Classifications

• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B21/00—Apparatus or methods for working-up explosives, e.g. forming, cutting, drying
  • C06B21/0008—Compounding the ingredient
  • C06B21/0016—Compounding the ingredient the ingredient being nitrocellulose or oranitro cellulose based propellant; Working up; gelatinising; stabilising
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B21/00—Apparatus or methods for working-up explosives, e.g. forming, cutting, drying
  • C06B21/0008—Compounding the ingredient
• • C—CHEMISTRY; METALLURGY
  • C06—EXPLOSIVES; MATCHES
  • C06B—EXPLOSIVES OR THERMIC COMPOSITIONS; MANUFACTURE THEREOF; USE OF SINGLE SUBSTANCES AS EXPLOSIVES
  • C06B21/00—Apparatus or methods for working-up explosives, e.g. forming, cutting, drying
  • C06B21/0033—Shaping the mixture
  • C06B21/0066—Shaping the mixture by granulation, e.g. flaking
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B5/00—Preparation of cellulose esters of inorganic acids, e.g. phosphates
  • C08B5/02—Cellulose nitrate, i.e. nitrocellulose
  • C08B5/04—Post-esterification treatments, e.g. densification of powders, including purification
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
  • C08B5/00—Preparation of cellulose esters of inorganic acids, e.g. phosphates
  • C08B5/02—Cellulose nitrate, i.e. nitrocellulose
  • C08B5/04—Post-esterification treatments, e.g. densification of powders, including purification
  • C08B5/06—Isolation of the cellulose nitrate

Definitions

• This invention relates to the manufacture of tiny particles of densified nitrocellulose and more particularly to the production of tiny particles of densified nitrocellulose which are well suited for use in casting large propellant grains by the slurry casting process and for use in other applications requiring such a product.
• the casting powder consisting of precolloided, fully densified, solid particles or granules of nitrocellulose composition
• a predetermined quantity of casting liquid comprising nitroglycerin and/or suitable densensitizing plasticizers, such as triacetin, with or without stabilizers and/ or other adjuvants included to control or regulate burning rate of the resulting propellant grain when fired, is then introduced into the mold to completely fill all voids between the dry casting powder granules and to just cover the casting powder granules.
• the mixture of prec-olloided nitrocellulose particles and casting liquid is then cured in the mold, usually at a suitable elevated temperature until the particles of nitrocellulose casting powder absorb all of the casting liquid and the whole mass consolidates and welds together into a solid, unitary, colloided structure conforming to the shape of the mold.
• in-situ casting of propellant grains is subject to certain restrictions and limitations.
• in-situ casting methods have required a relatively large inventory of casting powder formulations.
• in-situ casting requires relatively long curing times and does not lend itself to the manufacture of grains of irregular configuration such as may be necessary to fit in certain types of rocket motors to provide the desired type of ballistic functioning.
• known methods for preparing casting powder formulations are tedious and expensive since these methods involve all of the steps necessary in the manufacture of smokeless powder granules, since, in reality, casting powder granules heretofore have been smokeless powder granules.
• the small particles of colloided densified nitrocellulose employed for this purpose should desirably have certain characteristics as to shape, size and density. More particularly, the tiny particles should desirably be smooth and rounded, preferably into substantially ellipsoidal and/or spheroidal shape for uniform dispersal and distribution in the casting liquid, and formation of a slurry with smooth, uniform pouring properties.
• the particles of nitrocellulose desirably should be densified at least to the point where there is a smooth, hard, dense shell of colloided nitrocellulose forming the surface of each tiny particle.
• the interior of the tiny particles may be, but need not necessarily be, as completely colloided and densified as the surface shell; in fact, experience indicates that some porosity associated with only a partially colloided or partially gelled state in the interior of the particles may be desirable.
• the hard, dense shell of colloided nitrocellulose forming the surface of the particles is an important physical characteristic which imparts satisfactory "pot life to the slurry, for this dense shell resists rapid absorption of the casting liquid and, therefore, delays swelling of the nitrocellulose and thickening of the slurry during the period necessary to prepare and uniformly mix the slurry and then pour it into the mold.
• Fibrous nitrocellulose particles, or partially densified nitrocellulose particles having a substantially porous surface layer absorb the casting liquid much too rapidly for satisfactory slurry casting techniques, for such particles swell and thicken the slurry too rapidly for satisfactory mixing and pouring of the slurry into the mold.
