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
• • 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
• • 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
  • C08B5/12—Replacing the water by organic liquids

Definitions

• Nitrocellulose in the dry state is extremely hazardous and dangerous. Consequently, all commercial nitrocellulose is supplied to the trade wet with a non-solvent liquid in order to minimize fire hazards during storage, shipping and handling of the nitrocellulose.
• the Wetting liquid employed is an alcohol such as ethanol, isopropanol or butanol.
• the nitrocellulose may be supplied wet with water, instead of with an alcohol.
• a volatile hydrocarbon liquid such as toluene rather than with an alcohol or water.
• methods which have been proposed for producing nitrocellulose wet with a volatile hydrocarbon liquid have been deficient in variou respects.
• the resulting fibrous nitrocellulose wet with hydrocarbon liquid retains far too much hydrocarbon liquid, and must then be subjected to pressure in a conventional hydraulic press to squeeze out excess hydrocarbon liquid, after which the compressed blocks must be broken and fluffed up for packing into barrels.
• the above pressing and block breaking steps are inherently quite expensive and hazardous.
• the bulk density of fibrous nitrocellulose is quite low, the nitrocellulose must be packed into the barrels by compressing it with a hydraulic ram to increase barrel loadings, in order to reduce shipping costs.
• nitrocellulose users find the fibrous material quite difiicult to unload from the barrels.
• An additional disadvantage of fibrous nitrocellulose is the tendency to agglomerate and form large slow-dissolving lumps when added to solvents in certain types of dissolving equipment.
• fibrous nitrocellulose conventionally dehydrated with an alcohol such as ethanol, isopropanol, or butanol can be further processed to produce a substantially hydrocarbon-wet nitrocellulose by displacing the alcohol with a hydrocarbon liquid in an additional series of steps comparable to the alcohol dehydration steps.
• an alcohol such as ethanol, isopropanol, or butanol
• fibrous nitrocellulose conventionally dehydrated with an alcohol such as ethanol, isopropanol, or butanol
• fibrous nitrocellulose conventionally dehydrated with an alcohol such as ethanol, isopropanol, or butanol
• fibrous nitrocellulose conventionally dehydrated with an alcohol such as ethanol, isopropanol, or butanol
• Another object of this invention is to provide a nitrocellulose product of improved form which in the presence of excess hydrocarbon liquid drains freely to produce a hydrocarbon-wet nitrocellulose wetted with between about 10% and about 40% by weight of sorbed hydrocarbon liquid.
• sorb and sorbed are used herein in the description and claims in their 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 the force of gravity.
• water-wet fibrous nitrocellulose after conventional treatments for stabilization and viscosity adjustment, is mixed and agitated with a large quantity of water to produce an aqueou slurry of nitrocellulose.
• Nitrocellulose solvent is then added with agitation to the aqueous nitrocellulose slurry heated approximately to the boiling point of the water-solvent azeotrope in an amount sufiicient to change the physical form of the nitrocellulose from fibrous to smooth, hardened, densified, irregular granules having a degree of densification corresponding to a bulk density between about 20 and about 40 pounds per cubic foot, dry basis, upon removal of the solvent by distillation.
• the organic solvent is partitioned to the nitrocellulose which is softened and the fibrous structure thereof is destroyed.
• the nitrocellulose is not dissolved, and the softened particles thus produced are hardened by boiling off substantially all of the solvent. Agitation is maintained until hardening is complete in order to minimize agglomeration during hardening.
• Excess water is then separated by any convenient means, such as by gravity drainage, centrifugation, or the like, and the nitrocellulose granules wet with sorbed water are then subjected to ordinary or azeotropic distillation in the presence of an excess of volatile hydrocarbon liquid, such as toluene or a petroleum distillate, until sorbed water has been substantially displaced by hydrocarbon liquid.
• Excess hydrocarbon liquid is then separated by any convenient means, such as by gravity drainage, centrifugation, filtration, or the like, to produce the novel hydrocarbon-wetted nitrocellulose of this invention.
