Abstract:
Silanised, structurally modified silicas, characterised by groups fixed on the surface, the groups being alkylsilyl (SiC n H 2n+1 , with n=2-18). They are produced in that pyrogenically produced silicas are treated with the silanising agent and structurally modified. They are used to improve scratch resistance in lacquers.

Description:
INTRODUCTION AND BACKGROUND 
     The invention relates to silanised, structurally modified, pyrogenically produced silicas, a process for the production thereof and their use. 
     Silanised silicas are used as thickeners, such as e.g. for water-thinnable lacquers and resins, such as e.g. epoxy resins. 
     From EP 0 672 731 B1, silanised, pyrogenically produced silicas are known, which are characterised in that the pyrogenically produced silicas are treated with a compound from the group (RO) 3 SiC n H 2n+1 , wherein n=10 to 18 and R=short-chained alkyl radicals. For example, the pyrogenically produced silicas have been treated with the compound (CH 3 O) 3 SiC 16 H 33  (hexadecyltrimethoxysilane) or with the compound (CH 3 O) 3 SiC 18 H 37  (octadecyltrimethoxysilane). 
     The production of the silanised, pyrogenically produced silicas takes place in that the pyrogenically produced silicas are placed in a mixer, the silicas are sprayed, optionally first with water and then with the compound from the group (RO) 3 SiC n H 2n+1  while mixing intensively, mixed for a further 15 to 30 minutes and then tempered at a temperature of 100 to 160° C. for a period of 1 to 3 hours. 
     SUMMARY OF THE INVENTION 
     The invention provides silanised, structurally modified, pyrogenically produced silicas characterised by groups fixed on the surface, the groups being alkylsilyl (SiC n H 2n+1 , with n=2-18), preferably octylsilyl and/or hexadecylsilyl. 
     The silica according to the invention can have the following physico-chemical characteristics: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 BET-surface area m2/g: 
                  25-400 
               
               
                 Average size of the 
                   5-50 
               
               
                 primary particles nm: 
               
               
                 pH value: 
                   3-10 
               
               
                 Carbon content %: 
                 0.1-25 
               
               
                 DBP value %: 
                 The DBP value is at least 10% lower than the 
               
               
                   
                 DBP value of the corresponding silanised, non- 
               
               
                   
                 structurally modified silica. With very marked 
               
               
                   
                 structural modification, the structure can be 
               
               
                   
                 broken down in such a way that the DBP value 
               
               
                   
                 can no longer be determined. 
               
               
                   
               
             
          
         
       
     
     A silica produced by a high-temperature hydrolysis route from SiCl 4 +H 2  and O 2  can be used as the pyrogenically produced silica. 
     In particular, a silica produced by high temperature hydrolysis having the following physico-chemical characteristics can be used: 
     
       
         
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
               
               
                   
                 90 
                 130 
                 150 
                 200 
                 300 
                 380 
                 OX 50 
                 TT 600 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Behaviour in respect of water 
                 hydrophilic 
               
               
                 Appearance 
                 loose white powder 
               
             
          
           
               
                 BET surface area 1 ) 
                 m 2 /g 
                 90 ± 15 
                 130 ± 25 
                 150 ± 15 
                 200 ± 25 
                 300 ± 30 
                 380 ± 30 
                 50 ± 15 
                 200 ± 50 
               
               
                 Average size of the 
                 nm 
                 20 
                 16 
                 14 
                 12 
                 7 
                 7 
                 40 
                 40 
               
               
                 primary particles 
               
               
                 Tamped density 2 ) 
               
               
                 standard material 
                 g/l 
                 ca. 80  
                 ca. 50  
                 ca. 50  
                 ca. 50  
                 ca. 50  
                 ca. 50  
                 ca. 130 
                 ca. 60 
               
               
                 compacted material 
                 g/l 
                 — 
                 ca. 120 
                 ca. 120 
                 ca. 120 
                 ca. 120 
                 ca. 120 
                 — 
                 — 
               
               
                 (additive “V”) 
               
               
                 Loss on drying 3 ) 
                   
                 &lt;1.0 
                 &lt;1.5 
                 &lt;0.5 9 ) 
                 &lt;1.5 
                 &lt;1.5 
                 &lt;1.5 
                 &lt;1.5 
                 &lt;2.5 
               
               
                 (2 hours at 1000° C.) 
                 % 
               
               
                 on leaving supplier&#39;s 
               
               
                 works 
               
               
                 Loss on ignition 4 ) 7 ) 
                 % 
                 &lt;1 
                 &lt;1 
                 &lt;1 
                 &lt;1 
                 &lt;2 
                 &lt;2.5 
                 &lt;1 
                 &lt;2.5 
               
               
                 (2 hours at 1000° C.) 
               