• Such fibrous or porous-surfaced particles therefore, impart an unsatisfactorily short pot life to the slurry.
• Some porosity in the interior of the particles is believed to facilitate a more rapid and uniform cure after casting, which is desirable.
• pot life of the slurry decreases with decreasing size of the nitrocellulose particles, and experience has shown that when a substantial majority of the casting powder particles are less than about 10 microns in size, pot life of the slurry is unsatisfactorily short, even though the particles are substantially completely densified. Experience has also shown that when a majority of the casting powder particles are substantially larger than about microns in size, especially when highly densified, pot life of the slurry is undersirably long. Such large, dense particles tend to settle from the slurry after casting and also unduly prolong curing of the grain, both effects being obviously undesirable.
• an object of this invention to provide an improved process for manufacturing tiny particles of densified nitrocellulose especially suited for use in casting large propellant grains by the slurry casting process.
• a still further object of this invention is to provide an improved process for manufacturing tiny particles of densified nitrocellulose wet with hydrocarbon liquid in stead of with alcohol or with water.
• a further object of this invention is to provide a hydrocarbon-wet nitrocellulose of improved form for use in slurry casting of large propellant grains and other applications where tiny particles of densified nitrocellulose are necessary or desirable.
• the above process produces a slurry of hard, tiny, rounded and smooth-surfaced particles of densified nitrocellulose of substantially ellipsoidal and spheroidal shapes in hydrocarbon diluent, from which the densified nitrocellulose product is readily recovered in a hydrocarbonwet state by any convenient means, such as by gravity drainage, centrifugation, suction filtration, or the like.
• water-wet fibrous nitrocellulose after conventional treatments for stabilization and viscosity adjustment, is slurried with water and beaten in a Jordan engine or similar fiber beating device to break up fiber aggregates and shorten the fibers and produce an aqueous slurry of nitrocellulose fibers substantially free of fiber aggregates. Excess water is then drained off, preferably by centrifugation or suction filtration to produce water-moist nitrocellulose fibers containing between about 35% and about 50% by weight of sorbed water, based on total weight of water-moist nitrocellulose fibers.
• sorb and sorbed are used herein in the usual sense to mean the ability of the nitrocellulose to take up and hold a liquid, either by adsorption or absorption, or by a combination of adsorption and absorption, substantially independent of gravitational forces.
• the resulting water-moist nitrocellulose fibers are then introduced and dispersed at substantially incapable of dissolving the fibers, and having a watersoluble protective colloid dispersed therethrough to [form a stirrable slurry of nitrocellulose fibers substantially free of fiber aggregates.
• the water-moist nitrocellulose fibers are introduced into the organic liquid mixture as rapidly as the agitating device can disperse the fibers, either in small increments or continuously, as desired.
• the time required to accomplish addition and dispersal of the water-moist nitrocellulose fibers in the organic liquid mixture is usually quite short, amounting at most to only a few minutes. Softening, swelling and breakdown of the nitrocellulose fibers commences as soon as the fibers have been introduced into the organic liquid mixture.
• the slurry is then subjected to high shear agitation with a Kady dispersion mill (Kady Dispersion Corporation, Botsford Place, Buffalo 16, New York), or the like, in a jacketed vessel with cooling water circulating through the jacket to remove at least some of the heat generated in the slurry by the high shear agitation.
• Kady dispersion mill Kady Dispersion Corporation, Botsford Place, Buffalo 16, New York
• This high shear agitation is important and necessary for it definitely contributes to softening and swelling of the nitrocellulose fibers and comminution of the softened and swollen fibers into tiny fragments, a majority of which surprisingly are relatively uniform in size.
• High shear agitation also is an important feature in helping to shape the comminuted fragments into smooth surfaced, rounded particles of substantially ellipsoidal and spheroidal shapes and to facilitate solution and uniform distribution of the water-soluble protective colloid over the surfaces of the comminuted particles.
• the protective colloid which is present in the slurry is believed to form a thin protective coating or layer around each fragmented particle, and thus keep the fragments from sticking together and agglomerating into substantially larger aggregates.
• the protective colloid also appears to aid in the rounding and shaping of the fragmented particles into desirable ellipsoidal and spheroidal shapes.
