US1842688A - Paper and the process of making cellulose xanthate from it - Google Patents

Description

2&2 H932. 5, A RICHTER L84288 PAPER AND THE PROCESS oF MAKING CELLULosE XANTHATE FROM 1T Filed May 26, 1927 oda ce) mercgrz'zing omhon leteritetl dan., lid, i932 la.. lttlHTllllR, @W BERLM, NEW' HAMPSHIRE, ASSIGNOR T0 BROWN COMPANY', 0F

lmflll, NEW HMPSHIRE, A CORPORATION 0F MAINE AND THE PRESS 01E' MAMXNG GELL'ULOSE XANTEA'TE FROM IT .application tiled may 26, i927. Serial No. 194,506.

ln the manutacture of `riscinie-rayon, it has been the practice to employ as a raw material, cellulose fiber in substantially" unbeaten condition. and in the forni ota drier sheets, so called. These sheets are thoroughly soaked with caustic soda solution, then pressed to remore eircess solution therelroin, and then disintegrated into a bullry mass, which is aged to ellect sullicient depolynierisation to undergo @o substentially complete ranthation.

ln my application, Serial lilo. ltnlo, filed June 2, i927, l have disclosed a process which comprises materially reducing cellulose liber in size prior to processingl asV hereinbelore described. Such reduction in liber site inolres possible a much shorter ageing period, and in some cases permits the elimination el ageing altogether. ll'urthermore, the reduced liber is substantially uniformly depolymerized und hence iranthates more readily completely than liber ot natural or originel sise.

ln accordance with the process ol the present intention, the reduced or shortened liber no is termed into rraterlea'l'I paper or tissue prior to processing', es l have lound that the liber may be handled and treated much more expeditiously and satislactorily while in such conditionu rlhus, the reduced or shortened so liber may be run oil into a continuous sheet ol paper, which ma be continuously soalrcd with caustic soda so` ution and pressed tree of excess solution, and, il necessary, continuously depolyinerized While in sheet term, thus en malrinp possible the practice ot continuous operation -Where batch operation tras heretolore iound to be necessary.

lin practieint;n the process ol2 my invention, cellulose liber ol any suitable type 'lor rayon to -manulacture may be employed lor raw material.= rlllius, ll may preferably employ cot ton liber, sulphite liber, or a relined chemical Wood ber composed essentially ot alpha cellulose., inasmuch as such liber unless further treated comprises component fibers ol Widely varying sizes, it has heretofore been necessary to age such ber until substantially all the large libere Were suiliciently depolymerized or activated l'or zganthation. ll-lence, the ageing period Was long and the aged Llli product non-uniformly depolymeriaed, the smaller fibers being depolymerized to a greater extent than the larger bers, someu times even being over-depolyrnerizteolc ln accordance With my process, 'the liber M, is materially reduced in size, as by beating, but this operation need not edecthydrationI '.lhe fiber is thereby activated :tor Xanthetion, as reduction of fiber size is apparently accompanied by depol merization. Thus, Where my as the original ber requires a lon ageing period-usually from two to fourl aye-to become sufficiently' depolymerized for rinnthation, the reduced or shortened ber may be Xanthated With little, if any, ageing. 'The @g5 reduced liber is run oil" into Waterleal paper, preferably ot light Weight, es such paper muy be processed, most eil'ectively. The paper may be passed through a caustic soda solution in continuous tashion, and then bey@ tween press rolls, 1which serve to remove ein cess solution therefrom, after which it may be depolymerized, il necessar While still inl continuous sheet form. The paper may linal ly be Xanthated in sheet :lorm or alter disinim tegration into a bulky mass, as usual. llnasmuch as the fibers of the mass are small and ol substantiall uniform size and substantially uniform y deolymerized, :ranthation takes place quite rea ily and completely, and a@ the Xanthated product dissolves in caustic soda solution to produce a nanthate solution containing;r only` a small amount oil unxanthated liber.

A more complete understandin ol my es process may be obtained from the rollowing more complete description thereol when considered in conjunction with the acoomponying drawing, which represents diagrammatiu cally and 'conventionally certain apparatus ao which may be employed.

As a raw material, ll may utilise cellulose liber or a mixture ot fibers of any desired origin and suitable for rayon manufacturen The liber is materially reduced in size from o5 its natural or original condition, but this need not be effected under conditions resulting in hydration, as I am not especially interested in. the production ofpaper having physical characteristics other than those necessary for me handling. Reduction in ber size may be accompllshed as by passing the ber through a jordan or charging it into a hollander having a beater roll e uip ed with sharp blades slightly clearing t 1e ed-plate. Jordaning or beating may take place at elevated temperature, this bein undesirable in usual papermaking proc ure, as it tends to decrease the hydratability of the ber, and may- 'be continued until a ber havingan average ber length of, say, 0.7 to 1.3 mm. is reduced to an average ber length below 0.2 mm.

The shortened ber is then run ofi on a paper machine into waterleaf paper or tissue of suitable caliper,-for instance, paper of 20 to pounds basis weight. Paper of low basis weightis preferable, as it may be processed more effectively than paper of high basis weight. If the ber has not been hydrated to any material extent, its freeness permits paper manufacture to be carried out at a high rate of speed.

