Abstract:
Functionalized silicas with 3-methacryloxypropylsilyl and/or glycidyloxypropylsilyl groups on the surface are prepared by mixing the silicas with the silane and heat-treating the mixture. The silicas are employed, for example, in solvent-containing coatings.

Description:
INTRODUCTION AND BACKGROUND 
     The present invention relates to functionalized silicas, a process for their preparation and their use. 
     It is known to react silicon dioxide obtained by flame hydrolysis and with a surface area of 40 to 200 m 2 /g with 3-methacryloxypropyltrimethoxysilane. The resulting silicon dioxide is then coated with a further shell of (meth)acrylate polymers and subsequently employed in dental compositions (EP 0 142 784 A1). 
     SUMMARY OF THE INVENTION 
     The present invention provides functionalized silicas, characterized by functional groups fixed on the surface, the groups being 3-methacryloxypropylsilyl and/or glycidyloxypropylsilyl. 
     The present invention also provides a process for the preparation of the functionalized silicas, which is characterized in that a silica is sprayed optionally first with water or dilute acid and then with a surface modification reagent or a mixture of several surface modification reagents in a suitable mixing vessel, with intensive mixing, the components are optionally re-mixed for 15 to 30 minutes and heat-treated at a temperature of 100 to 400° C. over a period of 1 to 6 h. 
     A silica prepared pyrogenically by the route of flame hydrolysis of SiCl 4  can preferably be employed as the silica. Such pyrogenic silicas are known from Ullmanns Enzyklopädie der technischen Chemie [Ullmanns Encyclopaedia of Industrial Chemistry], 4th edition, volume 21, page 464 (1982). 
     In a preferred embodiment of the invention, a pyrogenic silica with a surface area of approx. 200 m 2 /g can be employed (Aerosil® 200). 
     Monomeric substances, such as 3-methacryloxypropyltrialkoxysilane and/or glycidyloxypropyltrialkoxysilane, wherein alkoxy can be methoxy, ethoxy and/or propoxy, can be employed as the surface modification reagent. 
     The amount of silane can be metered with respect to the silica such that no or only a small excess results. The excess silane can optionally be removed during the heat treatment. 
     The silica according to the invention can be employed in solvent-containing coatings, for example 2-component polyurethane coatings. 
    
    
     DETAILED DESCRIPTION OF INVENTION 
     The functionalized silicas according to the invention have the following advantages: When used in solvent-containing coatings, such as, 2-component polyurethane coatings, the scratch resistance of the coating surface is increased. 
     According to the invention, the pyrogenically prepared silicas according to table 1 can be employed as the silica for the silanization. 
     
       
         
               
             
               
               
               
               
               
               
               
               
               
             
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Physico-chemical data of AEROSIL ® 
               
             
          
           
               
                   
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
                 AEROSIL 
               
               
                 Test method 
                 90 
                 130 
                 150 
                 200 
                 300 
                 380 
                 OX50 
                 TT600 
               
               
                   
               
             
          
           
               
                 Behaviour towards 
                 hydrophilic 
               
               
                 water 
               
               
                 Appearance 
                 loose white powder 
               
             
          
           
               
                 BET surface area 1)   
                 m2/g 
                 90 ± 15 
                 130 ± 25 
                 150 ± 15 
                 200 ± 25 
                 300 ± 30 
                 380 ± 30 
                 50 ± 15 
                 200 ± 50 
               
               
                 Average primary 
                 nm 
                 20 
                 16 
                 14 
                 12 
                 7 
                 7 
                 40 
                 40 
               
               
                 particle size 
               
               
                 Tamped density 
                 g/l 
                 80 
                 50 
                 50 
                 50 
                 50 
                 50 
                 130 
                 60 
               
               
                 approx. values 2)   
               
               
                 Compacted goods 
                 g/l 
                 120 
                 120 
                 120 
                 120 
                 120 
                 120 
               
               
                 (added “V”) 
               
               
                 VV goods 
                 g/l 
                   
                   
                 50/75 
                 50/75 
                 50/75 
               
               
                 (added “VV”) 12)   
                 g/l 
                   
                   
                   
