US 3402065 A
Description (OCR text may contain errors)
3,402,065 PHENYLOXYALKANOL COATING F PARTICLE Louis McDonald, Inyokern, and Norman A. MacLeod, Altadena, Calif., assignors to the United States of America as represented by the United States Atomic Energy Commission No Drawing. Filed Jan. 23, 1950, Ser. No. 140,148
12 Claims. (Cl. 117-100) This invention relates to surface conditioning materials and more particularly to a method of treatment of inv fusible pulverized mixtures. Specifically, this invention relates to a method and agents for protectively preparing the surfaces of pulverized materials so as to facilitate their ready incorporation into slurries which may be molded or cast into shaped articles.
The addition of an inert material to explosive compositions has been found useful as a means of regulating the rate and brisance of a detonation. The normal method of incorporating the inert material into the explosive com position is to add it in a finely-divided state to a melt or a solution of the explosive material to form a slurry having the desired proportions of the suspended inert component for the particular purposes at hand.
Furthermore, it is well known that detonation velocities, blast characteristics and brisance of cast or molded charges are significantly affected by the chemical composition and mass and degree of subdivision of the suspended inert component of explosive slurry which is utilized in the preparation of the explosive charge.
It has been further established that the suspended inert material must be introduced in a finely-divided state and preferably should be dispersed as thoroughly as possible throughout the fusible component to produce on cooling a solidified charge having a minimum porosity and a maximum uniformity of compositions. Such a composition is desirable only if there is no separation of the suspended component from the fusible component during the cycles of mixing, molding or casting the slurry into desired shapes.
Also, it has been determined that the presence of rather small amounts of moisture in a slurry may have extremely deleterious effects on the processing of many explosive compositions. Moisture present in the components of the explosive mixture may result in such increased viscosities in a slurry that it is difficult to insure proper mixing of the slurry and satisfactory molding into the desired dimension and mass. In every case, erratic results are obtained from the detonation of explosive castings which are cracked, chipped or which lack uniformity of composition.
This invention provides a method and agents to overcome this last mentioned difiiculty and will be disclosed in more detail following a delineation of the objects of this invention.
It is a primary object of this invention to provide a method for protectively preparing the surface of comminuted explosive components so as to facilitate their ready incorporation into a slurry.
It is an object of this invention to provide a method for protectively preparing newly-developed surfaces of comminuted materials against the adsorption of contaminants until said pulverized materials are incorporated into a slurry.
It is another object of this invention to provide a method for deposing surface conditioning agents on to newlycreated surfaces of finely-divided infusible materials.
It is another object of this invention to provide a class of compounds which are set forth as successful surface conditioning agents.
It is still another object of this invention to provide a nited States Patent Olfice 3,402,065 Patented Sept. 17, 1968 preferred class of compounds which have proven especially suitable as surface conditioning agents.
Still other objects will become apparent from the description and examples which follow.
The successful preparation of slurries containing dispersed solids is dependent, in part, upon the surface characteristics of the suspended particles, and upon such factors as the quantity of the solid or infusible component, the degree of subdivision and the completeness of dispersing the infusible component throughout the fusible explosive component. Maximum uniformity of slurry composition is obtained by introducing the solid component in a finely-divided form and dispersing it as thoroughly as possible in the fusible vehicle.
The specific surface of any solid comminuted component increases as the mean diameters of the particles comprising this component decrease. When powders of high specific surfaces are dispersed in fusible vehicles the viscosities of the resulting slurries increase rapidly as the proportion of the suspended solid component is increased. A concentration is readily obtained which results in the slurry becoming so viscous, immobile and plastic that it can be neither mixed, molded nor transferred to molds for shaping in articles of the desired dimensions and mass. By the addition of small amounts of dispersing agents, phase boundary lubricants, or other conditioning agents, such as nitrocellulose, benzocellulose and the like, it is possible to greatly increase the concentration of suspended solids in a specific slurry without significant effect on the chemical and physical properties of the product resulting therefrom. Thus the proper use of surface conditioning agents and/or phase boundary lubricants make possible the processing of slurries containing high concentrations of suspended pulverized materials of high specific surface which show maximum uniformity of composition and little or no tendency to segregate during the molding or mixing cycles.
