Thermal Insulation

Abstract

The present invention relates to inorganic fibres having a composition comprising: 61.0 to 70.8 wt % SiO 2 ; 28.0 to 39.0 wt % CaO; 0.10 to 0.85 wt % MgO other components, if any, providing the balance up to 100 wt %, The sum of SiO 2 and CaO is greater than or equal to 98.8 wt % and the other components comprise less than 0.70 wt % Al 2 O 3 , if any.

1 . Inorganic fibres having a composition comprising:
 61.0 to 70.8 wt % SiO 2 ;   28.0 to 39.0 wt % CaO;   0.10 to 0.85 wt % MgO   other components, if any, providing the balance up to 100 wt %,   
       wherein the sum of SiO 2  and CaO is greater than or equal to 98.8 wt % and the other components comprise less than 0.70 wt % Al 2 O 3 , if any. 
     
     
         2 . The inorganic fibres of  claim 1 , comprising 0.01 to less than 0.65 wt % Al 2 O 3 . 
     
     
         3 . The inorganic fibres according to  claim 1 , which after heat treatment at 1100° C. for 24 hours comprise surface crystal grains with an average crystallite size of 0.90 μm or less. 
     
     
         4 . The inorganic fibres of  claim 1 , wherein the other components account for at least 0.3 wt % of the composition of the inorganic fibres. 
     
     
         5 . The inorganic fibres of  claim 1 , wherein the sum of SiO 2 +CaO+MgO is greater than or equal to 99.3 wt % of the fibre composition. 
     
     
         6 . The inorganic fibres of  claim 1 , wherein the sum of SiO 2 +CaO+MgO+Al 2 O 3  is greater than or equal to 99.5 wt % of the fibre composition. 
     
     
         7 . The inorganic fibres of  claim 1 , wherein the fibre composition comprises less than 0.80 wt % MgO. 
     
     
         8 . The inorganic fibres according to  claim 1 , wherein the amount of Al 2 O 3  is less than 0.35 wt %. 
     
     
         9 . The inorganic fibres of  claim 1 , wherein the sum of SiO 2  and CaO is greater than or equal to 99.0 wt %. 
     
     
         10 . The inorganic fibres of  claim 1 , wherein the sum of SiO 2  and CaO is greater than or equal to 99.1 wt %. 
     
     
         11 . The inorganic fibres of  claim 1 , wherein the sum of SiO 2  and CaO is greater than or equal to 99.2 wt %. 
     
     
         12 . The inorganic fibres of  claim 1 , wherein the composition comprises less than 70.0 wt % SiO 2 . 
     
     
         13 . The inorganic fibres according to  claim 1 , wherein then composition comprises greater than 64.5 wt % SiO 2 . 
     
     
         14 . The inorganic fibres according to  claim 1 , wherein the composition comprises 65.7 wt % or greater SiO 2 . 
     
     
         15 . The inorganic fibres according to  claim 1 , wherein the sum of the other components is in the range 0.05 to 1.0 wt % of the fibre composition, said other components comprising one or more oxides or fluorides of lanthanides, Li, Na, K, Sr, Ba, Cr, Fe, Zn, Y, Zr, Hf; Ca, B, P or combinations thereof. 
     
     
         16 . The inorganic fibres according to  claim 15 , wherein the sum of the other components comprise one or more oxides or fluorides of lanthanides, Sr, Ba, Cr, Zr or combinations thereof. 
     
     
         17 . The inorganic fibres according to  claim 15 , wherein the sum of the other components is in the range 0.1 to 0.8 wt %. 
     
     
         18 . The inorganic fibres according to  claim 1 , wherein the composition comprises:
 65.7 to 69.0 wt % SiO 2 ;   30.0 to 34.2 wt % CaO;   0.10 to 0.60 wt % MgO;   0 to 0.50 wt % Al 2 O 3 ; and   the sum of SiO 2  and CaO is greater or equal to 99.0 wt %.   
     
     
         19 . The inorganic fibres according to  claim 1 , wherein the composition comprises:
 65.7 to 69.0 wt % SiO 2 ;   30.0 to 34.2 wt % CaO;   0.10 to 0.45 wt % MgO;   0 to 0.40 wt % Al 2 O 3 ; and   
       the sum of SiO 2  and CaO is greater or equal to 99.2 wt %. 
     
     
         20 . The inorganic fibres according to  claim 1 , wherein the other components comprise 0 to 0.25 wt % alkali metal oxides. 
     
     
         21 . The inorganic fibres according to  claim 1 , wherein the other components comprise 0 to 0.20 wt % alkali metal oxides. 
     
     
         22 . The inorganic fibres according to  claim 1 , wherein the arithmetic mean fibre diameter is less than 6.0 μm. 
     
     
         23 . A thermal insulation comprising inorganic fibres as claimed in  claim 1 . 
     
     
         24 . The thermal insulation according to  claim 23  in the form of a blanket of the inorganic fibres.