyrogenic silicic acid produced accumulates as white, fine powder. In a further step any adhering remnants of hydrochloric acid are removed from the silicic acid at an elevated temperature by a treatment with air containing water vapor. 
         [0041]    The BET surface of the pyrogenic silicic acid is 124 m 2 /g. 
         [0042]    The breadth of the distribution of the particle size is calculated as follows:
       d n =16.67 nm   d a =31.82 nm
 
The quotient
       
 
         [0000]    
       
         
           
             
               q 
               1 
             
             = 
             
               
                 
                   d 
                   n 
                 
                 
                   d 
                   a 
                 
               
               = 
               
                 0.52 
                 . 
               
             
           
         
       
     
         [0045]    The production conditions are summarized in Table 1. The analytical data of the silicic acid obtained is indicated in Table 2. 
       Example 2 
       [0046]    4.44 kg/h SiCl 4  are evaporated at approximately 130° C. and transferred into the central tube of the burner with a known design in accordance with DE 196 50 500 A1. 4.7 Nm 3 /h hydrogen as well as 3.7 Nm 3 /h air and 1.15 Nm 3 /h oxygen are additionally fed into this tube. This gaseous mixture flows out of the inner burner nozzle and burns into the combustion chamber of the water-cooled fire tube. 
         [0047]    Additionally, 0.5 Nm 3 /h (secondary) hydrogen and 0.3 Nm 3 /h nitrogen are fed into the jacket nozzle surrounding the central nozzle in order to avoid cakings. 
         [0048]    Approximately 10 Nm 3 /h air is drawn from the ambient into the fire tube standing under a slight vacuum (open burner operation). 
         [0049]    The second gaseous component that is fed into the axial tube consists of an aerosol produced from a 12.55% aqueous solution of potassium chloride. Two gas-atomizing nozzles with an atomization power of 255 g/h aerosol function thereby as aerosol generator. This aqueous saline aerosol is conducted by 2 Nm 3 /h carrier air through externally heated conduits and leaves the inner nozzle with an exit temperature of approximately 180° C. The aerosol containing potassium salt is introduced into the flame. 
         [0050]    After the flame hydrolysis the reaction gases and the pyrogenic silicic acid produced are drawn through a cooling system by applying a vacuum and the gaseous particle current cooled off thereby to approximately 100 to 160° C. The solid matter is separated from the current of waste gas in a filter or cyclone. 
         [0051]    The pyrogenic silicic acid doped with potassium that is produced accumulates as white, fine powder. In a further step any adhering remnants of hydrochloric acid are removed from the silicic acid at an elevated temperature by a treatment with air containing water vapor. 
         [0052]    The BET surface of the pyrogenic silicic acid is 131 m 2 /g. 
         [0053]    The production conditions are summarized in Table 1. The analytical data of the silicic acid obtained is indicated in Table 2. 
       Example 3 
       [0054]    4.44 kg/h SiCl 4  are evaporated at approximately 130° C. and transferred into the central tube of the burner with a known design in accordance with DE 196 50 500 A1. 4.7 Nm 3 /h hydrogen as well as 3.7 Nm 3 /h air and 1.15 Nm 3 /h oxygen are additionally fed into this tube. This gaseous mixture flows out of the inner burner nozzle and burns into the combustion chamber of the water-cooled fire tube. 
         [0055]    Additionally, 0.5 Nm 3 /h (secondary) hydrogen and 0.3 Nm 3 /h nitrogen are fed into the jacket nozzle surrounding the central nozzle in order to avoid cakings. 
         [0056]    Approximately 10 Nm 3 /h air is drawn from the ambient into the fire tube standing under a slight vacuum (open burner operation). 
         [0057]    The second gaseous component that is fed into the axial tube consists of an aerosol produced from a 2.22% aqueous solution of potassium chloride. Two gas-atomizing nozzles with an atomization power of 210 g/h aerosol function thereby as aerosol generator. This aqueous saline aerosol is conducted by 2 Nm 3 /h carrier air through externally heated conduits and leaves the inner nozzle with an exit temperature of approximately 180° C. The aerosol is introduced into the flame and correspondingly alters the properties of the pyrogenic silicic acid produced. 