               
                 pH value 5 ) (in 4% 
                   
                 3.6-4.5 
                 3.6-4.3 
                 3.6-4.3 
                 3.6-4.3 
                 3.6-4.3 
                 3.6-4.3 
                 3.8-4.8 
                 3.6-4.5 
               
               
                 aqueous dispersion) 
               
               
                 SiO 2   8 ) 
                 % 
                 &gt;99.8 
                 &gt;99.8 
                 &gt;99.8 
                 &gt;99.8 
                 &gt;99.8 
                 &gt;99.8 
                 &gt;99.8 
                 &gt;99.8 
               
               
                 Al 2 O 3   8 ) 
                 % 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.08 
                 &lt;0.05 
               
               
                 Fe 2 O 3   8 ) 
                 % 
                 &lt;0.003 
                 &lt;0.003 
                 &lt;0.003 
                 &lt;0.003 
                 &lt;0.003 
                 &lt;0.003 
                 &lt;0.01 
                 &lt;0.003 
               
               
                 TiO 2   8 ) 
                 % 
                 &lt;0.03 
                 &lt;0.03 
                 &lt;0.03 
                 &lt;0.03 
                 &lt;0.03 
                 &lt;0.03 
                 &lt;0.03 
                 &lt;0.03 
               
               
                 HCl 8 ) 9 ) 
                 % 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
               
               
                 Sieving residue 6 ) 
                 % 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.2 
                 &lt;0.05 
               
               
                 (acc. to Mocker, 
               
               
                 45 μm) 
               
               
                   
               
               
                   1 )based on DIN 66131 
               
               
                   2 )based on DIN ISO 787/XI, JIS K 5101/18 (not sieved) 
               
               
                   3 )based on DIN ISO 787/II, ASTM D 280, JIS K 5101/21 
               
               
                   4 )based on DIN 55 921, ASTM D 1208, JIS K 5101/23 
               
               
                   5 )based on DIN ISO 787/IX, ASTM D 1208, JIS K 5101/24 
               
               
                   6 )based on DIN ISO 787/XVIII, JIS K 5101/20 
               
               
                   7 )based on the substance dried for 2 hours at 105° C. 
               
               
                   8 )based on the substance ignited for 2 hours at 1000° C. 
               
               
                   9 )HCl content is a component of the loss on ignition 
               
             
          
         
       
     
     Pyrogenic silicas of this type are known. They are described, inter alia, in: 
     Winnacker-Küchler, Chemische Technologie, volume 3 (1983), 4 th  edition, page 77 and 
     Ullmanns Encyklopädie der technischen Chemie, 4 th  edition (1982), volume 21, page 462. 
     The pyrogenically produced silicas are treated with a compound from the group (RO) 3 SiC n H 2n+1 , wherein n=2 to 18 and R=alkyl, such as e.g. methyl, ethyl or similar. 
     In particular, the following compounds can be used:
 
Silane I (CH 3 O) 3 SiC 16 H 33  (hexadecyltrimethoxysilane)
 
Silane II (CH 3 O) 3 SiC 8 H 17  (octyltrimethoxysilane)
 
     The silicas according to the invention can be produced in that the pyrogenically produced silicas are placed in a mixer, the silicas are sprayed, optionally first with water and then with the compound (organosilane) from the group (RO) 3 SiC n H 2n+1  while mixing intensively, mixed for a further 15 to 30 minutes and then tempered at a temperature of 100 to 160° C. for a period of 1 to 3 hours, structurally modified and/or optionally post-ground. A further tempering can optionally take place after the structural modification and/or post-grinding. 
     The structural modification can take place e.g. with a ball mill or a continuously operating ball mill. The post-grinding can take place e.g. using an air-jet mill or pin mill. The tempering can take place batchwise, e.g. in a drying cupboard, or continuously, e.g. in a fluidised bed. The tempering can take place under protective gas, e.g. nitrogen. 
     The water used can be acidified with an acid, e.g. hydrochloric acid, down to a pH value of 7 to 1. 
     The organosilane used can be dissolved in a solvent, such as e.g. ethanol. 
     The tempering can be performed in a protective gas atmosphere, such as e.g. under nitrogen. 
     The pyrogenically produced silicas according to the invention silanised with silane I have the physico-chemical characteristics listed in Table 2 before structural modification: 
     
       
         
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Educt 
                 A 90 
                 A 130 
                 A 150 
                 A 200 
                 A 300 
                 A 380 
                 OX 50 
                 TT 600 
               
               
                   
               
             
             
               
                 Average size of the 
                 20 
                 16 
                 14 
                 12 
                  7 
                  7 
                 40 
                 40 
               
               
                 primary particles 
               
               
                 [nm] 
               
               
                 BET surface area 
                 40-90 
                  60-130 
                  75-150 
                 100-200 
                 150-300 
                 200-380 
                 20-50 
                 100-250 
               
               
                 [m 2 /g] 
               
               
                 Tamped density 
                  40-140 
                  40-140 
                  40-140 
                  40-140 
                  40-140 
                  40-140 
                  40-140 
                  40-140 
               
               
                 [g/l] 
               
               
                 Loss on drying [%] 
                 &lt;2 
                 &lt;2 
                 &lt;2 
                 &lt;2 
                 &lt;2 
                 &lt;2 
                 &lt;2 
                 &lt;2 
               