• the protective colloid is a necessary element of this invention, for in the absence of protective colloid, the fragmented particles tend to stick together and agglomerate into undesirably larger aggregates and do not shape properly into rounded ellipsoidal and spheroidal shapes.
• the slurry is diluted with hydrocarbon diluent while continuing high shear agitation to initiate hardening of the comminuated and shaped articles.
• High shear agitation may, if desired, be continued for several minutes, permitting solvent, water, and hydrocarbon vapors to escape from the slurry, to promote further initial hardening of the particles.
• nitrocellulose solvent and water are substantially all removed from the slurry by distillation to complete the hardening and densification of the particles.
• the slurry desirably should be agitated during the distillation step, but such agitation need not necessarily be high shear agitation; any agitating means will suffice.
• hydrocarbon diluent Since a portion of the hydrocarbon diluent also distills off with the nitrocellulose solvent and water, sufficient hydrocarbon diluent should be added to the slurry either prior to or during distillation to insure a large excess of hydrocarbon diluent at all stages of the distillation.
• the resulting hardened and densified particles of nitrocellulose are readily recovered in a hydrocarbon-wet state by draining off excess hydrocarbon liquid by any convenient means, such as by gravity drainage, suction filtration, centrifugation, or the like.
• nitrocellulose stabilizers such as nitrocellulose stabilizers, carbon black, and other desirable additives which are soluble or dispersible in the organic liquid mixture can be introduced into the slurry at any convenient point in the process and become very uniformly distributed into the nitrocellulose product.
• the hydrocarbon-wet product of this invention is composed of tiny, hard, densified, substantially rounded, particles of nitrocellulose, preferably of substantially ellipsoidal and spheroidal shapes having a diversity of particle sizes, a substantial majority of which are between about 20 microns and about 80 microns, preferably between about 40 microns and about 75 microns in size, with an overall range of particle sizes between about 1 micron and about 200 microns.
• the absolute density of these tiny particles, dry basis is at least about 1.3 gms./cc., the absolute density of completely densified nitrocellulose being approximately 1.65 gms./ cc.
• these particles When magnified, these particles are seen to have smooth, dense, glazed surfaces, and, generally, to have some degree of porosity in the interior of the particles.
• the bulk density of these particles is at least about 40 pounds per cubic foot, preferably at least about 45 pounds per cubic foot, dry basis. While some irregularity in particle shape diverging from ellipsoidal and spheroidal shapes is acceptable, no more than about 5% of such irregular shaped particles are in the form of elongated fiber-like particles.
• the tiny densified particles of this invention are readily dispersed in aqueous or organic liquid mixtures to form hydrosol, organosol, or plastisol compositions which are uniformly smooth, pourable slurries of relatively high solids content.
• a plastisol mixture of 30 parts by weight of the densified particles of this invention uniformly mixed with 70 parts by weight of triacetin, which is a solvent-type plasticizer for nitrocellulose forms a smooth, pourable slurry which, after one hour at room temperature, is still pourable and has a viscosity less than 4000 centipoises.
• the tiny densified nitrocellulose particles of this invention are wetted with between about and about 30% by weight of sorbed hydrocarbon liquid and are further characterized by being free flowing and relatively incompressible.
• the chemical characteristics of the product of this invention are apparently the same as conventional nitrocellulose, since no chemical action is involved in the process of producing this product.
• the densified nitrocellulose particles of this invention are also especially well suited for formulating nitrocellulose wood fillers substantially free of a tendency to shrink when overcoated with nitrocellulose lacquers and other coating materials having solvent vehicles which are solvents for nitrocellulose. This use will be more fully described hereinafter.
• EXAMPLE 1 Water-wet fibrous nitrocellulose, 12.6% nitrogen by weight, 5 seconds A -inch falling ball viscosity measured in accordance with Military Spec. JAN-N-244, after conventional treatments for stabilization and viscosity adjustment, was slurried with water and jordaned to break up fiber aggregates and shorten the fibers and produce a slurry of nitrocellulose fibers substantially free of fiber aggregates. This slurry was then dewatered by centrifugal drainage to 63.83% total solids.
• the charge was then transferred to a jacketed Kady dispersion mill provided with a cover, with cooling water circulating through the jacket, and was subjected to high shear agitation at approximately 16,000 rpm. in the covered Kady dispersion mill for approximately 30 minutes.