         [0058]    After the flame hydrolysis the reaction gases and the pyrogenic silicic acid produced are drawn through a cooling system by applying a vacuum and the gaseous particle current cooled off thereby to approximately 100 to 160° C. The solid matter is separated from the current of waste gas in a filter or cyclone. 
         [0059]    The pyrogenic silicic acid doped with potassium that is produced accumulates as white, fine powder. In a further step any adhering remnants of hydrochloric acid are removed from the silicic acid at an elevated temperature by a treatment with air containing water vapor. 
         [0060]    The BET surface of the pyrogenic silicic acid is 104 m 2 /g. 
         [0061]    The production conditions are summarized in Table 1. The analytical data of the silicic acid obtained is indicated in Table 2. 
       Example 4 
       [0062]    4.44 kg/h SiCl 4  are evaporated at approximately 130° C. and transferred into the central tube of the burner with a known design in accordance with DE 196 50 500 A1. 4.7 Nm 3 /h hydrogen as well as 3.7 Nm 3 /h air and 1.15 Nm 3 /h oxygen are additionally fed into this tube. This gaseous mixture flows out of the inner burner nozzle and burns into the combustion chamber of a water-cooled fire tube. 
         [0063]    Additionally, 0.5 Nm 3 /h (secondary) hydrogen and 0.3 Nm 3 /h nitrogen are fed into the jacket nozzle surrounding the central nozzle in order to avoid cakings. 
         [0064]    Approximately 10 Nm 3 /h air is drawn from the ambient into the fire tube standing under a slight vacuum (open burner operation). 
         [0065]    The second gaseous component that is fed into the axial tube consists of an aerosol produced from a 4.7% aqueous solution of potassium chloride. Two gas-atomizing nozzles with an atomization power of 225 g/h aerosol function thereby as aerosol generator. This aqueous saline aerosol is conducted by 2 Nm 3 /h carrier air through externally heated conduits and leaves the inner nozzle with an exit temperature of approximately 180° C. The aerosol is introduced into the flame. 
         [0066]    After the flame hydrolysis the reaction gases and the pyrogenic silicic acid produced are drawn through a cooling system by applying a vacuum and the gaseous particle current cooled off thereby to approximately 100 to 160° C. The solid matter is separated from the current of waste gas in a filter or cyclone. 
         [0067]    The pyrogenic silicic acid doped with potassium that is produced accumulates as white, fine powder. In a further step any adhering remnants of hydrochloric acid are removed from the silicic acid at an elevated temperature by a treatment with air containing water vapor. 
         [0068]    The BET surface of the pyrogenic silicic acid is 113 m 2 /g. 
         [0069]    The production conditions are summarized in Table 1. The analytical data of the silicic acid obtained is indicated in Table 2. 
       Example 5 
       [0070]    4.44 kg/h SiCl 4  are evaporated at approximately 130° C. and transferred into the central tube of the burner with a known design in accordance with DE 196 50 500 A1. 4.7 Nm 3 /h hydrogen as well as 3.7 Nm 3 /h air and 1.15 Nm 3 /h oxygen are additionally fed into this tube. This gaseous mixture flows out of the inner burner nozzle and burns into the combustion chamber of a water-cooled fire tube. 
         [0071]    Additionally, 0.5 Nm 3 /h (secondary) hydrogen and 0.3 Nm 3 /h nitrogen are fed into the jacket nozzle surrounding the central nozzle in order to avoid cakings. 
         [0072]    Approximately 10 Nm 3 /h air is drawn from the ambient into the fire tube standing under a slight vacuum (open burner operation). 
         [0073]    The second gaseous component that is fed into the axial tube consists of an aerosol produced from a 9.0% aqueous solution of potassium chloride. Two gas-atomizing nozzles with an atomization power of 210 g/h aerosol function thereby as aerosol generator. This aqueous saline aerosol is conducted by 2 Nm 3 /h carrier air through externally heated conduits and leaves the inner nozzle with an exit temperature of approximately 180° C. The aerosol is introduced into the flame. 
         [0074]    After the flame hydrolysis the reaction gases and the pyrogenic silicic acid produced are drawn through a cooling system by applying a vacuum and the gaseous particle current cooled off thereby to approximately 100 to 160° C. The solid matter is separated from the current of waste gas in a filter or cyclone. 
