US1632802A - Process of and apparatus for treating fiber - Google Patents

Description

June 21 1927.

- G, A. RICHTER PROCESS OF AND APPARATUSFOR TREATING FIBER a -l e XIT www

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Filed Aug. l0, 1926 Patented June 21, 1927. e

[UNITED STATES GEORGE A.

y 1,632,802 PATENT oFFlca.'

RICHTER, OF BERLIN, NEW HAMPSHIRE, ASSIGNOR TO BROWN COMPANY, 0F BERLIN, NEW HAMPSHIRE, A CORPORATION OF MAINE,V

PROCESS 0F AND APPARATUS FOR TREATING FIBER.

Application led August v10, 1926. Serial No. 128,398.

This invention relates to a process of treating fiber with a chemical solution, and has for its ob'ect to provide a process of treating such fiber in a continuous, etlicient and economical manner.

After iberhas been lliberated by suitableA digestion from wood chips 'or other cellulose-bearing material, it is frequently desired further to treat such fiber with a chemical solution. For example, it may be ,desired to treat raw sulphite fiber with a solution of caustic soda to effect a removal of the non-alpha. cellulose constituent present therein andthus to produce a fiber containing a high percentage of alpha or resistant cellulose.

If such alkaline treatment is carried out under the proper conditions for the requisitev period of time, the resultant fiber will contain upward of 93% alpha cellulose,..and is bleachable to a high degree of whiteness-- with a low strength bleach solution. Such alpha or purified cellulose fiber is suitable for use as a new rafr or cotton fiber substitute in the manufacture of high grade papers and the preparation of cellulose derivatives. In commercial practice, the chemical present in the spent treatin liquoris recovered. In my a plication or atent, Serial No. 26,361, file April 28,1925, have described a method of economicall recover- :ing such chemical. Themethod t erein set forth, however, is dependent upon the use of a" raw fiber which hasbeen dried or concentrated to a consistency of, say 50% before alkaline treatment. Consequently a 10% to 12% raw fiber resultin from washing and screening such ber a ter its liberation must be concentrated as by passage .through a high pressure thickener, press rolls, or the like.

One feature of the process of the present invention is that the chemical presentin the spent liquor may be recovered without requiring such hi h concentration of raw fiber,

thus eliminatmg the necessity vof a high 'i pressurethickener or the like.- Another feachemical content of the spent liquor conserved. f

In accordance With the process of the present invention, the chemical treatment of the fibertakes place while such fiber'is being passed through and washed in continuous, counter-current flow. This may be done in apparatus of the general type shown and described in United States Letters Patent No. 1,421,664, issued July 4, 1922, to Brown, Moore, Parker and Martinson. e A'series of' treating baths gradually increasing in concentration of treating chemical from substantially only water at one end ofthe apparatus toa solution of maximum chemical concentration at an intermediate portion thereof and then gradually decreasing in concentration from the intermediate portion to substantially only water at the other end thereof, is maintained in the apparatus. Water is continuously introduced into one end of the apparatus, and a flow of solution is produced from bath tobath toward the other end of the apparatus, from which Water is discharged, and into which iber to be treated is continuously passed through the apparatus in countercurrent flow to the water. A volume of spent solution containing the chemical being spent is continuously withdrawn from and s utlicient fresh chemic'al solution lto make up mechanical losses and to replace chemical in the solution being withdrawn `is continuously introduced into the intermediate portion of the apparatus.

. For a more complete understanding of this invention, reference vmay be had to the accompanying drawings, wherein Figure 1 represents somewhat vdiagrammatically and conventionally a section throughan apparatus for carrying out the process4 of the present invention.

Figure 2 represents a fragmentary section through an .apparatus which is lengthened intermediate its ends.

The apparatus comprises -a series of sections, each consisting of a storage tank containing a` pool of treating solution, and a treating tank associated therewith and lo'l cated thereabove. The treating solution in the'successive storage tank flows in a direcc tion opposite to the flow ofthe fiber. These 110 tanks are indicated as 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10, in The solution overflows a series of partitions 1.1` placed between the tanks and gradually decreasing in height from the tankl to thev tanklO so that a substantially continuous ow of solution from the tank 1 to the tank results.

