US1872996A - Process of making paper pulp - Google Patents

Description

WIL IAM H. iaAson, or LAUREL,

, No Drawing.

-' Patented Aug. 23, 1932 fumrso STATES. P EN terrier;

' or LAUREL, urssrssirrr, A COBPORA'IIQN or DEL ARE rnooiiss or MAKING PAPEB. rum

7 My invention relates to'a processof making paper pulp, and particularly to a process of making paper pulp of ligno cellulose material, by exploding same into a state of line subdivision and treating such finely subdivided material with chemical reagents.

1n the usual practice of making chemical paper pulp from wood chips, which always vary more or less in. size, the smaller pieces and the outer surfaces of all the pieces-are liable to be overtreated by the chemicals, whereas the inner portions of the larger pieces are frequently found incompletely digested. In the chip making a greatdeal of the comminuted wood has to be discarded as sawdust and the like prior to chemical treatment because of being too finely subdivided to be treated with the digester size chips.

The chemical action is uneven from other ly closed and filled with resins and, other wastematerial, while in the sap wood the cells are active and much more open. The diiference in age of the various trees from which the wood is takenis also a factor in causing uneven chemicalreaction with certain parts overdigested and others mcompletely digested. I When wood is prepared for pulp making by grinding, the fibers are broken and torn and reduced in length and are not well adapted for the production of paper pulp from' which strong, tough paper canbe made.

According to the present invention in order to give the chemicals full access tothe wood fibers and to provide enormously large sur faces for chemical attack, the wood or other ligno-cellulose material which is to be made use of for the production of paper pulp, is

*Appllcatlon'flled May 21,

and whereby 1925. Serial No. 31,785.

mssrssrrrnAssrenonro Asom'rn conron rron, I

exploded by being forcibly expelled from a high pressure chamber within which: the material'has been subjected to the, penetrating action of a high pressure gas, such as steam, the ligno-xcellulose material, .is reduced to very finely subdivided state, being in fact in large partreducedto its component 'ultiinate fibers. lVithsuch treatment there is practically no reduction of fiber length, the fibers being practically all of their full natural length, and the exploded;ligno-cellu1ose material islong fibered and well adaptedfor the production ofpaper pulp from which strong, tough paper can bemade. [Practi cally every bit of the wood is recovered as pulp, includingthe excessively dense and hard portions, such as knots, k'nurls which are thoroughlyreduced to the fibrous stateand available for making pulp.

In Patent N 0. 1,578,609 granted March 1926, I have shown and described apparatus for performing the explosion operation- The explosion is preferably produced by high pressure steam which is, of course, at a cor-f respondlngly high temperature. By leading the exploded wood and exhaust.. steam-into a digester or vessel in whichthe chemicals for pulpmaking are contained, substantially all the otherwise waste heat can ibe"'absorbed by the chemical liquid. The heat made use of toobtain the explosion can thus bepractically all conserved.

According to the preferred embodiment of the invention the wood, chippedinto pieces of about the size customarilymade-use ofin chemicaldigesters, is introduced into a high pressurechamber andsubjected to penetraand the like,

tion by high pressure steam. After the pres- 'sureis balanced within and without themate'ri-al to be exploded, an,orific e is opened and the contents ofthe chamber discharged,

the wood disrupting'into astate of fine sub- A division as it passes the orifice. The pressure is preferably maintalnedwithin the chamber during the explosion discharge so as to secure substantially. uniform, subdivisionand disin- 5 tegration from the-first stages of the discharge right up to the completion thereof;

The pressures made use of in the explosion operation are in excess of 250# per'square 800 er square inch. 1 I Ifiia e-found that when the wood .used is of a uniform moisture content, des rably at inch. [As the pressures are higher this, morecomplete and better disintegration 1S btained; A very desirably hi h state of dis integration has been obtaine with steam at or below the fiber saturation point? of the wood-,za most-desirable condition is produced for explosion.

I heat up to the high temperatures, and a a ing fiber it may ,dry the wood so 'ture content anddesirably at or'near the arently the penetration of the steam into t e interior of thewood is much more rapid and com leteand explosion thereof can. done much quicker with wood of substant ally'umform low moisture content.