• the temperature in the slurry reached, and was then maintained by jacket cooling, in the range between about 60 C. and 64 C. during this period of high shear agitation.
• the slurry was then diluted with 11.2 parts by weight of lactol spirits, the cover of the Kady mill was removed, and the high shear agitation was continued for an additional 30-minute period.
• the charge was then further diluted with lactol spirits and transferred to a distillation kettle provided with a conventional propeller type agitator, where the remaining water and methyl ethyl ketone were removed by distillation while agitating the charge.
• a tot-a1 of approximately 48.5 parts by weight of additional lactol spirits were employed for dilution of the slurry during the latter period of high shear agitation with the cover removed from the Kady dispersion mill and prior to removal of remaining water and methyl ethyl ketone in the distillation kettle. Distillation was discontinued when the distillation temperature reached the boiling point of lactol spirits, approximately .C.
• the resulting slurry of tiny, densified nitrocellulose particles in petroleum diluent was then deliquefied on a suction filter to 80% total solids by Weight.
• the resulting densified nitrocellulose particles had an absolute density, dry, of 1.357 gins/cc. and a bulk density, dry basis, of 52 pounds per cubic foot.
• the overall particle size was in the range from 40 microns to microns with a majority of the particles in the range from 50 microns to 75 microns.
• Visual examination with the aid of magnification showed the particles to be smooth and rounded with dense glazed surfaces, and for the most part to be of ellipsoidal and spheroidal shapes.
• the dried material flowed easily like dry sand.
• Viscosity Time (minutes): (centipoises) 15 102 30 112 45 127 60 145 75 170 90 188 105 210 120 235 180 460 240 1,040 300 2,920
• the A inch falling ball viscosity characteristic of the nitrocellulose was measured in accordance with Military Spec. JAN-N-244 on a 10% by weight solution of the nitrocellulose in a solvent composed of 11.1% denatured ethyl alcohol and 88.9% acetone by weight at 25 C., noting the time in seconds for a W -inch steel ball to fall freely ten inches through the solution.
• EXAMPLE 2 Water-wet fibrous nitrocellulose, 11% nitrogen by weight, approximately 154 seconds ASTM inch falling bal-l viscosity, after conventional treatments for stabilization and viscosity adjustment, was slurried with water and jordaned to break up fiber aggregates and shorten the fibers and produce a slurry of nitrocellulose fibers substantially free of fiber aggregates. This slurry was then dewatered by centrifugal drainage to 64.1% total solids.
• the ASTM ;-incl1 falling ball viscosity characteristic of the nitrocellulose was measured on a 12.2% by weight solution of the nitrocellulose in a solvent composed of 55% toluene, 25% denatured ethyl alcohol and 20% ethyl acetate by weight at 25 C., noting the time in seconds for a -inch steel ball to fall freely ten inches through the solution.
• the charge was then transferred to a jacketed Kady dispersion mill provided with a cover, with cooling water circulating through the jacket, and was subjected to high shear agitation in the covered Kady dispersion mill operating at approximately 16,000 rpm. for approximately 30 minutes.
• the temperature in the slurry reached, and was then maintained by jacket cooling, in the range between about 60 C. and 64 C. during this period of high shear agitation.
• the slurry was then diluted with 7.45 parts by weight of lactol spirits, and high shear agitation was continued for an additional 2 minutes, approximately, with the cover removed.
• the resulting densified nitrocellulose particles had an absolute density, dry, of 1.570 -gms./cc., and a bulk density, dry basis, of 51.6 pounds per cubic foot.
• the overall particle size was in the range from 25 microns to microns, with a majority of the particles in the range from 40 to 60 microns.
• Visual examination with the aid of magnification showed the particles to be smooth and rounded with dense glazed surfaces. A few fiberlike particles, substantially less than about 1% in number, were observed.
• hydrocarbon-wet nitrocellulose particles of this example were employed in a wood filler application, as follows:
• the following ingredients were mixed and blended together in a pony mixer to prepare the wood filler composition.
• Silver bond silica (filler grade) 42.0
• This composition was thinned to 60% solids with V.M. & P. naphtha and brushed on open-grained mahogany panels, which had previously been given a nitrocellulose wash coat with a 6% solution of nitrocellulose in a conventional nitrocellulose solvent mixture and dried.