               
                 Loss on ignition 
                 0.1-10  
                 0.1-10  
                 0.1-10  
                 0.5-15  
                 0.5-20  
                 0.5-25  
                 0.1-10  
                 0.1-20  
               
               
                 [%] 
               
               
                 C content [%] 
                 0.1-10  
                 0.1-10  
                 0.1-10  
                 0.5-15  
                 0.5-20  
                 0.1-25  
                 0.1-10  
                 0.5-20  
               
               
                 pH value 
                 3.5-5.5 
                 3.5-5.5 
                 3.5-5.5 
                 3.5-5.5 
                 3.5-5.5 
                 3.5-5.5 
                 3.5-5.5 
                 3.5-5.5 
               
               
                   
               
             
          
         
       
     
     The silanised, structurally modified, pyrogenically produced silicas according to the invention can be used to improve scratch resistance in lacquers. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Examples 
     The pyrogenically produced silicas used have the physico-chemical characteristics listed in Table 1. 
     As organosilanes, the following compound with the general formula (RO) 3 SiC n H 2n+1  is used:
 
(CH 3 O) 3 SiC 16 H 33   (Silane I)
 
     The silica is placed in a mixer and sprayed first with water and then with organosilane, mixing intensively. 
     When the spraying is complete, stirring is continued for a further 15 to 30 minutes and then the mixture is tempered for 1 to 3 hours at 100 to 160° C. The tempering can also take place under protective gas, e.g. nitrogen. 
     The individual reaction conditions can be taken from Table 3. 
     The physico-chemical characteristics of the silanised silicas obtained are listed in Table 4. 
     
       
         
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                   
                   
                   
                   
                   
                   
                   
                 Tem- 
               
               
                   
                   
                   
                 Silane 
                 Water 
                 Ethanol 
                 Tem- 
                 pering 
               
               
                 Ex- 
                   
                   
                 quantity 
                 quantity 
                 quantity 
                 pering 
                 temper- 
               
               
                 am- 
                   
                   
                 (g/100 g 
                 (g/100 g 
                 (g/100 g 
                 period 
                 ature 
               
               
                 ple 
                 Aerosil 
                 Silane 
                 Aerosil) 
                 Aerosil) 
                 Aerosil) 
                 (h) 
                 (° C.) 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 A 300 
                 Silane I 
                 1 
                 0 
                 9 
                 2 
                 120 
               
               
                 2 
                 A 200 
                 Silane I 
                 2.5 
                 0 
                 0 
                 2 
                 140 
               
               
                 3 
                 A 200 
                 Silane I 
                 20 
                 5 
                 0 
                 2 
                 140 
               
               
                 4 
                 A 200 
                 Silane I 
                 10 
                 2.5 
                 0 
                 2 
                 140 
               
               
                 5 
                 A 200 
                 Silane I 
                 5 
                 1.25 
                 0 
                 2 
                 140 
               
               
                 6 
                 A 200 
                 Silane I 
                 2.5 
                 1.25 
                 0 
                 2 
                 140 
               
               
                   
               
             
          
         
       
     
                                                                           TABLE 4                       Tamped       Surface   Loss on   Loss on               density   C content   area   drying   ignition       Example   pH value   (g/l)   (%)   (m 2 /g)   (%)   (%)                                1   4.3   50   1.3   253   0.4   1.8       2   4.4   49   1.7   176   0.3   2.5       3   4.6   68   10.1   116   0.6   12.7       4   4.5   72   5.7   144   0.6   7.1       5   4.7   52   2.6   167   0.6   3.4       6   4.5   51   1.9   171   0.7   2.5                    
Production and Physico-Chemical Properties of the Silicas According to the Invention
 
Production of the Silicas According to the Invention:
 
     The silicas, which can be produced as described in EP 0 672 731, are then structurally modified by mechanical action and possibly post-ground in a mill. A tempering can possibly take place after the structural modification and/or post-grinding. 
     The structural modification can take place e.g. with a ball mill or a continuously operating ball mill. The post-grinding can take place e.g. using an air-jet mill or pin mill. The tempering can take place batchwise, e.g. in a drying cupboard, or continuously, e.g. in a fluidised bed. The tempering can take place under protective gas, e.g. nitrogen. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Overview of the production of the comparative silicas and 
               
               
                 the silicas according to the invention (Examples) 
               
             
          
           
               
                   
                   
                   
                 Post- 
                   
               
               
                   
                   
                   
                 grinding 
               
               
                   
                   
                   
                 after 
                 Tempering 
               
               
                   
                 Surface-fixed 
                 Structural 
                 structural 
                 after 
               
               
                 Designation 
                 group 
                 modification 
                 modification 
                 post-grinding 
               
               
                   
               
               
                 Comparative 
                 Hexadecylsilyl 
                 No 
                 — 
                 — 
               
               
                 silica 1 
               
               
                 Comparative 
                 Octylsilyl 
                 No 
                 — 
                 — 
               