The treating tanks are designated as 1',

y,The ber is removed from the cylin er and depofsited in an agitatin 'compartment 12* 'containing the treating so ution, b a scraper A 16 acting against the cylinder an stationed l on a partition 17 dividing the'thickening and 'tatin' compartmentsU A sup l of solutln -is lgiaintain'ed in each treating7 tank b withdrawing solution from the corres on ing storage tank by a pump 27 and elivering it -t rough a pi 28 into the agitating compartment. The geber is agitated -in the solution maintained in the treating -comartment, by a air of agitators` 18, and ows over a partition 19 into the next adjacent thickening compartment.

thus a constant circulation of the treating solution from each storage phi, to be purified'- from the treating tank 10", throu 23. The treati lent compound.

tank, through the agitating compartment of the treating tank, and thence through the straining cylinder backk to its storage tank. l

The ber is introduced into the first treating tank 1* through a pipe 22, and is withdrawn at the other end of the aparatus a 1 h solltlion il, intr ucg in d t e treat'4 ta 5 rou a pipe an wateris 1iiigtroduced into tg through a ipe 24- and withdrawn from the storage tank 10 through a pipe 26.` y

Where'a raw ber e. g., unbleached sullnto ber of high alpha cellulose content, the\treating solution may be a -solutionof caustic soda or equiva- `The raw ber may be delivered into the. apparatus, as it comes from the washing and screening o rationsnas, sa a 10% to 12% aqueo `pu p suspension. Ag it passes through theuguccessive treating tanks toward the center of the a paratus the weer minted vtherewith iv lsplwed.

byl a caustic soda" sohtion of increasing stre, h so that it aeuires a maximum caustic soda concentration when it reaches the treating tank 15'*v into which the caustic soda solution is introduced. On passing for wardly from the tank 5, the 'caustic soda solution associated with the-l ber is displaced by a solution of progressively de- Therev is stituent of which has been s e storagetank 1' rifed ber dlscha'rgedthrough the pi creasing strength, so'that when the beris discharged from the last treating tank 10, the solution is substantially entirely displaced by water. l

Operation may be initially commenced by maintaining the volume of caustic soda solution continuously delivered into the treating tank 5* and the volume.- of wash water continuously introduced into the storage tank 1 substantially equal to the volume of water associated with the raw ber. The apparatus is controlledto discharge `a ber having a water content equal to that of the raw ber. Substantially only water is discharged through the outlet pipe 26. After the uilibrium concentration of caustic soda as been attained in the tanks, only suicient caustic soda solution to makeup sodium constituent spent' and contained 1n spent solution bled o from the st ora tank 5 through a valved pipe 29 and to ma e up mechanical.

losses, need be introduced into the treating tank 5*. The volume of wash water introduced into the storage tank 1 islthen maintained substantially equal to the waterlcontentof the raw ber as it is introduced and the water discharged through the dutlet pipe 26 so that the concentration of active or nt caustic soda in eachof they stora e and treating tanks remains substantial y constant during the continuous operation of the apparatus. The ow bled roil throu h the pipe 29 is regulated to rovide for t e withdrawal of the solution, e sodium vcont by reaction with- Vthe nonalpha cellulose constituent of the ber so that accumulation of dissolved organic matter in the apparatus is prevented. 0 course, some unspent sodium constituent l caustic soda solutionis'eected. First, the

displacement of the water content Vof the raw beriby a solution of caustic soda occurs and then the displacement of the solution of caustic sodaby water. Consefluently, substantially all the'. treati solution except that drawn of throughe pi 29 is maintained within lthe apparat su stantially only water accompanying px at one end of the apparatus, andfsu antially only water bolug-discharged through thefoutlet pipe 26st the'o posits end thereof. If thetreatment isearri out at an elevated temperature as by introducing steam` into the central poolfmainta-ned in the storage tank 6, the heat-'content (e pt for that qf the bleed solution), in tion to the chemical content of the solution, is maintained within the apparatus.

When a concentrated solution of `caustic soda is employed in treating the ber, only a relatively short treating period, say, ve to ten minutes, at about room temperature, is necessasry to produce an alpha ber having characteristics rendering it especially applicable for viscose preparation.

When a relatively dilute solution of.k caustic soda is employed in treating the ber, a longer treating period temperature are necessary to produce ber of the desired alpha cellulose content. The time of treatment may be prolonged by operating the apparatus at lower` capacity or by constructing one or more of the intermediatestorage and corresponding treating tanks of the apparatus longer than the otheis. Figure 2 shows an apparatus the central section of which is provided with a treatingtank, the agitating compartment of which is about four times the length of the other treating compartments and which is shown provided with four pairs of agitators. A longer period of treatment is thus permitted at the section of the apparatus Where the solution is strongest 'and .the rate of ber purification greatest. v

It is evident that, if desired, a certain amount of bleach liquor or other equivalent oxidizing liquor may be introduced with the caustic soda solution into the tank 5EL to aid in the purication of the ber.

While the processs of the present invention has been described'in `-connection With treatment of raw ber toy purify the same, it is obvious that this is illustrative only, and that the processmay be practised to veect aI treatment of ber with other chemical solutions.`

What I claim is:

1. A process of treating ber with a chemical solution and Washing the same, which comprises maintaining a series of treating baths, introducing ber into an end bath and passing said ber from bath to bath toward the other end bath, introducing Water into the other end bath and the chemical solution into an intermediate bath, and producing a flow of Water from bath to bath in countercurrent flow to that of the ber.

