Granular Fibre-Free Microporous Thermal Insulation Material and Method

Abstract

A granular fibre-free microporous thermal insulation material, having a thermal conductivity less than 0.05 W/mK and a shrinkage of not more than 10%, which is free flowing and consists of granules of an intimate mixture of: 30-95% dry weight microporous insulating material; 5-70% dry weight infrared opacifier material; 0-50% particulate insulating filler material; and 0-5% binder material. The material is made by mixing together the microporous insulating material and the infrared opacifier material to form an intimate aerated mixture with a first density; conveying the intimate mixture at a first volumetric flow rate to an extrusion means ( 5 ); extruding the intimate mixture as a compressed material with a second density greater than the first density at a second volumetric flow rate lower than the first volumetric flow rate; venting a proportion of air from the aerated intimate mixture through a porous membrane to relieve pressure generated within the intimate mixture due to the change from the first volumetric flow rate to the second volumetric flow rate; and granulating the compressed material.

1 . A granular fibre-free microporous thermal insulation material, having a thermal conductivity less than 0.05 W/mK, when measured at a mean temperature of 400 degrees Celsius and at the tap density of the material, and a shrinkage of not more than 10%, which is free flowing and consists of granules formed from an intimate mixture of:
 30-95% dry weight microporous insulating material;   5-70% dry weight infrared opacifier material;   0-50% particulate insulating filler material; and   0-5% binder material.   
     
     
         2 . A thermal insulation material as claimed in  claim 1 , wherein the thermal insulation material has substantially the following composition:
 40-85% dry weight microporous insulating material;   15-60% dry weight infrared opacifier material;   0-50% particulate insulating filler material; and 0-5% binder material.   
     
     
         3 . A thermal insulation material as claimed in  claim 1 , wherein a granule size of the granular fibre-free microporous thermal insulation material is in a range from 0.25 mm to 2.5 mm. 
     
     
         4 . A thermal insulation material as claimed in  claim 1 , wherein a bulk density of the granular fibre-free microporous thermal insulation material is in a range from 180 to 350 kg/m 3 . 
     
     
         5 . A thermal insulation material as claimed in  claim 1 , wherein the tap density of the granular fibre-free microporous thermal insulation material is in a range from 250 to 450 kg/m 3 . 
     
     
         6 . A thermal insulation material as claimed in  claim 1 , wherein the opacifier material is selected from titanium dioxide, iron titanium oxide, zirconium silicate, zirconium oxide, iron oxide, silicon carbide, and mixtures thereof. 
     
     
         7 . A thermal insulation material as claimed in  claim 1 , wherein the microporous insulating material comprises silica. 
     
     
         8 .- 12 . (canceled) 
     
     
         13 . A thermal insulation material as claimed in  claim 1 , wherein the particulate insulating filler material is selected from vermiculite, perlite, flyash, volatilised silica, and mixtures thereof. 
     
     
         14 . A thermal insulation material as claimed in  claim 1 , wherein the binder comprises an organic binder. 
     
     
         15 . A thermal insulation material as claimed in  claim 14 , wherein the organic binder comprises polyvinylalcohol. 
     
     
         16 . A thermal insulation material as claimed in  claim 1 , wherein the binder comprises an inorganic binder. 
     
     
         17 . A thermal insulation material as claimed in  claim 16 , wherein the inorganic binder is selected from sodium silicate, potassium silicate, aluminium orthophosphate, and mixtures thereof. 
     
     
         18 . A method of manufacturing a granular fibre-free microporous thermal insulation material, having a thermal conductivity of less than 0.05 W/mK, when measured at a mean temperature of 400 degrees Celsius and at the tap density of the material, and a shrinkage of not more than 10%, which is free flowing and consists of granules formed from a mixture of 30-95% dry weight microporous insulating material, 5-70% dry weight infrared opacifier material, 0-50% particulate insulating filler material, and 0-5% binder material comprising the steps of:
 mixing together the microporous insulating material and the infrared opacifier material to form an intimate aerated mixture with a first density;   conveying the intimate mixture at a first volumetric flow rate to an extrusion means ( 5 );   extruding the intimate mixture as a compressed material with a second density greater than the first density at a second volumetric flow rate lower than the first volumetric flow rate;   venting a proportion of air from the aerated intimate mixture through a porous membrane to relieve pressure generated within the intimate mixture due to the change from the first volumetric flow rate to the second volumetric flow rate; and   granulating the compressed material.   
     
     
         19 . A method according to  claim 18 , wherein the first volumetric flow rate is in a range from 2.0 to 4.5 times the second volumetric flow rate. 
     
     
         20 . A method according to  claim 18 , wherein the first volumetric flow rate is in a range from 100 to 300 litres/hour. 
     
     
         21 . (canceled) 
     
     
         22 . A method according to  claim 18 , wherein the second volumetric flow rate is in a range from 20 to 90 litres/hour. 
     
     
         23 . (canceled) 
     
     
         24 . A method according to  claim 18 , wherein the method includes the step of conveying the intimate mixture to the extrusion means ( 5 ) by means of a screw conveyor ( 7 ). 
     
     
         25 . A method according to  claim 18 , wherein the method includes the step of extruding the intimate aerated mixture by at least one roller ( 5 ). 
     
     
         26 . A method according to  claim 25 , wherein the intimate aerated mixture is extruded by a pair of opposing rollers ( 5 ). 
     
     
         27 . A method according to  claim 18 , wherein a pressure in a range from 2.5 to 20 bar is exerted to extrude the intimate aerated mixture. 
     
     
         28 . (canceled) 
     
     
         29 . A method according to  claim 18 , wherein the porous membrane is metallic and has pores with nominal diameters in a range from 5 to 50 microns. 
     
     
         30 . (canceled) 
     
     
         31 . A method according to  claim 18 , wherein the compressed material is in the form of a sheet of compressed material. 
     
     
         32 . A method according to  claim 18  and including the step of breaking up the compressed material into smaller pieces prior to granulation. 
     
     
         33 . A method according to  claim 32 , wherein the compressed material is broken up by rotary chopping. 
     
     
         34 . A method according to  18 , wherein granulation of the compressed material includes the step of forcing material through apertures in a mesh ( 19 ) using a rotor ( 9 ). 
     
     
         35 .- 51 . (canceled)