Compositions – Preservative agents – Anti-caking – separative or protective coatings or zones
Reexamination Certificate
2000-09-29
2002-05-28
Anthony, Joseph D. (Department: 1714)
Compositions
Preservative agents
Anti-caking, separative or protective coatings or zones
C252S384000, C252S385000
Reexamination Certificate
active
06395198
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to compositions that can be applied onto granules of inorganic salts, particularly granules of sodium chloride, to reduce the tendency to cake on storage and to minimize fugitive dust.
2. Related Prior Art
Many hard crystalline materials, particularly inorganic salts and mineral ores, tend to contain fines or to be friable and form fines, and these fines can be a nuisance. Also, these materials tend to harden and form large, agglomerated masses upon exposure to moisture in humid environments, particularly during long periods of storage. These hardened masses are generally referred to as cakes. Some cake formations become very rigid and resistant to separation, making the material very difficult to transport and to break apart so as to facilitate its use in particular applications. In certain situations where an enormous amount of a material has formed as a solid cake, explosives may be necessary to separate the cake into particulate matter.
It is desirable to provide an anticaking agent, in either solid or liquid form, that will be effective when applied to salts in a small amount to minimize dusting and to reduce the caking tendencies for extended periods of time so that the coarse granular crystalline materials will remain easily movable, despite long term storage, and ready for use by the consumer.
Economization and automation of industrial processes for inorganic salts require the salt to be in a granular form so that it can flow freely during subsequent processing steps. In emptying storage silos containing tons of inorganic salt, for example, there is increased operational expense and potential danger on account of the tendency of the salt to cake. The salt cakes must be disintegrated by a mechanical auxiliary apparatus in order to be emptied or loaded from the silos. Additionally, during commercial use of the salt, any step of dosing or mixing agglomerated or caked salt together with other substances is difficult due to the extent of the caking.
Many attempts have been made to find ways and means to reduce or entirely eliminate the tendency of inorganic salts to harden. One of the best known processes consists of dry mixing with such salts finely divided fillers, such as silica, alkali, alkaline earth and aluminum silicates, aluminum oxide, magnesium oxide, calcium oxide or alkaline earth carbonate. These additives form a loose jacket around the individual salt crystals or granulates that in the recrystallization of the salt prevent a formation of bridges between the individual particles and therefore the potential for caking. The disadvantage of these additives is that they must be used in relatively large amounts in order to produce a suitable anticaking effect. Through the use of large amounts of these additives the products tend to lose most of their clear solubility in water.
Organic additives such as oils, glycerine, paraffins, paraffin oils, alkyl sulfonates or fatty amines, are also effective in the prevention of anticaking in organic salts. However, these additives for the most part are disadvantageous in that they can only be placed on the salt at great industrial expense. For example, a dosing of a hot salt, as it comes out of production, by means of cocofatty amines is practically impossible because of the odor troubles and danger to health associated therewith. The amines cannot be added during the salt production step, but rather must be added in an additional step after the salt cools. In the interim storage of the salt there is no protection against the possibility of caking.
It has long been known that the hardening of alkali chlorides can be reduced by an addition of complex ferrocyanides. These products are expensive and are typically utilized in large amounts based upon the total amount of alkali chloride product being treated. Additionally, the use of ferrocyanides is of some concern due to its potential toxic effect to the environment, e.g. in road salt applications where run-off of treated road salts may wind up in lakes and streams.
It is the object of the present invention to provide an effective anticaking and antidusting agent for inorganic salts that is environmentally safe and contains only metals such as alkali metal or alkaline earth metals.
It is a further object of the present invention to provide an anticaking and antidusting agent that is highly effective when added in relatively low dosage amounts to inorganic salts in either a powder form or a liquid spray form.
It is yet another object of the invention to provide a modified inorganic salt product containing the anticaking and antidusting agent that is resistant to caking when exposed to high humidity and other moisture conditions.
SUMMARY OF THE INVENTION
The aforementioned objects are accomplished by providing an agglomeration preventing or anticaking agent for inorganic salts, as well as a process for the production of such agent, wherein the agent comprises a protein, a saccharide, an alkali metal or alkaline earth metal salt and an acid. The anticaking agent of the invention is especially suited for the prevention of caking together and for preserving the flowability of salts, specifically alkali chlorides, e.g. sodium chloride or potassium chloride, and alkali chloride containing salt mixtures. The protein in the agent is preferably a prolamine, most preferably zein. The saccharide is preferably a polysaccharide, most preferably a guar gum. The salt is preferably sodium chloride, most preferably sodium chloride with trace amounts of magnesium chloride and calcium chloride. The acid in the agent is preferably an organic acid, and most preferably at least one of citric acid and ascorbic acid. In a most preferred embodiment of the invention, the anticaking agent composition comprises predominantly guar gum with small amounts of the prolamine, salt and acid.
The present invention also relates to a method of making the anticaking agent, comprising mixing a protein, a saccharide and a salt in an aqueous organic solvent that contains an acid until a complex is formed. The resultant complex is then separated from the solvent and dried so as to form the anticaking agent of the invention.
The present invention further relates to methods for applying an effective amount of the anticaking agent to an inorganic salt to prevent the modified salt mixture from caking, wherein the application of the anticaking agent to the inorganic salt can be in a solid or liquid form. A modified salt product that contains an effective mixture of the anticaking agent is also encompassed by the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In accordance with the present invention, an agglomeration preventing or anticaking agent comprises a complex of a protein, a saccharide, preferably a polysaccharide, an alkali metal or alkaline earth metal salt and an acid, preferably an organic acid. The components of the complex are preferably not toxic and are environmentally friendly, unlike some of the other commercially available anticaking agents (e.g. ferrocyanide compositions).
The anticaking agents are also useful in the prevention of dust formation in normally dusty solid materials, namely particulate organic and inorganic material such as wheat, coal fines and the like. It is noted that the agent compositions disclosed in the invention for use as anticaking agents may be applied in the same manner and proportions to various materials to prevent the formation of dust at the surface of those materials.
The anticaking agent compositions of this invention may be employed by spraying the agent in liquid form onto coarse granules of salts, particularly sodium chloride or dietetic salt. The typical coarse granules are usually in the range of 1 to 5 millimeters in diameter, usually from 2 to 3 millimeters. The anticaking agents may also be employed by dry blending the agent in powder form into the salt compositions or dissolution into a salt brine prior followed by crystallization of the modified salt from solution.
Protein and polysacch
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