                 120 
                 120 
               
               
                 Loss on drying 3)   
                 % 
                 &lt;1.0 
                 &lt;1.5 
                 &lt;0.5 9)   
                 &lt;1.5 
                 &lt;1.5 
                 &lt;2.0 
                 &lt;1.5 
                 &lt;2.5 
               
               
                 (2 hours at 105° C.) on 
               
               
                 leaving supply 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 5)   
                   
                 3.7-4.7 
                 3.7-4.7 
                 3.7-4.7 
                 3.7-4.7 
                 3.7-4.7 
                 3.7-4.7 
                 3.8-4.8 
                 3.6-4.5 
               
               
                 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 2   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)10)   
                 % 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
                 &lt;0.025 
               
               
                 Sieve residue 8)   
                 % 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.05 
                 &lt;0.2 
                 &lt;0.05 
               
               
                 (Mocker method, 45 
               
               
                 μm) 
               
               
                 Drum size (net) 11)   
                 kg 
                 10 
                 10 
                 10 
                 10 
                 10 
                 10 
                 10 
                 10 
               
               
                   
               
               
                   1) in accordance with DIN 66131  
               
               
                   2) in accordance with DIN ISO 787/XI, JIS K 5101/18 (not sieved)  
               
               
                   3) in accordance with DIN ISO 787/II, ASTM D 280. JIS K 5101/21  
               
               
                   4) in accordance with DIN 55921, ASTM D 1208, JIS K 5101/23  
               
               
                   5) in accordance with DIN ISO 787/IX, ASTM D 1208, JIS K 5101/24  
               
               
                   6) in accordance with 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) special packaging protecting against moisture  
               
               
                   10) HCl content is a constituent of the loss on ignition  
               
               
                   11) V goods are supplied in sacks of 20 kg  
               
               
                   12) VV goods are currently supplied only from the Rheinfelden works  
               
             
          
         
       
     
     EXAMPLE 1 
     Aerosil® 200 is mixed with 4 parts water and 18 parts 3-methacryloxypropyl-trimethoxysilane (for example DYNASILAN MEMO) and the mixture is heat-treated at 140° C. under an inert gas. 
     The silica obtained has the following properties: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 BET [m 2 /g] 
                 138 
               
               
                   
                 Tamped density [g/l] 
                 52 
               
               
                   
                 pH 
                 4.6 
               
               
                   
                 C content 
                 5.7 
               
               
                   
                 Loss on drying [%] 
                 0.8 
               
               
                   
                 Loss on ignition [%] 
                 9.7 
               
               
                   
                 DBP number [%] 
                 228 
               
               
                   
                   
               
             
          
         
       
     
     EXAMPLE 2 
     Aerosil® 200 is mixed with 3 parts water and 16 parts 3-glycidyloxypropyl-trimethoxysilane (for example DYNASILAN GLYMO) and the mixture is heat-treated at 140° C. under an inert gas. 
     The silica obtained has the following properties: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 BET [m 2 /g] 
                 165 
               
               
                   
                 Tamped density [g/l] 
                 53 
               
               
                   
                 pH 
                 4.9 
               
               
                   
                 C content 
                 5.5 
               
               
                   
                 Loss on drying [%] 
                 1.5 
               
               
                   
                 Loss on ignition [%] 
                 8.7 
               
               
                   
                 DBP number [%] 
                 242 
               
               
                   
                   
               
             
          
         
       
     
     Experiment 1 
     A conventional 2-component polyurethane coating has been used to investigate the improvement in the scratch resistance. The recipe for the coating and the preparation, including the application, are summarized in the following: 
     
       
         
               
               
             
               
               
               
             
           
               
                   
               
               
                   
                 Parts by 
               
               
                 Recipe: 
                 wt. 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Millbase 
                 Setalux C 1152, 
                 53.3 
               
               
                   
                 XX - 51.50% (Akzo Nobel) 
               
               
                   
                 Butyl acetate 98% 
                  6.7 
               
               
                   
                 Xylene 
                  6.7 
               
               
                   
                 AEROSIL (silica according to example 1) 
                  5.0 
               
               
                 Σ 
                   
                 71.7 
               
               
                 Lacquer 
                 Setalux C 1152, 
                  1.1 
               
               
                 constituents: 
                 XX - 51.50% (Akzo Nobel) 
               
