The Dow Chemical Company

Donald W Calvin

Joel F Leathers

Harry S Burney

Robert M Harnden

Used or contaminated pieces of fluoropolymer membrane or sheet materials are salvaged for re-use by particulating the materials into powders, granules, or fibers, or otherwise reforming it, treating the particulated material, as desired, to cleanse or modify the material, and utilizing the material in subsequent applications.

Re-use of fluoropolymer membranes

A method of recovering fumed hydrophobic SiO.sub.2, produced by the flame hydrolysis of a ternary azeotrope of H.sub.2 SiF.sub.6, HF, and H.sub.2 O, is disclosed. The method involves passing the fumed hydrophobic silica, as it leaves the combustion chamber, through a nonclassifying agglomerator at a residence (travel) time of from about 0.5 to several seconds, preferably about 1.0 to about 5.0 seconds, then separating the fumed silica from the product stream in a cyclone separator or other means for collecting dispersoids.

Recovery of fumed SiO.sub.2

The present invention provides a selective process for the manufacture of diethylenetriamine from ethylenediamine, ethanolamine, and urea. The process comprises a reaction cycle in which ethylenediamine, ethanolamine, and urea are first reacted in step (a) to form aminoethylethyleneurea and ethyleneurea, which in turn are hydrolyzed in a second reaction step (b) to diethylenetriamine and ethylenediamine. The ethylenediamine made in the second reaction step (b) may be recycled to the first reaction step (a).

Process for the manufacture of diethylenetriamine

Hydrophobic silica, containing sorbed HF values, is used to remove oil from water by sorption of the oil onto the silica and then separating the oil/silica mixture from the water. Furthermore, the present invention pertains to recovering the silica from the oil by aqueous treatment in such a manner that the hydrophobicity of the silica is overcome and the silica becomes hydrophilic, thereby releasing the oil.

Removing oil from water

Fluorosilicic acid solutions, which normally undergo decomposition when distilled, thereby creating unwanted forms of SiO.sub.2, are rendered stable during distillation by providing in the fluorosilicic acid solution an amount of HF which is at least about 10 parts of HF per 36 parts of H.sub.2 SiF.sub.6 and an amount of H.sub.2 O which is at least about 54 parts of H.sub.2 O per 36 parts of H.sub.2 SiF.sub.6. The mixture is distilled to remove any excess H.sub.2 O and excess HF that is present, without encountering formation of SiO.sub.2, until an azeotropic solution containing about 36% H.sub.2 SiF.sub.6, about 10% HF and about 54% H.sub.2 O is reached. The ternary azeotrope, being of constant quality and concentration, is more suitable for use in various processes, such as processes for making fumed SiO.sub.2, than H.sub.2 SiF.sub.6 solutions which are not of constant quality or concentration.

Method of preparing fumed SiO.sub.2

Amorphous silica is rendered hydrophobic by treating the silica with hydrogen fluoride vapors. The hydrophobic silica thus produced is useful in applications wherein either the sorbed fluoride values are desired or else the hydrophobic properties are desired. The hydrophobic properties are overcome by extended contact with water and the silica then becomes hydrophilic.

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Zachary, LA, United States of America

Donald W Calvin