US 1960551 A
Description (OCR text may contain errors)
Paterlted May 2 9,?19 34 I I a t l v 'unl'rao S AT S PATENT; oFFlcs CELLULQSIC l' ltolfiigNsGm METHOD George A. Richter, Berlin, N. IL, assignor to Brown Company, Berlin, N. 11., a corporation No Drawing. Application March 24, 1931,"
"- Serial No. 525.037 4 18 Claims- (Cl. 260-10) This invention relates to the manufacture of the market. The bulk or sheeted pulp is initially cellulosic products wherein cellulose fiber of the transformed into a non-hydratable condition, by type of cotton or chemical wood pulp servesas which I mean that the cellulose is so altered that the starting material. Among the cellulosic prodit does not take on a slimy or gelatinous condi- 5 ucts comprehended by the present invention are tion when beaten in water. This can well be acno papers and cellulose esters or derivatives, such mpli hed y merc izing the fibers as with a as the xanthate, nitrate, and acetate. caustic soda solution. .The solution employed In making papers and cellulose derivatives, it may be of a concentration designed to mercerize is desirable to use as a raw material white celluthe pulp at the particular temperature at which lose fiber of high purity and stability, such as it is used. Should the treatment he carried out 05 cotton or bleached chemical wood pulps of high at room temperature (about 0.), as is usually alphacellulose content, In some instances, too, preferable, the solution ShOllld. be of about 18% a pulverulent cellulose derived from such fiber caustic soda content. When lower treating temmy be ui us to great advantage. Thus, peratures are resorted to, the solution may be of 15 when mechanically pulverized cellulose fiber of a strength below 18%, since lower temperatures the kind describedisincorporated into papermakare conducive to mercerization with weaker soing'furnishes, the opacity and surface characterlutions. When bulk pulp-is used, the mer I istics of the finished paper may be easily and 8 S lut n m y .be ni ormly mixed with the economically controlled by the use of a suitable pull) to form a stock suspension of about 10%. 2o amount of cellulose powder of the appropriate After the required period of exposure to the ac- 76 particle size. The cellulose powder constitutes tion of the memorizing-solution, the excess liquor an excellent filler'for high grade papers and may Se v ng asa Suspension vehicle maybe removed so be applied as to appear throughout the body as by a thickener. or in a centrifuge, whereupon: of the paper or as a surface coating. For inthe thickened, mercerized stock may be washed 25 stance, as already indicated, the powder may be free from residual alkali, as in a countercurrent 80 incorporated into paperm'aking furnishes, inpulp washer. When drier sheets are being hancluding a high grade rag stock, the usual chemical dled, they may be subjected to processing steps wood pulps such as sulphite, or refined white similar to those constituting the initial steps oi.v wood pulps of high alpha cellulose content, tothe usual visc seay n p oce s; a s. t e s eets 30 gether with, if desired, the usual paper-making may be steeped in a mercerizing solution for an ingredients, such as rosin size and mineral fillers. appropriate period f m and e excess 111- On the other hand, the cellulose powder, together tion imbibed by the sheets then pressed therewith suitable adhesives such as dextrine paste, from. Rather than maintaining a fixed amount glue, rosin size, or the like, may be spread as a of alkali in the pressed, mercerized sheets, as in 35 coating on either or both faces of the fabricated the viscose-rayon process, however, the alkali paper. Depending on the fineness of the cellulose content of the sheets is, in accordance with the V powder, the surface qualities of the paper may be present invention, removed by washing. The varied from a. comparatively rough finish, knownmercerizing solution, in addition to transforming as egg shell" to a; perfectly smooth or fiat finish, the fiber into a non-hydratable condition, effects so suchas is sometimes desired in'printing or writa purification thereof, as non-alpha. cellulose ing papers. Cellulosic powder or waterleaf pacomponents of the fiber are-soluble and go into Zpers containing such powder are eminently suitsolution in the mercerizing liquor. This purificaable for-conversion into cellulose derivatives such tion may be