Abstract:
A method is provided for producing a glass batch. The method involves use of a calcium magnesium silicate as a batch component substitution for a lithium melting aid. The amount used is effective to produce a beneficial viscosity character and reduced batch free time.

Description:
FIELD OF THE INVENTION 
     The present invention relates to glass batch forming methods. In particular, it relates to a method wherein a calcium magnesium silicate is substituted for lithium as a melting aid in glass batches. 
     BACKGROUND 
     Glass batches can contain certain materials as melting aids. These aids assist in creating a homogeneous batch having complete reactions and performed at lower melting temperatures or times. One such melting aid is lithium, which while effective is relatively expensive to use. There remains a need to further develop useful melting aids which can be used in conjunction with or in the absence of lithium compounds. 
     SUMMARY 
     One object of the present invention is a method of producing a glass batch composition having favorable viscosity characteristics. Another objective is to provide a melting aid for a glass batch which can work in conjunction with or as a partial or total replacement for lithium melting aids. These and other objectives are achieved by a method of forming a glass batch composition by the admixing of a calcium magnesium silicate composition. 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     One embodiment of the present invention is a method of producing a glass batch composition composed of a calcium magnesium silicate and other glass components to produce a glass batch. The glass batch composition is then melted to form a melted glass batch composition. The amount of said calcium magnesium silicate used is selected effectively to produce a viscosity character and batch free time in the glass batch composition less than or equal to that which results from use of an equivalent amount of a lithium compound in a comparative glass batch. An equivalent amount is the use of the same mass percent of the calcium magnesium silicate or lithium compound in the total glass batch before heating. 
     The calcium magnesium silicate of the present invention can be a natural resource or one attained by synthetic production. A preferred calcium magnesium silicate compound is that described in U. S. Pat. No. 6,211,103 B1 (Fairchild, et al.). A more preferred calcium magnesium silicate has an empirical formula of Ca x Mg y SiO 2 , and the values of x and y are independently from about 0.1 to about 0.6 and z is a value to balance the oxidation state of the compound. 
     The respective amounts of the calcium magnesium silicate compound and other glass components is dependent upon the glass formula being produced. As used herein, the term “comparative glass batch” or “comparative glass product” means a glass batch or product which is equivalent in oxide values, except that the value of boron oxide equivalent is less for an embodied glass product made with the present invention than that made with known processes which do not use a calcium magnesium silicate compound as described herein. It has been unexpectedly discovered that by using the calcium magnesium silicate compound described herein that less lithium values are needed to attain the same or better result as the amount used in known methods. Accordingly, a preferred method is one in which the other batch components comprise less than about one percent by total batch weight of lithium. It was further unexpectedly found that in the method using calcium oxide silicate compounds to reduce the amount of lithium needed for a particular purpose, that the use of an embodied calcium magnesium silicate compound enabled as a preferred method to reduce the amount of said magnesium oxide compound to about zero. 
     The amount of the calcium magnesium silicate compound used can be adjusted so that the viscosity of the formed glass batch is at least about ten percent less than that of the comparative glass batch. Similarly, the amount of the calcium magnesium silicate compound used can be adjusted so that the batch free time of the formed glass batch is at least about ten percent less than that of the comparative glass batch. 
     In a preferred method, an amount of feldspathic compound can be combined with the calcium magnesium silicate compound to achieve similar results. In another preferred embodiment, the above method is modified by the additional mixing of a feldspathic component. Such feldspathic material can be of one of any of the numerous material or synthetic forms of feldspar or feldspar-type material. Such feldspathic material is an aluminosilicate with barium, calcium, potassium, or sodium component preferably is a potassium aluminosilicate having the formula KAlSi 3 O 8  with little sodium values. 
    
    
     The following examples are intended to illustrate, but not limit, the invention herein. 
     An inventive sample is made by adding together feldspar, calcium magnesium silicate and other glass forming components. The calcium magnesium silicate is Synsil® silicate, from Synsil Products Inc., and has the following composition: 
     
       
         
               
               
               
             
               
               
               
             
           
               
                   
                   
               
               
                   
                 Oxide Component 
                 Mass Percent 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 CaO 
                 24.5 
               
               
                   
                 MgO 
                 17.8 
               
               
                   
                 SiO 2   
                 53.5 
               
               
                   
                 Al 2 O 3   
                 3.4 
               
               
                   
                 Fe 2 O 3   
                 0.12 
               
               
                   
                 Na 2 O 
                 0.40 
               
               
                   
                   
               
             
          
         
       
     
     The feldspar is a potassium aluminosilicate. Of the glass produced from the glass batch, the Synsil® silicate is 13 mass percent, the feldspar is 3 mass percent, and the other glass forming components are 84 mass percent. A comparative batch is produced using 7 mass percent dolomite, 5 mass percent spodumene, and the balance being the other glass forming components. A comparison of the glasses produced show that the experimental glass is produced with reduced batch free time while retaining similar glass properties as the comparative glass.