• the hydrocarbon-Wetted product produced by the process of this invention is composed of small, hard, densified irregular particles of nitrocellulose having a diversity of particle sizes, and which when magnified appear to have smooth, glazed surfaces. As noted above, these particles have a degree of densification corresponding to at least about 20 pounds per cubic foot and not more than about 40 pounds per cubic foot, dry basis, and are Wetted with between about 10% and about 40% by weight of sorbed hydrocarbon liquid.
• the hydrocarbon-wetted product of this invention is further characterized by being free flowing, fast dissolving, 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 said product.
• EXAMPLE 1 One hundred fifty (150) parts by weight, dry basis, of fibrous, water-wet nitrocellulose, 11.5% nitrogen by weight, 4.8 seconds ASTM inch falling ball viscosity, and having a bulk density, dry basis, of 13.3 pounds per cubic foot, were mixed with sufficient water to prepare an aqueous slurry containing by weight of nitrocellulose. This slurry was heated and agitated in a closed vessel equipped with a turbo blade agitator, an inlet for solvent introduction, a thermometer, a condenser, and heated by sparge steam.
• methyl ethyl ketone in an amount equal to one part by weight for each part by weight of nitrocellulose was added to the agitated slurry through the solvent inlet. Heating and agitation were continued, and the solvent was substantially all removed by azeotropic distillation at atmospheric pressure. The temperature in the slurry at the end of the distillation was 94 C. During this solvent treatment the fibrous nitrocellulose was transformed into small, smooth, hardened, irregular particles having a bulk density, dry basis, of 24 pounds per cubic foot.
• the toluene slurry of nitrocellulose particles was then subjected to gravity drainage to remove excess toluene, and substantially all excess toluene had drained off after two hours.
• the resulting toluene-wet nitrocellulose product contained 70% by Weight nitrocellulose, 29.2% sorbed toluene and 0.8% water, and had a bulk density, dry basis, of 21.7 pounds per cubic foot.
• the toluene-wet particles of nitrocellulose flowed freely over each other and retained their sorbed toluene content on storage in a closed container without an objectionable amount of sorbed toluene being lost by gravity drainage.
• the fibrous nitrocellulose employed in this example wasin the form of relatively uniformly sized fiber aggregate particles obtained by nitrating cellulose fiber aggregate particles prepared by cutting sheets of pulp board into particles approximately inch x inch x inch in dimension. These cellulose fiber aggregate particles were not materially changed in physical form or dimension during nitration thereof.
• the ASTM inch 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.
• Table 1 following presents pertinent data relative to the nitrogen content and viscosity characteristic of the nitrocellulose, weight of fibrous nitrocellulose in the aqueous nitrocellulose slurry, parts of solvent for each part by weight of nitrocellulose, temperature in the slurry when solvent was added, temperature at the end of azeotropic distillation of the solvent at atmospheric pressure from the aqueous nitrocellulose slurry, bulk density of the altered form of the nitrocellulose particles following solvent treatment and removal, reduced pressure applied for azeotropic distillation displacement of sorbed Water by toluene, temperature in the toluene slurry of nitrocellulose at the beginning and end of azeotropic distillation displacement of sorbed water by toluene, bulk density of the toluene-wetted nitrocellulose product, and composition of the final toluene-wet nitrocellulose product in terms of nitrocellulose content, sorbed toluene content, and residual water remaining in the product.
• Example 31 picked cotton linters.
• the fibrous nitrocellulose employed in Example 31 was in the same form of fiber aggregate particles as described in Example 1.
• the fibrous nitrocellulose starting materials employed in at y O Parts 0 acetorne P Welght at 25 Examples 25 28 were in the form of loose bulk fibers C., noting the time 1n seconds for a V lIlCh steel ball to obtained by nitrating picked cotton linters.
• Table 3 followlng Presents same klnd 0f Pertlnent a d 30 wa ble l o in the form of loose b lk fib data relative to these examples that Table 1 presents for obtained by nitrating shredded wood pulp instead of Examples 2-10.
