Insulation board

Claim 1

AS A NEW ARTICLE OF MANUFACTURE, A LIGHT WEIGHT, HARD AND STRONG HEAT-INSULATING SHEET MATERIAL COMPOSED ESSENTIALLY OF CHRYSOTILE ASBESTOS FIBRES, WHOSE CHARACTERISTICS ARE SUCH THAT WHEN GRADING NOT HIGHER THAN 2-8-4-2 AS DETERMINED ON THE QUEBEC STANDARD ASBESTOS TESTING MACHINE, HAVE A MINIMUM WET VOLUME VALUE OF 40 CUBIC INCHES PER POUND OF FIBRE, AND A HYDRAULIC BINDER SELECTED FROM THE GROUP CONSISTING OF THE PRODUCT RESULTING FROM THE RACTION IN ADMIXTURE WITH MOISTURE OF HYDRATED LIME AND FINELY DIVIDED SILICA SUBSTANTIALLY IN STOICHIOMETRIC PROPORTIONS, THE PRODUCT RESULTING FROM THE REACTION TION IN ADMIXTURE WITH MOISTURE OF PORTLAND CEMENT AND FINELY DIVIDED SILICA, SUBSTANTIALLY IN THE PROPORTIONS OF TWO PARTS OF PORTLAND CEMENT TO ONE PART OF SILICA, AND MIXTURE THEREOF, SAID FIBRES CONSTITUTING FROM 35 PER CENT TO 65 PER CENT OF THE DRY WEIGHT OF THE FINISHED MATERIAL, AND SAID MATERIAL HAVING A DENSITY OF LESS THAN 45 POUNDS PER CUBIC FOOT, A MODULUS OF RUPTURE SUBSTANTIALLY IN EXCESS OF 1200 POUNDS PER SQUARE INCH, AND THERMA, CONDUCTIVITY OF LESS THAN ONE WHEN MEASURED AT A MEAN TEMPERATURE OF 100 DEGREES FAHRENHEIT.