US1822174A - Method for the treatment of cellulose and product resulting therefrom - Google Patents

Description

Sept. 8, 1931. s. E. SEAMAN 1,322,174 METHOD FOR THE TREATMENT OF GELLULOE AND PRODUCT RESULTING THEREFROM Filed July 3, 6 2 Sheets-Sheet 1 I7we71/t07 Siewa 56am an J aawwg 1,822,174 METHOD FOR THE TREATMENT OF CELLULOSE AND PRODUCT RESULTING THEREFROM.

Sept. 8, 1931. s. E. SEAMAN Filed July 3, 192 2 Sheets-Sheet 2 l i @i [7?)6'677/607 SiezuarZZZSeanz'an Q W MW, 51%

fiZZ i9 METHOD FOR THE TREATH manta Sept. 193i or nausea, MAINE,

Assrenon To nas'man nnmzrrnoronmo COMPANY, OF SOUTH BREWER, MAINE, A CORPORATION OF MASSACHUSETTS OF CELLULOSE AND PRODUCT RESULTING TEBOK Application filed July 3, 1928. Serial No. 120,372.

' cial quantities) it hasheretofore been conconsidered, or some of the sidered as a standard and preferred raw material for the manufacture of cellulosic derivatives such as nitrocelluloses and the like, in which control of the conversion reactions,

certainty of the final chemical composition and uniformity of physical properties of the resulting product are essential elements. However, when contrasted with the cost of other sources of cellulosic materials, cotton has been relatively expensive. Consequently, numerous efforts have been made to render such cheaper materials available for the purpose of chemical conversion into various cell-ulosic derivatives. In this endeavor, wood has usually been the rimary source y products of Wood such as sawdust, or in a few instances cellulosic substances of other derivation.

Without enumerating the various courses which such efforts have taken or the measure of success or failure by which they have been ultimately attended, it is here sufiicient to state that in general they did not recognize, or they disregarded those chemical and physical chracteristics of cellulosic materials or fibres which facilitate or are essential to .the subsequent reactions required, leading to ments of t e prior art have not produced a suitable cellulose for purposes of converting it into its derivatives. v

In this connection it is to be observed that while cotton possesses the qualities above-set forth to recommend it for chemical treatment, the raw cotton fibre itself is not, in the first instance, susceptible to a ready and uni-- removal of impurities, including a superficial 5 form conversion into cellulos1c derivatives. v

On the contrary, it requires the preliminary filmv consisting of a more resistant Wax-like v substance which covers and efiectively protects the cellulosic body portion of the individual vfibre. Inorder to adequately efiect this removal, the cotton must be subjected to a suitable treatment, sufficiently active to remove this outer waxy layer. In the course of such treatment, the inner cellulosic substance is unavoidably reacted upon and, in

the use of aqueous solutions, is invariably changed. This will occur as a condition in: herent to such processes, even though the utfurther action by the reagents or by the mechanical treatments employed, before removal of the wax-like coating has been accomplished.

- A similar condition is presented byother quently purified to the degree desirable for.

esterification or like purposes.

It is to be observed and emphasized as an inherent part of the general concept of the present invention that, while the chemical condition of the cellulosic material to be reacted upon is of fundamental importance, the physical characteristics which are manifest in the esterification process are equally as important if not in actual practice functionally more controlling. For example, attention is directed to the specific qualifications, that in order for the esterifying reagent to react uniformly upon the individual cellulosic fibres, it must come into intimate and uniform contact therewith. It must also 70 most precautions and care are taken to avoid efiect such contact rapidly in order that the time of reaction upon all portions of the charge of the cellulose base under treatment may be approximately the same. Otherwise, since the composition of the cellulosic deriva tive actually-produced (as with the nitrates) is a direct function of the time of reaction, those portions which are first brought into Contact with the esterifying agent may be over-converted, relative to those acted upon afterwards.

This would imply asubstantially instantaneous penetration of the esterifying reagent upon and into each and every portion and particle of the cellulosic material under treatment, lncidental'to such penetration, there is also involved the simultaneous displacement of entrained volumes of air or other gaseous inclusions, as well as the superficially adsorbed gaseous components which may be associated with the surfaces of the individual cellulosic fibres. Moreover, the reagent must also reach all. parts of the cellulosic substance in quantities sufiicient to bring about the desired conversion.