               
                 silica 2 
               
               
                 Silicas 1 
                 Hexadecylsilyl 
                 Yes 
                 No 
                 No 
               
               
                 Silicas 2 
                 Octylsilyl 
                 Yes 
                 Yes 
                 No 
               
               
                 Silicas 3 
                 Hexadecylsilyl 
                 Yes 
                 Yes 
                 Yes 
               
               
                 Silicas 4 
                 Octylsilyl 
                 Yes 
                 No 
                 Yes 
               
               
                 Silicas 5 
                 Octylsilyl 
                 Yes 
                 Yes 
                 No 
               
               
                 Silicas 6 
                 Hexadecylsilyl 
                 Yes 
                 Yes 
                 No 
               
               
                 Silicas 7 
                 Hexadecylsilyl 
                 Yes 
                 Yes 
                 No 
               
               
                 Silicas 8 
                 Hexadecylsilyl 
                 Yes 
                 No 
                 No 
               
               
                 Silicas 9 
                 Octylsilyl 
                 Yes 
                 Yes 
                 No 
               
               
                 Silicas 10 
                 Octylsilyl 
                 Yes 
                 No 
                 No 
               
               
                 Silicas 11 
                 Octylsilyl 
                 Yes 
                 Yes 
                 No 
               
               
                 Silicas 12 
                 Octylsilyl 
                 Yes 
                 No 
                 No 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Physico-chemical data of the silicas according to the invention (Examples) 
               
               
                 and the comparative silicas 
               
             
          
           
               
                   
                 Tamped 
                   
                 Loss on 
                   
                   
                 DBP 
                 BET specific 
               
               
                   
                 density 
                 Loss on 
                 ignition 
                   
                   
                 adsorption 
                 surface area 
               
               
                 Designation 
                 [g/l] 
                 drying [%] 
                 [%] 
                 pH value 
                 C content [%] 
                 [%] 
                 [m 2 /g] 
               
               
                   
               
             
          
           
               
                 Comparative silica 1 
                 57 
                 0.5 
                 1.8 
                 4.6 
                 1.2 
                 302 
                 195 
               
               
                 Comparative silica 2 
                 51 
                 0.6 
                 6.8 
                 5.3 
                 5.4 
                 263 
                 175 
               
               
                 Silicas 1 
                 137 
                 0.7 
                 1.9 
                 4.9 
                 1.3 
                 217 
                 193 
               
               
                 Silicas 2 
                 112 
                 0.7 
                 7.0 
                 5.8 
                 5.5 
                 145 
                 175 
               
               
                 Silicas 3 
                 118 
                 0.7 
                 2.3 
                 5.1 
                 1.3 
                 228 
                 176 
               
               
                 Silicas 4 
                 163 
                 0.9 
                 6.7 
                 5.3 
                 5.4 
                 134 
                 176 
               
               
                 Silicas 5 
                 114 
                 0.5 
                 7.1 
                 6.0 
                 5.4 
                 142 
                 175 
               
               
                 Silicas 6 
                 113 
                 1.3 
                 2.2 
                 5.1 
                 1.4 
                 221 
                 193 
               
               
                 Silicas 7 
                 123 
                 0.7 
                 2.6 
                 6.0 
                 1.4 
                 208 
                 197 
               
               
                 Silicas 9 
                 146 
                 1.1 
                 2.3 
                 5.8 
                 1.4 
                 182 
                 195 
               
               
                 Silicas 9 
                 240 
                 0.8 
                 6.7 
                 4.8 
                 5.3 
                  87 
                 169 
               
               
                 Silicas 10 
                 322 
                 0.3 
                 6.9 
                 6.0 
                 5.3 
                 Could not 
                 172 
               
               
                   
                   
                   
                   
                   
                   
                 be 
               
               
                   
                   
                   
                   
                   
                   
                 determined 
               
               
                 Silicas 11 
                 204 
                 0.7 
                 6.4 
                 5.7 
                 5.4 
                 101 
                 173 
               
               
                 Silicas 12 
                 276 
                 0.3 
                 6.6 
                 6.6 
                 5.3 
                 Could not 
                 168 
               
               
                   
                   
                   
                   
                   
                   
                 be 
               
               
                   
                   
                   
                   
                   
                   
                 determined 
               
               
                   
               
             
          
         
       
     
     Application Examples 
     Example 1 
     For the investigation of the improvement in scratch resistance, a conventional 2-component polyurethane lacquer was used. The formulation of the lacquer and its production, including application, are summarised below: 
     Formulation: 
     
       
         
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Parts 
               
               
                   
                 by wt. 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Millbase 
                   
               
               
                   
                 Acrylic resin, 50% in xylene/ethylbenzene 3:1 
                 53.3 
               
               
                   
                 Butyl acetate 98% 
                 6.7 
               
               
                   
                 Xylene 
                 6.7 
               
               
                   
                 Silica 
                 5.0 
               
               
                   
                 Σ 
                 71.7 
               
               
                   
                 Lacquer make-up 
               
               
                   