               
                   
                 Xylene 
                 12.2 
               
               
                   
                 Ethoxypropyl acetate 
                  1.5 
               
               
                   
                 Butylglycol acetate 
                  1.5 
               
               
                 Hardener: 
                 Desmodur N 75 (Bayer) 
                 17.0 
               
               
                 Σ 
                   
                 105.0  
               
               
                   
               
               
                 Binder concentration: 40%  
               
               
                 AEROSIL ® calculated with respect to the milibase (SC): 18.8%  
               
               
                 AEROSIL ® calculated with respect to the coating (total): 5%  
               
               
                 AEROSIL ® calculated with respect to the coating (SC): 12,5%  
               
             
          
         
       
     
     Preparation and Application of the Coatings 
     The Setalux is mixed with the solvents. For predispersion, the AEROSIL® is then incorporated into this mixture with a dissolver (disc Ø 45 mm) and predispersed for 5 min at 2000 rpm. The mixture is dispersed in a laboratory bead mill for 30 min at 2500 rpm and a pump output of 60% using glass beads (Ø approx. 1 mm). The dispersing quality is checked with a grindometer, 25 μm, in accordance with DIN ISO 1524. It must be smaller than 10 μm. 
     The lacquer constituents are added to the millbase in accordance with the recipe, the components being mixed with a blade stirrer at 2000 rpm. The hardener is stirred into the mixture in the same manner. 
     After the coatings have been adjusted to the spray viscosity according to DIN 53411, the coatings are applied to black-lacquered metal sheets, for example DT 36 (Q-Panel), by means of spraying application (layer thickness about 40-50 μm). After the spraying, the metal sheets are dried for 24 h at room temperature and then for 2 h in a drying oven at 70° C. 
     Scratching Experiments: 
     The metal sheets are scoured with a quartz/water slurry (100 g water+1 g Marlon A 350, 0.25%+5 g Millicarb BG) with the aid of a scouring and washing resistance testing machine (Erichsen, brush with pig bristles). The shine before and 10 min after scouring is determined with a reflectometer (20° incident angle). 
     
       
         
               
             
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Summary of the coating-relevant properties 
               
               
                 of the liquid coatings and of the films applied and dried: 
               
             
          
           
               
                   
                 AEROSIL 
                 Silica/(example 
                   
               
               
                   
                 200 
                 1) 
                 Reference 
               
               
                   
                   
               
             
          
           
               
                 Grindometer value 
                 [μm] 
                 &lt;10 
                 &lt;10 
                 — 
               
               
                 Viscosity (millbase) 
                 [mPas] 
               
               
                   
                  6 rpm 
                   
                 1000 
                 180 
               
               
                   
                 60 rpm 
                 464 
                 600 
                 143 
               
               
                 Viscosity 
                 [mPas] 
               
               
                 (coating + hardener) 
                  6 rpm 
                 166 
                 180 
                 75 
               
               
                   
                 60 rpm 
                 141 
                 147 
                 62 
               
               
                 Dilution (adjustment 
                 [%] 
                 11.5 
                 8.5 
                 1.7 
               
               
                 to 20 s DIN 4 mm) 
               
             
          
           
               
                 Scratch resistance 
                   
                   
                   
               
               
                 20° reflectometer value before 
                 90.9 
                 87.6 
                 91.3 
               
               
                 scratching 
               
               
                 40 strokes with Sikron F 500 
                 66.4 
                 73.0 
                 50.7 
               
               
                 20° reflectometer value residual 
                 73.0 
                 83.3 
                 55.5 
               
               
                 shine 
               
               
                 100 strokes with Millicarb 
                 79.2 
                 80.5 
                 68.4 
               
               
                 BG 20° 
               
               
                 reflectometer value residual 
                 87.1 
                 91.9 
                 74.9 
               
               
                 shine [%] 
               
               
                   
               
             
          
         
       
     
     Further variations and modifications of the foregoing will be apparent to those skilled in the art and are intended to be encompassed by the claims appended hereto. 
     European priority application 00 122 954.1 is relied on and incorporated herein by reference.