Corrosion-inhibiting thermal insulation for stainless steel

Claim 2

A stress-corrosion-inhibiting molded thermal insulation for austenitic stainless steel, consisting of from about 65 to about 70 percent by weight of cellular expanded perlite having a bulk density in the range of about 2.0 to 2.5 lb./cu. ft., from about 8 to about 12 percent of sodium silicate having a molecular ratio of silica to sodium oxide of at least 3.6 to 1.0, frOm about 8 to about 12 percent of potassium silicate having a molecular ratio of silica to potassium oxide of at least 3.6 to 1.0, from about 4 to about 5 percent of sodium hexametaphosphate, from about 4 to about 5 percent of short asbestos fiber having a gradation conforming to Group 7 of the Canadian Standard Fiber Classification (Q.A.M.A.), and from about 3 to about 4 percent of a styrene-butadiene polymer latex as a plasticizer, said mixture of silicates and sodium hexametaphosphate being at least about 20 percent by weight of the total composition and constituting a composite binder for said expanded perlite to bond the particles and fibers into a monolithic molded mass, said thermal insulating material showing no significant change from mold dimensions, having a density in the range of 10 to 12 lb./cu. ft. and high-thermal-insulation efficiency in the temperature range from about 100* F. up to about 1,300* F., having high flexural strength both dry and wet, and being highly resistant to structural deterioration by boiling water.

Claim 3

A stress-corrosion-inhibiting molded thermal insulation for austenitic stainless steel consisting of about 67.8 percent by weight of finely divided, cellular, expanded perlite having a bulk density in the range of about 2.0 to 2.5 pounds per cubic foot, about 10.3 percent of sodium silicate binder having a silica/soda weight ratio of about 3.75 to 1.0, about 10.3 percent of potassium silicate binder having a silica/potash weight ratio of about 2.50 to 1.0, about 4.1 percent of sodium hexametaphosphate, about 4.4 percent of 7W Grade short amosite asbestos fiber, equivalent in gradation to Group 7 of the Candian Standard Fiber Classification (Q.A.M.A), and about 3,1 percent of a styrene-butadiene polymer latex as a plasticizer, said composition being bonded into a monolithic mass, said thermal insulation showing no significant change from mold dimensions, having a density of about 11.6 pounds per cubic foot, having high-thermal-insulating efficiency in the temperature range from about 100* F. up to about 1,300* F., having high flexural strength, both dry and wet, and being highly resistant to structural deterioration by boiling water.

Claim 4

A binder composition for a pressure-molded mass of finely divided, cellular, expanded perlite thermal insulating material, consisting of a major proportion of a mixture of sodium silicate and potassium silicate in water solution, and a lesser proportion of sodium hexametaphosphate dissolved in said silicate solution, said sodium hexametaphosphate being about 20 to about 40 percent by weight of the total silicates in said binder composition, said soluble silicates each having a molecular ratio of silica to alkaline oxide of at least 3.6 to 1.0, said potassium silicate being at least 40 percent by dry weight of the total silicate in the dried binder, said binder solution being of free flowing consistency and readily sprayable for application to said expanded perlite, and said binder composition being a corrosion inhibitor for austenitic stainless steel surfaces on which the perlite insulation bonded therewith is installed.

Claim 5

A binder composition for a pressure-molded mass of finely divided, cellular, expanded perlite thermal insulating material, consisting of a water solution of a mixture of sodium and potassium silicates, said silicates each having a molecular ratio of silica to alkaline oxide of at least 3.6 to 1.0, and sodium hexametaphosphate dissolved in said mixed silicate solution, said potassium silicate being in the range of about 40 to about 60 percent of the total weight of soluble silicates in the binder composition, said sodium hexametaphosphate being in a smaller proportion than the soluble silIcates, in the range of about 20 to 30 percent of the total weight of said silicates, said binder solution containing about 20 percent by weight of dissolved solids, said binder solution being of free flowing consistency and readily sprayable for application to said expanded perlite, and said binder composition being a corrosion inhibitor for austenitic stainless steel surfaces on which the perlite insulation bonded therewith is installed.

Claim 6

A binder composition for A pressure-molded mass of finely divided, cellular, expanded perlite thermal insulating material, consisting of a water solution of a mixture containing equal amounts by weight of sodium and potassium silicates, said sodium silicate having a silica/soda weight ratio of about 3.75 to 1.0, said potassium silicate having a silica/potash weight ratio of about 2.50 to 1.0, and sodium hexametaphosphate dissolved in said mixed silicate solution in a minor proportion of about 20 percent of the total dry weight of said silicates, said binder solution containing about 20 percent by weight of dissolved solids, said binder solution being of free flowing consistency and readily sprayable for application to said expanded perlite, and said binder composition being a corrosion inhibitor for austenitic stainless steel surfaces on which the perlite insulation bonded therewith is installed.