         [0075]    The pyrogenic silicic acid doped with potassium that is produced accumulates as white, fine powder. In a further step any adhering remnants of hydrochloric acid are removed from the silicic acid at an elevated temperature by a treatment with air containing water vapor. 
         [0076]    The BET surface of the pyrogenic silicic acid is 121 m 2 /g. 
         [0077]    The production conditions are summarized in Table 1. The analytical data of the silicic acid obtained is indicated in Table 2. 
       Example 6 
       [0078]    4.44 kg/h SiCl 4  are evaporated at approximately 130° C. and transferred into the central tube of the burner with a known design in accordance with DE 196 50 500 A1. 4.7 Nm 3 /h hydrogen as well as 3.7 Nm 3 /h air and 1.15 Nm 3 /h oxygen are additionally fed into this tube. This gaseous mixture flows out of the inner burner nozzle and burns into the combustion chamber of a water-cooled fire tube. 
         [0079]    Additionally, 0.5 Nm 3 /h (secondary) hydrogen and 0.3 Nm 3 /h nitrogen are fed into the jacket nozzle surrounding the central nozzle in order to avoid cakings. 
         [0080]    Approximately 10 Nm 3 /h air is drawn from the ambient into the fire tube standing under a slight vacuum (open burner operation). 
         [0081]    The second gaseous component that is fed into the axial tube consists of an aerosol produced from a 12.0% aqueous solution of potassium chloride. Two gas-atomizing nozzles with an atomization power of 225 g/h aerosol function thereby as aerosol generator. This aqueous saline aerosol is conducted by 2 Nm 3 /h carrier air through externally heated conduits and leaves the inner nozzle with an exit temperature of approximately 180° C. The aerosol is introduced into the flame. 
         [0082]    After the flame hydrolysis the reaction gases and the pyrogenic silicic acid produced are drawn through a cooling system by applying a vacuum and the gaseous particle current cooled off thereby to approximately 100 to 160° C. The solid matter is separated from the current of waste gas in a filter or cyclone. 
         [0083]    The pyrogenic silicic acid doped with potassium that is produced accumulates as white, fine powder. In a further step any adhering remnants of hydrochloric acid are removed from the silicic acid at an elevated temperature by a treatment with air containing water vapor. 
         [0084]    The BET surface of the pyrogenic silicic acid is 120 m 2 /g. 
         [0085]    The production conditions are summarized in Table 1. The analytical data of the silicic acid obtained is indicated in Table 2. 
       Example 7 
       [0086]    4.44 kg/h SiCl 4  are evaporated at approximately 130° C. and transferred into the central tube of the burner with a known design in accordance with DE 196 50 500 A1. 4.7 Nm 3 /h hydrogen as well as 3.7 Nm 3 /h air and 1.15 Nm 3 /h oxygen are additionally fed into this tube. This gaseous mixture flows out of the inner burner nozzle and burns into the combustion chamber of a water-cooled fire tube. 
         [0087]    Additionally, 0.5 Nm 3 /h (secondary) hydrogen and 0.3 Nm 3 /h nitrogen are fed into the jacket nozzle surrounding the central nozzle in order to avoid cakings. 
         [0088]    Approximately 10 Nm 3 /h air is drawn from the ambient into the fire tube standing under a slight vacuum (open burner operation). 
         [0089]    The second gaseous component that is fed into the axial tube consists of an aerosol produced from a 20% aqueous solution of potassium chloride. Two gas-atomizing nozzles with an atomization power of 210 g/h aerosol function thereby as aerosol generator. This aqueous saline aerosol is conducted by 2 Nm 3 /h carrier air through externally heated conduits and leaves the inner nozzle with an exit temperature of approximately 180° C. The aerosol is introduced into the flame. 
         [0090]    After the flame hydrolysis the reaction gases and the pyrogenic silicic acid produced are drawn through a cooling system by applying a vacuum and the gaseous particle current cooled off thereby to approximately 100 to 160° C. The solid matter is separated from the current of waste gas in a filter or cyclone. 
         [0091]    The pyrogenic silicic acid doped with potassium that is produced accumulates as white, fine powder. In a further step any adhering remnants of hydrochloric acid are removed from the silicic acid at an elevated temperature by a treatment with air containing water vapor. 
         [0092]    The BET surface of the pyrogenic silicic acid is 117 m 2 /g. 
         [0093]    The breadth of the distribution of the particle size is calculated as follows:
       d n =20.99 nm   d a =24.27 nm
 