• the wood filler composition was allowed to flash dry for about 10 minutes, after which the excess filler composition was wiped off the panels in conventional manner across the wood grain with a rag, and the panels were allowed to dry for about an hour.
• a conventional system of nitrocellulose lacquer coatings was then applied by spray coating to the filled panels, consisting of one coat of nitrocellulose lacquer sealer and two finish coats of nitrocellulose lacquer, allowing each coat to dry tackfree before application of the next coat.
• the lacquered panels were then allowed to air dry overnight and were observed, both before and after polishing, for filling efficiency of the above nitrocellulose filler in direct comparison to similar panels filled with a conventional commercial oil-type filler prior to application of the nitrocellulose lacquer coats.
• EXAMPLES 3-9 A series of finely divided, densified nitrocellulose particles was prepared following substantially the same procedure described in Example 1. The same water-moist nitrocellulose prepared in the same manner described in Example 1 was employed in this series. In Examples 9 3-6, inclusive, lactol spirits was employed as the hydrocarbon diluent with methyl ethyl ketone as the nitro cellulose solvent, and the ratio of hydrocarbon diluent to nitrocellulose solvent was varied. In Examples 7-9, inelusive, heptane was employed as the hydrocanb on diluent 10 cedure described in Example 2.
• Examples 3 9 were details relative to dispersal agitation, high shear agitasatisfactory and well suited for use in slurry casting of H011 and dilution with hydrocarbon diluent, and P p large propellant grains, and also for use in formulating es 0f the particles obtained. 7 nitrocellulose wood fillers.
• the densified particles of any of Examples 10-13 were Table 1 Ingredients (Parts by Weight) Operational Details Ratio Additional Dilu- Ex. Hydro- High Initial Dilution High Shear Agition of Slurry No. Nitro- Methyl Watercarbon Cowles Shear of Slurry with tation.
• l L.S. designates Lactol Spirits.
• I H designates Heptaue.
• EXAMPLES 14-18 A series of finely divided, densified nitrocellulose particles was prepared following substantially the same procedure described in Example 2. In this series nitrocelluloses differing both in nitrogen content and 'y -inch falling ball viscosity characteristics were employed, and the resulting particles in each example were smooth and rounded, with dense glazed surfaces, and for the most part the particles were substantially ellipsoidal and spheroidal in shape.
• the hydrocarbon-wet nitrocellulose particles of each of these examples were employed in a wood filling application as described in Example 2, with substantially the same desirable results noted in Example 2.
• Table 3 presents pertinent data relative to the nitrogen content and falling ball viscosity characteristic of the nitrocelluloses employed, together with absolute density, bulk density, and particle size range of the particles obtained, and observations on the filling efficiency of the wood filler compositions prepared from the densified nitrocellulose particles.
• the tiny densified nitrocellulose particles of this invention can be produced from any fibrous nitrocellulose, obtained by nitrating natural or artificial cellulose fibers, such as cotton, purified cotton linters, purified wool pulp, regenerated cellulose fibers, and the like, in such forms as picked linters, shredded wood pulp, fiuffed bulk linters, finely' ground or cut fibers, fiber aggragate particles, and the like.
• fibrous nitrocellulose be substantially free of fiber aggregates for use in this invention, for such aggregates interfere with proper comminution and lead to formation of undesirably large particles.
• fibrous nitrocellulose it is both desirable and preferable to initially subject the fibrous nitrocellulose to a conventional jordaning, or similar fiber beating treatment, to break up fiber aggregates and generally shorten the fibers prior to use in this invention.
• water-wet fibrous nitrocellulose after conventional treatments for stabilization and viscosity adjustment, is slurried with water to the consistance of a conventional pulping slurry and is beaten in a jordan engine, or similar fiber heating device, to break up and disintegrate fiber aggregates and generally shorten the fibers.
• Nitrocellulose fibers dehydrated with one of the lower alkanols such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, or tertiary butanol can be employed in this invention.
• the alcohol of dehydration does not take the place of the water indicated to be necessary for the purposes of this invention, and an amount of water, as pointed out above, should be added to the alcoholdehydrated nitrocellulose, preferably before dispersing the nitrocellulose in the organic liquid swelling and softening medium. Instead, the alcohol of dehydration replaces active nitrocellulose solvent, approximately part for part by weight.