                 Acrylic resin, 50% in xylene/ethylbenzene 3:1 
                 1.1 
               
               
                   
                 Xylene 
                 12.2 
               
               
                   
                 Ethoxypropyl acetate 
                 1.5 
               
               
                   
                 Butyl glycol acetate 
                 1.5 
               
               
                   
                 Butyl acetate 98% 
                 — 
               
               
                   
                 Aliphatic polyisocyanate, approx. 75% in 1- 
                 17.0 
               
               
                   
                 methoxypropyl-2-acetate/xylene 1:1 
                   
               
               
                   
                 Σ 
                 105.0 
               
               
                   
                   
               
             
          
         
       
     
                                                 Binder concentration:     40%           Silica calculated on the basis of millbase (solids):   18.8%           Silica calculated on the basis of lacquer (total):    5.0%           Silica calculated on the basis of lacquer (solids):   12.5%                        
Production and Application of Lacquers
 
     The binder is mixed with the solvents. Then, for the purpose of predispersion, the silica is incorporated into this mixture with the high-speed mixer (disk Ø 45 mm) and predispersed for 5 min at 2000 rpm. The mixture is dispersed in a laboratory pearl mill for 30 min at 2500 rpm and 60% pump capacity using glass beads (Ø approx. 1 mm). The millbase is tested with a grindometer, 25 μm, according to DIN ISO 1524. It must be smaller than 10 μm. 
     The conversion of the millbase to lacquer takes place in accordance with the formulation, the components being mixed at 2000 rpm with a vane agitator. The hardener is incorporated in the same way. 
     After adjusting the lacquers to spray viscosity in accordance with DIN 53411, the lacquers are applied to black lacquered metal sheets, e.g. DT 36 (from Q-Panel), by spray application (coat thickness about 40-50 μm). After spraying, the metal sheets are dried for 24 h at room temperature and then for 2 h in a drying oven at 70° C. 
     Scratch Tests: 
     The metal sheets are abraded with a quartz/water slurry (100 g water+1 g Marlon A 350, 0.25%+5 g Sikron F500) and with a CaCO 3 /water mixture (100 g water+1 g Marlon A 350, 0.25%+5 g Millicarb BG) using an abrasion and washing resistance tester (Erichsen, brush with hog&#39;s bristles). The gloss before and 10 min after the abrading is determined with a reflectometer (20° irradiation angle). 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 Summary of the properties of the liquid lacquers relevant in terms of lacquer technology, 
               
               
                 and of the applied and dried films. 
               
             
          
           
               
                   
                   
                   
                   
                 Reference 
                   
                   
                   
                 Reference 
               
               
                   
                 Comparative 
                   
                   
                 without 
                 Comparative 
                   
                 Silica 
                 without 
               
               
                   
                 silica 1 
                 Silica 7 
                 Silica 8 
                 silica 
                 silica 2 
                 Silica 9 
                 11 
                 silica 
               
               
                   
                   
               
             
          
           
               
                 Grindometer value [μm] 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 / 
               
               
                 Viscosity (millbase) [mPas] 
               
               
                  6 Rpm 
                 409 
                 210 
                 220 
                 / 
                 5670 
                 935 
                 832 
                 / 
               
               
                 60 Rpm 
                 407 
                 210 
                 212 
                 / 
                 1260 
                 409 
                 407 
                 / 
               
               
                 Viscosity (lacquer + hardener) 
               
               
                 [mPas] 
               
               
                  6 rpm 
                 120 
                 80 
                 80 
                 60 
                 446 
                 195 
                 175 
                 55 
               
               
                 60 rpm 
                 113 
                 82 
                 82 
                 61 
                 194 
                 146 
                 144 
                 64 
               
               
                 Flow 
                 poor 
                 OK 
                 OK 
                 OK 
                 Orange peel 
                 OK 
                 OK 
                 OK 
               
               
                   
                 fine cracks 
                   
                   
                   
                 effect 
               
             
          
           
               
                 Scratch resistance 
               
             
          
           
               
                 20° reflectometer value 
                 81 
                 89.5 
                 89.1 
                 91.3 
                 38 
                 85.5 
                 85.3 
                 91.7 
               
               
                 before scratching 
               
               
                 Haze before scratching 
                 101 
                 9 
                 12 
                 2 
                 423 
                 18 
                 19 
                 2 
               
               
                 Black value My 
                 272 
                 286 
                 286 
                 291 
                 260 
                 283 
                 282 
                 294 
               
               
                 40 strokes with Sikron 
                 83.4 
                 88.5 
                 90.7 
                 51.8 
                 / 
                 80.4 
                 84.3 
                 56.1 
               
               
                 F 500 residual gloss [%] 
               
               
                   
               
             
          
         
       
     
     The silicas 7+8 and 9+11 according to the invention can be used in high concentrations without impairing the appearance of the lacquer surface owing to their substantially lower rheological efficiency compared with comparative silica 1+2. In addition, the silicas according to the invention display a substantial improvement in scratch resistance of the lacquer surface. 
     Example 2 
     In this example the influence of the structural modification was investigated on the basis of a high solids 2-component PU clear lacquer. The formulation of the lacquer and its production, including application and testing, are summarised below: 
     Formulation: 
     