• Table 4 following presents the same kind of pertinent data relative to this example that Table 2 presents for Examples 1124.
• nitrocellulose-water slurries containing from about 5% to about 20% by weight of fibrous nitrocellulose have been employed, and preferably from about to about by weight of nitrocellulose.
• slurry consistencies of any concentration of nitrocellulose below about 5% by weight can be employed, it is not presently considered to be economical to do so.
• the upper practical limit is governed by the ability to agitate the slurry effectively, and for some physical forms of fibrous nitrocellulose this upper practical limit can be appreciably higher than by weight of fibrous nitrocellulose in the slurry.
• the fibrous nitrocellulose to be densified may be jordaned, or ground in a ball mill, or otherwise comminuted, if desired, and such comminution makes it possible to increase the quantity of nitrocellulose which can be effectively agitated in the slurry.
• jordaned or otherwise comminuted fibrous nitrocellulose is employed. It will be understood, however, that jordaning, or otherwise comminuting fibrous nitrocellulose is not necessary for the practice of this invention.
• Nitrocellulose Alteration of Physical Form of Nitrocellulose Concentration of Nitrocellulose in Aqueous Slurry, Percent by Weight its Inch Falling Ball Viscosity Characteristic Seconds Nitrogen Content, Percent by Weight Parts of Solvent Per Part of Nitrocellulose, by Weight Reduced Pressure Applied for Distillation of Solvent from Aqueous Slurry, In. of Mercury Temperature in Aqueous Slurry at End of Solvent Distillation from Aqueo uiJ Slurry,
• the smooth, hardened, densified hydrocarbon-wet nitrocellulose granules 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 wood pulp, regenerated cellulose fibers, and the like, in such forms as picked linters, shredded wood pulp, flufied bulk linters, finely ground or cut fibers, fiber aggregate particles, and the like.
• a particularly preferred form of fibrous cellulose for the purposes of this invention is prepared by cutting pulp board or linter board sheets into relatively uniformly sized fiber aggregate particles which are not materially changed in physical form or size during nitration thereof.
• 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 1O centipoise type to exceedingly high viscosity types as exemplified by dynamite grade nitrocellulose.
• water-wet fibrous nitrocellulose after conventional treatments for stabilization and viscosity adjustment, is mixed and agitated with a large quantity of water to produce an aqueous slurry of nitrocellulose.
• aqueous slurry of nitrocellulose From an economic viewpoint is is desirable to employ slurries containing as much fibrous nitrocellulose as practicable, and the upper practical limit of nitrocellulose in the slurry is governed by the ability to agitate the slurry effectively.
• the fibrous nitrocellulose is contacted with agitation in the aqueous slurry with an amount of nitrocellulose solvent sufiicient to change the physical form of the nitrocellulose from fibrous to partially colloided irregular particles or granules, having a degree of densification corresponding to a bulk density between about 20 and about 40 pounds per cubic foot, dry basis, and having a physical structure capable of holding between about 10% and about 40% by weight of sorbed hydrocarbon liquid, upon removal of the treating solvent.
• the aqueous slurry of nitrocellulose should be heated to a temperature at or near the boiling point of the nitrocellulose solvent or water-solvent azeotrope prior to contacting the fibrous nitrocellulose with the solvent. Subsequent solvent removal is thus speeded markedly.
• Solvents suitable for use in practicing this invention are those having an active solvent power for nitrocellulose, and preferably having an appreciable vapor pressure at or below the boiling point of water.
• the most useful solvents are those which have limited solubility in water and which form a minimum boiling azeotropic mixture with water.
• the presence of two liquid phases, however, is not required for preparing the products of this invention, although two phases may be present, if desired.
• Suitable solvents include, by way of example but not in limitation of the invention, various ketones such as methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, and the like; and various esters such as methyl acetate, ethyl acetate, propyl acetate, butylacetate, ethyl propionate, ethyl butyrate, isopropyl butyrate, and the like.