In the preparation of comminuted materials, new surfaces are created on the cleavage planes of the crystals which have a particular avidity for moisture and other contaminants. This is especial-1y true when the non-fusible components is ground into finely comminuted particles of high specific surface before their incorporation in the fusible vehicle. Moisture present in the atmosphere or in other components of the mixture is most readily absorbed on the newly created surface planes of the crystals in the form of monomolecular or polymolecular layers. Such adsorption, even in minute quantities may have exteremely adverse effects on the resulting cast or molded product.
As the energy of desorption of moisture to ionic and other crystal surfaces is greater than the energy of adsorption of usable phase lubricants or dispersing agents, the types of surface active materials heretofore employed cannot function in the desired manner when even monomolecular layers of water are absorbed on the surface of the particles to be dispersed. Consequently, it is extremely difiicult to process some slurries containing high proportions of high specific surface particles when moisture in amounts of the order of 0.02 percent or more is present.
It has been found that certain materials which desirably function as conditioning agents and/or surface pro tective agents can be deposited in the vapor phase or liquid phase, either alone or mixed with a suitable inert diluent, as a vehicle, on the newly created surface of ionic, covalent, or molecular crystals at the time of their formation by plane cleavage or other means. As the deposed protection agents exhibit a high energy of adsorption to the noted classes of materials, preferential desorption and replacement by water molecules is not readily achieved. Thus it is seen that advantage is taken of the avidity of such newly developed surfaces before said surfaces can be contaminated by water or other contaminants.
Agents which can be employed to effectively eliminate water contamination and maintain protective coatings on the newly created surfaces of pulverized materials are composed of dipole molecules, i.e., one terminal group capable of adsorbing with high energy of adhesion to the surface of the suspended infusible component and other molecular groupings capable of orienting the molecule to the fusible component.
Compounds of the general formula have been founnd to be effective. R is an alkyl group or hydrogen atom, R is substituted or unsubstituted aryl or polyaryl nucleus. is an oxygen, nitrogen, sulphur, or phosphorous atom, R is an alkylene group of from 2 to 18 carbon atoms and X is a polar group, such as hydroxy, halide, nitrate, sulfonate, sulfate or phosphate radical.
Of the preferred components, the phenyloxy alkanols have been found to be particularly suitable. The phenyloxy alkanols which are preferable having boiling points in the range of 100 C. to 300 C. at a pressure of millimeters of mercury, molecular weights in the range of 124 to 400 and fire points above 100 C. In addition, these compounds are readily soluble in organic solvents such as carbon tetrachloride, naptha, acetone, ethanol and other alcohols, while at the same time difiicultly soluble in 'water.
Examples of aryl oxyalkanols which may effectively be employed to coat ionic, valence and other types of solids are tabulated hereinbelow:
Phenyloxyoctanol Several methods of deposing surface conditioning agents on to newly created surfaces of infusible components have been divided. One effective method is to add the conditioning agent to a volatile solvent, which, after deposition of the agent, may be readily removed by evaporation.
This invention discloses other methods for efficaciously deposing the surface active agent on to the newly formed surfaces. For example, the agent may be vaporized at atmospheric pressure and allowed to condense on to the freshly ground infusible component contained in an adsorption train. The vaporization may be produced by an external source of heat or, by the heat resulting from the mechanical work done in grinding. For example, by the proper selection of a surface active agent having a sufficiently low temperature of vaporization, the agent may be combined with the unground material, and, during the process of grinding, is then deposited on to the surfaces of the freshly pulverized material, simultaneously with the formation of said surfaces.
Other methods of coating newly formed surfaces have been developed, such as passing high boiling phenyloxyalkanols'over the newly formed surfaces by means of an inert vehicle such as helium or nitrogen at an elevated temperature. Crystal particles treated in this manner are effectively coated against the adsorption of moisture and other contamination and the protected pulverized material can be readily processed into products utilizing powdered infusible materials or safely stored for future use.