quite marked when an ordinary comasthe xanthate, particularlyas cellulose in finely mercial wood pulp, such as bleached sulphite, I 45 divided ;condition is highly reactive with con- -serves as the raw material. The purification efverting chemicals. fected by the mercerizing liquor is enhanced by In accordance with the present invention, l. the subsequent 1 washing operation, particularly may start with cotton, chemical wood pulp, or when hot wash water is relied upon to remove other preferably white cellulose fiber of high 'p'urresidual alkali, as the hot alkaline solution formed 7 50 ity and stability, as raw material. The pulp may during washing is an excellent solvent for varibe in bulk condition orin thick sheets known ous non-alpha cellulose components associated commercially asdrier sheets. This latter form with the fiber. The washed, merc'erized pulp, is that which chemical wood pulps, especially either'in bulk or sheet form, may then be dumped high grade refined wood pulps of high alpha celluinto a heater engine with the necessary quantity as lose content, are likely to assume when put on of circulating water, and the aqueous stock suspension thus formed subjected to hard beating until the fibers have been reduced to a pulverulent state. The beater roll cuts and bruises the mercerized fibers with little, if any, hydrating or gelatinizing action thereupon, so that the stock is gradually transformed into an aqueous slurry lacking the marked slimy or gelatinous feel of ordinary, well-beaten papermaking stock. The aqueous slurry may be incorporated into papermaking stocks while they are undergoing beater action, and the mixture formed into papers of a sized or waterleaf character. It may also be used together with suitable water-soluble adhesives for coating papers, fabrics, or the like. If desired, however, the powdered cellulose in the aqueous slurry may be separated from its excess aqueous component, as by settling or filtration, and the separated powder then dried for storage or shipment. After separation from the aqueous vehicle in which it is suspended, the concentrated or still wet powder may be pressed into coherent cakes or masses, and finally dried in such form for packaging. The dry product constitutes a step product for storing or marketing, and as such may be supplied to papermaking and cellulose derivative manufacturers.
The principles of the present invention extend to other forms of non-hydratable cellulose, for instance to celluloses regenerated as from vis- V cose syrup. In this connection, artificial silk waste, such as viscose-rayon yarns which have been spoiled or damaged in processing, may serve as the source of the powdered cellulose oi. the
present invention. A feature of importance residing in the present invention is that mercerized cellulose fiber or other non-hydratable cellulose may be pulverized in the presence of an aqueous medium by standard papermaking machines, such as beater engines. It is, however, within. the contemplation of my invention to practise a dry, rather than a wet, pulverizing operation, as in ball mills, to which mills the mercerized or other non-hydratable cellulose may be supplied in bulk form or as sheets. Pulverization may also be accomplished in the presence of non-aqueous wetting media, such as benzol, which may be readily volatilized from the cellulose powder after the major portion of such media has beengremoved,
' as by filtration, from the slurry of cellulose powder. The cellulose powder may be of a particle size ranging from about 40 to 200 mesh, or even In some instances, the powder may be composed of particles of varying sizes, as when a batch reduced to particles passing through a 40-mesh sieve is blended with a batch of fibers reduced to particles passing through a 200-mesh sieve. In some instances, raw or unbleached wood pulps may serve as the starting material, in which case such pulp undergoes a marked refinement, as well as mercerization, by contacting with the alkaline mercerizing liquon; The mercerizing liquor may contain suflicient oxidants, such as hypochlorite, to bleach or'yvhiten the pulp; or the mercerized, washed pulp may receive an independent bleaching treatment with suitable bleach liquors before the pulverizing operation. In any event, the pulverized product is preferably a pure white one of high stability and composed substantially only of alpha cellulose.