• Substantially all commercial types and grades of fibrous nitrocellulose are suitable for the purposes of this invention, having nitrogen contents from about 10.9% to about 13.5% nitrogen by Weight, and of any viscosity characteristic from the very low viscosity, 10 centipoise type to exceedingly high viscosity types as exemplified by dynamite grade nitrocellulose.
• the water-moist nitrocellulose fibers are introduced and dispersed in the organic liquid softening and swelling medium of this invention with vigorous agitation to form a uniformly smooth, readily stirrable slurry; and the upper practical limit for the amount of nitrocellulose fibers in the slurry is governed by the ability to agitate the slurry effectively.
• slurries containing from about 10% to about 20% by weight of fibrous nitrocellulose, dry weight have been employed and preferably between about 14% and about 18% by weight of nitrocellulose.
• slurry consistencies of any concentration below about 10% by weight can be employed, it is not considered economical to do so.
• the organic liquid mixture which is employed as the medium for the comminution and densification of the nitrocellulose is a mixture of hydrocarbon diluent and nitrocellulose solvent which is completely miscible with said diluent. It is important and necessary for the hydrocarbon diluent and nitrocellulose solvent to be proportioned in the mixture so that the mixture is only a swelling and softening agent for nitrocellulose fibers, incapable of dissolving said fibers. Suitable proportions of hydrocarbon diluent and nitrocellulose solvent to obtain this object varies depending principally on the particular hydrocarbon diluent and nitrocellulose solvent selected, and on the nitrogen content and viscosity characteristic of the nitrocellulose to be comminuted and densified.
• the ratio of lactol spirits to methyl ethyl ketone in the mixture can vary between about 1.25 and about 2.0 parts by weight.
• the ratio of heptane to vmethyl ethyl ketone in the mixture can vary between about 1.0 and about 1.2 parts by weight.
• the ratio of lactol spirits to acetone in the mixture can vary between about 2.6 and about 3.3 parts by weight.
• the ratio of lactol spirits to methyl ethyl ketone in the mixture can vary between about 1.3 and about 2.1 parts by weight.
• the ratio of lactol spirits to methyl ethyl ketone in the mixture can vary between about 3.3 and about 3.9 parts by weight.
• hydrocarbon diluent and nitrocellulose solvent it is a simple expedient to carry out a preliminary trial by slurrying the desired nitrocellulose in the selected hydrocarbon diluent and then progressively adding the selected nitrocellulose solvent with agitation until the point is reached where the mixture begins to swell the fibers, using the above 1 5 examples as a guide. It is then a simple matter in practicing this invention to make minor increases or decreases in the ratio of hydrocarbon diluent to nitrocellulose solvent to obtain the desired shapes, density, bulk density, range of particle sizes, and the like.
• Any volatile hydrocarbon which is liquid at ordinary temperatures and atmospheric pressure may be employed for the purposes of this invention including aliphatic, cycloaliphatic, aromatic, arylaliphatic and aliphaticaryl hydrocarbons, and mixtures of any of these.
• Some typical hydrocarbons include, by way of example, hexane, heptane, octane, isooctane, nonane, and the like, various proprietary petroleum distillate cuts such as textile spirits, mineral spirits, lactol spirits, V.M. & P.
• cyclopentane cyclohexane, methyl cyclohexane, benzene, toluene, xylene, ethyl benzene, styrene, a-methyl styrene, various proprietary aromatic hydrocarbon distilate cuts, mixtures of aliphatic and aromatic hydrocarbons, and the like.
• the preferred hydrocarbons for the purposes of this invention are aliphatic hydrocarbons which boil in the range of heptane or higher.
• Nitrocellulose solvents suitable for the purposes of this invention are the lower molecular weight ketones, esters, gylcol ether-alcohols and glycol ether-esters which are soluble in water to the extent of at least about 2.5% by weight.
• Some typical nitrocellulose solvents which are suitable for practice of this invention include, for example, methyl formatc, ethyl formate, methyl acetate, ethyl acetate, isopropyl acetate, methyl propionate, acetone, methyl ethyl ketone, diethyl ketone, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, methoxyethyl acetate, and the like.
• the nitrocellulose solvent should have a boiling point below the boiling point of the hydrocarbon diluent, or should form a minimum boiling azeotropic mixture with the hydrocarbon diluent and/or with water.
• Methyl ethyl ketone is especially preferred for the purposes of this invention since, in addition to having suitable solubility in water and forming a minimum boiling mixture with water, it is also free of any tendency to hydrolyze.