2. A process of treating ber with a chemical solution and Washing the same, Which comprises maintaining a series of treating baths gradually increasing in concentration of treating chemical from substantially only water at one end of the series and toward an intermediate bath thereof, and then gradually decreasingin concentration from the ber` into an end bath and passing said ber from bath to bath toward the other end bath, introducing water'into the other and an elevated intermediate bath to substantially only Water at the other end thereof, `introducing end bath and a chemical solution into the intermediate bath, and `producing a ow of Water from bath to bath in conntercurrent oW to that of the ber. v

3. A continuous process of treating ber with a chemicaly solution and washing the same, which comprises continuously feeding the ber to and agitating it in a series oi baths gradually Increasing 1n concentration of treating chemical fiomsubstantially only raw ber suspension, which comprises continuously feeding the raw ber' suspension to and agitating it in a series of alkaline baths gradually increasing in concentration of alkali from substantially only Water at one end of the series toward an intermediate bath thereof, and gradually decreasing in concentration from the intermediate bath to substantially only Water at the other end thereof, continuously introducing Water in. to the last bat-h of the series and alkaline solution into an intermediate bath, and

.causing the Water to ow in oppositeb direction to the flow of the ber through such series of baths.

5. A continuous process of removing nonalpha cellulose constituent from an aqueous raw ber suspension, which comprises con. tin'uously feeding the ber suspension to and agitating it in a series of alkaline baths gradually increasing in vconcentration of alkali from substantially only Water at one end of the series toward an intermediate bath thereof, and gradually decreasino" in concentration from the intermediate battlrto substantially only water at the other end thereof, continuously introducing Water into the last bath of the series in amount equal to the water content of the raw ber suspension and an .alkaline solution into an intermediate bath containin alkali in amount suiiieient to make up mec anical losses and alkali being spent by reaction, causing the Water to flow inopposite direction to that of the ber through such series of baths,

rials to discharge substantially `only an aqliieous suspension of high alpha cellulose er at onev e'nd of the series and Water at the other end of the series.

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4and regulating the relative flow of the mate- 6. A continuous process of removing non-I alpha cellulose constituent from an aqueous raw 'ber suspension, which comprises continuously feeding the fiber suspension and A agitating it in a series of alkaline baths `gradually increasing in concentration of alali from substantlallyonly water at one end of the series toward an intermediate bath thereof, and gradually decreasin vin concentration from the intermediate bat i to substantially only water at the other end thereof, continuously introducing water into the last bath of the series in amount equal to the water content of the raw liber suspension 'being introduced and an alkaline solution'into an intermediate bath containing alkali in amount'suicient Yto make up mechanical loes and alkali being spent by reaction, causing the water to flow in opposite direction to that of the liber through such series of baths continuously bleeding off spent solution from the intermediate bath, and regulatin the relative iiows'o the materials to disc argel substantially onlyl an ueous suspension of high alpha cellulose ber at one end of the series and water at the other end of the series.'

7. A process of treating a fiber suspension with a chemical solution and washing the same, which'com rises maintaining a series of pools of the so ution, producing` a iow of solution successively from pool to-pool, circulatin solution from each `pool 4to a treating bai, su plying water to an end ool and chemica solution to an interm iate treatin bath,l feeding the fiber suspension throu the successive baths in a dlrection o poslte to the flow ofthe water, agitating t e fiber in said' baths, removin a portion of the solution.- from said fiber before it is fed from one bath to another, circulatin such liquor to the corresponding pool, an regulating the relative flow ofthe materials to discharge substantially only-an aqueous liber suspension at one end of the series and water atthe other end of the series.

8. A process of treating a lfiber suspension with a chemical solution and Washlng the same, which comprises maintainin a se` ries of treating baths, introducin ber into an end bath and assing said ber from bath to bath towar the -other end bath, agitating the iberin' said baths, thickening said fiber before it is fed from one bath to another, introducing water linto the other end bath, introducing treating solution into. an intermediate bath, and roducingv a flow of water from bath to bath 1n countercurrent flow to that of the fiber.-

9. An apparatus for 4cheinicall treatin and washing liber, comprising a p urality o sections arrangedin serles, each section' comprising a storage tank containing a pool, of treating solution and a treating tank containin a bath of treating solution, means at eac section for causing a-circulation of solution from the stora e tank tothe treating tankv and thence ack to the storage tank, means for passing the fiber-into an end treatin tank and from one treating tank to the ad]acent treating tank, means for 1ntroducing water into the storage tank at the opposite end and for causing a flow of water from one storagetank toan adjacentstorage tank in opposite direction to the passage of the fiber, andmeans for introducing treating solution into a treating tank intermediate'the ends of said apparatus and for withdrawing solution from a storage tank intermediate the ends of said apparatus.

Inl testimony whereof I have affixed my si ture. e

gm GEORGE A. -RICHTER.

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