US2341221A - Pulping smokeless nitrocellulose - Google Patents

Description

Feb. 8,1944.

c. B. KINGERY PULPING SMOKELESS NITROCELLULOSE Filed Dec. 19, 1940 CLARK B. KINGERY INVENTQR.

Patented Feb. 8, 1944 PULPENG SMOKELESS NNITROCELLULOSE Clark B. Kingery, Parlin, N. J., assigner to Hercules Powder Company,Wilmington, Del., a

corporation of Delaware Application December 19, 1940, Serial No..370,751

' ('Cl. .2M-'223) This invention relates to the production of 1 Claim.

nitrocellulose and more particularly to the purification of nitrocellulose of the type adaptable for use in the manufacture .of n smokeless` powder.

The art has recognized the need of thoroughly purifying nitrocellulose which is to be used in the manufacture of smokeless powder and further the Government has issued specications as`t the number of washings and poaching treatments necessary in order that nitrocellulose may be purified to a degree where it is acceptable for use in the manufacture of smokeless powder. The purification of nitrocellulose is necessary in order to remove traces of acid remaining within the ber as even very minute., quantities of acidic nitrocellulose will cause deterioration of any smokeless powder which is produced therefrom. Smokeless powderproduced from nitrocellulose which is not thoroughly puried is vunstable in storage.

The purication procedure which the prior art has used for smokeless .nitrocellulose usually comprises boiling the nitrocellulose in Water, passing the nitrated cellulose through beaters and or Jordans in order to reduce the ber length to a minimum and to break any and all knots or mats into individual bers, and-passing the pulped material into tubs where it is poached by boiling in slightly alkaline water, boiling in fresh Water and washing `with neutral water at room temperatures,

The twomost expensiveitems in the purification of nitrocellulose are the power required' to run the beaters, Jordans and pumps and the cost of supplying water in tremendous volumes to the poaching and washing operation. 'I'he beating and J ordaning requires considerable time in order to reduce the material to a pulp ber length suitable for poaching as the material fis treated in a water slurry, and a large percentage of the power is consumed in overcoming the inertia of the water present. Further, the pulping procedure has been found to be inefficient as the extremely low concentrations of pulp required when the slurry is passed through the beaters and Jordans is not desirable at the end of the process.

The object of this invention is to provide an improved means of pulping nitrocellulose. A further object of this invention is to provide a means of pulping nitrocellulose which ismore emcent than those known heretofore. of this invention is to provide a means of reducing nitrocellulose to veryl short bers and maintaining the desired slurry concentration. A further object of this invention is to, -`provide a .50 A further object method whereby smokeless nitrocellulose may be puried and pulped more eiciently. A still further object of this invention is to provide a method of pulping nitrocellulose which requires a reduced vamount of Water. A further object of this invention is to provide a method of pulping nitrocellulose whereby water and pulped nitrocellulose are vprogressively removed from the process at the optimum point in the process for most eciency.

In generaL'the objects of this invention have been accomplished by pulping nitrocellulose by means of a series of Jordans, so arranged that the slurries of nitrocellulose in water proceed through them, and during the passage thereof the water content of the slurry 'is reduced so as to maintain a resistant factor to pulping which gives most efficient results. Thus, the pulping of nitrocellulose is accomplished by passing a slurry of predetermined pulping resistance through a series of Jordans in a manner, whereby when pulping resistance of the slurry altered due to disintegration of the ber in one Jordan, it may be re-established and maintained at the optimum point by removal of water beforevthe slurry is introduced into the next Jordan in the series. Thus, the slurry of smokeless nitrocellulose is passed through a series of Jordans and this slurry is maintained at a consistency which is so coordinated with the ber length-that maximumA pulping is accomplished under most eicient conditionswith the minimum amount of water andthe ,minimum consumption of power to give an Voptimum operating consistency.

Having now described in a general Way my invention,` there follows a more detailed description thereof in which preferred embodiments are described-with reference to the accompanying drawing in which:

t Fig. l represents a `diagrammatical ilow sheet of the pulping operation and,

Fig. 2 represents a cross sectional elevation of a Jordan unit.

`Referring now tothe ow `sheet (Fig. l), it will be apparent Vthat aslurry of nitrocellulose is processed lby maintaining a supply of the slurry in tank l and passing this slurry from tank l to a Jordan 2. The Jordan is of the type normally used in pulpirig operations and has an overow pipe 3 directed from ythe head boxrthereof back to the supply tank l. The slurry of nitro- -cellulose in tank I is of about 3% consistency and this large amount of water is necessary in order that the Jordan' 2 may break the knots or mats of nitrocellulose'into the individual bers. The

slurry leaves the Jordan and passes into a dewatering tank 5 where it passes over a screen 6 of sufficient size to allow a reduction of the Water content of the slurry to a point where the nitrocellulose present is raised to about 6%. The screen may be of such size that a certain quantity of nitrocellulose which has already been pulped to the desired fineness is removed along with the desired quantity of water.