       
         
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Parts by 
               
               
                   
                 wt. 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Millbase 
                   
               
               
                   
                 Acrylic copolymer, mod. with synthetic 
                 61.0 
               
               
                   
                 fatty acids, 70% in n-butyl acetate 
               
               
                   
                 Butyl acetate 98% 
                 7.3 
               
               
                   
                 Methoxypropyl acetate 
                 1.7 
               
               
                   
                 Solvesso 100 
                 2.0 
               
               
                   
                 Xylene 
                 2.0 
               
               
                   
                 Baysilon OL 17, 10% in xylene (silicone 
                 0.7 
               
               
                   
                 oil) 
               
               
                   
                 Silica 
                 5.0 
               
               
                   
                 Σ 
                 79.7 
               
               
                   
                 Lacquer make-up (hardener) 
               
               
                   
                 Aliphatic polyisocyanate, 90% in n- 
                 22.3 
               
               
                   
                 butyl acetate 
               
               
                   
                 Butyl acetate 98% 
                 2.0 
               
               
                   
                 Solvesso 100 
                 1.0 
               
               
                   
                 Σ 
                 105.0 
               
               
                   
                   
               
             
          
         
       
     
                                                 Binder concentration:   62.8%           Silica calculated on the basis of millbase (solids):   11.7%           Silica calculated on the basis of lacquer (total):   5.0%           Silica calculated on the basis of lacquer (solids):   8.0%                        
Production and Application of the Lacquers
 
     The binder is mixed with the solvents. Then, for the purpose of predispersion, the silica is incorporated into this mixture with the high-speed mixer (disk Ø 45 mm) and predispersed for 5 min at 2000 rpm. The mixture is dispersed in a laboratory pearl mill for 30 min at 2500 rpm and 60% pump capacity using glass beads (Ø approx. 1 mm). The millbase is tested with a grindometer, 25 μm, in accordance with DIN ISO 1524. It must be smaller than 10 μm. 
     The conversion of the millbase to lacquer takes place in accordance with the formulation, the components being mixed with a vane agitator at 2000 rpm. The hardener is incorporated in the same way. 
     After adjusting the lacquers to spray viscosity in accordance with DIN 53411, the lacquers are applied to black lacquered metal sheets, e.g. DT 36 (from Q-Panel), by spray application (coat thickness about 40-50 μm). After spraying, the metal sheets are dried for 24 h at room temperature and then for 2 h in a drying oven at 70° C. 
     Scratch Tests: 
     The metal sheets are abraded with a quartz/water slurry (100 g water+1 g Marlon A 350, 0.25%+5 g Sikron F500) using an abrasion and washing resistance tester (Erichsen, brush with hog&#39;s bristles). The gloss before and 10 min after the abrading is determined with a reflectometer (20° irradiation angle). 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
               
             
               
               
               
               
               
             
           
               
                 TABLE 8 
               
             
             
               
                   
               
               
                 Summary of the properties of the liquid lacquers 
               
               
                 relevant in terms of lacquer technology, and of the applied 
               
               
                 and dried films. 
               
             
          
           
               
                   
                   
                   
                   
                 Reference 
               
               
                   
                 Comparative 
                   
                 Silica 
                 without 
               
               
                   
                 silica 1 
                 Silica 7 
                 8 
                 silica 
               
               
                   
                   
               
             
          
           
               
                 Bulk density [g/l] 
                 50 
                 146 
                 123 
                 / 
               
               
                 Grindometer value [μm] 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 / 
               
               
                 Viscosity (millbase) 
               
               
                 [mPas] 
               
               
                  6 rpm 
                 767 
                 376 
                 376 
                 205 
               
               
                 60 rpm 
                 717 
                 359 
                 361 
                 205 
               
               
                 Viscosity (lacquer + hardener) 
               
               
                 [mPas] 
               
               
                  6 rpm 
                 459 
                 279 
                 281 
                 120 
               
               
                 60 rpm 
                 399 
                 272 
                 274 
                 120 
               
               
                 Flow 
                 poor (fine 
                 OK 
                 OK 
                 OK 
               
               
                   
                 “cracks”) 
               
             
          
           
               
                 Scratch resistance 
               
             
          
           
               
                 20° reflectometer 
                 82.3 
                 86.5 
                 86.3 
                 88.2 
               
               
                 value before 
               
               
                 scratching 
               
               
                 Haze before scratching 
                 3 
                 4 
                 4 
                 2 
               
               
                 Black value My 
                 275 
                 283 
                 282 
                 292 
               
               
                 40 strokes with 
                 63.2 
                 78.2 
                 75.4 
                 30.2 
               
               
                 Sikron F 500 
               
               
                 residual gloss [%] 
               
               
                   
               
             
          
         
       
     
