US1595052A - Process of deflocculating solids - Google Patents

Description

' relatively Patented Aug. 3, I926.

UNITED STATES GEORGE W. Ao'nEson, or GALDWEEE, NEW JERSEY.

PROCESS OF DEFLOCCULATING SOLIDS.

No Drawing.

This invention relates to the art of deflocculating solid bodies, and comprises a process whereby the defiocculation can be accomplished more readily, more rapidly and with greater yields than heretofore. The term deflocculation is used herein in its commonly accepted sense, as indicating the subdivision of solid bodies, such for instance as graphite, carbon black, clay, pigments, insecticides such as lead ars'enate, sulfur,

etc., etc. into particles of colloidal dimensions,

by a process of prolonged attrition in presence of moisture and of an organic deflocculating, agent, which ag nt has the general properties of tannin a tannin-like bodies. Among such deflocculating agents, as heretofore used in this art, I may mention tannin, cutch, and extracts from roasted cereals or starchy "bodies, usually employed in conjunction with ammonia. While all of these substances possess in common the property of deflocculating such solids as are mentioned above, they differ considerably among themselves, particularly with respect to rapidity of action and the stability of the resulting colloid. I

In the operation of deflocculating as ordinarily practiced, the deflocculating agent disappears, wholly or substantially, from the aqueousor ammoniacal solution, being absorbed by the particles of the solid. It is observed however that if an excess of deflocculating agent be used, or if the process of attrition be too prolonged, re-flocculation sets in, the previously deflocculated or colloidal particles're-uniting into aggregates which are-no longer of colloidal dimensions and subside when suspended in-water. Heretofore it has been universal practice to avoid carefully such conditions as lead toreflocculation in the mill such re-flocculation involving a limitation upon or even a reduction of the obtainable yield of particlesof colloid dimensions;- the result being, in the case of graphite for example, that only a small proportion [of the total charge can be defioccula'ted in a single operation. In a typical case the proportion of aphite' defiocculated or converted into the colloidal state in course of a single through the 'mill is of the order 0 six oreight percent. This percentage difiers of course. with difierent materials subjected to the operation, and also with the particular deflocculating agent used. ,1

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first stage, I prefer to assag'e' Application filed. March 8, 1926. Serial No. 93,323.

According to my improved process in its preferred embodiment, I first add to the solid to be deflocculated, for example graphits in the form of a heavy paste, a relatively smallproportlon, say six ercent by weight,

of one of the known de occulating agents,

for example tannin, referably together with a small amount 0 aqueous ammonia; and I sub ect the paste to attrition under the usual conditions until the deflocculating agent has been substantially adsorbed. I then repeat this operation, adding new por tions of'the deflocculating agent, a number of times, depending on the results sought; but always ultimately introducing suflicient deflocculatlng agent so that a thorough mixing operation, following the final addition of agent, will bring about the re-flocculation of most or all of the initially deflocculated solid. In a typical instance, where the material to be deflocculated was electric furnace graphlte, and the deflocculating agent used was tannin, the total amount of agent added amounted to about eighteen percent of the dry weight of the graphite.

At this stage a substantial proportion, in some cases upward of 80%, of the initial charge has passed through the deflocculated stage but had undergone re-flocculation. ThlS however does not mean that the original physical-condition of the solid has been restored; for the re-flocculated aggregates, being assemblies of particles which have once passed through the colloidal state, are extremely fragile, although. not capable of belng resolved again into their colloidal components by simple stirring.

I have discovered however that these re-' flocculated aggregates may be resolved again into their component particles of colloid dimensions by treating them with certain deflocculating or peptizing agents other than those used in Among such a ti'zing agents in order to distinguish them from the deflocculating agents used in the use infusions of grasses (Gramineae) such as hay, straw and the like; although .I may use other vege table infusions capable of the same peptizing efiect; or inorganic peptizing agents such as sodium silicate may be used. This peptization may be carried out in the same or other mill, and under essentially'the same conditions as the initial deflocculating treatment. The result of this treatment, involvfiocculating-agent; and thereafter peptizing ing an initial deflocculation carrried through the re-flocculated' aggregates. 1 to partial or complete re-flocculation, and 2. Process of treating solid bodies to prefollowed by peptization of the re-fiocculated pare particles of colloidal dimensions, comaggregates, is greatly to increase the ultimate prising deflocculating and re-fiocculating the yield of'colloid, as Well as to increase the said solid by attrition with an organic dcrate at which it is prepared from the iniflocculating agent; and thereafter peptiz- 20 tial raw material. I ing the re-flocculated aggregates by means I claim; I of an infusion of a grass.

1. Process of treating solid bodies to pre- In testimony whereof, I affix my signapare particlesof colloidal dimensions, comll prising deflocculating and re-flocculating the said solid by attrition with an organic de-' GEORGE W. ACHESON.