To obtain special conditions in the resultbe desirable to preliminarily that it is of uniform moisfiber saturation point. Predrying the wood enables the" exploding to. be done quickly and substantially avoids discolored products, which may be produced when the wood is held toolong under the highpressure steam. After the wood "isexploded and thereby reduced to fibrous" state it is placed intoa digester and Desirably, although-not necessarily, the exploded woodand exhaust steam isled direct into "the digester containing the chemical lost, but is in large part in somecases reduction of the steam is possible. There is more nearly the theoretical recovery of the complete cellulose content as pulp. 'A'more uniform product-is obtainable apparently because of the very extensiveexposure of the lignin's and othernon-cellulose 1 as'is' required for ver high grade 'pulip, a by components to the action of thechemical reagent. The pulp after digestion is ready for treatment in, a beater, Jordan'or thelike apparatus for the production of paper.

Instead ofdigestingthe fibers completely very-desirable class 0 pulp is obtaine only partiallyv digesting the exploded and exposed: fibers so that the lignin is'removed to anzextent from the individual fibers and it ispossible to hydrate material so obtained .bythe-usual process'of hydration, such as .beatinggordaning, etc. 1 1

Another mode of procedure in making pulp Less steam is required, on'ac' count apparently of there being less water to subjected to chemical diges- "-tion' either of the acid or alkaline type in order to digest and remove all or part of the, lignins and produce commercial cellulose I claim:

the diges- 1 ama sion treatment is to subject chips to complete a combination of chemical and exploorpartial chemicaltreatment prior to explosion. Such treatment may be carried out in an enclosed chamber, the surplus chemical removed as by draining it. out and then the chi smay be subjected in the chamber to very hig steam pressure, such as pressure .over"- 250# and preferably over-400.1; per square inch, "and ,rojected' from the container'as described a ove, so that the resulting fiber is hi hly disintegrated. Many of the cellureadily and more or lesscompletely hydrated by the ordinary beating; process, and made available for a good grade of paper. If desired, the pretreatment with a chemical may be carried out in a separate-vessel ordigester nor to the introduction into and explosion:

rom the high pressure chamber. After exlose here have lost part or all of their coating of encrusting lignms so that they may be losion a furthersecond treatment in a chemical digester maybe resorted to, if desired.

The pretreatment with chemicals prior to explosion, when resorted to, may be of various kinds. F orexample, discoloration produced b somewhat prolonged exposure to extra high pressure steam appears to be due to generation or liberation of acids, etc., and preliminary treatment with neutralizing chemicals can be resorted to with advantage, especially when the steam pressures are extra high and discoloration of the product is undesirable. v I

ulp, which con- 1. The process of makin Q jecting subdivi e wood to chemsists in su icaltreatment in a chamber, removing surplus chemicals, subjecting the treated mate-'2 rial to steam pressures in excess of 250#- r square inch in said chamber,-and discharging from said chamber at such pressure, whereby the material is exploded and thoroughly d1sintegrated.

2. The process of makin pulp, which conical digestion in a chamber, removing sur plus chemicals, subjecting the treated mate jecting subdivi ed wood to chemrial to steam pressures in excess of 250%: per

square inch in said chamber, discharging said chamber at such pressure, whereby the material is exploded and thorou hly disinte rated, and sub ecting the pre igested an exploded material to further chemical 'diges a 3. The rocess of makin pulp which consists in su jectingsubdivi ed ligno-cellulose I material to penetration by steam under pressure in excess of 250 pounds per square inch in a closed chamber, progressively discharging the ligno-cellulose material and steam through a constricted opening and leading the ex loded material and exhaust steam into a liquld containing a=chemical reagent-"for digesting, whereby the heat of the steam used for ex losion is absorbed in the chemical re agent ath.

4. The recess of making pulp, which consists in subdivision of wood into substantiall chip form, subjecting same to partial chemical digestion, draining off the surplus'liquid and exploding such pretreated wood into fibre b progressively discharging the same through a constricted opening from under pressure in excess of 250# pensquare inch. 5. The process of making pulp, which consists in subdivision of wood into substantially chip form, subjecting same to partial chemical digestion, drainingofi the surplus liquid, exploding such pretreated wood mto fibre b progressively discharging the same throug a constricted opening from under pressure in excess of 250# per square inch, I and subjecting the partially digested and exploded fibrous material to further chemical digestion. p

In testimony whereof, I have signed my name hereto.

- WILLIAM H. MASON.