     The silicas 7+8 according to the invention can be used in high concentrations without impairing the appearance of the lacquer surface owing to their substantially lower rheological efficiency compared with comparative silica 1. In addition, the silicas according to the invention display a substantial improvement in the scratch resistance of the lacquer surface. 
     Example 3 
     For the investigation of the improvement of the scratch resistance, a conventional 2-component polyurethane lacquer was used. The formulation of the lacquer and its production, including its application, are summarised below: 
     Formulation 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                   
                 Parts by wt. 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Millbase 
                   
               
               
                   
                 Acrylic copolymer, mod. with 
                 43.4 
               
               
                   
                 synthetic fatty acids, 60% solution 
               
               
                   
                 Butyl acetate 98% 
                 17.8 
               
               
                   
                 Xylene 
                 3.9 
               
               
                   
                 Silica 
                 5.0 
               
               
                   
                 Σ 
                 70.7 
               
               
                   
                 Lacquer make-up 
               
               
                   
                 Xylene 
                 11.3 
               
               
                   
                 Ethoxypropyl acetate 
                 3.4 
               
               
                   
                 Butyl glycol acetate 
                 1.6 
               
               
                   
                 Aliphatic polyisocyanate, approx. 
                 18.6 
               
               
                   
                 75% in 1-methoxypropyl-2- 
               
               
                   
                 acetate/xylene 1:1 
                   
               
               
                   
                 Σ 
                 105.0 
               
               
                   
                   
               
             
          
         
       
     
                                                 Binder concentration:     40%           Silica calculated on the basis of millbase (solids):   19.2%           Silica calculated on the basis of lacquer (total):    5.0%           Silica calculated on the basis of lacquer (solids):   12.5%                        
Production and Application of the Lacquers
 
     The binder is mixed with the solvents. Then, for the purpose of predispersion, the silica is incorporated into this mixture with the high-speed mixer (disk Ø 45 mm) and predispersed for 5 min at 2000 rpm. The mixture is dispersed in a laboratory pearl mill for 30 min at 2500 rpm and 60% pump capacity using glass beads (Ø approx. 1 mm). The millbase is tested with a grindometer, 25 μm, in accordance with DIN ISO 1524. It must be smaller than 10 μm. 
     The conversion of the millbase to lacquer takes place in accordance with the formulation, the components being mixed with a vane agitator at 2000 rpm. The hardener is incorporated in the same way. 
     After adjusting the lacquers to spray viscosity in accordance with DIN 53411, the lacquers are applied to black lacquered metal sheets, e.g. DT 36 (from Q-Panel), by spray application (coat thickness about 40-50 μm). After spraying, the metal sheets are dried for 24 h at room temperature and then for 2 h in a drying oven at 70° C. 
     Scratch Tests: 
     The metal sheets are abraded with a quartz/water slurry (100 g water+1 g Marlon A 350, 0.25%+5 g Sikron F500) using an abrasion and washing resistance tester (Erichsen, brush with hog&#39;s bristles). The gloss before and 10 min after the abrading is determined with a reflectometer (20° irradiation angle). 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
             
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 9 
               
             
             
               
                   
               
               
                 Summary of the properties of the liquid lacquers relevant in terms of lacquer technology, 
               
               
                 and of the applied and dried films. 
               
             
          
           
               
                   
                   
                   
                   
                 Reference 
                   
                   
                   
                 Reference 
               
               
                   
                 Comparative 
                   
                   
                 without 
                 Comparative 
                   
                 Silica 
                 without 
               
               
                   
                 silica 1 
                 Silica 7 
                 Silica 8 
                 silica 
                 silica 2 
                 Silica 9 
                 11 
                 silica 
               
               
                   
                   
               
             
          
           
               
                 Grindometer value [μm] 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 / 
                 &lt;10 
                 &lt;10 
                 &lt;10 
                 / 
               
               
                 Viscosity (millbase) 
               
               
                 [mPas] 
               
               
                  6 rpm 
                 409 
                 210 
                 220 
                 / 
                 5670 
                 935 
                 832 
                 / 
               
               
                 60 rpm 
                 407 
                 210 
                 212 
                 / 
                 1260 
                 409 
                 407 
                 / 
               
               
                 Viscosity (lacquer + hardener) 
               
               
                 [mPas] 
               
               
                  6 rpm 
                 120 
                 80 
                 80 
                 60 
                 446 
                 195 
                 175 
                 55 
               
               
                 60 rpm 
                 113 
                 82 
                 82 
                 61 
                 194 
                 146 
                 144 
                 64 
               
               
                 Flow 
                 Poor 
                 OK 
                 OK 
                 OK 
                 Orange-peel 
                 OK 
                 OK 
                 OK 
               
               
                   
                 fine cracks 
                   
                   
                   
                 effect 
               
             
          
           
               
                 Scratch resistance 
               
             
          
           
               
                 20° reflectometer 
                 81 
                 89.5 
                 89.1 
                 91.3 
                 38 
                 85.5 
                 85.3 
                 91.7 
               
