Glass compositions and fibers therefrom
TECHNICAL FIELD 
     This invention relates to sodium barium borosilicate glass compositions. Fibers from these compositions make glass fiber insulation. 
     BACKGROUND OF THE INVENTION 
     Glass fiber insulation is well known and has been a commercial product for a long period of time. The insulation is made from intertwined soda lime alumina borosilicate glass fiber which a binder holds together. The binder may be any suitable material but quite commonly is a phenolformaldehyde resin or a ureaformaldehyde resin. These binders are well known and a spray nozzle generally applies them to the glass fibers as hot gases attenuate the fibers from a rotating device, commonly called a spinner. A conveyer collects the binder-coated fibers in the form of a blanket, and heat cures the blanket to produce the final insulation. The process produces various densities by varying the conveyor speed and the thickness of the cured insulation. 
     The German government has proposed regulations for glass fibers. Glass fiber compositions meeting the regulations are considered to be free of suspicion. The problem, however, for the manufacturer is to produce glass fibers which meet the regulations and standard criteria. These glasses must meet the proposed regulations, be fiberizable in standard wool processes, have sufficient durability and have acceptable insulating properties. 
     DISCLOSURE OF THE INVENTION 
     We have developed glass compositions which meet all the criteria. Our glasses have a high BaO content, a high soda content and contain small amounts of alumina. The glass compositions meet the proposed German regulations. They have a numerical index (KI) greater than or equal to 40. Standard wool processes easily produce fibers from these compositions. The difference (delta T) between the temperature where the glass has a viscosity of 1,000 poise and the liquidus temperature generally is 50° F. and is often 200° F. or greater. Durability as shown by fiber weight loss is good and is often less than 5% fiber weight loss after 24 hours in water at 205° F. 
     Best Mode of Carrying Out Invention 
     We made measurements of viscosity, liquidus and durability for a number of glasses with KI≧40. The measurements indicated a compositional region of glasses which are useful for production of glass fiber insulation. This range is as follows for the major components: 
     
         ______________________________________                                    
Ingredients   Weight Percent                                              
______________________________________                                    
SiO.sub.2     45-60                                                       
Al.sub.2 O.sub.3                                                          
              0-3                                                         
B.sub.2 O.sub.3                                                           
               0-20                                                       
Na.sub.2 O + K.sub.2 O                                                    
              12-22                                                       
MgO + CaO      0-14                                                       
BaO            2-35                                                       
______________________________________                                    
 
    
     and less than about 10% of any or all of ZnO, TiO 2 , Fe 2  O 3 , ZrO 2 , SrO or Li 2  O, the total being 100% by weight, wherein each glass composition has a KI value equal to or greater than 40. 
     More preferably, the glass compositions consist essentially of: 
     
         ______________________________________                                    
Ingredients   Weight Percent                                              
______________________________________                                    
SiO.sub.2     45-57                                                       
Al.sub.2 O.sub.3                                                          
              0.8-3                                                       
B.sub.2 O.sub.3                                                           
               0-18                                                       
Na.sub.2 O + K.sub.2 O                                                    
              12-22                                                       
MgO + CaO      0-14                                                       
______________________________________                                    
 
    
     and less than about 5% of any or all of ZnO, TiO 2 , Fe 2  O 3 , ZrO 2 , SrO or Li 2  O, the total being 100% by weight, and wherein each glass composition has a KI value equal to or greater than 40. 
     Even more preferably, the glass compositions have a BaO content of 5 to 30 weight percent and less than about 2% of any or all of ZnO, TiO 2 , Fe 2  O 3 , ZrO 2 , SrO or Li 2  O. Even more preferably the glass compositions have a a BaO combat of 12 to 25 weight percent, and less than 2% of any or all of ZnO, TiO 2 , Fe 2  O 3 , ZrO 2 , SrO or Li 2  O. 
     Insulation products of these glass fibers can be produced from a conventional fiber forming process. 
     The German regulation requires a numerical index (KI) greater than or equal to 40 to be considered free of suspicion. The index is calculated by KI=Σ(Na 2  O, K 2  O, CaO, MgO, BaO, B 2  O 3 )--2Al 2  O 3 . This places severe restrictions on alumina levels and anything not included in the index, such as silica. The obvious choice is to lower alumina to very low levels. These glasses, however, have poor durabilities and most could not be fiberized by a standard wool process. We discovered that high BaO levels yielded glasses with significantly improved durability and fiberizability by standard processes. 
     We designed an array of glasses to show the effect of glass composition in this narrow field on select properties. All glasses are shown together with measured properties in the following table. 
    