The quotient
       
 
         [0000]    
       
         
           
             
               q 
               1 
             
             = 
             
               
                 
                   d 
                   n 
                 
                 
                   d 
                   a 
                 
               
               = 
               
                 0.86 
                 . 
               
             
           
         
       
     
         [0096]    The production conditions are summarized in Table 1. The analytical data of the silicic acid obtained is indicated in Table 2. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Experimental conditions in the production of doped, pyrogenic silicic acid 
               
             
          
           
               
                   
                   
                 Primary 
                 O 2   
                 H 2   
                 H 2   
                 N 2   
                 Gas 
                 KCl saline 
                 Aerosol 
                   
                   
               
               
                   
                 SiCl 4   
                 Air 
                 addit. 
                 core 
                 jacket 
                 jacket 
                 temp. 
                 solution 
                 amount 
                 Air 
                 BET 
               
               
                 No. 
                 kg/h 
                 Nm 3 /h 
                 Nm 3 /h 
                 Nm 3 /h 
                 Nm 3 /h 
                 Nm 3 /h 
                 C. 
                 % by wt. 
                 g/h 
                 Nm 3 /h 
                 m 2 /g 
               
               
                   
               
             
          
           
               
                 Example 1 without addition of salt 
               
             
          
           
               
                 1 
                 4.44 
                 3.8 
                 0.25 
                 2.9 
                 0.3 
                 0.3 
                 130 
                 Only 
                 250 
                 2 
                 124 
               
               
                   
                   
                   
                   
                   
                   
                   
                   
                 H 2 O 
               
             
          
           
               
                 Examples 2 to 7 with addition of salt 
               
             
          
           
               
                 2 
                 4.44 
                 3.7 
                 1.15 
                 4.7 
                 0.5 
                 0.3 
                 130 
                 12.55 
                 255 
                 2 
                 131 
               
               
                 3 
                 4.44 
                 3.7 
                 1.15 
                 4.7 
                 0.5 
                 0.3 
                 130 
                 2.22 
                 210 
                 2 
                 104 
               
               
                 4 
                 4.44 
                 3.7 
                 1.15 
                 4.7 
                 0.5 
                 0.3 
                 130 
                 4.7 
                 225 
                 2 
                 113 
               
               
                 5 
                 4.44 
                 3.7 
                 1.15 
                 4.7 
                 0.5 
                 0.3 
                 130 
                 9.0 
                 210 
                 2 
                 121 
               
               
                 6 
                 4.44 
                 3.7 
                 1.15 
                 4.7 
                 0.5 
                 0.3 
                 130 
                 12.0 
                 225 
                 2 
                 120 
               
               
                 7 
                 4.44 
                 3.7 
                 1.15 
                 4.7 
                 0.5 
                 0.3 
                 130 
                 20.0 
                 210 
                 2 
                 117 
               
               
                   
               
               
                 Explanation: Primary air = amount of air in the central tube; H 2  core = hydrogen in the central tube; gas temp. = gas temperature at the nozzle of the central tube; aerosol amount = mass flux of the saline solution converted into aerosol form; air-aerosol = carrier gas amount (air) of the aerosol 
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Analytical data of the doped silicic acids 
               
               
                 obtained according to examples 1 to 7 
               
             
          
           
               
                   
                   
                 pH 4% 
                 Potassium 
                 DBP in g/ 
                   
                   
               