Claim 7

A molded thermal insulation according to claim 1, containing as mechanical reinforcement for the monolithic mass of expanded perlite and binder a minor proportion of a heat-resistant, inorganic fiber, selected from the class consisting of short asbestos fiber and chopped spun glass fiber roving.

Claim 8

A molded thermal insulation according to claim 8, in which said heat-resistant inorganic fiber consists of up to 6 percent by weight of short asbestos fiber having a gradation conforming to Group 7 of the Canadian Standard Fiber Classification (Q.A.M.A).

Claim 9

A molded thermal insulation according to claim 8, in which said heat-resistant inorganic fiber consists of up to 10 percent by weight of chopped spun glass roving of from one-eighth inch to 1 inch length.

Claim 10

A stress-corrosion-inhibiting molded thermal insulation for austenitic stainless steel, consisting of from about 60 to about 75 percent by weight of cellular expanded perlite having a bulk density in the range of about 1.8 to about 3.5 lb./cu. ft., from about 5 to about 15 percent by dry weight of sodium silicate having a molecular ratio of silica to sodium oxide of at least 3.6 to 1.0, from about 5 to about 15 percent by dry weight of potassium silicate having a molecular ratio of silica to potassium oxide of at least 3.6 to 1.0, from about 3 to about 8 percent of sodium hexametaphosphate, and up to 10 percent of chopped spun glass roving of 1/8 -inch to 1-inch length as a heat-resistant, inorganic fibrous reinforcement, said mixture of silicates and sodium hexametaphosphate constituting a composite binder for said expanded perlite to bond the particles and fibers into a monolithic molded mass, said molded thermal insulation showing no significant change from mold dimension, having low density and high-thermal-insulating efficiency in the temperature range from about 100* F. up to about 1,300* F., having high flexural strength both dry and wet, and being highly resistant to structural deterioration by boiling water.

Claim 11

A stress-corrosion-inhibiting molded thermal insulation for austenitic stainless steel, consisting of from about 65 to about 70 percent by weight of cellular expanded perlite, having a bulk density in the range of about 2.0 to 2.5 lb./cu. ft., from about 8 to about 12 percent of sodium silicate having a molecular ratio of silica to sodium oxide of at least 3.6 to 1.0, from about 8 to about 12 Percent of potassium silicate having a molecular ratio of silica to potassium oxide of at least 3.6 to 1.0, from about 4 to about 6 percent of sodium hexametaphosphate, and from about 4 to about 8 percent of chopped spun glass roving of 1/4 -inch to 1/2 -inch length as a heat-resistant, inorganic fibrous reinforcement, said mixture of silicates and sodium hexametaphosphate being at least about 20 percent by weight of the total composition and constituting a composite binder for said expanded perlite to bond the particles and fibers into a monolithic molded mass, said molded thermal insulation showing no significant change from mold dimensions, having a density in the range of 10 to 12 lb./cu. ft. and high thermal insulating efficiency in the temperature range from about 100* F. up to about 1,300* F., having high flexural strength both dry and wet, and being highly resistant to structural deterioration by boiling water.

Claim 12

A stress-corrosion-inhibiting molded thermal insulation for austenitic stainless steel consisting of about 67.5 percent by weight of finely divided, cellular, expanded perlite having a bulk density in the range of about 2.0 to 2.5 pounds per cubic foot, about 11.0 percent of sodium silicate binder having a silica/soda weight ratio of about 3.75 to 1.0, about 11.0 percent of potassium silicate binder having a silica/potash weight ratio of about 2.50 to 1.0, about 4.5 percent of sodium hexametaphosphate, about 4.0 percent of chopped spun glass roving of 1/2 -inch length and about 2.0 percent of chopped spun glass roving of 1/4 -inch length as heat-resistant, inorganic fibrous reinforcement, said composition being bonded into a monolithic mass by said composite silicate binder, said molded thermal insulation showing no significant change from mold dimensions, having a density of about 11.8 pounds per cubic foot, having high thermal insulating efficiency in the temperature range from about 100* F. up to about 1,300* F., having high flexural strength both dry and wet, and being highly resistant to structural deterioration by boiling water.