The following examples will serve to illustrate with greater clarity the facility of the methods of this invention.
EXAMPLE I Two kilograms of pulverized barium nitrate are dried in an oven at C. for three hours. While still hot, the material is transferred to a distillation receiver which is then connected toa vaporizer containing phenyloxyethanol. The system is evacuated to about 10 mm. mercury absolute pressure and the phenyloxyethanol is heated to about C. The phenyloxyethanol vapor flows into the distillation receiver containing the pulverized barium nitrate and condenses on the dehydrated, cooler surfaces of the barium nitrate, forming an impervious, protective layer on same.
Another successful method of preparing moisture-avid surfaces of pulverized materials can be had by vaporizing an agent of the desired material into a mill or grinder with the material to be pulverized whereby the vapor condenses on the new surfaces of the pulverulent as they are created by the pulverizing action of the mill.
EXAMPLE II Five kilograms of dry calcium nitrate are placed in a ball mill fitted with a connection on the upper portion for the admittance of a gas. 250 milliliters of phenyloxyisopropanol are heated in a flask which is connected by means of a flexible tubing to the connection of the grinder. The mill is placed in operation at the time the phenyloxyisopropanol is volatized and the vapor replaces the air within the grinder immediately thereafter. As new surfaces are created by the grinding process the phenyloxyisopropanol vapor coats the new surfaces formed, effectively preventing the adsorption of moisture by said surfaces. In this manner it is virtually impossible for the finely-divided inert material to adsorb moisture or other contaminants before they are protectively coated with the organic material.
Still another technique applicable to the coating of new surfaces created by comminution is to disperse the conditioning agent or protective coating material in the unground inert material. Transient local temperatures in grinding may reach as high as 175 C. which is sufficient to cause substantial vapor pressure of the agent, or complete vaporization if the agent is selected with a sufficiently low boiling point. The following example illustrates the preferred method in which p-methylphenyloxyethanol is selected as the surface conditioning agent.
EXAMPLE III 1.5 kilogram of ammonium nitrate crystals previously dried for one hour at 105 C. are placed in a ball mill. 25 grams of p-methylphenyloxyethanol are added to the inert material, the mill is closed and rotated at r.p.m. until the unground material is completely pulverized. Heat produced by the grinding process combined with agitation effects substantial vaporization of the p-methylphenyloxyethanol and thus effectively coats all of the newly formed surfaces of the finely comminuted material.
While phenyloxyalkanols may be protectively coated onto pulverized solids in a mill or grinder by directly passing the oxyalkanol into the mill, they may be diluted and vaporized in a stream of hot, inert gas as described in the following example.
EXAMPLE IV Three kilograms of dry barium nitrate crystals are placed in a suitable enclosed grinder equipped with a gas admittance connection. Terbutylphenyloxyethanol vapor is admixed with nitrogen at a temperature of about 250 C. and admitted into the grinder to replace the normal atmosphere therein. The grinder is placed in operation and the ter-butylphenyloxyethanol-nitrogen gas mixture is permitted to flow into the grinder. Newly created surfaces of barium nitrate are thus effectively coated almost simultaneously with their formation with a thin film of ter-butyloxyethanol and protected from the influence of moisture in the air. The inert nitrogen is then flushed out with air leaving the protectively coated crystal surfaces free of moisture and other contaminants.
It is thus seen that many advantages of the method of the present invention are possible. The conditioning agents disclosed hereinbefore can be readily deposed in the most mobile phase, that is, the vapor phase, at the time of the formation of newly created surfaces.
The introduction of the surface conditioning or protective coating agents in the gaseous phase for adsorption on the surface of newly comminuted materials can be performed with standard laboratory equipment.