               
                   
                   
                 aqueous 
                 content in 
                 100 g with 
                 Bulk 
               
               
                   
                 BET 
                 disper- 
                 % by wt. 
                 16 g weighed 
                 density 
                 Stamping 
               
               
                 No. 
                 m 2 /g 
                 sion 
                 as K 2 O 
                 portion 
                 g/l 
                 density 
               
               
                   
               
             
          
           
               
                 Reference example without salt 
               
             
          
           
               
                 1 
                 124 
                 4.68 
                 0 
                 185 
                 28 
                 39 
               
             
          
           
               
                 Examples with addition of potassium salt 
               
             
          
           
               
                 2 
                 131 
                 7.64 
                 0.44 
                 No end 
                 28 
                 36 
               
               
                   
                   
                   
                   
                 point 
               
               
                 3 
                 104 
                 7.22 
                 0.12 
                 No end 
                 31 
                 43 
               
               
                   
                   
                   
                   
                 point 
               
               
                 4 
                 113 
                 7.67 
                 0.24 
                 No end 
                 32 
                 45 
               
               
                   
                   
                   
                   
                 point 
               
               
                 5 
                 121 
                 7.7 
                 0.49 
                 No end 
                 32 
                 43 
               
               
                   
                   
                   
                   
                 point 
               
               
                 6 
                 120 
                 7.96 
                 0.69 
                 No end 
                 30 
                 44 
               
               
                   
                   
                   
                   
                 point 
               
               
                 7 
                 117 
                 7.86 
                 1.18 
                 No end 
                 28 
                 38 
               
               
                   
                   
                   
                   
                 point 
               
               
                   
               
               
                 Explanation: pH 4% sus. = pH of the 4% aqueous suspension; DBP = dibutylphthalate absorption 
               
             
          
         
       
     
         [0097]    The subject matter of the invention is explained in detail with reference made to the drawings and figures: 
         [0098]      FIG. 1  shows an EM photograph of the pyrogenic silicic acid of reference example 1 (without doping). 
         [0099]      FIG. 2  shows an EM photograph of the pyrogenic silicic acid according to example 2 doped with potassium. 
         [0100]    It can be recognized that the aggregate and agglomerate structure is changed during the doping with potassium salts and that spherical primary particles are produced during the doping that are not very intergrown with each other. 
         [0101]    The differences in the “structure”, that is, the degree of intergrowth of the particles, are expressed in clearly different DBP absorptions (dibutylphthalate absorption) and in the different course of the DBP absorption curves. 
         [0102]      FIG. 3  shows the DBP curve of the powders of reference example 1 (weighed portion 16 g): The take-up of force and the measured torque (in Nm) of the rotating blades of the DBP measuring device (Rheocord 90 of the company Haake/Karlsruhe) shows a sharply pronounced maximum with a subsequent decline at a certain addition of DBP. This curve form is characteristic for known pyrogenic oxides that are not doped. 
         [0103]      FIG. 4  shows the DBP curve of the powder of the pyrogenic oxide doped with potassium in accordance with the invention (16 g weighed portion) according to example 2. 
         [0104]    No sharp rise of the torque with subsequent strong drop can be recognized. For this reason the DBP measuring device can also not detect an end point. 
         [0105]      FIG. 5  shows the electron microscope photograph of the powder of example 3 with an enlargement of 1:50000. 
         [0106]      FIG. 6  shows the electron microscope photograph of the powder of example 3 with an enlargement of 1:100000. 
         [0107]      FIG. 7  shows the electron microscope photograph of the powder of example 3 with an enlargement of 1:200000. 
         [0108]    The particle count by EM photography clearly shows the rather narrow particle distribution curve of the silicic acid doped by means of aerosol with potassium in accordance with the invention. 
         [0109]    Table 3 shows the results of the particle count of the powders of example 1 (reference example) by means of the EM photograph. These values are graphically shown in  FIGS. 8 ,  9  and  10 . 
         [0000]    
       
         
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
             
             
               
                 Total number of measured particles N: 
                 5074 
               
             
          
           
               