This 6% slurry runs from the dewatering tank 5 into a supply tank 1, while the Water removed from the slurry by means of a screen 6, leaves` the dewatering tank 5 and is directed to a poaching tub via line 9. The water removed from the slurry contains about 8% of the original nitrocellulose present in the slurry and this nitrocellulose is in such a fine state that it is ready for treatment in the poaching and washing tanks.

From the supply tank 1, the slurry of increased concentration, that is containing about 6% of nitrocellulose,.is` passed to the head box of a second Jordan lo which is similar to the rst Jordan and has an overflow pipe H connected to the head box and directed back to the supply tank l. From Jordan I El, the slurry is directed to the second dewatering tank l2 where any desirable amount of water is removed from the slurry by means of screen Ict which remo-ved Water is led is accomplished. From Jordan I6, the pulp slurry may be'passed to a dewatering tank or if desired may be passed directly to an additional Jordan or series of Jordans preceded by dewater- Ving tanks if desirable, or to a poaching tub.

Whether the pulp slurry will be directed through additional Jordans and additional dewatering boxes is dependent entirely upon the efficiency of the pulping operations in the preceding Jordans. It has been found preferable with most smokeless nitrocellulose to use a series of four Jordans to accomplish the desired pulping, and in most instances, the use of a dewatering tank between the first and second Jordans has been suicient to maintain the desired slurry concentration. IIowever,.the use of a dewatering box between the second and the third Jordan may be resorted to in order to closely control the nal slurry concentration. It has been found that devvatering boxes, after the third Jordan, are

usually unnecessary', but in certain instances such Jordan engines consist of acasing 2| of conical shape in which a cone 22 having knives 24 positioned about its periphery revolve at high speed.

The water containing the nitrocellulose pulp en-` ters via the head box 25 and passes between the cone 22 and casing 2l and the knives 24 Vtear and cut-the pulp into very ne individual fibers of extremely short length. The slurry leaves by the exit 25 provided at the base end of the cone In the jdewatering boxes described hereinbefore, a screen is used which may have any desirable 'numberof openings per inch and these openings are coordinated'in such a manner with the slurry that it is passed thereover as to allow the removal of any desired percentage of the water. The screen, in any case, is of sufficiently small mesh to prevent the passage of any pulp ber which is not of sucient neness to be suitable for introduction into the poaching or washing treatment. Control of the amount of Water removed is facilitated by means of devices which can partially cover the screen and leave exposed to the slurry only a predetermined portion of open mesh. A further means of controlling the water removed is by increasing or decreasing the angle of the screen, and therefore, the screen used is on adjustable bases. In the dewatering boxes, I have found that the use of either copper or Monel screening is desirable in order to prevent corrosion, contamination of the slurry, and to give long life, but Woven fabric or glass lter cloths are also useful in special instances.

The use of the dewatering boxes between Jordans positioned in series materially reduces the power consumed in driving the Jordan, and I have found that power consumption may be reduced as much as for any given amount of pulping. Further, it has been found that by the us'e of Jordans in series for pulping nitrocellulose with dewatering boxes between the Jordons, the capacity of any given set up may be materially increased. This is attributed to the fact that less water must be processed in the pulping operations by as high as 50%, 'based upon nitrocellulose passed from the supply tank to the poaching operation. Other advantages which are inherent Within the method in accordance with this invention are that there is less nitrocellulose lost from the poaching and vmaterial is removed from the pulp slurry and the excessive fine pulp Which Would be produced if this fine material passed another Jordon vis not present in the poaching operation, therefore, less nitrocellulose is lost during decantation vof the poaching and washing tub. Also, due to the reduction in excessive fine material, a faster separation is obtained prior to decantation which conserves time in purification.

It will be understood in accordance with this invention that I may use the pulping procedure for the pulping of any of the various grades of nitrocellulose, such as vfor example, nitrocellulose containing about 12.2% nitrogen usefulfin gelatin dynamite or nitrocelluloses containing above 12.6% nitrogen useful in the production of smokeless powder. However, the present Yinvention is directed in the main to pulping ofvsmokeless powdered nitrocellulose since this type of nitrocellulose has presented more problems in purification due to the great necessity of rendering the pulp stable.

It Will be understood that the details and examples hereinbefore set forth are illustrative only and in no way limiting on my invention as broadly described hereinbefore and in the appended claim.

What I claim and desire to protect by Letters Patent is: f

increase in concentration of` nitrocellulose iines; reducing the water content and simultaneously removing therewith nitrocellulose fines suitable for poaching to reestablish the slurry to optimum operating consistency and a concentration in the order of 8%; and pulping the slurry so obtained with resultant decrease in consistency and conversion of the remaining nitrocellulose to a state suitable for poaching.

CLARK B. KINGERY.

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