    
     Examples of the compositions are given in the following table. All the glass compositions have KI index of 40 or higher. 
     Example 1 
     Glass fibers of the present invention have the following compositions. Most of the compositions have measured forming temperatures (the temperature where the viscosity of the glass is about 1,000 poise) and liquidus temperatures. 
     
                                           TABLE                                   
__________________________________________________________________________
Weight Percent                                                            
Ingredients:                                                              
          1   2   3   4   5   6   7   8   9   10  11  12                  
__________________________________________________________________________
SiO.sub.2 54.5                                                            
              55.0                                                        
                  56.3                                                    
                      56.4                                                
                          56.5                                            
                              56.5                                        
                                  56.3                                    
                                      56.4                                
                                          54.5                            
                                              54.4                        
                                                  55.2                    
                                                      54.8                
Al.sub.2 O.sub.3                                                          
          0.9 1.0 1.0 1.0 1.0 0.9 1.0 1.0 1.0 1.0 1.6 1.7                 
B.sub.2 O.sub.3                                                           
          1.5 1.5 15.1                                                    
                      13.3                                                
                          9.8 6.2 13.3                                    
                                      11.6                                
                                          15.2                            
                                              15.4                        
                                                  --  --                  
Na.sub.2 O                                                                
          12.4                                                            
              12.5                                                        
                  14.5                                                    
                      14.4                                                
                          14.1                                            
                              13.8                                        
                                  14.6                                    
                                      14.5                                
                                          14.5                            
                                              14.4                        
                                                  15.5                    
                                                      16.5                
K.sub.2 O 6.0 6.0 0.8 0.8 0.7 0.7 0.8 0.8 0.8 0.8 --  --                  
MgO       1.1 1.1 2.6 2.6 2.5 2.5 3.1 3.0 2.6 2.6 --  1.8                 
CaO       3.1 3.1 7.3 7.1 7.0 6.9 8.5 8.4 7.2 7.2 --  4.0                 
BaO       17.8                                                            
              17.8                                                        
                  2.0 4.0 8.0 12.1                                        
                                  2.0 4.0 2.0 2.0 27.7                    
                                                      21.2                
TiO.sub.2 --  --  0.1 0.1 0.1 0.1 0.1 0.1 2.0 0.1 --  --                  
Fe.sub.2 O.sub. 3                                                         
          0.2 0.2 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 --  --                  
ZrO.sub.2 2.5 1.8 --  --  --  --  --  --  --  2.0 --  --                  
T (°F.) for viscosity                                              
          1903                                                            
              1882                                                        
                  1737                                                    
                      1738                                                
                          1761                                            
                              1789                                        
                                  1739                                    
                                      1747                                
                                          1714                            
                                              1740                        
                                                  1882                    
                                                      1867                
of 1,000 Poise                                                            
Liquidus  1524                                                            
              --  1498                                                    
                      1481                                                
                          1548                                            
                              1553                                        
                                  1578                                    
                                      1567                                
                                          1538                            
                                              1551                        
                                                  --  --                  
Temperature (F°)                                                   
KI        40.0                                                            
              40.0                                                        
                  40.3                                                    
                      40.3                                                
                          40.3                                            
                              40.3                                        
                                  40.3                                    
                                      40.3                                
                                          40.3                            
                                              40.3                        
                                                  40.0                    
                                                      40.0                
durability (% wt                                                          
          7.0 --  4.7 4.3 3.8 3.6 --  --  --  --  --  --                  
loss of fibers after                                                      
24 hrs)*                                                                  
__________________________________________________________________________
 *Exposure to water at 205° F.