In this aspect of the physical conditions of the esterii ying reaction, the course of the chemical reaction or reactions again becomes predominant, That is to say, upon the initial contact of the cellulose body with the esteriiijying reagent, an apparent gelatinization may take place, inhibiting further penetration of reacting agents. lhis retards or inhibits further penetration of the esterifying reagent into the cellulosic material and therefore ma not onl cause the formation of successive ayers o' cellulose structure characterized by successively reduced degrees of esterification from the outer surface to the center but may leave the central portions of the gall'ulose aggregates entirely-unafiected there- It is therefore an object of this invention to provide a mode or treatment for cellulosic material (other than cotton) for the purpose of reducing the same to both a physical condition and chemical state closely associated Withthe subsequent conversion of the same into esters or other derivatives, uniformly, and upon a commercial scale.- Further and more specific objects of the invent tion will bemanifest from the following disclosure.

The rocedure involving the subject mat ter of tfi is invention includes in general terms a preliminary reduction of the cellulosic material from the condition in which it is usually found in nature to the condition of a pulp, retainingsthe fibrous structure thereof so far as may consistent with an adequate opening up of the raw material, removing the reagents and other materials which are entrained in or associated with the cellulosic portion and may be regarded as impurities, putting the pulp thus produced nto any convenient form, a portion of the water being removed therefrom, then formin the fibrous mass into separated aggregates o a predetermined order of size or sizes, (without substantially compacting or consolidating the same) and finally drying the resulting mass of fibrous cellulosio aggregates.

More specifically, the invention will be described in its relationship to the preparation of wood cellulose by the sulfite process, resulting in a pulp of a relatively high degree of alpha cellulose. This is followed by a secend-stage treatment of the pulp generally characterized by reagents (such as allraline solutions, with or without alkaline metal rcactive compounds of sulfur) efiective to remove further impurities without appreciable detrimental action upon the cellulosic content, and finally partially dehydrating the pulp and subjecting it preferably to a succession of finely gauged and closely spaced picker teeth by which the individual groups of fibres are caught and rent apart (without appreciable disruption of the fibres them selves) into small tufts or aggregates. These aggregates are more or less uniform in size or volume and are characterized by a high alpha cellulose content and substantially free from resins and other reaction-inhibiting substances, in such condition as to facilitate penctration by the fibre-wetting liquids' without entrapped air or liberated gases of reaction to a commercially detrimental de reofi (The physical condition of the procedure of engaging the fibres with er;- tremely fine points at suitably spaced intervals and plucking the fibres engaged by one point and those more or less firmly intertwined with them from those engaged by an adjacent point (and the fibres intertwined with them) without destroying the length of individual fibres and at the same time without detrimentally compacting such clusters of iibres together. It is, nevertheless, believed that the picking points do compact the fibres immediately engaged thereby to a suificient extent to promote the interlocking arrangement and to thereby create an integrity of the aggregate of fibres which in experience is found to be persistently preserved throughout such subsequent handling as may be necessary in fibre form for baling, storage, etc.

He the ultimatesize or volume of such aggregates may be controlled and varied at will, the number of fibres which each aggregate contains will necessarily be varied. Hence, what. may be termed the fibre density of the separate tufts or aggregates produced by the present invention may be correspondingly controlled and varied (in the maximum size) to accommodate the product to specificr'equirements of the subsequent conversions to which it is to be subjected. In actual experience, for example in nitratfibrous aggregates so produced may be attributed to the Mill llllv lllli Mid ing the product with mixed acid, it has been v found that when the aggregates are approximately of the size of mustard seed, weighing approximately 1 milligram or less and containing approximately 40,000 fibres or less, a satisfactory nitration thereof may be accomplished and a uniform and stable nitrated product is obtained.

A typical succession of steps leading to a product of the desired chemical and physical characteristics with respect to asubsequent conversion, as to nitrocellulose will now be described, reference being had to the accompanying drawings, in-which:

Fig. 1 is a diagrammatic representation of a series of apparatus used, andto. be'considered as in the nature of a fiowsheet;

Fig. 2 is'a.side elevation more in detail of the picker element of the apparatus;

Fig. 3 is a front view of the picker teeth rollers; and i F ig. '4 is an enlargedview of the picker teeth'per se.

Referring now to Fig. 1' of the drawings, numeral 1 indicates the raw material in convenient form, 2 a conveyor leading to the hopper of shredder 3 which stands above the manhole 4 of rotary digester '5. The latter is mounted above the washing vat 6, disposed as to transfer the charge from'5 to'vat 6. Tank 6 has an outlet shown at? into bleach tank 8 from which conduit 9 leads through valve 11 and pump 12 to a thickener 13. This may be of other form but is'shown as comprising screen roll 14 andcouch roll 15, from'which the pulp may be delivered over chute 16 to conveyor 17 leading to squeeze rolls 18, followed by conveyor 21, 22, feed rolls 23, and picker 24. The latter may be of any desired type and delivers through chute 26 to tower 28 h'aving latticework 29 o'r'similar retarding means "for catching the product delivered to it and permittingit to fall on conveyor 31 leading to the picker 33.