• various ketones such as methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, and the like
• esters such as methyl acetate, ethyl acetate, propyl acetate, butylacetate, ethyl propionate, ethyl butyrate, isopropyl butyrate, and the like.
• Ketones such as methyl isobutyl ketone, methyl ethyl ketone,methyl isopropyl ketone, and the like, are especially preferred for the purposes of this invention, since, in addition to having a limited solubility in water and forming minimum boiling azeotropic mixtures with.
• thedesired degree of alteration of the physical structure of the nitrocellulose is to obtain a product which has a sorptive capacity for hydrocarbon liquid between about and about 40% by Weight of hydrocarbon liquid, preferably between about and about by weight, and still more preferably between about 20% and about-25% by weightbased on total weight of the hydrocarbon-wetted nitrocellulose product, andhav ing a bulk density between about 20 pounds per cubic foot and about pounds per cubic foot, dry basis.
• Solvent requirement to obtain .this objective is dependent on such factors as slurry consistency, initial physical form of the nitrocellulose, temperature, degree of agitation, and the particular solvent chosen for altering the physical form of the nitrocellulose. In general, however, it has been found that an amount of solvent between about 0.3 pound and about 2 pounds, and preferably between about 0.4 pound and 1.5 pounds per pound of nitrocellulose, dry weight, is suflicient to achieve the desired degree of alteration of the physical structure of the nitrocellulose for the purposes of this invention.
• the solvent treatment for altering the physical structure of the nitrocellulose can be accomplished by addi tion of the solvent to an agitated slurry of fibrous nitrocellulose in water, by addition of fibrous nitrocellulose to an agitated mixture of water and solvent, or by simultaneous addition of all ingredients, with agitation, as in a continuous process.
• softening of the nitrocellulose fibers by the active nitrocellulose solvent occurs very rapidly upon bringing the nitrocellulose and solvent into contact with each other in In this process the tiny fibrous projections the aqueous slurry.
• nitrocellulose stabilizers Any desired additives, such as nitrocellulose stabilizers,
• plasticizers, and the like which are soluble in the solvent employed to alter the physical form of the nitrocellulose and which are insoluble in water canbe introduced with the solvent and become very uniformly distributed into the nitrocellulose during alteration of the physical form of the nitrocellulose in accordance with this invention.
• Hardening of the softened nitrocellulose is carried out by boiling off the solvent until substantially all solvent is removed from the nitrocellulose, and this may be accomplished at atmospheric pressure, under vacuum, or under pressure, as desired. This may require from about 20 minutes to about 4 hours, depending upon equipment used and the solvent which has been employed. Vacuum distillation is preferred, since distillation temperatures are lower than with atmospheric or pressure distillation and usually requires less time.
• excess water is separated from the resulting hardened densified nitrocellulose particlcs by any convenient means, such as gravity drain age, suction, centrifugation, or the like, and sorbed water remaining in and on the nitrocellulose after such drainage is displaced by distillation in the presence ofan excess of volatile hydrocarbon liquid.
• the resulting hydrocarbon-wet nitrocellose may, and usually does, contain a small residuum of sorbed water, usually substantially less than 1% by weight of the final product.
• Such residuum of sorbed water may, however, be on the order of 1 to 4% by weight of the final product, preferably less than 2%, without significant interference with use of the hydrocarbonwet nitrocellulose in lacquers, protective coatings, adhesives, inks, 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, aryl, aralkyl and alkaryl hydrocarbons.
• any conventional hydrocarbon or hydrocarbon mixture commonly employed in nitrocellulose compositions is suitable.
• the hydrocarbon should have an appreciable vapor pressure at or below the boiling point of water and the most useful hydrocarbons form minimum boiling azeotropic mixtures with water, although this is not necessary for practice of the invention.