                 Particle diameter, arithmetic mean DN: 
                 16.678 
                 nm 
               
               
                 Particle diameter, average over the surface DA: 
                 31.825 
                 nm 
               
               
                 Particle diameter, average over the volume DV: 
                 42.178 
                 nm 
               
               
                 Particle diameter, standard deviation S: 
                 10.011 
                 nm 
               
             
          
           
               
                 Particle diameter, coefficient of variation V: 
                 60.027 
               
             
          
           
               
                 Specific surface OEM: 
                 85.696 
                 qm/g 
               
               
                 Median value numeric distribution D50 (A): 
                 12.347 
                 nm 
               
               
                 Median value weight distribution D50 (g): 
                 40.086 
                 nm 
               
             
          
           
               
                 90% span numeric distribution: 
                 3.166 nm-36.619 nm 
               
               
                 90% span weight distribution 
                 12.153 nm-72.335 nm  
               
               
                 Total span: 
                 7.400 nm-94.200 nm 
               
               
                   
               
             
          
           
               
                   
                   
                 Percent by 
                 Sum 
                 Percent by 
                 Sum 
               
               
                 Diameter 
                 Number 
                 Number 
                 Percent by 
                 weight 
                 Percent by 
               
               
                 D 
                 N 
                 N % 
                 number 
                 ND3% 
                 weight % 
               
               
                   
               
               
                 7.400 
                 593 
                 11.687 
                 11.687 
                 0.393 
                 0.393 
               
               
                 10.200 
                 1142 
                 22.507 
                 34.194 
                 1.984 
                 2.377 
               
               
                 13.000 
                 1046 
                 20.615 
                 54.809 
                 3.761 
                 6.138 
               
               
                 15.800 
                 693 
                 13.658 
                 68.467 
                 4.474 
                 10.612 
               
               
                 18.600 
                 498 
                 9.815 
                 78.281 
                 5.245 
                 15.857 
               
               
                 21.400 
                 281 
                 5.538 
                 83.819 
                 4.507 
                 20.364 
               
               
                 24.200 
                 193 
                 3.804 
                 87.623 
                 4.477 
                 24.841 
               
               
                 27.000 
                 124 
                 2.444 
                 90.067 
                 3.995 
                 28.836 
               
               
                 29.800 
                 86 
                 1.695 
                 91.762 
                 3.725 
                 32.561 
               
               
                 32.600 
                 74 
                 1.458 
                 93.220 
                 4.196 
                 36.757 
               
               
                 35.400 
                 62 
                 1.222 
                 94.442 
                 4.502 
                 41.259 
               
               
                 38.200 
                 65 
                 1.281 
                 95.723 
                 5.930 
                 47.189 
               
               
                 41.000 
                 37 
                 0.729 
                 96.453 
                 4.174 
                 51.363 
               
               
                 43.800 
                 35 
                 0.690 
                 97.142 
                 4.814 
                 56.176 
               
               
                 46.600 
                 30 
                 0.591 
                 97.734 
                 4.969 
                 61.145 
               
               
                 49.400 
                 30 
                 0.591 
                 98.325 
                 5.919 
                 67.065 
               
               
                 52.000 
                 16 
                 0.315 
                 98.640 
                 3.725 
                 70.789 
               
               
                 55.000 
                 14 
                 0.276 
                 98.916 
                 3.812 
                 74.602 
               
               
                 57.800 
                 15 
                 0.296 
                 99.212 
                 4.741 
                 79.343 
               
               
                 60.600 
                 10 
                 0.197 
                 99.409 
                 3.642 
                 82.985 
               
               
                 63.400 
                 7 
                 0.138 
                 99.547 
                 2.920 
                 85.905 
               
               
                 66.200 
                 8 
                 0.158 
                 99.704 
                 3.799 
                 89.703 
               
               
                 69.000 
                 8 
                 0.158 
                 99.862 
                 4.301 
                 94.005 
               
               
                 71.800 
                 1 
                 0.020 
                 99.882 
                 0.606 
                 94.611 
               
               
                 74.600 
                 3 
                 0.059 
                 99.941 
                 2.039 
                 96.649 
               
