US1806309A - Treatment of pulp and product of same - Google Patents

Description

results and realized from t Patented May I9, 1931 PATENT orrlca GEDBGE, A. RICHTER AND MILTON 0. SCHUR, F BERLIN, NEW HAMPSHIRE,

a s GNORS TO BROVTIT COMPANY, 01 BERLIN, NEW HAMPSHIRE, A. CORPORATION OF HAINE TREATMENT OF TULP AND PRODUGI' 0F SAME Ho Drawing.

This invention relates to a treatment of cellulose pulp l intended to permit optimum iglhest economic value to be e use of such ulp as a raw material in the manufacture 0% paper, cellulose derivatives and other cellulosic products.

Pulp liberated from raw cellulosic ma- I terial such as wood is fre uently characterized in terms of average fi er length, but if the pulp is closely examined, it will be observed that it consists of fiber units of ran-' dom sizes, some being above and some below the average. The long-fibered portion of pulp has characteristics quite distinct from its short-fibered portion. For instance, if wood pulp refined to high alpha cellulose content is'sep'arated or c assified into, say, two equal. portions, one containing the longer fibers and the other the shorter ones together with fiber fragments and cellulose in colloidal condition, these portions will have distinctly different characteristics. The long fibered portion is very free and tough being comparable to high grade rags in stability, and, when made into paper, in stren h, tear resistance, folding endurance, etc. oreover, it yields derivatives of a stability and purity substantially equal to those producible from high grade cotton, even though the pulp from which it was separated 1s inferior to cotton. Hence, as disclosed in application, Serial No. 207,314, filed July 20, 1927, by Milton.O. Schur and Robert A. Webber, when it is desired to produce high grade drivatives from wood pulp, it is advantageous to separate the longfibered portion from the rest of the pulp and convert this portion alone. The shortfibered portion possesses only moderate strength, but is easy-beating, this latter characteristic being ascribable toithe presence therein of most ofthe colloidal and hydrated cellulose in the. original pulp.

One of the drawbacks to a process involvmg the classification of pulp into por- Applicatlon filed August 5 1927. Serial No. 210,999.

only in the manufacture of comparatively.-

inexpensive papers and derivatives. Even in the case of pul refined to high al ha cellulose content, t e short-fibered portion, if removed from the long-fibered portion, is unsuitable for the preparation" of hlgh grade derivatives, for most of the impumties present to the extent of, say, about 0.2% p

to 0.4% in the original pulp become concentrated in this portion. The retentlon of the impurities b this portion is apparently attributable to t e hi h adsorptivlty of cellulose fiber in finely ivided condition, particularly in the form of fiber fragments and colloidal cellulose. It is hence not surprising that the short-fibered portion of pulp preferentially or selectlvely adsorbs the 1murities, the lon -fibered portion being far ess contaminate While the percentage of impurltles 1n the short-fibered portion of a pulp depends largely upon its size relative to the plulp as a whole, the chemical processln w 10 the.

pulp has received, and upon t a character grades 'of paper and derivatives. Nevertheless, where color or a high degree of purity in derivatives are of secondaryconsidera tion, low rice being more important, as in the manu acture of cheap celluloid toys, ads vertising novelties, and the like, this shortfibered portion offers an attractive source of.

raw material. While the 'color may be brightened to a limited extent by the appli- 'cat1on of bleach, this'tends to weaken the pulp, requires an extra bleachery, and at best is but a makeshift cure, for the pulp still retains an objectionable grayish cast, and is of inferior color stability.

It is the object of the present invention to produce from pulp long-fibered and short bered portions, each of which is better ada ted to fill certain useful and valuable nee s both in papermaking and inthe preparation of cellulose derivatives than the originalunclassified' pulp, so that classification may increase 'not only the value of one portion, but of both portions. By removing these impurities, particularly those of a resinous character, before classification, or

separation of the reviousl liberated pulp into its long and shortber portions is effected, this object may be realized. More specifically, this object is attained by digesting the pulp in a saponaceous re ent before classification intoportion's of di erent fiber len hs. .Digestionof this charaeterefi'ectsaispersion or collodial solution of the resins, s eeks, and other im urities adsorbed mainly y the 'short-fibere portion, so that when the pul is subsequently classified, this portion is su stantially as white and stable as the long-fibered portion;

' A process such as described finds important utility in the case of pul which is being refined to high a] ha celiiilose content, for the product may e classified into two stocks of. different fiber len hs, both of which are clean, white, and sta le,'possess1n different characteristics and hence adapted for different uses. Thus, the long-fibered stock which is free and tough may be used as a rag fiber substitute in the manufacture of high grade writing bond, and ledger papers. It may also be used in the manufacture of high, grade cellulose derivatives substantially equal to those producible from 'hlgh grade cotton. The slmrt-fibered portion is of good color and is easy-beating, and may be used to great advantage with diflicultly beata' e stocks, particularly rag stocks,

to increase their beatability and hence enhance their suitability for papermaking. This portion is also well adapted for use as a raw material for the preparation of derivatives, as its short component fibers are of high reactivity and hence undergo quick reaction with converting chemicals.