• hydrocarbon liquids include, by way of example, heptane, octane, isooctane, petroleum spirits, mineral spirits, gasoline, various proprietary petroleum distillate cuts, cyclopentane, cyclohexane, methyl cyclohexane, benzene, toluene, xylene, ethyl benzene, styrene, a-methyl styrene, various proprietary aromatic hydrocarbon distillate cuts, and the like.
• Toluene is a particularly desirable hydrocarbon for the purposes of this invention because of the very wide use of this diluent in nitrocellulose compositions.
• hydrocarbon liquid is then separated from the resulting hydrocarbon wet nitrocellulose product by any convenient 13 means, such as gravity drainage, centrifugation, suction, or the like. It has been found that substantially all of the excess hydrocarbon liquid drains off freely by gravity within a period of 1 to 2 hours to produce a product uniformly wet with the desired amount of sorbed hydrocarbon liquid within the range between about and about 40% by weight, based on total weight, without having to resort to the costly and hazardous use of hydraulic presses to reduce the volatile content to the desired level, as in necessary in conventional dehydration practice with fibrous nitrocellulose.
• any convenient 13 means such as gravity drainage, centrifugation, suction, or the like. It has been found that substantially all of the excess hydrocarbon liquid drains off freely by gravity within a period of 1 to 2 hours to produce a product uniformly wet with the desired amount of sorbed hydrocarbon liquid within the range between about and about 40% by weight, based on total weight, without having to resort to the costly and hazardous use of hydraulic presses to reduce the volatile content to
• Fibrous nitrocellulose in loose bulk form which has not had its physical form altered by the process of this invention has been found upon gravity drainage to retain between about 55% and about 60% by weight of sorbed hydrocarbon liquid based on total weight of hydrocarbon-wet nitrocellulose, and thus must be subjected to hydraulic pressing to reduce the volatile content to an acceptable level.
• the present invention provides a distinct advantage over conventional dehydration practice.
• the products of this invention can be loaded into shipping containers as soon as excess hydrocarbon liquid has been separated by drainage, centrifugation, or the like. Since the hydrocarbon-wet nitrocellulose particles of this invention flow freely over each other without any substantial tendency to cling together, they can be readily discharged from shipping and storage containers simply by pouring the product from the container. Fibrous nitrocellulose, by contrast, clings together and must be laboriously forked out of the shipping container.
• Fibrous nitrocellulose has a loose bulk density of about 12 to 13 pounds (dry basis) per cubic foot.
• the product of this invention having a bulk density between about 20 pounds and about 40 pounds (dry basis) per cubic foot, permits substantially heavier .barrel loadings.
• the products of this invention dissolve in lacquer solvents more rapidly than conventional fibrous nitrocellulose because there is substantially no tendency for the smooth, hardened, densified particles to agglomerate into large lumps, as is the case with fibrous nitrocellulose.
• hydrocarbon-wet nitrocellulose products of this invention can be used in any application where commercial nitrocellulose is now used, such as lacquers, plastics, paints, adhesives, coatings, inks, irnpregnations, propellants, and the like.
• a process for preparing hydrocarbon-wet nitrocellulose which comprises (a) contacting a slurry of fibrous nitrocellulose with agitation in a heated aqueous bath with an organic liquid solvent which has active solvent power for said nitrocellulose;

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Citations (2)

• 0
  • BE BE652163D patent/BE652163A/xx unknown
• 1963
  • 1963-08-27 US US304985A patent/US3284253A/en not_active Expired - Lifetime
• 1964
  • 1964-08-11 GB GB32767/64A patent/GB1023570A/en not_active Expired
  • 1964-08-19 FR FR45070A patent/FR1412595A/fr not_active Expired
  • 1964-08-26 SE SE10283/64A patent/SE355187B/xx unknown
  • 1964-08-26 DE DEH53642A patent/DE1226014B/de active Pending
  • 1964-08-27 NL NL6409965A patent/NL6409965A/xx unknown
  • 1964-08-27 CH CH1120964A patent/CH435706A/fr unknown

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