As il ustrated on the accompanying drawing, the paper thus produced is unwound rom a reel 1, and as shown is passed over and under suitable guide rolls 2, through a caustic soda solution bath maintained in a tank 3. The solution may be of a strength and at a temperature to effect a conversion of the ber into soda cellulose. Thus, a solution of the usual 18% strength and, if desired, containing a certain amount of caustic potash and lithium hydroxide, may be employed at'room temperature. The paper is rapidly permeated by the solution, and becomes substantially uniformly converted into soda cellulose. In. lieu of passing the paper through one bat-h of solution as shown, it may be passed through a series of such baths while passing the solution from bath to bath in counter-current flow to the direction of travel of the paper. This procedure produces a purer soda cellulose, as in passing through the successive baths, non-alpha cellulose components such as pentosans, lignin, and other coloring impurities present in the fiber are dissolved therefrom, the concentration of these impurities in solution decreasing from bath to bath toward the last bath, so that when the paper emerges from the last bath, it contains substantially pure solution. This latter procedure is particularly effective when treating an ordinary ber of wood origin, as it results in a xanthate solution containing a low amount of coloring impurities.I

Provision is -now made to remove excess solutlon fromv the saturated paper. As shown, this is accomplished by passing the paper as it emerges from the solution bath` over a suction boxI 4,. and thence between press rolls 5 stationed close to the suction box.

The solution thus removed may be reused by passing it from the suction box through the pipe 20 into the tank 3.

At this stage rin the process,`r it may be desirable to depolymerize the ber somewhat, or to prevent depolymerization. If depolymerization is desired, the paper may be heated somewhat and/or treated with an accelerator of depolymerizamedium therethrough. For instance, thev rolls may be maintained at, say, 40 to 50 C., at which'temperature depolymerization takes place quite rapidly. After such heating, the paper may be cooled, as by running it over cooling rolls, to the temperature at which it is desired to carry out xanthation.- Inasmuch as cooling greatly reduces the rate of depolymerization, upon reaching the desired depolymerized condition of the paper, it may be cooled quickly to prevent further material depolymerization. If desired, air, oxygen, or other depolymerization` accelerator, at roomor elevated temperature, may be delivered onto the paper while it is supported on the rolls, without circulating a medium through the rolls, or while it is festooned, in case rolls are not used. On the other hand, if depolymerization is to be prevented. the paper may be maintained in contact with the atmosphere for only a very short time, or may be cooled to below room temperature while supported on the rolls 6. If depolymerization is effected by passing the paper over heated dryer rolls, a certain amount of water contained in or disintegrated into a bulky mass prior to xanthation, as is usually done. As shown the paper passes into a disintegrator 7, which may be of the usual shreddertype and which serves to disintegratexthe paper into a uff or bulky mass of crumbs of high specific vo ume,-1000 cc. for instance, weighing about 200l grams. The crumbs may be discharged through a spout 8 into a storage hopper 9, from which they may be `withdrawn for xanthation. As indicated, they gravitate through a valved dischargeconduit 10 andymingle with carbon bisulphide'fed into the conduit in controlled amount from a tank 11, both materials passing into one end of a rotary reacting drum 12, wherein they under- Leia go reaction under controlled temperature conditions to 'form cellulose xanthate. The

cellulose xanthatc is delivered from the other end ont the drum into a spout 13 discharging 5 into a dissolving tank 14, Whereinto caustic soda solution from a storage tank 15 and Water trom a supply pipe 16 are ted in requisite amount to term an aqueous solutionv of the desired concentration. Any unxanthated liber present in the solution may be separated therefrom by filtration, a pump 17 heilig shown for withdrawing the solution from the tank la for further processing. lnasmuch as the soda cellulose crumbs are composed of small fibers depolymerized approximately to the same degree, substantially complete xanthation takes place quite readily in the drum, and the xanthated libers dissolve to form a solution containing only a small amount oi" unitanthated liber. v

lWhere it is desirable to carry out the processing up to shredding independently of the ,remainder oi the processing, the paper Wound up quite tightly into rolls as it comes troni the roll `S in the desired depolyineriaed condition. 'llhese rolls of paper `ein a relatively small amount oit' air, so i at depolyinerization does not take place at room temperature to a material extent., even number of days.

i hereinbelore described may iornied upon several plies ol paper saine time. Thus, several rolls ot' palbe univound sin'niltaneously, and spective plies passed separately in elution 'through the solution in the ""hercui'ion they may be united and 'Ween the press rolls 5, and subsej i 'handled as a single sheet. Using relatitelJ nin papers, ready and complete penetration the solution is secured. lllherc son'iewlit heavy papers are used, 'they may be porto ited to aid pcrmeation by the solution, depolymerization, and subsequent shredding.

do not herein claim broadly the subject matter et my application Serial No. 196,135, tiled dune 2, i921?, -which discloses the advanti fes oi materially reducing cellulose liber in 5@ site prior to conversion into cellulose derivatives such as cellulose itanthate, nor do l herein speciiically claim the subject mattei' of my application `Serial lll o. 122,2?1, tiled duly lil, i926, which discloses the advantages of beating those pulps which undergo disintegration il soaked in unbeaten sheet torni in a. solution ot caustic soda, prior to conversion into cellulose xanthate.

ll'laving thus described this invention, it is obvious to those skilled in the art that change and modilieation might be made therein without departing from the spirit or scope oi the appended claims.