               
                 80.200 
                 1 
                 0.020 
                 99.961 
                 0.844 
                 97.494 
               
               
                 88.600 
                 1 
                 0.020 
                 99.980 
                 1.138 
                 98.632 
               
               
                 94.200 
                 1 
                 0.020 
                 100.000 
                 1.368 
                 100.000 
               
               
                   
               
             
          
         
       
     
         [0110]    Table 4 shows the results of the particle count of the powders of example 7 by EM photograph. These values are graphically shown in  FIGS. 11 to 13 . 
         [0000]    
       
         
               
               
             
               
               
               
             
               
               
             
               
               
               
             
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
             
             
               
                 Total number of measured particles N: 
                 4259 
               
             
          
           
               
                 Particle diameter, arithmetic mean DN: 
                 20.993 
                 nm 
               
               
                 Particle diameter, average over the surface DA: 
                 24.270 
                 nm 
               
               
                 Particle diameter, average over the volume DV: 
                 26.562 
                 nm 
               
               
                 Particle diameter, standard deviation S: 
                 5.537 
                 nm 
               
             
          
           
               
                 Particle diameter, coefficient of variation V: 
                 26.374 
               
             
          
           
               
                 Specific surface OEM: 
                 112.370 
                 qm/g 
               
               
                 Median value numeric distribution D50 (A): 
                 18.740 
                 nm 
               
               
                 Median value weight distribution D50 (g): 
                 23.047 
                 nm 
               
             
          
           
               
                 90% span numeric distribution: 
                 12.615 nm-29.237 nm 
               
               
                 90% span weight distribution 
                 14.686 nm-44.743 nm 
               
               
                 Total span: 
                  7.400 nm-55.000 nm 
               
               
                   
               
             
          
           
               
                   
                   
                 Percent by 
                 Sum 
                 % by 
                 Sum 
               
               
                 Diameter 
                 Number 
                 number 
                 % by 
                 weight 
                 % by 
               
               
                 D 
                 N 
                 N % 
                 number 
                 ND3% 
                 weight 
               
               
                   
               
               
                 7.400 
                 1 
                 0.023 
                 0.023 
                 0.001 
                 0.001 
               
               
                 10.200 
                 11 
                 0.258 
                 0.282 
                 0.024 
                 0.025 
               
               
                 13.000 
                 233 
                 5.471 
                 5.753 
                 1.051 
                 1.075 
               
               
                 15.800 
                 805 
                 18.901 
                 24.654 
                 6.517 
                 7.592 
               
               
                 18.600 
                 1034 
                 24.278 
                 48.932 
                 13.656 
                 21.248 
               
               
                 21.400 
                 913 
                 21.437 
                 70.369 
                 18.364 
                 39.613 
               
               
                 24.200 
                 607 
                 14.252 
                 84.621 
                 17.656 
                 57.269 
               
               
                 27.000 
                 311 
                 7.302 
                 91.923 
                 12.564 
                 69.833 
               
               
                 29.800 
                 164 
                 3.851 
                 95.774 
                 8.908 
                 78.740 
               
               
                 32.600 
                 63 
                 1.479 
                 97.253 
                 4.480 
                 83.220 
               
               
                 35.400 
                 35 
                 0.822 
                 98.075 
                 3.187 
                 86.407 
               
               
                 38.200 
                 28 
                 0.657 
                 98.732 
                 3.203 
                 89.610 
               
               
                 41.000 
                 18 
                 0.423 
                 99.155 
                 2.546 
                 92.156 
               
               
                 43.800 
                 10 
                 0.235 
                 99.390 
                 1.725 
                 93.881 
               
               
                 46.600 
                 16 
                 0.376 
                 99.765 
                 3.323 
                 97.204 
               
               
                 49.400 
                 5 
                 0.117 
                 99.883 
                 1.237 
                 98.441 
               
               
                 52.200 
                 3 
                 0.070 
                 99.953 
                 0.876 
                 99.317 
               
               
                 55.000 
                 2 
                 0.047 
                 100.000 
                 0.683 
                 100.000