US2480998A

US2480998A - Process for disintegration of moist fibrous alkali cellulose masses

Info

Publication number: US2480998A
Application number: US552967A
Authority: US
Inventors: Brackett John
Original assignee: American Viscose Corp
Current assignee: Akzo Nobel UK PLC
Priority date: 1944-09-07
Filing date: 1944-09-07
Publication date: 1949-09-06
Anticipated expiration: 1966-09-06

Description

p 1949- J. BRACKETT PROCESS FOR DISINTEGRATION OF MOIST FIBROUS ALKALI CELLULOSE MASSES Filed Sept 7, 1944 INVEN TOR.

atented Sept. 6, i949 PRlDfiESS BFQR DKSEN'EEGRdTHQN @F MUES'E FMRWUS AL CELLULQSE MASSES .lohn raclsett, New Yorh, N. it... assignor to crloan Viscose tiorporation, Wgton, Met, a corporation ct Delaware Application September 2?. 19%, Serial No. 552,965?

Mil. b ti d @la.

This invention relates to methods for the disintegration of moist fibrous masses, such as moist masses of cellulose, alkali cellulose, cellulose xanthate or other cellulose derivatives, as well as fibrous masses of other materials.

In accordance with the present invention, it has been found that moist fibrous masses can be converted extremely rapidly into a desirable light and fluffy product in which the fibers are all thoroughly loosened by allowing the fibers to be drawn into a fan rotating at high peripheral velocity so that the masses are subjected first to the shearing action which occurs upon their initial striking of the blades and then to the shearing that occurs as the masses slide along the surface of the blade, and finally to the im pact and shearing action which occurs when the fibers strike the scroll or casing of the fan and slide along it under the action of the air velocity to the exit of the fan. In the case of an axial flow 'fan, the final impact and shearing action takes place upon the channel about the fan blades instead of in the scroll thereabout. Regardless of whether a tangential or axial flow fan is used, the impact is cushioned by the air flow and the highly turbulent force of the violent flow of air contributes a major part of the disintegrating action. In addition, the evaporative action of the gas flow upon the surface of the particles as it progressively is more and more exposed prevents sticking or the particles after impact. This evaporative action also has a definite cooling effect which prevents overheating of the equipmeat.

The arrangement in accordance with the invention is such that the lan itseli acts as the conveyor or the fibrous masses both before and after disintegration. Provision is also made for recirculation of the air or gaseous medium. This is important when the fibrous material is such as to react with certain constituents of the atmos phere, such as the absorption of carbon dioxide by Referring to Figures 1 and 2, a hopper 2 is provided for supplying the moist fibrous masses and the fan 6. A motor '8 drives the fan through a shaft 8 which is secured to the rotor carrying the blades 9 of the fan. The blades 9 may merely be radial or they may be curved backward or forward in the conventional manner. Preferably, the blades 9 are arranged to provide a central pocket iii which first receives the moist fibrous masses from the suction conduit 5.

The scroll or casing it may be of cylindrical form or may be of volute form and communicates with a tangential discharge conduit ii. The conduit 52 branches into two channels it and it, the former of which connects with the suction side ii of the fan and the latter It discharges tangentiallyinto a cyclone type separator E5 in which the particles or fibers are allowed to settle and are collected in the receptacle it. A bafiie ii" is arranged concentrically within the upper portion of the settler l5 and a conduit it connects the region within the baiiie l l to the suction conduit t for recirculating air or other gas to the fan. A pipe it] controlled by a valve 20 is connected to the suction conduit 5 and is used when it is desirable not only to exclude or minimize certain atmospheric ingredients, such as carbon dioxide when disintegrating alkali cellulose, but to maintain an'inert gaseous atmosphere within the disintegrating system. Thus, the conduit id may be connected to a supply of nitrogen, helium, hydrogen, carbon dioxide or the like, the particular as depending upon the specific material being disintegrated.

A three-way valve or damper 2! may be turned to direct the fibers discharged by the fan either into the separator lb or back into the suction side of the fan through conduits l3 and 5.

In Figure 3, the fan t is replaced by the fan to and the suction conduit 5 is replaced by the suction conduit to which is in substantial alignment with the discharge conduit 112a. The conduit 620: may branch as in Figures 1 and 2. As shown, the fan is provided with two propeller-type fan blades to disposed on opposite sides of the motor la.

In order to obtain satisfactory disintegration, it has been found that it is necessary to operate the fan at a peripheral velocity of 10,000 feet per minute or higher. For many types of products which are not tenaciously adhesive, it has been found that a single pass through a fan operating at a peripheral velocity of 10,000 to 15,000 feet per minute is capable of producing a light fluffy product of desirable characteristics. This amounts to a treatment period of less than a minute and, in the preferred case, of less than a quarter of a minute. Instead of recirculating in the manner shown in Figures 1 and 2, the arrangement of Figure 4 may be substituted for the single fan 6 of Figures 1 and 2. As shown in Figure 4, the moist fibrous masses are first fed through the conduit 5b into the suction side of the fan 6b which is operated at low speed, it may be less than 10,000 feet per'minute, and this fan discharges through the conduit 23 into the suction side of the fan 61')" rotatingat high speed of 10,000 or more feet per minute, and this fan discharges into the conduit 12b which may be branched out as in Figure 1 into a recirculating conduit and into a conduit leadin to a cyclone separator. In this arrangement, the fibrous masses are preliminarily broken down to smaller aggregates by the first fan and subsequently completely disintegrated in the second fan.