In carrying out the mercerization of the fiber prior to its pulverization in accordance with the present invention, it is possible to add chemicals, such as oxidizing or reducing agents, to the mercerizing liquor, to efi'ect reaction on impurities or coloring matters associated with the fiber.
render the fibers more easily disintegratable into 0 a powder under pounding action, as in a ball mill. So, too, reducing agents, such as sodium sulphide, may constitute additions to the mercerizing liquor, particularly when the liquor employed is one derived from the smelted sodium compounds produced during the recovery operations practised in a kraft mill, which operations lead to the production of a liquor containing sodium sulphide, as well as caustic soda. In some instances, the mercerized fiber may be one which is aged in accordance with the practice followed in making viscose syrup such as intended for rayon manufacture; that is, the pulp in sheet form may be submerged in a mercerizing liquor, then pressed free of excess liquor, then fiufied, and permitted to age in fiuifed condition under controlled temperature conditions. Inasmuch as the aged pulp contains alkali and has been somewhat degraded during ageing, it is then washed free of alkali and is preferably digested in a refining solution of hot, dilute alkali, as disclosed and claimed in my application Ser. No. 132,319,
filed August 28, 1926. The washed, aged, and
preferably refined cellulose fiber may then be .dried and in such condition serve as the raw material for the preparation of the powdered cellulose of the present invention.
So far as certain subject matter is concerned, this is a continuation in part of my application Serial No. 196,135, filed June 2, 1927, which has matured into Patent No. 1,842,689, dated Jan.
What I claim is:
1. A paper containing powdered, non-hydratable cellulose fiber whose particle size is not 116 greater than about 40 mesh.
2. A paper containing powdered, mercerized cellulose'fiber whose particle size is not greater than about 40 mesh.
3. A process which comprises converting cel- 120 lulose fiber into a non-hydratable condition and then pulverizing the fiber in the presence of water to a particle size not greater than about 40 mesh. I
4. A process which comprises mercerizing cellulose fiber and then pulverizing the mercerized fiber in the presence of water to a particle size not greater than about 40 mesh.
5. A process which comprises incorporating pre-powdered, non-hydratable cellulose fiber into an aqueous suspension of papermaking stock, and
'then forming paper from the mixture.
6. A process which comprises incorporating pre-powdered, non-hydratable cellulose fiber into an aqueous suspension of papermaking stock, forming paper from the mixture, and converting the paper into cellulose esters.
7. A process which comprises pulverized nonhydratable cellulose fiber in the presence of water to a particle size not greater than about 40 mesh, and converting the powder into cellulose esters.
8. A process which comprises pulverizing mercerized cellulose fiber in-the presence of water to a particle size not greater than about 40 mesh, and converting the powder into cellulose esters.
9. A process which comprises pulverizing mercerized cellulose fiber, incorporating the powder into an aqueous suspension of papermaking stock, 150
forming paper from the mixture, and converting the paper into cellulose esters.
10. A process which comprises steeping cellulose fiber in a mercerizing liquor, removing excess liquor from the fiber, washing the fiber, and beating the mercerized and washed fiber in water to form an aqueous slurry of powdered cellulose of a particle size not greater than about40 mesh.
11; A process which comprises pulverizing mercerized cellulose fiber in water to form an aqueous slurry, incorporating the slurry into an aqueous suspension of papermaking stock, and forming the mixture into paper.
12. A process which comprises pulverizing mercerized cellulose fiber in water to form an aqueous slurry, removing excess water from the slurry to concentrate the pulverized cellulose, and drying the concentrate.
13. A process which comprises pulverizing mercerized cellulose fiber in water to form an aqueous slurry, removing excess water from the slurry to concentrate the pulverized cellulose, pressing the concentrate into cake form, and drying the cake.
entirely of powdered, mercerized cellulose fiber of the character or cotton and chemical wood pulp, said powder being of a particle size not exceeding about 40 mesh.
18. A cellulose product consisting substantially entirely of powdered, regenerated cellulose, said powder being of a particle size not exceeding about 40 mesh.
GEORGE A. RICHTER.