US1945862A - Manufacture of paper pulp - Google Patents

Description

Patented Feb. 6, 1934 TES PATENT OFFICE MANUFACTURE OF PAPER PULP Aimwell Gordon Maclntyre, Decatur, to A. E. Staley Manufacturing Company,

catur, 111., a corporation of Delaware Ill., assignor I NoDrawing. Application Augustfi, 1930 Serial N0. 473,770

10 Claims.

The invention relates to the manufacture of wood pulp and more particularly to improvements in the cooking of pulp whereby a softer,

stronger and purer fiber is obtained.

In the manufacture of paper pulp the wood is first chipped and then placed in a digester. In

either the alkaline or the acid process the cooking liquor is then or by indirect by the introduction 0 added and the pulp cooked either f live steam into the digester heating. The cooking operation removes the resins, pitch and lignins from the Prolonged cooking or at high temperatures the cell structure of resulting product.

drastic treatment and pressures breaks down the fibers and weakens the At the same time, it is desirable to remove all or substantially all of the resins, lignins and other impurities from the pulp so that at the present time in actual practice a compromise is usually of the impurities is remov seriously injur I have found be carried on to much b loid is added to the chippe liquor in the efiected and as much ed as can be without ing the fiber structures. I

that the cooking of pulp can etter advantage if a cold wood and cooking digester. The colloid apparently disperses the pitch and lignins in the wood so that the cooking liquor atacks the impurities more efiectively and result a purer An important feature of the ability to remove dissolves them more readily. As a pulp is obtained.

invention is thethe lignins and resins from the wood with apmilder cooking operation, that is the period of time may temperatures be reduced or lower and pressures may be employed.

breaking down of the cell walls of the cellulose and a stronger product is obtained. cooking varies As the greatly mechanical procedure of both as to time of treatment and temperatures and pressures, I am 0 unable to give any specific obtained when a colloid examples of results is added to the cooking liquor compared to results obtained according to the present practice,

but it is recognized by everyone skilled in the -art that a drastic and prolonged cooking operation destroys or partially destroys sulting in an the cell walls of the cellulose reinferior product and by the use of my invention either the time of treatment can be reduced or lower temperatures and pres- 0 sures can be used and injury'to the cellular structure eliminated.

As stated, the invention may be aplied both to the cooking of by the acid process. In preparing to the sulphat pulp by the alkaline process or pulp according e, soda or kraft process, the causdecanted caustic liquor is then used to prepare the cookingliquor in the usual manner. The pulp and cooking liquor are introduced into the digester, and a cold water solution of a colloid added thereto prior to cooking. The quantity of colloid added may vary within wide limits but in actual practice I have found that 25 pounds to a Ger 8 ton digester is suitable. Even when smaller quantities of the colloid.are employed, the same results are obtained to a less degree substantially proportionate to the amount of colloid added.

In the acid process the chipped wood is placed in the digester in the usual manner and the sulphite cooking liquor added. The colloid is placed in the digester in the form of a cold water solution. The use of a cold water solution prevents coagulation of the starch or other colloid added when steam is introduced and thus insures the colloid being dispersed throughout the cooking mass and serving its function. i

1 In either the alkaline or acid process the cooking operation is then carried out in the usual manner except that milder cooking practice may be employed resulting in less breaking down of the cell walls of-the cellulose. A further advantage of the process is that in cooking woods of high resinous content by the alkaline process 90 the presence of the colloid reduces or minimizes the formation of foam in the diffusing and washing operation immediately after digestion.

Recent investigations have disclosed the fact that the fibrous structure of wood consists of a' wall having a plurality of small diaphragms therein. These diaphragms are provided with openings through which the cooking liquor must penetrate to reach the interior of the fiberand remove the resins and lignins therein. In ordinary practice it is difficult to penetrate the interior of the fibers although the lignins, resins and other impurities located between the fibers can be readily removed. When greater pressures are employed in an attemptto force the cooking 105 liquor into the fibers the diaphragm is forced against its seat in such manner that the openings therethrough are closed and it is necessary to employ pressures that will break the walls of the cell structure to penetrate the flbersand reaccuses move the impurities therefrom, As stated alcove, this results in a pulp that is weak and is not par= ticularly suitable for paper manufacture. it ho lieve thatthe addition of the colloid to the coolr ing liquor assists the cooking liquor in seeping through the openings in the diaphragm and re moving the resins and li 'nlns from the interior or the cell Without breaking the cell wall.

'llhe colloids mentioned alcove are Toy "way oi example only" and other colloids may he em ployed, So-called stuns formed from starch particularly adapted for use practicing" process,

It is thought that the invention many of otl'ier than that contained in Wood.

2. The step in the manufacture of wood pulp which comprises cooking Wood in the presence of a gum consisting of converted starch,

3. The step in the digestion of wood for themanufacture of Wood pulp which comprises in= troducing a dispersing colloid other than that contained in Wood into the digester prior to I cooking.

d. In the digestion of wood for the manufac= ture oi wood pulp by the allralineprocess the steps comprising a colloid. other than that conta ed wood to the carp-lie liquor, per

"mitting it to settle, decanting the liquor, prepar ing coolrins" liquor therefrom, introducing the cooking liquor and wood into a digester, adding" a dispersing colloid thereto and cooking.

5. In the digestion of Wood for the manuiac ture of Wood pulp by the acid process the steps comprising placing the Wood to form the pulp in a director, oding sulphite liquor thereto, adding a cold solution oi a colloid other than that contained in Wood, and cooking.

o. digestion of wood for the manuiac ture or" wood pulp by the alkaline process, steps comprising placing the Wood to form. the pulp in adig'cster, adding cooking liquor thereto, addin dispersing colloid other than that con tained in wood thereto, and cooking.

7. The step in the manufacture of wood pulp which comprises introducing a stun consisting oi converted starch in the digester prior to.

cooking,

8. In the manufacture of wood pulp by the alkaline process the stepsv comprising adding a gum consisting of converted starch to the caustic liquor, permitting it to settle, decanting the liquor, preparing cooking liquor therefrom, in= trcducing' the cooking liquor and wood into a digester, adding a gum consisting or converted starch thereto, and cooking.

9. In the manufacture of Wood pulp by the acid process, the steps comprising placing the wood to form. the. pulp in a digester, adding sulphite liquor thereto, adding a cold water solution of a guru consisting" of converted starch, and ccokin it. In the manufacture of Wood pulp by the alkaline process, the steps comprising placing the wood to i'orrn the pulp in a cligester, adding cooleing liquor thereto, adding a, sum [consisting oi converted starch thereto, and cooking.

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