• water-soluble protective colloid is necessary for practice of this invention, and substantially any water-soluble protective colloid can be employed in this invention.
• Some typically suitable water-soluble protective colloids include, by way of example, water-soluble alkyl ethers of cellulose, hydroxyalkyl ethers of cellulose, mixed alkyl hydroxyalkyl ethers of cellulose, such as methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, and the like; watersoluble alkyl ethers of starch, hydroxyalkyl ethers of starch, mixed alkyl hydroxyalkyl ethers of starch, such as methyl starch, ethyl starch, hydroxyethyl starch, hydroxypropyl starch, methyl hydroxyethyl starch, methyl hydroxyethyl starch,
• the water-soluble protective colloid can be added either in dry powdered or granulated form, or as a Water solution thereof. However, it is preferred to add the protective colloid in dry form, since the water present in the water-moist nitrocellulose fibers is sufficient to effect solution and uniform distribution of the water-soluble protective colloid over the surfaces of the comminuted particles. f.
• the amount of water-soluble protective colloid employed should be no more than is consistent with the ability of the colloid to coat the comminuted particles with a thin but effective protective film, and will generally be between about 0.1% and about 0.5% by weight, based on the total slurry weight. Amounts substantially less than about 0.1% are generally insufficient for the purpose of this invention, and amounts greater than about 0.5%, although effective for coating the comminuted particles with a protective layer, unnecessarily increase the presence of a water-sensitive ingredient in the final product.
• the invention is by no means limited in this respect, since any high speed attrition mill is effective, as for example, a Premier colloid mill, or similar device.
• a process for preparing a densified, fine-particle nitrocellulose product which comprises (a) forming a slurry with agitation of Water-moist nitrocellulose fibers substantially free of fiber aggregates in a volatile organic liquid mixture of hydrocarbon diluent and nitrocellulose solvent which is completely miscible with said diluent in the presence of a water-soluble protective colloid;
• said organic liquid mixture being only a softening and swelling agent for said nitrocellulose fibers incapable of dissolving said fibers;
• a process for preparing a densified fine-particle nitrocellulose product which comprises (a) forming a slurry with agitation of water-moist nitrocellulose fibers substantially free of fiber aggre gates in a volatile organic liquid mixture of petroleum hydrocarbon diluent and methyl ethyl ketone in the presence of a water-soluble protective colloid;
• said organic liquid mixture being only a softening and swelling agent for said nitrocellulose fibers incapable of dissolving said fibers;
• nitrocellulose is a smokeless type having a nitrogen content of at least about 12.6% by weight
• the petroleum hydrocarbon diluent is a petroleum distillate fraction boiling between about 201 F. and about 217 F.
• the initial ratio of said hydrocarbon diluent to methyl ethyl ketone in the slurry is between about 1.25 parts and about 2.0 parts by weight
• the water-soluble protective colloid is methyl cellulose.
• nitrocellulose is a smokeless type having a nitrogen content of at least about 12.6% by weight
• the petroleum hydrocarbon diluent is heptane
• the initial ratio of said heptane to methyl ethyl ketone in the slurry is between about 1.0 part and about 1.2 parts by weight
• the water-soluble protective colloid is methyl cellulose.
• nitrocellulose has a nitrogen content of about 11% by weight
• the petroleum hydrocarbon diluent is a petroleum distillate fraction boiling between about 90 F. and about 240 F.
• the water-soluble protective colloid is methyl cellulose.
• nitrocellulose has a nitrogen content of about 12% by weight
• the petroleum hydrocarbon diluent is a petroleum distillate fraction boiling between about 190 F. and about 240 F.
• the water-soluble protective colloid is methyl cellulose.

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• 1964
  • 1964-04-08 US US358366A patent/US3236702A/en not_active Expired - Lifetime
• 1965
  • 1965-02-22 GB GB7660/65A patent/GB1075193A/en not_active Expired
  • 1965-03-08 DE DE19651446879 patent/DE1446879A1/de active Pending
  • 1965-03-11 CH CH343365A patent/CH431946A/fr unknown
  • 1965-04-02 FR FR45840A patent/FR1436182A/fr not_active Expired
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  • 1965-04-08 NL NL6504498A patent/NL6504498A/xx unknown

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