Patent Publication Number: US-5294653-A

Title: Three-component water-based varnish for glass for interior use

Description:
DESCRIPTION OF THE INVENTION 
     The water-based varnish according to the invention is prepared by mixing--just before use--an acrylic and urethane polymers aqueous dispersion (component A), an alkoxysilane containing at least one epoxy functional group (component B), and zirconium and ammonium double carbonate in the form of an aqueous solution (component C). The alkoxysilane containing an epoxy functional group is used to create a chemical bond between the silica present in glass and the ammonium ions of zirconium and ammonium carbonate. The carbonate can form bonds with the polymeric component containing free hydroxy groups (acrylic polymer with free OH groups), owing to the property of zirconium of forming complexes with zirconium coordinated hydroxy groups. 
     The hydroxy groups of the polymeric component can also react with the epoxy group of alkoxysilane, thus enhancing the reaction rate. 
     A fundamental property of the varnish composition according to the invention is that the polymeric film adheres to the glass substrate through real chemical bonds and not by a simple physical adhesion as is the case of the usual varnishes for glass. 
    
    
     The following schemes can be hypothesized for the various possible reactions and for the organometallic complexes that form. The implementation of the invention, however, is not limited to the said schemes. ##STR1## 
     In this case, the chemical bond between glass and the zirconium and ammonium carbonate alkaline solution is represented by OH -  ion, which plays the determinant role of reacting with the network and breaking the oxygen bridge bonds: ##STR2## 
     The breaking of the epoxy group with ammonium ions can be represented as follows: ##STR3## 
     Varnish formulation 
     Component A consists of an aqueous dispersion of an acrylic polymer containing hydroxy functional groups (0.8 to 1.2 wt.-% OH groups on dry polymer basis), mixed with a lower amount of polyurethane resin produced from aliphatic polyisocyanate as well as with the usual additives of a varnish polymeric aqueous dispersion, e.g. surfactants, antifoam and thickening agents, pigments, special extenders for appearance improvement, etc. The dispersion viscosity can be adjusted, by addition of H 2  O, to 40-60 sec. (Ford 4 viscosity at 20° C.). 
     The dispersion obtained contains acrylic resin (15% to 18% by wt.) and polyurethane resin (9% to 12% by wt.). 
     The typical formulation of component A is reported hereinbelow (% by weight). 
     
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                            % AS                                          
COMPONENT A                 DRY PRODUCT                                   
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Acrylic resin dispersion                                                  
                53.577      28-32                                         
with free hydroxy groups                                                  
Aliphatic polyurethane                                                    
                30.388      32-36                                         
resin dispersion                                                          
Polypropylene wax                                                         
                4.850       100                                           
Water           3.250       --                                            
Polyurethane-based                                                        
                0.856       48-52                                         
thickening agents                                                         
Preservatives   0.001       10-12                                         
Silicone-based antifoam                                                   
                1.215       100                                           
agents                                                                    
Pigments        4.758       34-50                                         
Glitter&#39;s       1.105       100                                           
                100.000%                                                  
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     Component B consists of a trialkoxysilane containing epoxy functional groups; particularly fit is gamma-glycidoxypropyltrimethoxysilane: ##STR4## 
     Component C consists of a commercially available 10 wt.-% aqueous solution of zirconium and ammonium double carbonate with a ZrO 2  (+HfO 2 ) content of 19% to 20% by weight. 
     Weight ratio among the three components 
     Components A, B, and C are mixed to obtain the varnish ready for use. 
     Component B, which is liquid, is used as is. 
     The components weight ratio is as follows: 
     
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Component A         100 parts by wt.                                      
Component B          3 parts by wt.                                       
Component C          2 parts by wt.                                       
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     The physicochemical properties of the varnish obtained are as follows: 
     
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Density at 20° C.                                                  
                     1.120 to 1.240 g/cm3                                 
Ford 4 viscosity at 20° C.                                         
                     40 to 60 sec.                                        
Dry residue (2 hrs at 130° C.)                                     
                     35% to 45% by weight                                 
Gelling time (time of use) at 20° C.                               
                     240 to 280 hrs.                                      
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     Performance of the varnish according to the invention 
     The performance tests carried out on the varnish in actual use gave the results shown in the following table: 
     
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GENERAL TESTS    STANDARDS    RESULTS                                     
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Adhesion         ISO-4624      0*                                         
Light fastness (60 hrs)                                                   
                 ISO-2809     4/5                                         
Salt fog test    UNI-5687     S                                           
(24 hrs)                                                                  
Salt fog test    UNI-5687     S                                           
(100 hrs)                                                                 
Resistance to staining                                                    
                 BS-3962/4                                                
Acetone                       5                                           
Ethyl/Butyl acetate           5                                           
Tea                           5                                           
Coffee                        5                                           
Ethyl alcohol (96%)           4                                           
Ethyl alcohol (48%)           5                                           
Resistance to oil and grease                                              
                 BS-3962/5    5                                           
Tables (lower surface):        G**                                        
bearing points compression                                                
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 Note                                                                     
 In the estimates, marks from 1 to 5 are assigned to performance levels: 5
 is the highest mark according to the specific standard.                  
 *The results of adhesion tests are indicated as follows: N = negative, I 
 insufficient, S = sufficient, G = good, O = optimum.                     
 **Velcro selfadhesive tapes are fastened to two panes, which are held    
 together at a pressure of 2.5 kg/cm.sup.2 for 7 days. The results obtaine
 are indicated as under (*). This test simulates the stress undergone by  
 the varnish at the glass panes bearing points.                           
 
    
     APPLICATION PROPERTIES 
     On the basis of wide experimentation carried out in industrial plants producing usual solvent varnishes, the application properties of the water-based system as per this invention were found to be good. The coating film adhesiveness, performance and appearance were found to be excellent. 
     ADHESION 
     The tests showed an excellent adhesion to the panes produced by the main European manufacturers (see table illustrating the adhesion tests).