Fire resistant glazing

Abstract

Fire resistant glazings comprise a fire resistant interlayer based upon a silicate waterglass are characterised by the incorporation of aluminium ions. The aluminate is incorporated as a solution which has been partially neutralised using hydroxycarboxylic acid which is preferably citric acid. The incorporation of aluminium provides glazings have improved fire resistance and impact properties.

1 . A clear stable aqueous solution comprising an alkali metal silicate waterglass, a water soluble aluminate and a hydroxy carboxylic acid.  
   
   
       2 . A solution according to  claim 1  wherein the water soluble aluminate is an alkali metal aluminate.  
   
   
       3 . A solution according to  claim 1  wherein the water soluble aluminate is a sodium aluminate.  
   
   
       4 . A solution according to  claim 1  wherein the hydroxycarboxylic acid is an α-hydroxy carboxylic acid.  
   
   
       5 . A solution according to  claim 4  wherein the hydroxycarboxylic acid is selected from the group comprising tartaric acid, malic acid, gluconic acid, lactic acid, saccharic acid and citric acid.  
   
   
       6 . A solution according to  claim 5  wherein the hydroxycarboxylic acid is citric acid.  
   
   
       7 . A solution according to  claim 1  wherein the alkali metal silicate waterglass having a weight ratio SiO 2 :M 2 O of from 2.0:1 to 4.0:1 where M represents an alkali metal cation.  
   
   
       8 . A solution according to  claim 7  wherein the sodium silicate waterglass has a weight ratio SiO 2 :Na 2 O of from 2.5:1 to 3.0:1.  
   
   
       9 . A solution according to  claim 7  further comprising a potassium silicate waterglass  
   
   
       10 . A solution according to  claim 9  wherein the potassium silicate has a weight ratio SiO 2 :K 2 O of from 1.43:1 to 2.05:1.  
   
   
       11 . A solution according to  claim 9  wherein the molar ratio of sodium ions to potassium ions is at least 2:1.  
   
   
       12 . A solution according to  claim 1  wherein the molar ratio of silicon to aluminium is in the range 20:1 to 35:1.  
   
   
       13 . A solution-according to  claim 12  wherein the molar ratio of silicon to aluminium is in the range 25:1 to 32:1.  
   
   
       14 . A solution according to  claim 1  wherein the weight ratio of silica to alkali metal oxide is in the range 2:1 to 4:1.  
   
   
       15 . A solution according to  claim 1  further comprising a polyhydric compound.  
   
   
       16 . A solution according to  claim 15  wherein the polyhydric compound is glycerol.  
   
   
       17 . A clear intumescent interlayer produced by drying a solution according to  claim 1  under controlled conditions.  
   
   
       18 . An interlayer according to  claim 17  comprising from 10 to 35% by weight of water.  
   
   
       19 . An interlayer according to  claim 17  comprising from 0.1 to 5.0% by weight of aluminium.  
   
   
       20 . An interlayer according to  claim 17  wherein the interlayer has a thickness of form 0.5 to 2.0 mm.  
   
   
       21 . A glass sheet having an interlayer according to  claim 17  on one surface thereof.  
   
   
       22 . A laminated glazing which comprises one or more interlayers according  claim 17  and two or more sheets of glass.  
   
   
       23 . A method for producing a solution according to  claim 1  wherein a solution comprising a water soluble aluminate, a hydroxycarboxylic acid and a polyhydroxy compound is added to an alkali metal silicate solution.  
   
   
       24 . A method according to  claim 23  wherein the aluminate is sodium aluminate.  
   
   
       25 . A method according to  claim 23  wherein the hydroxycarboxylic acid is citric acid.  
   
   
       26 . A method according to  claim 23  wherein the polyhydroxy compound is glycerol.  
   
   
       27 . A method according to  claim 23  wherein the solution comprising the aluminate is formed by partially neutralizing the aluminate with the hydroxy carboxylic acid.