"What ll elaim'is:

l. Waterleaf paper especially suited for Xanthation, having perlorations therein and comprising liber having an average liber length below about 0.2 mm.

2. A process which comprises markedlyreducing cellulose liber in size, running such reduced fiber oli into Waterleai` paper,'and converting such paper into cellulose Xanvthate.

3. A process Which comprises markedly reducing cellulose ber in size, running such reduced fiber off into Water-leaf paper, treating such paper with caustic soda solution, and converting the treated paper into cellulose xanthate. i

4. A process which comprises' reducing cellulose liber in size, running such reduced liber oft into waterleaf paper, treating such paper with caustic soda solution, disintegrating the treated paper into crumbs, and Xanthating the crumbs.

' 5. A process which comprises beat-ing cellulose liber until its average liber length is reduced to below about 0.2 mm., running such beaten fiber ed into paper, and converting such paper into cellulose xanthate.

6. A. process Which comprses treating a continuous sheet of'ivaterleatpaper composed of markedly shortened fibers to form soda cellulose, and continuously depolymerizing the paper in an atmosphere ot oxidizing gas While in sheet form. l l. lli process which comprises passing a continuous sheet ot waterleat paper composed oit' markedly shortened libere through caustic soda solution, continuously removing excess solution therefrom, and continuously depolyinerizing such paper in an atmosphere of oxidizing gas while in sheet term.

8. A process which comprises passing a continuous sheet ot' waterleai paper composed oit' markedly shortened libcrs through caustic soda solution, continuously removing excess solution therefrom, and. continuously dcpolymerizing such paper in an atmosphere ol oxidizing gas under accelerated depoly1nerizing conditions While in sheet form.

9. A process Which comprises passing a continuous sheet et Waterleat paper composed ot markedly shortened libers through caustic soda solution, continuously removing excess solution therefrom, and continuously dcpolymerizing such paper in a heated atmosphere of oxidizing gas While in sheet form.

10. A process which comprises passing a continuous sheet ot Waterleat paper composed of markedly shortened fibers through caustic soda solution, continuously removing excess solution therefrom, and continuously depolyinerizing such paper in a heated atmosphere of oxidizing gas and in the presence of an accelerator ot' dcpolylnerization While in sheet form.

11. A process which comprises passing a continuous sheet ot Waterleaf paper composed of shortened fibers through a caustic soda solution, continuously removing excess soluconverting the depolymerized paper into celtion therefrom, continuously depolymerizing lulose xanthate.

such paperA While suspended and guided in In testimonyl whereof I have aliixed my sigsheet form, and continuously disintegrating nature.

5 the de olymerized paper into crumbs. GEORGE A. RICHTER. 70

12. E process which comprises passing a continuous sheet of waterleaf paper composed of shortened fibers through a caustic soda solution, continuously removing excess solution therefrom, continuously depolymerizi-ng 75 i such paper while suspended and guided in sheet form, continuously disintegrating the depolymerized paper into crumbs, and xanthating the crumbs.

continuous sheet of paper compose of markedly shortened fibers through a series of baths of caustic soda solution While passing the solution from bath to bath in counter-current flow to the direction of travel of the paper, 85

continuously removing excess solution therefrom, and converting the paper into cellulose xanthate.

14. A process which comprises passing a plurality of continuous sheets of waterleaf 90 paper composed of markedly shortened fibers separately through a caustic soda solution, uniting said sheets into a single sheet, pressing excesssolution from 4said sheet, and converting said sheet into cellulose y 95 xanthat-e.

15. A step product in the manufacture of cellulose xantl1ate,consisting of paper whose fibers not only are markedly reduced in size from their natural or original condition but 100 are combined with caustic soda as soda cellulose and are substantially uniformly depolymerizcd. l

16. A step product in the manufacture of cellulose xanthate, consisting of paper com- 105 prising substantially uniformly depolymerized fibers combined With caustic soda as soda cellulose and of an average fiber length below about 0.2 mm.

17. A process which comprises beating celno lulose pulp to reduce the length of the pulp fibers, forming the beaten pulp into Waterleaf paper, saturating such paper with a solution of caustic soda, pressing excess solution from such paper, shredding the paper, H5 and converting the shreds of paper` linto viscose.

18. A process Which comprises beating cellulose pulp to reduce the length of the pulp fibers, forming the beaten pulp into Waterleaf 120 paper, and converting such paper into cellulose xanthate. 19. A process which comprises beating ce1- ]ulose pulp to reduce markedly the length of the pulp fibers, sheeting into waterleaf paper, passing a continuous sheet of such papel' through a caustic soda solution of mercerizing strength to form'soda cellulose, progressively depolymerizing such fiberv in an atmosphere of oxidizing gas while in sheet'form, and

13. A process Whichcomprises assing a 30.

Images