It is well known that the normal effect of throwing moist masses against an impact wall tends to increase the density and compact the masses. However, in accordance with the present invention this compacting effect is avoided because of the turbulent action of the aircurrents in the vicinity of the impacts. It is difiicult to explain just what is the precise action that accounts for the maintaining of a light fluffy product instead of the production of compact undesirable slugs because of the impact forces involved. However that may be, it is probable that a major portion of the effect is the result of the high velocity air currents, the impacts serving merely to break the larger masses into smaller ones and the air currents serving to completely disintegrate the smaller masses and the exposed surfaces of the larger masses. An important factor in the procedure is the fact that the air currents do not have the same direction as the fibrous masses at the instants of impact. Another important factor is the moistcondition of the masses which causes them to have some slight tendency to stick to the surfaces of the fan blades or of the scroll or casing thereabout, thus tending to resist the action of the air currents and thereby increasing th disintegrating effect of such currents during the time the fibrous particles or masses are subject to them as they slide along such surfaces. However, this adhesion is not sufficient to cause the fibrous masses to be deposited and to accumulate in any portion of the casing or scroll or fan system. In all of the systems contemplated by the present invention, the fibrous masses being disintegrated are not allowed to accumulate or remain within the fan over a prolonged period, the high velocity air currents continuously moving the particles as they are disintegrated along through the fan system.

It has been found that the use of the high speed fan for disintegrating moist pressed masses of alkali cellulose fibers results in fiufiy products having a lightness and reactive quality that have never been obtainable by the use of equipment, such as the Pfeidlerer mill, which has heretofore been conventional for this purpose. The products of the present invention have been found to be, as a general rule, fully a third lower in density than the products obtained in accordance with the conventional processes of the prior art and this low density is obtained in a period of 5 to 15 seconds as compared to 1 to 2 hours milling in a Pfeidlerer. When these lighter products are subsequently converted to derivatives, such as wnue preferred embodiments are disclosed, it v is to be understood that the description is merely illustrative and that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. The process of preparing moist aggregates of alkali cellulose for conversion to cellulose derivatives comprisin introducing the aggregates into the suction stream of a fan operating at a linear peripheral velocity of at least 10,000 feet per minute in a closed channel having inlet and discharge openings, carrying the aggregates in the stream through the fan so that the disintegrating masses are subjected to the successive action of impact and sliding friction on the surfaces within the fan system while simultaneously subjecting them to the turbulent action of the gas currents developed within the fan while avoiding the introduction of any substantial amount of heat whereby the channel is maintained close to normal room temperatures and sufiicient evaporation occurs from the surfaces of the disintegrating masses to prevent adhesion thereof to the system whereby the alkali cellulose is converted to a light, fiuify condition capable of rapid reaction to produce derivatives of improved uniformity, settling the fibers from the fluid stream discharged from the fan, and returning a substantial portion of the fluid stream to the suction side of the fan to minimize the amount of carbon dioxide carried into the suction stream of the fan.

2. The process of claim 1 in which the disintegration of any given aggregate is conducted within a period of less than one minute.

3. The process of claim 1 in which the disintegration of any given aggregate is conducted within a period of less than a quarter of a minute.

4. The process of preparing moist aggregates of alkali cellulose for conversion to cellulose derivatives comprising introducing the aggregates into the suction stream a fan operating at a linear peripheral velocity of at least 10,000 feet per minute in a closed channel having inlet and discharge openings, carrying the aggregates in the stream through the fan so that the disintegrating masses are subjected to the successive action of impact and slidin friction on the surfaces within the fan system while simultaneously subjecting them to the turbulent action of the gas currents developed within the fan while avoiding the introduction of any substantial amount of heat whereby the channel is maintained close to normal room temperatures and sufiicient evaporation occurs from the surfaces of the disintegrating masses to prevent adhesion thereof to the system whereby the alkali cellulose is converted to a light, flufiy condition capable of rapid reaction to produce derivatives of improved uniformity, settling the fibers from the fluid stream discharged from the fan, maintaining a gaseous medium substantially free of carbon dioxide in contact with the aggregates and disintegrated masses substantially throughout the disintegrating system, and returning a substantial portion of the fluid stream to the suction side of the fan. l

5. The process of claim 4 in which the disintegration of any given aggregate is conducted within a period of less than one minute.

6. The process of claim 4 in which the dia- 5 integration of any given aggregate is conducted Number within a period of less than a quarter of a minute. 1,677,725 JOHN BRACKE'I'I. 1,717,661 1,873,393 REFERENCES CITED- 5 1,892,233 The following references are of record in the i'ggggg the of this patent. 1,986,301 UNITED STATES PATENTS 2,285,508 Number Name Date 10 1,385,447 Hamilton July 26, 1921 N be 1,571,518 Foster Feb. 2, 1926 1 2 1,577,545 Bodez l'und Mar. 23, 1926 Name Date Montgomery July 17, 1928 Calvert June 18, 1929 Hallam Aug. 23, 1932 Chappell Dec. 27, 1932 Neuman June 6, 1933 Richter May 29, 1934 Stockton Jan. 1, 1935 Goss June 9, 1942 FOREIGN PATENTS Country Date Great Britain July 26, 1921