               
                 value before 
               
               
                 scratching 
               
               
                 Haze before scratching 
                 101 
                 9 
                 12 
                 2 
                 423 
                 18 
                 19 
                 2 
               
               
                 40 strokes with Sikron 
                 83.4 
                 88.5 
                 90.7 
                 51.8 
                 / 
                 80.4 
                 84.3 
                 56.1 
               
               
                 F 500 
               
               
                 Residual gloss [%] 
               
               
                   
               
             
          
         
       
     
     The silicas 7+8 and 9+10 according to the invention can be used in high concentrations without impairing the appearance of the lacquer surface owing to their substantially lower rheological efficiency compared with comparative silica 1 and 2. In addition, the silicas according to the invention display a substantial improvement in the scratch resistance of the lacquer surface. 
     Example 4 
     Direct comparison of the silicas according to the invention with a scratch-resistant lacquer according to DE 198 11 790 A1, in which AEROSIL R 972 is used to improve the scratch resistance. 
                                                                   Silicas 2)           Prior art   according to the           1)   invention                                        Millbase                   Desmophen A 2009/1       190.2           Methoxypropyl acetate:       36.8           Solvesso 100 1:1           Silica       23.0           Σ       250.0           Lacquer make-up           Desmophen A YEP4-55A,   96.0   —           contains AEROSIL R 972           Millbase   —   48.9           Desmophen 2009/1   —   24.9           OL 17, 10% in MPA   —   —           Modaflow 1% in MPA   —   —           MPA:   11.6   33.8           Solvesso 100 1:1           Butyl glycol acetate   10.5   10.5           Byketol OK   7.5   7.5           Byk 141   0.8   0.8           Addition of hardener           Desmodur N 3390   23.6   23.6           Σ   150.0   150.0                        
Production and Application of the Lacquers
 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 1) 
                 Comparative silica 1 is incorporated into the binder in accordance 
               
               
                   
                 with DE 198 11 790 A1 using a jet disperser. 
               
               
                 2) 
                 The binder is mixed with the solvents. Then, for the purpose of 
               
               
                   
                 predispersion, the silica is incorporated into this mixture with the 
               
               
                   
                 high-speed mixer (disk Ø 45 mm) and predispersed for 5 mm at 2000 
               
               
                   
                 rpm. The mixture is dispersed in a laboratory pearl mill for 30 min 
               
               
                   
                 at 2500 rpm and 60% pump capacity using glass beads (Ø approx. 1 
               
               
                   
                 mm). The millbase is tested with a grindometer, 25 μm, according to 
               
               
                   
                 DIN ISO 1524. It must be smaller than 10 μm. 
               
               
                   
               
             
          
         
       
     
     The conversion to lacquer of the millbases corresponding to 1) or 2) takes place in accordance with the formulation, the components being mixed at 2000 rpm with a vane agitator. The hardener is incorporated in the same way. 
     After adjusting the lacquers to spray viscosity in accordance with DIN 53411, the lacquers are applied to black lacquered metal sheets, e.g. DT 36 (from Q-Panel), by spray application (coat thickness about 40-50 μm). After spraying, the metal sheets are dried for 24 h at room temperature and then for 2 h in a drying oven at 70° C. 
     Scratch Tests: 
     The metal sheets are abraded with a CaCO 3 /water slurry (100 g water+1 g Marlon A 350, 0.25%+5 g Millicarb CaCO 3 ) using an abrasion and washing resistance tester (Erichsen, brush with hog&#39;s bristles). The gloss before and 10 min after the abrading is determined with a reflectometer (20° irradiation angle). 
     
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 10 
               
             
             
               
                   
               
               
                 Summary of the properties of the liquid lacquers 
               
               
                 relevant in terms of lacquer technology, and of the applied 
               
               
                 and dried films. 
               
             
          
           
               
                   
                   
                 Prior art 
                 Silica 7 
                 Reference 
               
               
                   
                   
               
             
          
           
               
                   
                 Grindometer value 
                 &lt;10 
                 &lt;10 
                 / 
               
               
                   
                 [μm] 
               
               
                   
                 Viscosity (millbase) 
               
               
                   
                 [mPas] 
               
               
                   
                  6 rpm 
                 58 
                 30 
                 30 
               
               
                   
                 60 rpm 
                 48 
                 43 
                 40 
               
               
                   
                 Surface 
                 Orange 
                 OK 
                 OK 
               
               
                   
                   
                 peel 
               
               
                   
                 20° reflectometer 
                 88.0 
                 86.5 
                 98.5 
               
               
                   
                 value before 
               
               
                   
                 scratching 
               
               
                   
                 100 strokes with 
                 88.6 
                 96.3 
                 59.6 
               
               
                   
                 Millicarb 
               
               
                   
                 Residual gloss [%] 
               
               
                   
                   
               
             
          
         
       
     
     It is shown that a substantially better improvement in the residual gloss is achieved after a scratch stressing of the lacquer surface by using the silica according to the invention than with the prior art. In addition, owing to its low rheological efficiency, the silica according to the invention does not cause an orange-peel effect.