The process of the present invention may be practised to advantage upon bleached sulphite or other wood ulp, but is particularly advantageous in t e case of pulps refined to high alpha cellulose content and intended to supplant high grade cotton fiber as a raw material in the preparation of paper or derivatives. Soap-digestion in such case may "be expediently performed while the pulp is undergoing a chemical refinin which effects an increase in the alpha cellu ose content of the pulp and its whitening. The pulp employed as a raw material may, for instance, be unbleached sulphite pulp containing resinous impurities to theextent of about 0.5% to 0.8%, or even higher,las determined by extract on from the fiber with organic solvents such as alcohol,

ether, or chloroform.- Such pulp may berefined'by a series of' chemical treatments, including a treatment with chlorine'water, followed by alkaline digestion, and finally by bleaching. While we may soap-digest the pulp before or after any one ,of these treatments, such digestion may be expediently and economically performed while the pulp is being alkaline-digested and/or bleached, as this permits the stri ping of resinous impurities and specks mm. the pulp without additional a aratus or time of treatment. If soap is addedtothe bleach, liquor, it is preferable to use sodium base bleach, as the use of the usual calcium base bleach Would-result in the fixation of insoluble soa s on the fiber. The use of soap while t e pulp is being hot-digested in an alkaline liquor has been found to be espe-' cially satisfactory, as this permits soap-' forming substance to be used in lieu of previously. prepared soap. In such case,

suflicient alkali is used not only to effect the desired reaction on the ulp, but also to eii'cct a saponification of the soap-forming substance. Moreover, under the influence of heat and the motion of the fibers, very effective 'deresinification and cleansing of the pulp is effected, as the resinous impurities are believed to. exist in a softened or .plastic condition quite amenable to the disparsing or solvent action of the soap solution. A specific series of chemical treatments may, for instance, be substantially as follows. Unbleached sulphite pulp is treated with about 2% to 4% of its weight of chlorine in the form of'chlorine water, then is digested at a consistency of, say,

' 10% for five or six hours, at 212 F in an 1% to 3% of its weight of calcium h pochlorite preferably in the presence of out 3/4% caustic soda, based on fiber. A bright white product results, high in alpha cellulose content, free from ligneous matter. low in copper number, and containing well under 0.1% of its weight of substance soluble in organic solvents.

When the product is classified after bleaching, the short-fibered portion is found to have a bright, pleasing white appearance, and to .be of hi h color stability. Classification may be e 'ected as by washing the pulp as a thin layer on fine mesh screen, say, -mesh Fourdrinier wire, or on plate aving fine perforations, for instance, of .02 inches in'diameter, as is more fully disclosed in application, Serial No. 755,730, filed December 13, 1924, b George A. Richter and Elwood Ebie. be longfibered portion remains on the screen or plate, while the short-fibered portion passes through and may be recovered from the wash water on a thickener or other suitable means. Or the washing may be performed by repeatedly diluting the pulp with fresh filtered water and flowing 1t over wire or perforated late maintained in an inclined position. r it may be more expedient to effect a classification by removing the longfibered portion by passing edge-presenting members capable o picking up the 1on fibers, throu h the pulp, and washing and recovering t cse fibers, the short fibers remaining in the residual pulp. This method is full disclosed in application, Serial No. 206,477: filed July 18, 1927, by Robert A. Webber, and permits the removal of longiibered stock from pulp in predetermined controlled amount.

to our application, Serial No. 202,454, filed wl'une 29, 1927, which discloses the soapdigestion of pulp to effect a removal of resins therefrom. Nor do we herein claim the subject matter of our application Serial No. erases, sac August 5, 1927, which discloses the separation or removal of fine and broken fibers from pulp, followed by the deresinification of the removed material in a g%onaceous reagent.

Y at we claim is:

L A process which comprises deresinifying previously liberated cellulose pulp, and then classifym portions of di erent fiber lengths.

Q. A process which comprises preparin a.- bleached and substantiall deresmifie wood pulp of high alpha cel ulose content,

duct into long-fibere the deresinified pulp into the digested pulp, and classifying the bleached product into long-fibered and short-fibered portions.

6. A process which comprises digesting pulp in an alkaline liquor containing soap, bleaching the digested pulp in bleach liquor containing soap, and separating the bleached product mto portions of different fiber lengths.

7. A process which comprises bleaching pulp in bleach liquor containing soap, and separating the bleached product into portions of different fiber lengths.

8. A process which comprises bleaching pulp in sodium base bleach liquor containmg soap, and classif ing the bleached proand short-fibered portions.

9. A process which comprises chlorinating unbleached pulp, alkaline-digesting the chlorinated pulp in a liquor containing soap, bleaching the digested pulp, and classifyin' the bleached product into long-fibered an short-fibered portions.

10. A process which comprises treating unbleached sulphite pulp with water, digesting the treate pulp at elevated temperature in caustic soda liquor containing soap, washing the digested pul bleaching the washed pulp, and classiFying the bleached product into long-fibered'and shortfibered products.

11. A process which comprises subjecting previously liberated Wood pulp to the action of a reagent capable of deresinifying such pulp, and then separating the deresinified pulp into portions of different fiber lengths.

12. A process which comprises digesting pulp at elevated temperature in a liquor containing soap-forming substance and alkali in excess of that necessary to saponify said substance, and separating the di ested pulp into long-fibered and shortfibere portions.

13. A product consisting of white, cellulose pulp containing well under 0.1% of its weight of substance soluble in organic solvents, said pulp being substantially free from chlorine white, wood pulp refined to high alpha cellulose content and containing well under 0.1% of its weight of substance soluble in organic solvents, said pulp bein substantial- 5 1y free from fine, short and roken fibers and bein convertible'into papers comparable in sta ility, stren h, tear resistance and fold endurance to t ose'. made from high 1 grade ra s.

In testlmony whereof we have afiixed our signatures."

' GEORGE 1A. RICHTER,

' O. SCHUR.