The latter comprises a central drum 34 mounted for rotation on trunnions 35 and having parallel and adjacent to the upper arc of its periphery a series of smaller picker roll workers shown as 36, 37, 38, 39, 40, 41' and 42 conveniently spaced. The largerdrum or cylinder 34 (see Figs, 2 and 3 is provided with teeth 43 properly formed along the margin of a continuous metal strip 44 as shown in Fig. 4. This strip may be mounted in helical grooves in the surface of the cylinder 34, and firmly seatedtherein and peened in position. The adjacent rows of teeth 45 may be spaced apart by varying distances but are in any event relatively close together, as shown in Fig. '3 (by which satisfactory results have been obtained using 22 rows to the linear inch). The smaller picker rolls 36 to 42 inclusive may be similarly provided with picker teeth 46 in rows 47 spaced apart to correspond to the rows upon cylinder 34.

ample, the teeth upon the strips used in picker roll 36 maybe of the order of 10 to the linear inch while those on succeeding rolls 37 to 42 may be successively more closely spaced, so that the teeth on picker roll 42 will be 26 or moreto the linear inch. Again, it should be understood that these rows or the teeth thereon maybe differently spaced,

53 toa chute 54 which in turn exists to' a baling or compressing chamber 55 in which a piston 56 maybe slidably mounted and eccentrically connected by'driving rod 57 to the eccentric 58. The exit to the baling chamber may be at 59 from which the bales of compressed pulp may be withdrawn.

' I11 operation the raw material may be pulp which has. been obtained by methods now the usualbisulfile treatment, which is pref- 'erably diminished in duration or in intensit of action or both to constitute a raw cook or even somewhat less than what, for purpgses of paper making, would beregarded as a suitable raw cook,-then washed and subjected to a bleachin treatment if desired. The-material (woo pulp 1 as obtained above) is fed onto the conveyor beltv2 by which it is delivered to the shredder 3. It is torn apart and discharged through the manhole 4 into digester 5. Here it is treated with an alkaline solution preferably containing a reactive compound of sulfur, such as sodium sulfite. This solution may be of a concentration of approximately 3% by weight of reagent materials, but preferably contains substantially equal parts of the caustic soda and of bisulfite (see copending application of C. A. Blodgett and H. H. Hanson, Serial N0.'87,806, filed February 12,

2. A process for-the preparation of cellulosic materials especially suitable for esterification purposes which comprises reducing Wood to the condition of a fibrous pulp,'puri,- fying the same by removal of impurities contained therein, conducting and controlling said treatment so as to alter the physical and chemical properties of the cellulose, to a condition adapted for rapid wetting of the same by esterifying reagents, partially removing moisture, and forming the same into fibre aggregates of a predetermined order of size, by the operation of picking, and finally'drymg.-

3. A process for treating cellulose from wood, comprising purifying the same with an alkaline solution, washing the thus treated pulp free from extraneous materials, bleaching,'separating the bleaching liquor therefrom, removing excess water, passing the pulp thus obtained through a succession of picker rolls having teeth thereon closely spaced and in closely arranged rows, to form cellulosic fiber aggregates of approximately one milligram in weight or less and containing an approximate maximum of forty thousand individual fibers per aggregate, and finally drying.

4. A process for treating cellulose from wood, comprising purifying the same with an alkaline solution containing sodium sulfite,

washing the thus treated pulp free from extraneous materials, bleaching, separating the bleaching liquor therefrom, removing excess water, passing the pulp thus obtained through a succession of picker rolls having teeth thereon closely spaced and in closely arranged rows, to form cellulosic aggregates of approximately onemllhgram in weight or less and containing an approximate maximum of forty thousand individual fibers pe aggregate. and finally drying. v 5. A cellulosic product consisting essentially of. separated, purified, independent wood cellulose fibers, characterized by being assembled into independent aggregates or clusters. the individualfibers of the same being in interlocking engagement with each other and radiating therefrom in -mutually spaced relationship to form independent highly absorbent masses.

6. An aggregate or cluster of purified, separated wood cellulose fibers, said fibers contacting with each other in interlocking engagement, and radiating freely in mutually spaced relationship therefrom to form a highly absorbent mass.

7. An aggregate or cluster of purified, separated wood cellulose fibers, said fibers contacting with each other in interlocking engagement, and radiating freely in mutually spaced relationship therefrom to form a highly absorbent mass, said aggregate or

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