By prior coating of the adsorption-avid new surfaces, the method greatly retards their subsequent contamination by air, water or other undesirable components, and substantially eliminates the nuisance usually associated with the adsorption of said contaminants by freshly comminuted materials. The method therefore lends itself to wide and diverse applications for the control of surface characteristics of finely ground materials such as pigments, metallic powders, dusting materials and the like. Slight excesses of conditioning agents are not harmful in most applications of the method. Ionic, valence and other crystals treated in the manner disclosed hereinbefore are thus protectively coated against moisture adsorption and can readily be dispersed in any explosive component for the formation of moldable and castable explosive charges useful in sundry ordnance materials.
While many embodiments of the methods and compositions of matter are possible, it is to be understood that the present invention is not limited except as indicated in the appended claims.
What is claimed is:
1. A method of coating comminuted materials with a surface protective agent which comprises contacting .a finely ground solid material with an aryloxy alkanol having a boiling point substantially below the melting point of the comminuted material.
2. A method of coating newly comminuted materials with a surface protective agent which comprsies contacting a newly comminuted material with a liquid phenyloxyalkanol.
3. A method of coating freshly pulverized particles by deposition of surface protective agents thereon which comprises contacting a freshly ground solid material with a substituted aryloxy alkanol having a mm. mercury boiling point of at least 100 C.
4. A method of coating newly formed pulverized particles of deposition of surface protective agents thereon which comprises contacting a freshly ground solid material with the vapor of any aryloxyalkanol having a molecular weight of at least 124 and not in excess of 400.
5. A method of protectively coating freshly comminuted surfaces of moisture-avid materials which comprises volatilizing a protective substituted oxyalkanol in the presence of the freshly comminuted material.
6. A method of protectively coating the surfaces of newly comminuted, moisture-avid materials against the adsorption of moisture which comprises contacting a newly comminuted material with the vapor of phenyloxyalkanols having a molecular weight of at least 124.
7. A method of protectively coating the surfaces of newly comminuted materials which comprises mixing a low boiling phenyloxyalkanol with the unground material, comminuting the unground material to a finely-divided state whereby the phenyloxyalkanol is vaporized by the heat produced by comminution and is intimately dispensed throughout the comminuted material.
8. A method of protectively coating the surfaces of newly comminuted moisture-avid materials against the adsorption of moisture which comprises contacting the surface of a newly comminuted material with the vapor of a phenyloxyalkanol having a molecular weight of at least 124, said protective coating vapor being in contact with said surfaces of the newly comminuted material at the instant of formation of said surfaces of said newly comminuted material.
9. A method of protectively coating the surfaces of newly comminuted, moisture-avid materials against the adsorption of moisture which comprises contacting the surfaces of a newly comminuted material with a gaseous mixture comprising ,an inert gas and the vapor of a phenyloxyalkanol having a molecular weight of at least 124, said gaseous mixture elevated to a temperature sufficiently above the melting point of said phenyloxyalkanol at the instant of contact of said phenyloxyalkanols with said surfaces of the newly comminuted material.
10. A method of protectively coating the surfaces of newly comminuted, moisture-avid materials against the adsorption of moisture which comprises contacting the surfaces of a newly comminuted material with a gaseous mixture comprising an inert gas and the vapor of a phenyloxyalkanol having a molecular Weight of at least 124, said gaseous mixture elevated to a temperature sufficiently above the melting point of said substituted phenyloxyalkanol at the instant of contact of said 'subsitued phenyloxyalkanol with said surfaces of the newly comminuted material.
11. A method of protectively coating the surfaces of newly comminuted, moisture-avid materials against the adsorption of moisture which comprises contacting the surfaces of a newly comminuted material with the vapor of a substituted aryloxyalkanol having a molecular weight of at least 124, said protective coating vapor being present at the instant of formation of said surfaces of said newly comminuted material.
12. A method of protectively coating the surfaces of newly comminuted moisture-avid materials against the adsorption of moisture which comprises contacting the surfaces of a newly comminuted material with the vapor of a para-substituted phenyloxyalkanol having a molecular weight of at least 124, said protective coating vapor being present at the instant of formation of 'said surfaces of said newly comminuted material.
References Cited UNITED STATES PATENTS 6/ 1945 Burdett et al. 52-21 7/1919 Snelling 117-100