| 摘要 |
Molded thermal insulation material for use in contact with austenitic stainless steel chemical-processing equipment, to inhibit stress corrosion cracking thereof, consists of at least 60 percent by weight of cellular expanded perlite, bonded by a dried, inorganic, water soluble binder. The binder consists of a major proportion of a mixture of sodium silicate and potassium silicate and a minor proportion of sodium hexametaphosphate, and the molecular ratio of the silica to the alkaline oxide is at least 3.6 to 1.0. The potassium silicate consists of at least about 40 percent, by dry weight, of the total silicate in the dried binder, and the total binder constitutes at least about 20 percent, by weight, of the total insulation composition. In the manufacture of the molded insulation, the mixture of perlite and the binder, in slightly damp condition, is placed in the mold cavity and subjected to light molding pressure, sufficient to compact the material into the exact configuration of the mold cavity without expelling water from the mixture. The molded insulation is removed from the mold and oven dried at a temperature of about 250 DEG F.
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